John S, you said "prevent overtaxing the alternator. It is not made to recharge but to maintain" in the "Refrigerator Fire" post.
I have heard this mentioned by others also, but do not agree with this statement!
I run my refer from the inverter when travelling all the time and have not experienced failures.
The alternator is a mechanical/electrical device which will wear out even if the available electrical energy is not used.
The alternator will impose a HP load on the engine which is directly related to the amps being supplied, and the alternator will also run hotter with increasing load. However, even with high loads (i.e. 50% of capacity) an alternator will provide trouble free electrical current for years. When an alternator requires repairs, shops are readily available at reasonable cost.
Feedback please, particularly from those who disagree with my belief on alternators.
@Wyatt I'm with you on this one. The only real downside to using the alternator in this fashion is the heat issue. The Powerline in a lot (most?) rigs is almost totally enclosed and can build heat. One of the reasons I replaced mine with a Delco Remy 24si. It has much better ventilation to dissipate the heat. IMHO the heat would only be an issue at the extremes of operation such as trying to charge the house batteries after dry camping via engine alternator only. Much better to run generator to bring up the house batteries if they are depleted. This can even be done while on the road, don't need to wait on batteries before leaving.
see ya
ken
It has to do with design. It may put out 180amps, but if it isn't designed to put out 180amps continuously, it will overheat and life will be shortened. Continuous duty alternators (I had one in my old transit bus that ran huge 24volt fans for the A/C condensor) are MASSIVE.
So...when running the genset and engine at the same time, is there a priority as to which charges the house batteries? Does the converter get 120 VAC from the genset to then charge the house batteries overriding the 12 VDC from the alternator?
Hmmm Good question Peter. I just assumed it did. Hopefully someone with actual knowledge will chime in... :)
see ya
ken
The device set for the higher voltage will to the majority of the charging, unless battery voltage is below the voltage of the second device.
So, when first turned on, the generator/inverter-charger in bulk mode may be higher than the alternator/regulator voltage and would do most of the heavy lifting. But once the inverter-charger reaches float mode, the alternator voltage will likely be higher and do most of the remaining lifting.
Here is one way to find out, add some Ammeters and Voltmeters at strategic locations. Just keep your eyes on the road while driving.
DC 0 300V 200A Shunt Voltage Current Panel Meter Digital LED Voltmeter... (http://www.ebay.com/itm/DC-0-300V-200A-Shunt-Voltage-Current-Panel-Meter-Digital-LED-Voltmeter-Ammeter-/271729368180?hash=item3f44551c74)
This one is rated at 200A, which should do the trick. Rather inexpensive, and 50A, 100A models are even less.
Put one on each charging source and you will know exactly how the work is being shared.
I upgraded to a 250 amp 28si alternator and 250 amp isolator right after I bought my coach. I also run my refer on the inverter while under way. With headlights on, inverter on, and juice to run the Detroit and Allison electronics, I estimate the alternator is running at about 100 amps down the road. Not any problems for many miles.
You can run your fridge underway with the alternator. It will keep up with the draw, especially in the day but if you have gone overnight, you will have a deeper discharge on the house batteries and it will cause the alternator to run constantly and it will burn up faster. James Triana did a session on this at the grandvention one year. Also they covered it in Ladies Driving school. Your stock alternator is not designed to recharge your house battery bank after a night of discharging. IF they are fully charged then the alternator will maintain the charge. I think there was even a Motorcader magazine article on it as well. I think you would need a second alternator or a bigger one and a bigger isolator before you could recharge the batteries.
Also the new IHs have 340 amp alternators or some huge number so they can run the AC while they are running down the road off an inverter. We have 180 amp on the 320 and I think it is a 160 amp on the 270.
Here is a link to the alternator site.
Prestolite - Leece Neville (http://www.prestolite.com/pgs_training/training_3.php)
It says in there that An alternator can become damaged if it operates too long at excessive temperatures.
They go over dirt and lack of air flow but over charging also causes high heat and if it has to replace lots of amp hours, first from the start drain and then the house batteries, it will not shut off and it will not cool down.
So running down the batteries at night running a residential refer might benefit from a heavier duty Alternator designed for the deeper discharge on a regular basis?
Most auto alternators at rated amp load will only provide about 10 volt output. Even the ones provided on our coach's, yes making lots of heat too.
There are units that will do 250 or more amp load at 14.5VDC, you would not want to pay the price for it. Nor could you fit it on my 320, ISM500. Weight & physical size would be the issue
If the sensing wire is hooked up on the engine battery side of the isolator then the alternator voltage regulator shouldn't be able to see the voltage in the house batteries due to the door being shut in the isolator. If this is the case then it seems like if you run your coach batteries low during the night then crank up and move in the morning all the charge your coach batteries will be getting will be the dregs (like a trickle charge) after your cranking batteries get full. If this is the case then your coach batteries can be low at your next stop if you aren't traveling a long distance. If this is not the case then how does the alternator voltage regulator see the house battery voltage unless you equalize your battery system through the "Boost" then the voltage regulator will see a need to get up and go?
Pamela & Mike
The easiest way to explain the isolator is to compare electricity to water. The isolator has one (water) input and has two (water) outputs to fill 2 buckets - 1 (chassis battery) and 2 (house batteries). It doesn't care what it is filling, but the input has to keep up with the combined flow of the 2 outputs. More water will flow to the bucket that has the lowest water.
The sense wire is connected to measure bucket 1.
So, say bucket 1 is almost full, but needs a little more water. So the alternator supplies some water to top off bucket 1, but to top off bucket 1, it also has to fill bucket 2, which is low and takes almost all the water.
The sense wire tells the alternator to increase water output to try to top off bucket 1, but the water still continues to mostly flow to bucket 2. This increase continues to the max output of the alternator (water), and bucket 2 continues to get most of the water until it reaches the level of bucket 1.
Then when the alternator can finally make progress filling bucket 1 (and also bucket 2), the sense wire then detects this, and when bucket 1 (and bucket 2) are both topped off, the sense wire then says "both buckets are full".
So the isolator will always try to equalize the batteries, giving the lower bank more charge current until full charge is reached in both banks.
The fridge does not use most of my power. Two C paps and lights and blower motors on the heaters and water pump and TV and dvr and computers and charging cell phones. Dual alternators might be an idea to help it out but really a bit of bulk charge will help you save your alternator.
My "stock" 1991 coach 12 volt setup (160 amp alternator and 160 amp isolator) was adequate for the coach intended use back in the day, and no doubt was chosen to meet the necessary price point at the time in 1991.
But, to meet the 12 volt demands in my current setup with a little reserve, I upgraded the 12 volt system - 250 amp alternator and 250 amp isolator. High output alternators and isolators available now are efficient, run cool, and are relatively inexpensive.
People with gas refrigerators have a different situation than people with electric refrigerators. If you have a gas refrigerator it's unlikely you'll deeply discharge your battery overnight, or at least I've never been able to, even after running the gas furnace for a while in cold weather. I never start my genset to charge my battery before driving away in the morning. My alternator produces a much higher voltage and amperage than the charger so my batteries are all fully charged very quickly when driving. I have a 160 amp Leece Neville and a single 8D flooded cell coach battery and I do just fine traveling all over the country. I do this all the time and it's never been a problem. Running the genset takes twice as long to charge the batteries. The genset is expensive to overhaul and it's a waste of fuel unless it's really needed. The alternator is a cheap little thing by comparison that's inexpensively rebuilt at an alternator shop, and you can rebuild it yourself if it's an AC/Delco. I've done a bunch of them over the years, some for as little as $5 in parts, although that was many years ago and it probably costs more now. If you're trying to run a residential electric refrigerator you should probably stay plugged in at a commercial campground, just saying. Boondocking is for gas refrigerators unless you're prepared to do extremely expensive electrical upgrades and still have drastically less endurance than an old coach like mine with a gas refrigerator. I fill my propane tank once a year. I can run my refrigerator on gas six months between fillups according to my calculations... This information is coming from someone who seldom has time to write on here because I'm always too busy traveling. I've got half a dozen national parks to write about just from the past couple of months. I haven't even gotten my slide film developed yet because I just barely got a mailing address! :))
Please excuse my limited information but I do not know for sure how the alternator and freedom 25 inverter/charger in our coach works.
My understanding is that you should charge batteries at a max of 20% of their CCA ratings which matches the way Foretravel engineered the coaches electrical system.
My three 8g8d's have roughly 675 amp hour capacity so a max charge into them would be the 130 amps the freedom 25 is designed for and the magnum 2812 also has a max 130 amp rating.
The alternator while rated for 160 amp seems to be correct at roughly the same charge rate as the charger built in to the freedom 25.
Especially as it has only bulk charge versus the acceptance and float programmed into the freedoms charger.
My question is that if I add a larger high output charger will it try to overcharge the batteries?
I have seen countless grey batteries with bulging cases from overcharging it seems long ago.
Will a higher output alternator than the nominal 160 amp one from Foretravel try to input more power into the battery than it can accept which will damage the batteries over time?
I understand if you are smart enough to divert any extra DC power over the charger to battery needs as it occurs it's posdible to not overcharge the batteries capacity but that would have to occur in real time?
In other words load the alternator not to overcharge the batteries? Good luck.
Enough instrumentation it could be done I am sure but using the refer on inverter power might be required?p
What happens when the refers thermostat switches the input off when it reaches its low temp shutoff point then?
Just looking for info. Will a higher amp output alternator try to overcharge the house batteries?
Tell me how the system works? If extra amps hurts nothing why did Foretravel not put a higher output alternator on the coach?
And the matching output of the charger and alternator to the three gel batteries that our coach came with is why I am asking these questions.
Does the alternator simply reduce its DC output if its overcharging the batteries?
Caflashbob:
Excellent questions. The thing to remember is alternators with a lower or higher amp capacity will have a similar voltage setpoint. So no overcharging will occur once the voltage set point is reached, but a higher amperage alternator will be able to recharge a battery bank faster, or, handle a higher continuous load.
Compared to say 20 years ago, higher amperage alternators/isolators are available now for less money due to advances in technology. I think the RV manufacturers supply what the market will bear at the time...and what is competitive with SOBs...
I removed the diode combiner and installed a Yandina Isolator. It's rated at 160amps. It's relay based, with no voltage drop.
There is a neat downside that is actually an upside to it though---if it is flowing a fair amount of current it gets warm and opens up to allow itself to cool off. This also allows the alternator to cool off!
The slickest way to run roof A/C and residential refrig while driving, as well as recharging the depleted batteries through an onboard smart charger, is to bolt up a belt driven 120v generator to the main engine. Cruising sailboats (and powerboats) have been using them for decades. I haven't researched them recently, but I do remember that there were major advances in stabilizing output regardless of engine rpm's.
I try to limit running my generator while going down the road to power the roof AC's.
My solution is the one Brad Metzger taught me years ago when I first met him. His solution is to simply take all his clothes off and drive naked. Says you can tolerate much more heat in the coach while driving that way.
Very creative guy that Brad.😎
The dash A/C is on my spec sheet is 17,250 btu/hr. The roofs are 13,500 each. The problem is the dash has horrible ducting and doesn't let all the cooling typical get to the coach.
Crazy project, but I might try to add another evaporator in the future mid coach. If I can get a used dash HVAC unit, I can add heater core too for heat going down the road---since no aquahot.
Can the charge rate from a larger than the 160 amp alternator I have into my three batteries exceed the batteries 20% of CCA limit?
How does the system work? Can you be below the set voltage on bulk charge and exceed the batteries design limits?
I understood you could and remember have seen many damaged batteries from this long ago.
But I may have a faulty memory?
I have set up a few coaches long ago with 120 volt alternators. 3 or 5,000 watts if memory serves me.
Yes the coach slowed down a bit.
My current research so far shows I guess is that if I'm going to try to improve the alternator charging of my battery bank some day that the same 160 amp alternator output that's in my coach now might be better to be a heavier duty unit designed for that continious output and/or locate a link 2000r or similar alternator control which then will have the same steps in the charging as the inverters do.
Bulk, acceptance and float.
Would seem to be necessary if the batteries are going to be more than 20% overnight running a residential refer to me.
Or have a much shorter battery life?
Would love to have a link 2000r setup if someone wants to sell one?
The MK battery engineer mentioned 10 year life from Foretravel owners already using their 8g8d's before the latest plate mounting mods that he said could potentially double the life cycles of the batteries.
I would bet the IH-45's 340 amp alternator uses a similar stepped output control to not fry the batteries.
Am I wrong? Can you bulk charge house batteries at more than the 20% rated input with a larger alternator than the batteries max charge rate input? Especially if it's bulk charge only as most here are?
Don't most boat batteries have the bulk, acceptance and float cycles in their systems to prevent gassing/damage?
Can I overdo the input charge amps damaging the batteries?
My gels I think on the inverter are set at 14.15 max. AGMS would I think be at 14.4?
Thinking of pulling my alternator for a preventive maintenance rebuild but adding a stepped charging controller and a continious duty unit is not out of the question for me if it helps over the long run.
I would think with 4 batteries for a residential refer install I would have a matching the batteries max charge rate input continious higher output alternator installed with a stepped power controller.
The original systems in the coach was not designed I think for the extra draws the system is now being subjected to.....
I had a battery guy 30 years ago show me his suburban with 400k miles and a fifteen year old battery under the hood.
Perfect maintenance and I think a stepped charging system he sold was how.
Never exceeding 20% discharge and going between 70-90% discharge seems to work ok with the stock Foretravel setup on the inverter/charger as the last 10% acceptance charge takes a lot of gen run time.
The freedom 25 manual mentions this.
Does the higher output alternators lower the amp output or just the voltage?
It's a system and I want to make sure I understand how it works and what mods are needed if the usage and loads change in the future.
Thanks
Bob
My guru buddy mentioned he has done that with a few SOB's now that you mention it.
The 99's and up have a larger dash heat and air unit. 23,000?
May have to work on that.
Older foretravels had a curtain track installed in the flat ceiling and had a heavy material hung from it to seperate the dash area from the rest of the coach. Worked well.
Unit has enough output maybe for just the dash area.
Ugly install to put a track in the ceiling.
If you want to peruse that idea you can contact me for my buddies info?
Located in San Clemente, ca. Btw.
Not a structure or furniture guy but deadly on electronics and cooling systems.
Makes dashboards up for busses.
Bob, concerning your concerns about overcharging batteries with higher output alternator...
If you haven't already, go to Bay Marine Supply website (forum sponsor) and look at the Sterling Alternator-To-Battery chargers and remote control panels. That would seem to be the answer to setting up a safe (for the batteries) system.
I don't think any modern residential refrigerator presents any issues vis-a-vis charging or current draw. Our ideas of power use have changed radically. Back in the 70s it was possible for a double-door residential fridge to draw 10,000kwhr a day. Power was cheap and hardly anyone paid attention to it. But a modern residential refrigerator can easily be run by a 600-watt pure-sine inverter with a duty cycle far less than back in the day. Heck, lots of RVers are installing separate always-on small pure-sine inverters that only power their residential fridge.
Lighting has also undergone a revolution. We built a sailboat in the late 70s with florescent lights to reduce power requirements. Back then it was normal for boats to have small incandescent lights for everything and 12vdc florescent lights were new on the market (and not easy to find). But florescent lights were much more friendly to small boat electrical systems.
Today we all have florescent lights in our motor homes as OEM fixtures and many of us are moving to LEDs to further reduce power loads. Most of us have moved to LED HDTV upgrades and those draw far less power than the old CRTs; even the tiny CRTs they installed in our coaches. And the HDTVs are much bigger! Power loads on the batteries, even with cell phone and laptop/tablet chargers and TPMS monitors and all the rest has to be a lot less than we used to need.
I think that the biggest demand on an alternator now would be headlights and I don't think I've driven more than 500 miles in the dark since I bought my FT 10,000 miles ago.
I have long thought that long trips with an engine-drive alternator pumping over 14 vdc into my battery system might be counter-productive. Especially in summer when heat build-up in both systems (both the alternator and the batteries) just makes things worse. With all the attention on "smart" chargers for expensive batteries it's hard to imagine the alternators as "smart".
Maybe the idea of a 5,000-watt AC engine-drive alternator and letting a smart battery charger take care of the DC systems is the best idea after all. Especially if we move to Lithium-type batteries.
Edit: Just wondering whether an engine-driven alternator would actually get close to 60Hz since that's usually speed-related. There has to be a bettery system though.
Craig
Doesn't a 120 volt AC alternator have to stay at exactly 1800 rpm, or some other multiple of 60 Hz, in order to produce 60 Hz AC power? How will an engine in a moving vehicle stay at exactly 1800 rpm while safely negotiating traffic including coming to complete stops and idling at intersections? Won't the 60 Hz AC motors in the roof air conditioners and residential refrigerator burn out if the Hz slows down too much? I presume they're all capacitor start single phase AC motors with centrifugal switches that close at low rpm to engage the capacitor start. I suspect someone must manufacture a 12 volt DC electric refrigerator specifically designed for RVs. This would eliminate all the AC power problems while driving, but add new DC power problems while plugged in to shore power. The same would be true if someone manufactured a 12 volt DC roof air conditioner, but I doubt anyone does.... A seemingly good solution might be a permanent magnet AC motor refrigerator / rooftop air conditioner which could run acceptably well at most Hz while driving and shouldn't be a problem when plugged in to shore power... sorry if I think too hard about this :)
Currently large aircraft typically use a Variable Speed Constant Frequency (VSCF) generator system to generate their AC power. Such a system would be nice for motorhome use (such as powering refrigerators & roof air conditioners while driving) but is cost-prohibitive. Who knows what the future may hold?
Here's some info to add to an already interesting discussion. Not trying to sell anything or be an advocate.
From Mobile Electric Power Solutions website...
Mobile AC Power Solutions
The demand for "green" mobile electric power solutions continues to grow at a rapid pace worldwide, as do the applications that require it. MEPS has been the leader in designing and manufacturing belt-driven, pure sine wave, AC power systems for more than a decade now.
Our systems, marketed under the RoadPower, MobilePower, SeaPower, ReeferPower and GreenPower trade names, utilize a vehicle's engine as the primary mover to turn our underhood- or PTO-mounted generator(s). The electricity produced by our systems is pure sine wave AC power. Our frequency is crystal-controlled, so no matter what RPM your engine is turning the frequency will be either 60Hz or 50Hz as set at the factory.
Another unique feature of our systems is our ability to start and run motors and compressors. We do not require a "balancing" of loads to start and run a rooftop A/C unit or compressor motor. With a .1 lagging power factor, where other "competitors" have trouble running at .8, our systems require no resistive loads to offset your inductive loads.
If you are looking for a rugged, reliable, field-proven AC power system, MEPS has a solution.
Get with the times. The small honda generators and even the cummins RV generators run variable speed and use inverters to make the AC power. If one is really going to make a science project, at least make it out of modern technology!
If I had a big desire to do some type of compressor driven fridge, I'd say going with a DC based one would be a good option. There's a member or two here that have done that. The problem still comes that energy is needed. 2nd law of thermodynamics. Using mechanical energy to do heat work is kinda foolish when the absorption cooling system works great in this environment.
That MEPS site shows an alternator one mounts. It's probably slightly modified, and maybe better built. But the idea is that it takes the AC electricity from the alternator and runs it through an inverter.
The alternators on cars/trucks are AC devices...they just are connected to diodes to rectify the AC into DC.
The "generator" that runs roof A/C's and battery charger also has an ALTERNATOR on it. But, tradition and convention calls those and the big ones at nuclear and coal plants "generators" (AC generator). The old days cars had generators, that were DC devices, and a pain in the but, and not powerful.
I'm just curious: Who needs to "Get with the times"?
It's a joke. If we want to discuss an overcomplicated science project, at least use modern electronics technology in our internet designs!
Yes, I'm one of them.
So I run my Sea Freeze fridge/freezer on DC. No inverter needed.
And heat is the source of the energy needed: 1200 watts on the roof. Plus the Sun.
And at night I can turn the DC fridge/freezer down and defrost over night since no one will be openiing the fridge/freezer much overnight (aka not use much DC at all in a well insulated fridge/freezer)
PLUS, restaurant quality door handles! And world class Dan Foss compressor.
By the way, our 1999 40ft U320 is still for sale. Check out the classifieds. And see it at Bernd's shop on Main St in NAC
best, paul
Any reason you don't have it on consignment at MOT? Btw I will be in NAC all week getting the coach blowout repair completed
Why I don't have our 1999 40ft U320 on consignment at MOT?
I simply didn't think it was needed.
Plus our FT will appeal to only some of the prospects: For example, those who want to live/camp/full time "off the grid."
Then there are those who like not having to worry about their fridge causing a fire. I doubt MOT would even mention this feature because it would cause prospects to wonder about all the other FT's on the lot that use absorption technology.
best, paul
Reply 18 from Caflashbob
I will attempt to answer some of these questions:
"My understanding is that you should charge batteries at a max of 20% of their CCA ratings"
I have not seen CCA used this way before. The most accepted charge limit is based on amp hour capacity or "C" and is one third of "C", so about 70amps for an 8D battery at 70F. With three 8D batteries, about 210amps total which our alternators cannot provide. Some folks have been experimenting and have indicated that at 70F, the real max is C, or 220amps per 8D battery. I do not subscribe to this.
NOTE: the maximum amps that a battery can accept without damage is temperature sensitive, so at 110F during a Texas summer, best to have temperature compensation on your charger.
"My three 8g8d's have roughly 675 amp hour capacity"
When they were new and cycled about 15 times, they had that capacity, however, as batteries are cycled their capacity reduces.
After five to ten years and one or two thousand cycles their capacity will be half of new or less. I test my batteries to determine their actual amp hour capacity.
"Alternator has only bulk charge versus the acceptance and float programmed into the freedoms charger."
Alternator regulators have both bulk and accept but, as you indicated, do not have float. The regulator holds the voltage at the set point (if it can) which is typically 14.6 volts. If the battery is deeply discharged, the voltage will be less than 14.6 and alternator will be providing the maximum amps that it is capable of (bulk mode). When battery voltage reaches 14.6 volts and attempts to go higher, the regulator reduces the amps going into the field to reduce the amp output of the alternator (accept mode). The reason that there is little need for "Float Mode" with an alternator is that it only provides amps when the engine is running. If you had multiple drivers and drove for 100 hours non stop, your batteries would be over charged.
"My question is that if I add a larger high output charger will it try to overcharge the batteries?"
It will not overcharge if it is functioning correctly.
"I have seen countless grey batteries with bulging cases from overcharging it seems long ago."
Are you sure that overcharging caused the bulging? Bulging grey (Gel or AGM) batteries is most likely caused by "Equalizing" during hot summers. Equalizing is a controlled overcharge which desulfates the battery. I use desulfators all the time instead and never equalize my batteries.
"Will a higher output alternator than the nominal 160 amp one from Foretravel try to input more power into the battery than it can accept which will damage the batteries over time?"
With good regulator - NO.
"In other words load the alternator not to overcharge the batteries?"
IMO, not required.
"What happens when the refers thermostat switches the input off when it reaches its low temp shutoff point then?"
The 12 volt power into the Inverter drops to very low and regulator cuts down amps being provided by the alternator.
"If extra amps hurts nothing why did Foretravel not put a higher output alternator on the coach?"
Cost and not needed by most.
Reply 24 from Caflashbob
I will attempt to answer questions not in Reply 18
"My gels I think on the inverter are set at 14.15 max. AGMS would I think be at 14.4?"
Those are the voltage set points recommended by battery manufacturers.
Because I use desulfators all the time, the finish voltage of my batteries are 14.1 to 14.2 volts. Finish voltage of flooded batteries are 12.75, AGM 12.80 and Gels 12.85. I have both my solar controller and alternator set to 14.5 volts.
"Thinking of pulling my alternator for a preventive maintenance rebuild and adding a stepped charging controller"
Preventative maintenance (cleaning) is a good idea because many alternator failures are caused by corroded terminals. Adding a stepped charging controller will add little value and may not work well - I would not do it.
"I would think with 4 batteries for a residential refer install I would have a matching the batteries max charge rate input continious higher output alternator installed with a stepped power controller."
Higher output alternator could be valuable, but stepped power controller of little value.
"The original systems in the coach was not designed I think for the extra draws the system is now being subjected to....."
I agree with comments of others. Residential refer is larger load, however, LED lights and TVs are lower loads.
"I had a battery guy 30 years ago show me his suburban with 400k miles and a fifteen year old battery under the hood."
Must have been in deep south, in Canada during the winter, he would need a boost.
"the last 10% acceptance charge takes a lot of gen run time."
Because of this, I believe that most folks who charge batteries with a generator never charge above 95%, which will cause a shorter battery life due to chronic sulfation. This is where a solar charger has a great advantage.
"Does the higher output alternators lower the amp output or just the voltage?"
The regulator limits the voltage at the set point (14.6v) by controlling the amps output. The only time the voltage will be lower than the set point is when the battery is so heavily discharged or loads are so high that the alternator is providing the maximum current it can. This is the most dangerous time for the alternator, because it will be running hot.
Thanks Wyatt. Meant amp hours. Not CCA.
The manual for the freedom mentioned the last ten percent of charge was not easily attainable or necessary for most uses.
Long drive or using a solar system for the last percent seems to be one the best finishing methods during daily use.
I see minimum charging into gels at various sites are 15-25% of the amp hours.
Lots of references to 1/5 C although Dropping to 1/10 C at the end of the cycle.
Will check with my guru just to toss ideas around. Weird fun.
Ia higher amp alternator supplying a isolater rated for the load might be a good alternative if having to do any major work.
Thanks for the reminder that periodic measuring of actual capacities is the only good test.
Had a short discussion with my electrical buddy today and he agreed with most here that the alternators that come in most Rv's are not capable of overcharging any batteries unless they are set at too high of a voltage.
His comment was that most all alternators are set around 13.6 volts and will not fully charge house batteries.
Made that way on purpose so that continious driving will not overcharge any batteries.
Said the inverter or a solar system were designed to fully charge the batteries.
We must be fortunate that Foretravel selected and have enough air flow around the alternator to have it not overheat.
When he specs out a prevost he uses two alternators. One for the chassis batteries the other for the house.
Then he likes to install the marine alternator controller as it has the three stage charging and a alternator temp sense wire in its harness.
So a higher amp output , more heat capable alternator cannot damage a battery as as long as the set voltage is not exceeded it will only charge the batteries as fast as they will accept it.
Probably slows the coach down up a hill with a big alternator. Haha.
Although the 4000 watt constant speed controlled ac alternator did slow the older coaches long ago when turned on.
Smaller engines.
No battery damage unless voltage is too high.
Everything else being equal he personally prefers the 1/5 C charge rate like most inverters have running into three 8g8d's.
He reminded me of my conversation with the MK engineer who mentioned 8-10 year gel service lifes with the 130 amp charge from the inverter and 160 from the alternator on foretravelers he had had contact with.
Has anyone done this:
My dash air needs a charge so no cooling. I am considering getting this transfer switch:
120V transfer switch (http://www.amazon.com/Terminals-Positions-Rotary-Changeover-Switch/dp/B009IS7SN2/ref=pd_sim_328_1?ie=UTF8&refRID=0PRAKP03QXSSTECPA0V6&dpSrc=sims&dpST=_AC_UL160_SR160%2C160_)
and switch the front roof air between coach power and my new Xantrex 2000 watt sine inverter. The roof air is 13500 BTU which will draw approx 1250 watts. I estimate this will add 100 amps to my 12VDC alternator load. (A/C compressor will cycle, so not on 100%) My upgraded 250 amp alternator and isolator should be able to handle this running down the road.
Update: Just bought the switch (needed a project this weekend). Will update on how this works out.
I will be following this one with interest! ^.^d
Don
I suspect you will need to add a soft starter to the A/C - they have two amperages - LRA (locked rotor amps) and RLA (Run Load Amps) - while the inverter may have the 13 or so amp capacity to run the A/C, it will likely trip off line when the 60+ amp LRA hits it for about 1/3 of a second. PM me and I will sen you my phone number and we can discuss. In the meantime look up the LRA and RLA of your A/C units.
BTW, most A/C's already have a "hard start" type device (capacitor) already helping to start the motor - so that is not the solution....
here is a youtube that illustrates the problem and the solution - the AC compressors in the example are 208 three phase and 208 single phase, but the same company also makes a 115V unit for RLA's from 12 - 20 amps. (In fact Dometic OEM's it from Hyper Engineering, puts the name secure start or smart start on it and sells it as an accessory to their marine air units so that boaters can start their marine air units with much smaller generator sets (in many cases a Honda 2000i inverter).
video : http://www.youtube.com/watch?v=ApscKchMybM
These units are already in use in the "off grid" application where folks living primarily off large solar arrays and battery banks in the southwest are using investors and batteries to run their homes and use these units to allow smaller investors to start residential A/C units. They also have application where poor utility power exists and homeowners do not like the "blink" of their lights when the AC kicks on.
bottom line, your idea might work, but you may need a larger buffer (battery bank) and maybe a stouter inverter, and for sure a soft starter.
Interesting info Tim! Sounds like I may be in a good situation to implement this option on our coach... Now having 4 8D AGM's with 4-0 cabling and a 3000W Magnum inverter. Not high on my long list yet, but I will be gathering information as I find it. Cool thing is, that I have already done the hard stuff to be able to pull this off. The Sterling alternator to battery charger would be a plus as well, though we would probably still need to go bigger on the alternator (only 160amps now).
Don
Yes, Tim, I am a mad-man searching on Google now...good stuff!
Do you think this will handle a 13,500 BTU roof air compressor, says it can handle 1 HP @ 120 VAC, price is do-able...
Soft starter (http://www.grainger.com/product/DAYTON-1-PhaseEnergy-Saving-Soft-45W827?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/45W826_AS01?$smthumb$)
Don, I installed a Delco 28SI from Quality Power and have been real happy with it:
Delco 28SI Alternator (http://www.qualitypowerauto.com/item_506/Delco-28SI-Series-High-Output-Alternators.htm)
I called them late on a Friday afternoon asking about a 200 amp unit, they had one on the shelf that tested out at 250 amps, said I could have it for the 200 amp price, so I just about ripped my pants pulling out my credit card...
Has the remote sense wire so I get full voltage at the batteries.
Also put in a Sure Power 250 amp isolator at the same time - now available as a 300 amp:
Sure Power 300 amp isolator (http://www.waytekwire.com/item/80061/Sure-Power-3002-Multi-Battery/)
For Fun, I looked up a Dometic Brisk Air RV AC specifications. For a 15,000 BTU model - the RLA (Rated or Run Load amps range from 12 - 12.9 Amps - the LRA (Locked Rotor Amps) ranged from 71 - 77 amps. So to run this air conditioner off an investor, the investor would need to tolerate a surge in excess of 70 amps for 1/3+ second. Check your inverter and see what is it's surge capacity.
The application of a Hyper Engineering soft starter (about $250.) would reduce the LRA to below 28 amps for this unit.
Please post the RLA and LRA from your roof air units when you get a chance.
We have two of the 15,000 BTU A/C's with heat pumps (I wish they were heat strips... almost never use the heat pumps). I will have to dig up the manuals for our roof A/C's, but I think the specs you listed are the same as the ones I read on ours. I would definitely be adding the soft starter to do this mod! The Hyper Engineering unit sounds great, 28 amps would be doable and stress every part of the system less. I believe the compressor RLA is 12.9 amps and the fan RLA is 2.5 amps, so just under fifeteen and a half total.
Don
I think it would be easier, cheaper, and more effective to fix the dash A/C. Parts aren't that bad and the only special tool would be a vacuum pump. Worth buying one just to save the cost and be able to do yourself.
Tim:
I have the Coleman 13,500 BTU roof airs. According to the spec I found on-line the LRA is 54 amps. The running watts is 1560 - so RLA is say 13 amps.
Do you have a link where I can order the Hyper Engineering unit. Would like to get it by this weekend, planning to do some serious coach work... ^.^d
If I were planning on using my engine alternator to operate my roof air conditioner while driving, then I would seriously consider using a Delco Remy 40si instead of a 28si.
http://www.delcoremy.com/Documents/Brochures/28SI-Brochure.aspx
http://www.delcoremy.com/Documents/Brochures/40SI-Brochure.aspx
The 40si is more expensive, but it is a much heavier-duty unit and is much better suited to long-term, high-output applications. Devices such as alternators provide much more reliable service when operated for long periods well under their rated output.
David:
Yes, I have looked at the 40SI, awesome alternator. May want to get one, they occasionally show up on eBay. Would need to beef up the alternator wiring to the isolator and batteries.
Has anyone put one of these bad boys on their coach?
Www.gen-pro.biz
I am guessing you either have or will upgrade the wiring from the alternator to the batteries and possibly the inverter if you plan to run the roof air with the alternator output. I'm not sure what gauge wiring currently exists in your coach, but I suspect an upgrade would be at least desirable and perhaps required.
This thread has morphed from "alternator" to "run A/C from inverter" at reply 42.
I find it very interesting, so would it be possible for a moderator to start a new thread at circa reply 42?
There is also the mention of using an engine driven A/C generator, which is perhaps basically the same thing, but there are apparently products aimed at the marine market that may be a different option than a big battery bank and large inverter that is used in the normal coach loads. It would be interesting to open this subject up to all the methods that don't involve firing up the generator run the roof air while driving.
Don
Prevosts all have options to run AC off the main engine. Some have a whole setup called over the road air and others just have a large compressor and others a big alternator.
Just for useless info my MCI alternator was 275 amp @ 28VDC, compressor was 9 ton belt driven, condenser fan required 95 amps, evaporator /heater fan 55 amps. Of course it had to keep 48 folks comfy. Point is: You can make anything you can dream up.
Here's another idea I had, and may do one day as I likely will come across a spare dash A/C Heater module. I'd "tee" into the high and low refrigerant lines and add a second evaporator and air handler mid coach. Also add the heater, because in u270 no way to throw engine heat.
If needed, up the size of the compressor ("cheap" a couple hundred bucks) and worst case, increase size of condensor. Think front/rear A/C like on a suburban or van. The dash AC is rated 17,000 btu/hr. I doubt it puts this out due to poor airflow (very cold air and low side pressure are always very low). So there is possibly more "cold" in the lines without a bigger compressor/condenser.
Not a horrible thing to try, just need to tee into the lines--beg, borrow, buy the crimp tool for A/C lines.
IMO, alternator to charger add-on is for "dumb" alternators, not needed with the remote sense technology of the Delco 28SI and 40SI.
Someone do the math (Please) to see how many hours a generator would run for the expense of one of these modified systems.. pc
Peter,
I think that the point of the Sterling alternator to battery charger is really to have customizable multistage charging capabilities and to provide a better charging rate for the house batteries once the chassis battery gets what it needs. It also provides isolation between the house bank and chassis batteries, removing the need for the diode based isolator (or other type). You can also (for a price) have a remote control and display for it. Alt least that is my take on it... I haven't done mush research on these more advanced alternators, but I don't see why they wouldn't work well together even if it isn't as much of an improvement as with the "dumb" alternators.
Don
For me at least, it isn't about saving money on diesel fuel to run the generator, but about reducing the vibration and noise while going down the road. Without running the generator (and front roof air!), our coach is nice and quiet and smooth going down the road. Better than most cars... with the generator running, not horrible, but very noticeably less peaceful. Running the rear roof air and the dash air increases the comfort level without the commotion, or would if we didn't have to run the generator to make that happen. Not super high on the priority list as we have found the dash A/C to be adequate for the most part. But since we have a good sized house bank (4 8D AGM's) and reasonable inverter (3000W), it is kind of an attractive idea to add a couple of bits to the kit to make it happen. Just my take on it...
Don
Don,
Interesting, my 10 kW 4 cylinder genset can only be detected by the light on dash control when running down the road. Guess the 8 kW, 3 cylinder Isuzu does not share the same trait.
My generator fuel burn is 10 gal per 24 hrs max, considering the comfy, the cost is forgotten.
I do not need to run The roof a/c, the dash a/c is plenty while on the road,
My biggest mistake is when I get up, the genset is started for the S,S,Shave routine, breakfast & topping off the 4 8D Gel's, then getting on the road forgetting the genset running for hours or until I notice the light on. Never hear nor feel it, so wonder what the difference could be ? Mounts, exhaust bumping ?
I have zero need to re engineer a very fine functioning system.
Thanks
I agree with Don...I think with the older coaches (at least mine with the Onan 7.5 kw) the generator noise is noticeable inside the coach, and I prefer not to run it, the cost of diesel really doesn't weigh into it.
For me, half the fun of owning a coach is tinkering, trying new things, and by doing all the work myself I'm not spending a lot of money. Also, my wife says it keeps me home at night... ^.^d
I'm in Dave's camp. Thanks to the dash light for alerting me to shut down the generator. It's the 12kw Isuzu.
Me too, I can barely feel it running when I am sitting still and not at all when I am rolling.
Don, with the noisy generator when driving.
Check the rubber mounts under the generator. My 4 cylinder Kubota got very noisy one day last year and it was metal to metal clanging caused by broken rubber mounts.
One more question, what is RLA? Needs to be 12 or more
Run or Rated load amps is correct, I was actually asking what the value for his unit is, not a definition.😊
Thanks Wyatt, I have looked at the mounts many times and as far as I can tell visually, they appear to be sound. As I said, it isn't horrible, just noticeable. I think there is something rattling in sympathy with the generator frequency which adds to it though. I want to try and source some air spring isolator mounts for it but haven't got any leads yet on how to spec them out, other than weight of the unit and the mounting height dimension. I want to be able to add or remove air to find the mounts acoustically satisfying solution. Also, I will separate the radiator mounting from the generator as others have done with the 8KW units.
Don
The Coleman spec sheet I found says RLA is 13.
Ok, more than 12, sure Start will work. (Requires RLA on 115V unit to be in range of 12/20 Amps)
Do what Willie Did!!
On the Road Again: Willie's Dual Generator is Awesome (http://blog.rvshare.com/dual-generator/)
Stump,
Nice pair of Kubota units, Nice, no limit $$$$, & 45' Prevost, Have seen one of his old units that the IRS sold, very smoked up & dull inside. Do not recall the make or year, but was about 10-12 yrs ago at bus event.
Pulled my 8kw gen. out for service yesterday
combination radiator & 3 cylinder on one frame, earlier U270 application. Noticed I had broken 3 out of the 4 radiator isolator mounts.
Most likely have been broke for some time, Really no movement because of the tight fit within the insulated generator box. Should think about separating the radiator from the Isuzu like others have done.
Small Isolator Mount by Power Tech | Power Technology Southeast Inc (http://www.powertechgenerators.com/collections/mounts/products/small-isolator-mount)
The isuzu seems to have a lot worse vibration than the four cylinder kubotas. Ive seen two of them with a lot of broken mounts
I think the most severe vibration / shake happens during a cold start or shutdown.
Radiator isolator mounts are small and they just come apart, quarter inch stud pulls away from rubber.
I cranked up the RPM slightly to about 62-63hz no load and that helps some with the vibration on the izuzusususus. Relocated the radiator overlfow tank off the radiator too. Still shake...4cyl kubota is much nicer machine. I'd rather a honda inverter unit thoguh..super quiet and small.
Replacing generator mounts every decade (or sooner) is a good maintenance move.
Rubber (like concrete) never stops curing. At a certain point mounts may look acceptable
but are worthless just like an old tire.. pc
Look at the mounts from the bottom. While they may look 100% from a normal top view, they may be shot when viewed from underneath.
Pierce
Always make sure the hold down bolts for the slide tray are nice & tight. If not, the commotion is greater.