Engine Alternator use:

Topic: Engine Alternator use: (Read 2061 times) previous topic - next topic

Re: Engine Alternator use:

Reply #25 – August 29, 2015, 11:39:03 am

Quote from: krush – August 29, 2015, 11:09:09 am

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.

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.

Re: Engine Alternator use:

Reply #26 – August 29, 2015, 11:54:05 am

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.

Re: Engine Alternator use:

Reply #27 – August 29, 2015, 12:08:11 pm

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

Re: Engine Alternator use:

Reply #28 – August 30, 2015, 12:26:51 am

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

Re: Engine Alternator use:

Reply #29 – August 30, 2015, 08:02:53 am

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?

Re: Engine Alternator use:

Reply #30 – August 30, 2015, 10:06:23 am

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.

Re: Engine Alternator use:

Reply #31 – August 30, 2015, 10:09:27 am

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.

Re: Engine Alternator use:

Reply #32 – August 30, 2015, 10:14:42 am

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.

Re: Engine Alternator use:

Reply #33 – August 30, 2015, 10:22:13 am

Quote from: krush – August 30, 2015, 10:09:27 am

Get with the times. If one is really going to make a science project, at least make it out of modern technology!

I'm just curious: Who needs to "Get with the times"?

Re: Engine Alternator use:

Reply #34 – August 30, 2015, 10:23:33 am

Quote from: D.J. Osborn – August 30, 2015, 10:22:13 am

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!

Re: Engine Alternator use:

Reply #35 – August 30, 2015, 10:32:38 am

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

Re: Engine Alternator use:

Reply #36 – August 30, 2015, 10:57:34 am

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

Re: Engine Alternator use:

Reply #37 – August 30, 2015, 11:24:18 am

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

Re: Engine Alternator use:

Reply #38 – August 30, 2015, 02:38:30 pm

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.

Re: Engine Alternator use:

Reply #39 – August 30, 2015, 03:34:39 pm

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.

Re: Engine Alternator use:

Reply #40 – August 30, 2015, 06:21:48 pm

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.

Re: Engine Alternator use:

Reply #41 – August 31, 2015, 09:01:07 pm

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.

Re: Engine Alternator use:

Reply #42 – August 31, 2015, 09:34:19 pm

Has anyone done this:

My dash air needs a charge so no cooling. I am considering getting this transfer switch:

120V transfer switch

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.

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Engine Alternator use:

Reply #43 – August 31, 2015, 11:02:11 pm

I will be following this one with interest!

Don

Quote from: prfleming – August 31, 2015, 09:34:19 pm

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.

Re: Engine Alternator use:

Reply #44 – August 31, 2015, 11:19:39 pm

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.

Re: Engine Alternator use:

Reply #45 – August 31, 2015, 11:32:51 pm

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

Quote from: Tim Fiedler – August 31, 2015, 11:19:39 pm

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.

Re: Engine Alternator use:

Reply #46 – September 01, 2015, 12:11:05 am

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

Re: Engine Alternator use:

Reply #47 – September 01, 2015, 12:34:33 am

Quote from: Don & Tys (AKA acousticart) – August 31, 2015, 11:32:51 pm

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

Don, I installed a Delco 28SI from Quality Power and have been real happy with it:

Delco 28SI Alternator

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

Re: Engine Alternator use:

Reply #48 – September 01, 2015, 12:56:40 am

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.

Re: Engine Alternator use:

Reply #49 – September 01, 2015, 01:41:02 am

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

Quote from: Tim Fiedler – September 01, 2015, 12:56:40 am

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.

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