Hello,
I have the coach home getting it ready for a trip to South Dakota and was investigating an issue with my house batteries not charging while going down the road. The only way they charge is if I turn on the boost solenoid. This got me investigating and I found that the battery isolator has the #2 post with nothing attached. It should be the alternator lead which is now on post 4 with . So my questions are how do you check a 4 post isolator? Beam alarm's instructions cover a 3 post and I'm not sure of how the internals set up on the 4 post. Will a 3 post work in the 4 post isolators place? I'm not sure why FT installed the jumper from post 1 to 2. I have a 3 post 200 Amp isolator on hand and thought I would use it if it has enough capacity. Attached are some photos of the isolator and my wiring diagram. Any help would be appreciated.
The 3 post isolator will work fine. The original 4 post isolator had a jumper between two of the battery posts. The theory around here is that this increased the capacity by using 2 diodes to control voltage going to the house battery bank. Photo below of the OEM isolator on our coach. Numbering the posts from left to right, #1 and #3 are house battery posts with jumper cable. #2 is alternator input, and #4 is start battery.
The way your OEM isolator is wired, it is doing nothing. It probably quit working and the "fix" (by somebody) was to remove it from the charging circuit. Or, it could have been mis-wired due to ignorance of the isolator's intended function (this is very common).
Many members (including me) have replaced the 4 post isolator with a 3 post and this works fine. 200 amp capacity is more than enough.
Search "isolator" with the forum search tool for many posts on this subject.
Just to be sure I understand, since I have the 3-post isolator, the diode drops the voltage 0.7v and the sense wire from the alternator ups the input voltage to the isolator to make everything fine on the other side?
Correct. The sense wire (if connected correctly) reads the voltage on the start battery. The alternator does whatever necessary to insure the start battery voltage is correct. If that means raising the charging voltage to compensate for the drop through the isolator diode, so be it.
Thanks for the quick response and description of the isolator and FT's thought process.
I agree with the quick fix idea. Its these types of things that I keep finding as we work through her systems. Its been fun!
I would investigate replacing the isolator with an auto combiner. The industry switched to combiners across the board. Less voltage drop? Magnetic connection internally, no power consumption.
Either bank gets a charge it combines them. Disconnects on discharge. If wired to the starter relay auto disconnects to not cover up the engine start batteries true condition.
If you change to a combiner from an isolator, be sure to check voltages as it may be a little high. Our alternator on our 1993 U300 has an easy to adjust voltage screw on top of the alternator.
Pierce
No reason voltage output from alternator should need adjustment. The sense wire is on the chassis battery side of the diode-based isolator so it tells alternator what it needs to do to put the proper voltage to the battery. Basically, it compensates for voltage loss in the diode-based isolator.
Said another way, if voltage is OK with the diode-based isolator, it should be OK with a combiner.
Don't think there is any reason not to check voltages after changing components especially if one component's possible failure was the reason for the change. Another good argument for having digital voltmeters in view on the dash when driving. I have a switch for them but since they don't use any juice to speak of, I keep them on 24/7.
Pierce
Agree, ALWAYS a good idea to keep an eye on charging voltage-- from alternator, solar, converter or inverter/charger.
Just don't think going from diode-based isolator to a battery combiner will change the alternator charge voltage.
And, there is always the KISS way to combine-- a marine simple ON-OFF switch. Alternator B+ and chassis to one lug, house to the other. OFF, chassis battery is charged. ON, both banks are charged and a heck of a battery combiner. If going from CG with power to CG with power, I always left the switch OFF. No point in burning diesel to over work the alternator to over charge the house bank.
Several very good ways to do it! IMO, the diode-based isolator is at the bottom of the list.
Agree with your KISS method. Have solar and house batteries on one side and alternator and start batteries on the other. But use a modified boost solenoid to connect the two banks together. Seldom necessary. My dash has two cigarette lighter outlets, one on house, and one on start batteries, use plug in voltmeters with usb outlets, to monitor voltages.
Because of the difference in house and start battery voltages, have small inverter and trickle charger on house batteries to charge start batteries when dry camping.
No one is perfect. Requires automation. If you manually combine the battery banks and either side inadvertently has a draw you could ruin a lot of expensive batteries. They are never the same
Versus the auto disconnect if either bank is being discharged.
Impossible to damage both banks that way. You would always have a backup bank.
Is the money and time needed to update the systems the issue here?
I am getting the impression that almost any financial outlay is beyond some here's ability.
Rv'ers are notoriously frugal. That's good.
Cheap was almost always more expensive long run.
I want what the new million dollar boys have but at a fraction of the investment.
I have killed countless battery banks from one mistake. Way too expensive over the long run
Having a voltmeter on both the house bank and start bank right in front of you on the dash will give you a pretty good indication of what is going on battery wise. With the ability to combine or seperate them as necessary. Really don't trust some device 40 ft away in the engine compartment to do my thinking for me.
Worked on ships for 50 years, lots of safety and automation devices to make life easier and less stressful. But in most cases, still have an engineer watching the gauges to make sure the safety and automation devices do their job.
In my case certainly not the financial outlay, have close to $10000 in solar, batteries etc. and would rather be hands on and proactive, instead of waiting for the bestest, newest device to mess up.
Think I have explained to Bob in the past, that you cannot us a standard battery combiner with agm start batteries and lithium ion house batteries because of the voltage differences.
Foretravel I think uses a combiner with optima red tops and gels on their new coaches as far as I know.
My guru buddy when asked the same exact question said he had no issues with using combiners with the two battery types.
His answer covers a lot of non optima batteries.
All the manufacturers use a combiner.
Almost no one here has a battery temp controlled alternator that I am aware of.
As hot batteries can be overcharged by as low as 13 volts and in winter weather they need as much as 14 volts or over the voltage mismatch can obviously happen but the incorrect alternator charging voltage would seem to be more of a problem.
Maybe that's why every Unicoach ever made had optima spiral wound engine batteries and mk gels and either an isolator or now a combiner.
My understanding is the both battery brands can take low or high charging volts and non corrected by temp charging voltages or non 1/5th or 1/20 C charging rates .
My buddy has replaced every problem isolator with a non manual combiner for 10 years. Regardless of battery types with no issues.
Like I said I asked the same question.
AGM engine and AGM house would lessen anyone's concern.
Damaged agm's from mischarging is normally not fixable.
All inverters for the last twenty years have had a battery temp control available.
Unfortunately the engine batteries temp is way different.
Everything is a compromise. I would rather eliminate the run the batteries flat and kill them versus a voltage mismatch which is already present from the locations of the battery banks.
I killed two sets or red tops from failed small chargers.
Versus the combiner and using a small solar panel set to make sure when I open the coach up that both batteries are at 100%
We a sort of preppers in shaky town.
Dead batteries is not an option. If they last 10 years versus 12 or more so be it.
Bought a new geared Delco starter just to be sure I can start the engine even with low volts in the start battery bank.
The isolator consumes power. The combiner has 100k cycle magnetic latching. Versus 3 amps and getting hot.
I have both dash plugs filled with second digit digital meters and monitor the dash gauge and the digital ones and the audit one.
Plus the VPMS shows the engines ECU voltage.
As Wolfe mentioned I turned down the alternators nominal voltage as well as the solar output to be 13.6 at the batteries.
In that same vein I added a magnum Battery Monitoring System.
It's connections to its control box are directly at the battery terminals themselves..
At the same area I already had a Xantrex power pro gauge.
Both the inverter and the Xantrex gauge and the audit have voltage drops because of the longer wire runs.
The Magnums short 5' leads should be more accurate.
My guru said I would be able to compare the magnum and the Xantrex units for accuracy.
The magnum auto resets at 100% versus manual matching on the Xantrex.
Plus integrates better with the inverter with the me-arc new panel.
Working up the the ME-AGS-N and the power trace 100 amp solar controller and the integrated heat and air auto gen start.
The link 2000R control panel that was available for the heart freedom 25's did adjust the alternators voltage depending on battery temps as far a I have seen
Yes, the marine A, B, both and off is the perfect solution. Almost. Your boat is probably that way but there is always going to be a certain percentage of people that will rotate the knob when the engine is running and create a voltage spike. We always turned the switch to off when the apparatus was parked. We switched A to B each morning with a new crew but the Detroits didn't like one 8D so we went from off to both (two 8Ds) before hitting the starter. In this case, both battery banks were single conventional 8Ds.
My little jumper from lighter plug to lighter plug works great when the coach is parked to keep both battery banks at about 13.20 volts when only one bank is connected to the charger. Engine is conventional, house AGM.
Very few owners manage to label the cables so there is a high percentage of isolators that are not connected correctly. Age fades the factory label on most wires in this exposed environment. Label and take a smart phone photo. Hard to make a mistake this way.
Pierce
An emphatic, NO-- for the reason you mention.
You want only an ON-OFF switch like this one: e-Series On Off Battery Switch - Blue Sea Systems (http://www.bluesea.com/products/9003e/e-Series_On_Off_Battery_Switch)
Totally idiot proof and rated at 350 amps continuous and 1200 amps cranking.
Or use a boost type circuit that you control by looking at bank voltages. Alternator is ALWAYS connected to start battery, and you decide if you want to connect house bank as well.
Li -ion has tempature,restrictions. Needs to be in a temp controlled area if you intend to be below freezing or above 100 much.
Temps at the battery itself. No river trips at 120 or skiing at zero degrees
Love the idea. Our electric bikes have li-ion as does our off road bikes.
Dr Goodenough has developed next generation li-ion using silicone instead. He invented li-ion 40 years ago
Tesla is rumored to be building a new model S. I wonder if it will have the new cells in it.
No temp issues, 3 times the density and charge rates
Li-ion requires a "warm up" to produce max power.
My dirt bike turns over slowly.
Turn the headlight on for a couple of minutes to get the battery "going" and it starts right up.
Different chemistry
I still subscribe to the most "KISS" battery bank. Three 8D AGM batteries in one bank with NO isolator (not required).
Alternator adjusted to 14.3 volts (ask if you want to know how to do this very simple modification).
The refer is powered from the inverter when driving with propane turned off (illegal in most states and provinces to have propane "on" when driving).
Batteries are fully charged at the end of a day of driving (from alternator and solar panels).
This single battery bank configuration cannot be done with Lithium batteries because they do not have sufficient cranking amps.
BattleBorn LiFePO4 batteries suggest that the batteries will no longer accept a charge once the temperature drops to 24 degrees F, but they will continue to discharge until the temperature reaches -4 degrees F and that the batteries will shut down once the temperature hits 135 degrees F.
High temp is not likely to be an issue, I will shut down long before that. Low temp charge and discharge limits are on batteries at those temperatures. A heated space is not required. but it is easy and cheap to overcome these limits to much lower temps. BattleBorn sells heating pads for their batteries for $200 each. Similar products are available for 10% of that.
And the "Charge While Driving" is not an issue either. Easy to do.
Lots of battery, isolator, combiner, charger options out there.
Wyatt why the 14.3? Is that at the batteries?
Would be great in real winter weather. Would seem way over volts if the batteries are not at zero degrees?
Would seem to be partially desulphating the bank all the time. Was that the idea?
I thought you were using gels?
PowerStart 12V Lithium-Ion Starter Battery (https://www.powertechsystems.eu/home/products/12v-lithium-ion-starter-battery/)
Systems - Lithium-ion 12V Starter Battery | A123 Systems (http://www.a123systems.com/automotive/products/systems/12v-starter-battery/)
Won't be long before they make one big enough to start your diesel.
On a asphalt parking area at the colorado river in the summer the battery compartment can exceed the high temp limit.
Battery heaters consume lots of power. We dry camped in the winter skiing long ago a lot.
Woke up one morning at lower than -32 F.
New flooded cell 8d's.
Volts. No amps. Every green light off in the coach.
Luckily the snow plow barn was next to us and they jumped the cat to get it to start
A aquahot , dual pane window with AGM or gels is a true four season useable coach without any thought needed.
14.3 VDC on an "all day long drive" will overcharge the batteries!
Options:
Get a smart regulator-- we have used one for decades on our boats.
Set voltage at a "compromise" between bulk rate and float rate. Perhaps 13.5 VDC at the batteries. And, to fine-tune further, a little lower in summer and a little higher in winter.
Wow, quite the discussion!
I have the isolator installed and now no power to the alternator exciter to the alternator won;t come on line. Looking down the wiring diagram i have a 15 amp CB in line to a relay with a/c related items on it. Anything else to flash the alternator? I now have found another problem or worse, caused one!
Crimp on connections at either end of the excite and sense wires are common failure points. If they are suspect, replace them. Use heat shrink adhesive filled crimp on connectors or an adhesive filled heat shrink tubing to seal and reinforce the connector.
Brett:
I experimented with different alternator voltage settings to keep refer powered and batteries charged.
I found less than 14.0 volts would result in undercharged batteries by the end of the day (based on Amphour meters).
I live and travel in Canada during the summer when ambient temperatures are low compared to Texas, but spend winters in California, Arizona, or Mexico when ambient temperatures are similar to Canadian summers.
The fridge, when heater is "on", requires 40 amps to the inverter, while the freezer compressor (for ice maker) requires 10 amps continuously to the inverter.
Note that the solar controller is helping the alternator, but is temperature compensated.
Now for something most folks do not know about constant desulfating. Each of the three batteries have a desulfator most of the time, which raises the fully charged voltage of the batteries about 0.2 volts, so 13.0 volts, rather than 12.8 volts.
I am concerned about overcharging the batteries so do check "state of charge" on every trip and can adjust the alternator charge voltage down when ambient temperatures are very high.
The refer on inverter is the unusual draw.
Thought about it. I do not think most rv's turn off propane on the road.
At higher voltage I would routinely check capacity myself just to verify no long term capacity loss.
I almost feel stupid advising Wyatt about electrical stuff.
Added a magnum BMS. It's source and feed in is at the batteries. Not a long cable run away.
.1 to .2 voltage variation from the Xantrex power pro remote voltage sensing versus the BMS 5' run location with its thicker twisted pair hookup
The voltage sense wire to the alternator on my 1996 U320 was connected to a terminal on the A/C relay which was located behind the driver side rear tires, so constantly attacked by water, salt, and sand. This sense wire was corroded off at the alternator. I moved all relays and the battery isolator to under the foot of the bed. I also moved all + 12 volt wires to a common brass bolt under the bed, including the sense wire to the alternator. Now, wiring stays clean and corrosion free while being easily accessible.
I'm definitely moving the panel inside. Just not today.
I did find the exciter wire broken at the alternator but don't know what lug it should be attached to. there are 3, two yellow that have wires going into the alternator and the main power lug that carries the current out of the alternator. There are no wire terminal ends left from the broken wire. where does this wire go? The wiring diagrams are not that specific for the alternator connection.
Correction on my last. I have four lugs. One with nothing on it next to the output lug
Remember, the sense wire can originate from any place that is electrically on the chassis battery side of the diode-based battery isolator. There is no "here is where it has to connect". So, chassis battery, chassis battery lug of the battery isolator, chassis battery side of the battery combine/boost solenoid, etc, etc.
And as others have mentioned, one of the first things I did was move the "behind the driver's side rear wheel" electrical panel to under the front of the bed electrical compartment. Yes, from wet and muddy to clean and dry. As I recall, did not have to cut/splice a single wire. Just disconnect battery grounds, label all wires VERY CAREFULLY, move the panel (replacing corroded or questionable relays, etc) and reconnect. I drilled a larger than needed hole through the driver's side floor of the "under the bed compartment", installed a hose through which all the wires could be fed and sealed it in with polysulfide.
Mike probably has pictures of this.
Thanks Brett. I have 12 volts from the battery to the alternator. The wire going to the alternator was removed at some point. I was going to re attach it but don't know what lug to put it on. I have 4 and one next to the output has nothing on it.
Look closely at the back of the alternator. Quite likely there will be some embossed markings for things like IGN, Sense, etc.
If you don't see them, do a search for your alternator make/model installation instructions. Should give you exact connection details.
This approach is better than ASSUMING that you have exactly the OE alternator that was fit in 1992 with exactly the same connections.
On the back of your alternator will be four lug bolts, two heavy and two light.
The heavy lug bolts are for charging, one negative with cable to engine block and one positive to the diode isolator.
The light lug bolts are for ignition power (hot when ignition is in the "ON" position) and for battery sense wire.
Note: it is very possible that you will not be able to easily remove the nuts from these four lug bolts because they are corroded and imbedded in plastic. I had to use penetrating oil and a lot of patience to remove all the nuts without breaking the lug bolts.
Solid advice Brett.
Ian,
After seeing the "custom" wiring on your old isolator, I am guessing there is a good chance that the alternator on your coach has been replaced at some time. If so, there is also a good chance that it is not a DUVAC alternator. A DUVAC alternator has the proper configuration to allow the use of a remote "sense" wire, which is required when you have a diode based isolator. The "sense" wire is connected to "always hot" source that sees START battery voltage. Some Duvac alternators may also require a "excite" wire, which is connected to a "hot with ignition" source.
What is DUVAC? (https://www.foreforums.com/index.php?topic=33250.0)
SO, as Brett has suggested, you must first determine exactly what model alternator you have. Google the model number to find the technical info and installation instructions for that model. You are looking for something that says it accepts "remote sense" input. If it has that feature, you are in good shape. If it does not, we can offer you some alternatives.
Thanks Chuck. I could not find the data plate on the alternator and just put everything back the way it was for now. Its pushing 100 degrees here so I figured I had enough. Its putting out 14 VDC just not with isolated batteries. More tomorrow early, before the high temps get here.
Very likely you have a "one wire" alternator that is self-excited. Very common on GM vehicles, and many others. All it requires is a single positive cable to the battery, and a negative ground. The way your isolator was wired, with the alternator output connected to the start battery post, that type alternator would be perfectly happy. Once you move the alternator output cable to the center post on the new isolator, the alternator is no longer "seeing" the start battery voltage, and it will not initiate charging.
Let us know if you are able to I.D. the alternator, and we can go from there.
I'm going to stick my neck out here and, even after all of the help Mr. Wolfe has given me, respectfully disagree with Mr. Wolfe on this one.
The (A) voltage sense wire is essentially one lead from a voltmeter built into the source (alternator.) As such it needs to be connected as close, if not directly to, the load (battery,) so that the load is given the voltage it requires regardless of line losses.
Agree in theory. And on our sailboat also a practical one, as cabling size is "not robust".
But, on the Foretravel, from a practical standpoint, those very large gauge cables from chassis battery to battery isolator, boost solenoid, etc show exactly the same readings as at the batteries. If not, there is a (serious) connection or cable issue.