Battery isolator

[tderonne]

I posed a question over at rv.net that has brought up a Winnebago specific question. Does my 2004 Adventurer have a battery isolator? I know the alternator charges all my batteries. Is there an isolator? Or just a simple solenoid? I thought it was a solenoid (every once in a while, with my engine running the coach batteries don't get voltage from the alternator - haven't figured that out, separate issue.)

The reason I ask, and the question I posed, is, when I'm driving, charging all my batteries, am I doing somethig bad with respect to the batteries. Stock I was charging three batteries in parallel, a bad thing I'm told. I've switched to 2 6 volts for the coach, and wondering if I've made a bad situation worse. That is, from one charge source (the alternator) I'm trying to charge two vastly different batteries - the chassis battery, and my big 12 volt (the paired 6 volts) coach battery.

First thing I thought of is dual alternators, one for the chassis battery, and one for the coach battery. I'm finding this is very common on Limos, odd no one seems to discuss it for RVs.

I've also found mention of using a charge controller (like ones designed for solar systems) to control the charge getting to the coach batteries. Seems like that could only limit the voltage the coach batteries get, but that may be the most important thing to do, be sure there aren't overcharging.

Before I get too long, isolator or not? And, battery gurus, am I thinking straight?

[tderonne]

I posed a question over at rv.net that has brought up a Winnebago specific question. Does my 2004 Adventurer have a battery isolator? I know the alternator charges all my batteries. Is there an isolator? Or just a simple solenoid? I thought it was a solenoid (every once in a while, with my engine running the coach batteries don't get voltage from the alternator - haven't figured that out, separate issue.)

The reason I ask, and the question I posed, is, when I'm driving, charging all my batteries, am I doing somethig bad with respect to the batteries. Stock I was charging three batteries in parallel, a bad thing I'm told. I've switched to 2 6 volts for the coach, and wondering if I've made a bad situation worse. That is, from one charge source (the alternator) I'm trying to charge two vastly different batteries - the chassis battery, and my big 12 volt (the paired 6 volts) coach battery.

First thing I thought of is dual alternators, one for the chassis battery, and one for the coach battery. I'm finding this is very common on Limos, odd no one seems to discuss it for RVs.

I've also found mention of using a charge controller (like ones designed for solar systems) to control the charge getting to the coach batteries. Seems like that could only limit the voltage the coach batteries get, but that may be the most important thing to do, be sure there aren't overcharging.

Before I get too long, isolator or not? And, battery gurus, am I thinking straight?

[MrTransistor]

Hi tderonne,
As long as the batteries are of the same type, manufacturer and age (best to start off with new), you can connect as many 12 Volt batteries in parallel as you like as long as the resistance of the paralleling connection cables is nice and low i.e. 8 to 12 inches of ˜0' up through '0000' or larger (but 250 MCM starts to get real tough to work with). You can stick with the #2 (I think that's what came originally on the Adventurer) but electrically I would recommend the heaver gauge wire especially if you have installed an inverter. There is a proper way to connect the plus and minus cables to the bank. With 2 ea. 12 Volt batteries in parallel, connect at the plus of one battery and the minus of the other battery to equalize the resistance and therefore the voltage drops. With 3 ea. In parallel, again connect to the end batteries - plus of one and minus of the other. With 4 and 5 ea. it's a little different connection and the resistance cannot be made to come out exactly equal but if anyone would be interested in paralleling this many 12 Volt batteries, let me know and I can supply the proper connection point information.

As for charging your chassis batteries, I believe that a battery isolator is installed on most coaches (don't quote me on that one) allowing both the coach and chassis batteries to be charged in parallel from the engines alternator. Although a solenoid may be installed and really accomplishes the same thing. But if the contacts were to weld there would be a permanent tie between the coach and chassis batteries and that's not a good thing.

This normally doesn't cause any problems with dissimilar coach and chassis batteries since the charge voltage from the alternator is normally in the 13.8 to 14.2 Volt range and that is an acceptable value for flooded ˜start', ˜deep cycle', and GEL, and AGM batteries for the shorter charge times encountered when running the engine (8 to 10 hours at a time verses plugged into shore power).

Charge controllers are for the most part designed for use with Solar Panels that have a much higher open circuit voltage than lead acid batteries can tolerate. They take the 17 or so volts of the Solar Panel and drop it to the 13.8 or so required to float charge the batteries. A better choice I think would be the Echo~Charge from Xantrix. It uses the coach battery chargers output and shunts a variable charge current to the chassis batteries to keep them topped off via the converter whenever you are connected to shore power or the generator is running. With this, you don't have to worry about installing a separate charger and finding an appropriate 120VAC source to connect it to. Coupled with a ˜battery sense' Auto Generator Start device and you should be set and your batteries ought to last for years and years.

For additional reading, there are several web sites out there that go much deeper into battery technology. One of many is - http://www.trojan-battery.com/Tech-S...intenance.aspx - also see what - http://www.concordebattery.com/ - has to say about AGMs. Trojan is now selling AGMs as well.

[Stan Birch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tderonne:
when I'm driving, charging all my batteries, am I doing somethig bad with respect to the batteries. Stock I was charging three batteries in parallel, a bad thing I'm told. I've switched to 2 6 volts for the coach, and wondering if I've made a bad situation worse. </div></BLOCKQUOTE>
You've received bad advise. Charging 3 batteries in parallel is the standard configuration in motorhomes; and it's working just fine for the rest of us. Battery similarity isn't all that important when connected in parallel; but battery matching is critical when connecting batteries in series.

The battery isolator solenoid on your rig connects all the batteries together when your ignition switch is in "run" position. If you are getting an intermittent solenoid connection to your coach batteries, then it could be that some scorching or pitting has built up on the interior solenoid terminals causing a high-resistance connection. That's pretty common on rigs over three years old. But they are cheap. A "continuous duty" only runs $20. Whether you call it an isolator, solenoid, or relay; it's the same thing.

[tderonne]

I suspected I'd findsome better expertise here.

I have my six volts all in, that was the easy.

Marc and Dony's comment about the alternator not having enough voltage, nor time running (we do often drive 20 hours straight, but even that isn't really that long) to do any harm to either battery makes sense, and is something I had just begun to think about.

And Stan confirms I have a simple solenoid, as long as my key is on, my new six volts are paired to the 12 volt chassis battery. And that I probably need a new one at 20 months in service.

Thanks,
Tim

[Stan Birch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tderonne:
Marc and Dony's comment about the alternator not having enough voltage, nor time running (we do often drive 20 hours straight, but even that isn't really that long) to do any harm to either battery makes sense, and is something I had just begun to think about. </div></BLOCKQUOTE>
There is absolutely no problem in having your coach batteries being charged on a continous basis by the alternator; any more that your chassis battery will be harmed under the same circumstances. When the batteries become fully charged, then they merely stop sucking up any more current. Same goes for charging them with your converter.

Keeping them on charge as much as possible with an appropriate charger such as your alternator or converter, will actually extend their life significantly.

If you have a rooftop solar charger, then the battery disconnect switch should be left in "disconnect" position while in storage. This will allow the solar charger to keep the coach batteries charged without allowing parasitic loads such as the propane detector, fridge, etal to draw more current from the batteries that the solar panel can supply.

In the absence of a solar panel, then if possible, keep the rig plugged in 24/7 with the battery disconnect switch in "connect" position; otherwise the converter won't be able to keep the coach batteries up to snuff. Following these principals, our seven-year-old coach batteries are still doing just fine.

As for the chassis battery, it's charge is not maintained by either the solar panels or the converter. You don't mention which chassis you have. With a Ford, maintaining the chassis battery while in storage isn't an issue. Ford chassis batteries can sit for months at a time without need of recharging. GM rigs don't do nearly as well. With a significantly higher current draw in storage, they require somewhat more aggressive maintenance to keep the chassis battery alive between excursions. The same probably applies to Freightliner rigs.

[Stan Birch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tderonne:
I have a simple solenoid, as long as my key is on, my new six volts are paired to the 12 volt chassis battery. And that I probably need a new one at 20 months in service. </div></BLOCKQUOTE>
I wouldn't rush right out and buy a new solenoid unless the current one is obviously defective. A defective solenoid will become most apparent after a night of boondocking; and after a couple hours on the road, your coach batteries are still registering less than 12 volts. Notwithstanding, that this seldom happens at a convenient time or location. The last time I replaced mine, was during a rainstorm in a Wal-Mart parking lot 3000 miles away from home.

[MrTransistor]

Hi tderonne,
Stan is correct on the Freightliner, at least the newer ones. I have measured a parasitic drain on the chassis batteries of .35 Amps. That coupled with the self discharge on the batteries themselves means you can't let them sit for too long with out a recharge (about two weeks drains ours down to 12.3 Volts). Please reread my statement on the alternator charge voltage provided by the alternator. I didn't say that the voltage was too high or too low for any given battery. But if you check a particular battery's spec sheet, you may find that it requires a slightly different float voltage than any given alternator may put out. Fortunately, most all lead acid batteries are fairly tolerant of these slightly different float voltages. Good luck to all.

[Guvnor]

Gang!

I thought that when my 2000 Suncruiser was new; that I could go look at both battery sets on the "One Place" panel voltmeter and see about 14 volts when the engine was running.

Perhaps I was mistaken then, because now, after a few years, I find that only the chassis battery registers as being charged from the engine alternator.

I've the wiring diagrams from Winnebago, but I don't see a clear path from the engine alternator to charge both battery while on the road.

My solution was to put in place a unit from West Marine called an Automatic Charging Relay. This provides user adjustable connection and disconnection voltages between the chassis and house battery. When the alternator is charging, say about 13.9v, the contactor closes allowing limited current (about 60A) to flow to the house batteries. When the engine is turned off, and the surface charge bleeds off to about 13.4v, the contactor opens, thus not allowing either the chassis or coach batteries to discharge the others. Seems to work so far.

Also, I took the opportunity to split the charge from the 10w solar panel through two shottkey diodes (.3v forward drop) to separately ensure both battery sets are kept up to snuff while the coach is in storage.

Am I missing some relay on the wiring diagram? I only see the "battery disconnect or Storage" relay and the "Battery boost relay" on the Winnebago wiring diagrams.

[John_Canfield]

Are you sure you don't have battery isolaters? Give Winnie a call and ask them to be sure. As it comes from the factory, the chassis battery is not charged from the inverter/charger, but that is fairly common knowledge.

[ppeter313]

The Blue Sea BatteryLink ACR that Guvnor mentions also works great to charge the chassis batteries when plugged into shorepower.

Paul

[CalTex]

quote from Stan Birch:

"Keeping them on charge as much as possible with an appropriate charger such as your alternator or converter, will actually extend their life significantly."

Maybe the key word here is "appropriate charger". It has been my experience the many chargers(even the new three stage units) will boil the water from a flooded cell battery in a short period of time. If you keep the water level up maybe that's not a problem, but if you forget to top off - you have a fried battery. I prefer to turn off the main charger and use a smart trickle charger when in storage.

[roadtrec]

new 2012 winnebago journey
resdentail refererater
6 agm batteries
2800 inverter
going down the road I lost all 120 volts. Inverter failed. Gen would run but not supply any power to refererater etc.
Called winn and drove 600 miles back to the factory,
They replaced the inverter and the transfer swith.
That night before leaving I noticed that the voltage would drop during the night to 11.5 even though it was plugged in to 50 am service.
In the m morning winnebago said that was lower than they would like and check battery condition and found some lose wires etc.
It still will drop at night when plugged in to shore power to 11.9 and will drop with ervery light you turn on.
What should my voltage be???
It charges to 13.5 when the engine is on but i dont think that it charges when plugged in. ??????
thanks for help
John

[YC1]

As mentioned there is probably a solenoid and you should find it. One way may be to have someone cycle the ignition key and listen for a clunk. If you don't hear one, place the key in the run position and press the emergency/aux start switch that should make the solenoid go clunk. Once you find it, disconnect your batteries for safety by disconnecting the negative leads or if you have large battery cutoff knobs turn those off. Then tighten every nut that has a wire connected to it. Clean your battery connections and follow the negative leads to ground and clean those.

With the engine running a bit above idle you should see 13.5 volts at least across all the batteries. If you see lower on the chassis batteries than the engine batteries then the emergency solenoid is not working well. This is assuming it was going clunk. Just measure the voltage on the small terminal/s and then on each large terminal. If the solenoid is activated the two large terminals should be the same voltage.

If your batteries have been run down a bit overnight start your generator and let the charger build them back up for an hour or two even if driving. This will keep the heavy load off your alternator and should extend its life.

[YC1]

Roadtrec I agree with you. Your charger/converter is not charging the batteries. You need to get a diagram and start at the wires coming from it. It may be a simple loose connection. Turn some lights on so you have a load while measuring the voltage. You should have at least 13.5 at the batteries.

[clyon51]

Roadtrec

With engine running, the chassis and coach batteries should see 14+ volts. If working properly, all automotive alternators put out 14.1 to 14.5 volts. The voltage reading can vary depending on where it's taken in the system. The best place is right at the batteries with a voltmeter.

When on shore, either you have a converter/charger or more likely your inverter also charges the batteries. That said, either way, the charger is going to have 3 charging voltages. 14+ if the batteries are below 90% charged. 13.6 if they are above 90% and 13.2 if fully charged, which maintains the batteries. A fully charged battery, 2 hours off the charger with NO load will be 12.7 volts.

That said, when on shore, you should never see anything less than 13.1 volts at the batteries. Your best reading of 11.9 v reflects a 60% discharge on the batteries. The rule of thumb for best battery care is never let them get below 12.0 - 12.1v, which is 50% discharged.

So, whatever is suppose to charge your batteries on shore power is not charging your batteries.