Different batteries

[berger]

My tuck has two different batteries and I was wondering if this is a bad thing? It basically looks like the lower battery was just thrown in to get the truck running (Porsche/Audi stamped), as it is definitely larger and longer than the other. I haven't had any issues with batteries, just curious. I remember reading something on the Iltis forum that you want both batteries in a 24v system to be identical.

Thoughts?

[undysworld]

It's not recommended. Hopefully Jim or some other electrical guru will chime in with the specifics.

It's my understanding that two different batteries, or even the same batteries of different ages, will charge differently, leading to a charge disparity between the two batteries. In this situation, the truck's voltage regulator will charge until the battery system gets to 24v, but one battery will be overcharged and the other undercharged.

When I bought new Optimas, I even got two with the same batch code, so they are as close to identical as possible.

[Jimm391730]

Paul is correct. The goal is to have two batteries that are as close as possible to being the same: Same age, same capacity, same chemistry, etc.

The Pinzgauer charging system puts the same current through both batteries; but the batteries themselves split up the voltage between them. Whichever "takes" more voltage is getting more power; whichever gets less voltage gets less power. These voltage/power differences will overcharge one of them and undercharge the other. Lead acid batteries tend to not charge as well as they are more depleted; this means that it won't get as much of a charge as might be expected and it is therefore even less charged than it was before. Gradually this imbalance gets greater and greater. Both eventually die, but you will have problems as the first one dies, of course.

Starting the truck with two different sized batteries is not the bad thing - it is the truck trying to charge them "equally" (because they are in series) that really damages them. So if you periodically (perhaps once/twice a month) charge each battery independently, with it's own 12V charger, then they will both get properly fully charged and they will last for years as expected from vehicle batteries. It is important to also check the electrolyte level and add distilled water as needed (AFTER charging) because water loss will happen during overcharging. While this independent charging is a pain to do and remember, it is effective at prolonging the battery life. Even those of us with "matched" batteries would benefit from independent battery charging once or twice a year.

So while two matched batteries are good in that the need for battery maintenance is greatly reduced, unmatched batteries are bad only in that they require effort to keep them working (charged) properly and neglecting this maintenance will leave you stranded eventually. You will either pay to get a matched set of batteries or have to work at keeping the unmatched set alive. Your choice.

[pcolette]

As Jim said and others have pointed out in past posts (which of course I now can't find ), periodically charging the batteries from an outside source helps to balance their power and prolong the battery life.

I've used this charger with good results and since it comes with battery harnesses that can be left in place, it's also convenient.
http://batterytender.com/products/rv/2- ... phere.html

It's available on Amazon for significantly less $$.

41gA6Yp0aRL._SL500_AA300_.jpg (12.16 KiB) Viewed 2740 times

[berger]

Thanks for the replies guys!

Just because I am a stickler for such things, I may just replace them with two identical batteries and keep these around for other purposes.

[berger]

As Jim said and others have pointed out in past posts (which of course I now can't find ), periodically charging the batteries from an outside source helps to balance their power and prolong the battery life.

I've used this charger with good results and since it comes with battery harnesses that can be left in place, it's also convenient.
http://batterytender.com/products/rv/2- ... phere.html

It's available on Amazon for significantly less $$.

41gA6Yp0aRL._SL500_AA300_.jpg

I may just grab one of those, as I use the tiny wall plug deltran already and swear by it. I have had the same battery in my 2007 Ural and the battery still runs strong.

[M Wehrman]

I play musical chargers with all my stuff. I put each battery on a regular charging cycle,24hrs 2amp auto chg. I do not disconect my batteries. Ground switch off,I just "toggle" between the batteries,let them a rest a day and ck voltage @ each battery. You must test at the respective battery post. It has worked for me a long time,allowing me to know when one batt is heading South. The cheap load tester from (sigh) Harbor Freight is another good diagnostic tool. BTW I am a battery freak,that is what having waaaay 2 many toys will do 2 you!

Mark