Batteries

[Gunrunner128]

Anyone out there ever tried charging both batteries while wired in series with a standard 6-12-24v battery charger?

 

[ToddJK]

No. I always charge one at a time. Everytime I've tried in series, it takes much longer and usually one battery takes majority of the charge and isn't sufficient to start engine.

I would however, if I'm using a trickle charger along with a battery equalizer.

 

[Gunrunner128]

No. I always charge one at a time. Everytime I've tried in series, it takes much longer and usually one battery takes majority of the charge and isn't sufficient to start engine.

I would however, if I'm using a trickle charger along with a battery equalizer.

Thanks for your answer. I've had a really hard time with the batteries in my jeep, and your answer is the only one I've gotten with an explanation for one battery being undercharged. Thanks David

 

[MarkM]

One thing to remember when using dual batteries it is imperative that they must be of the same age and model. If not then one of those batteries will have less potential than the other so inevitably one battery will be overcharged and the other undercharged. As already stated when installing two new batteries you should charge them separately to full charge then in our case install them in series for 24 volt and they will balance out during normal operation. If you have one good battery and replace a dead one you will greatly diminish the life span of the dual batteries. Hope this helps,

Mark

 

[ToddJK]

One thing to remember when using dual batteries it is imperative that they must be of the same age and model. If not then one of those batteries will have less potential than the other so inevitably one battery will be overcharged and the other undercharged. As already stated when installing two new batteries you should charge them separately to full charge then in our case install them in series for 24 volt and they will balance out during normal operation. If you have one good battery and replace a dead one you will greatly diminish the life span of the dual batteries. Hope this helps,

Mark

Yup. I've done that a time or two before I figured that out!

 

[ToddJK]

Thanks for your answer. I've had a really hard time with the batteries in my jeep, and your answer is the only one I've gotten with an explanation for one battery being undercharged. Thanks David

No problem. Like Mark said, that also affects your charging/battery system. You can also get a jump from another truck charging one at a time. When my batteries were going bad, it took about 15-20mins per battery using my Dakota that has a decent alternator and a V8. Smaller vehicles with smaller engines and alternators will take much longer.

 

[Mullaney]

Thanks for your answer. I've had a really hard time with the batteries in my jeep, and your answer is the only one I've gotten with an explanation for one battery being undercharged. Thanks David

.
Another thing to add to comments that @ToddJK and @MarkM made is to consider rotating "Battery A" and "Battery B" maybe twice a year. That way, if one battery is getting more charging attention than the other - you don't end up with a battery that fails early.

 

[JEB]

I have asked the restorer of my M38A1 about this issue.
Up here in the Northwest, I won't be driving it in the winter, so it will share the tender I rotate between my other 3 summer only vehicles.
I have a 12v "Battery Tender"-brand unit.
I'll attach the plug in cables to each battery (fitted with O -rings on each post) so I won't have to use the alligator clips.
My restorer said it will work fine, but I should disconnect the two batteries.
So, I'll simply disconnect the bridge cable.

Sound correct?

 

[DeetFreek]

I have asked the restorer of my M38A1 about this issue.
Up here in the Northwest, I won't be driving it in the winter, so it will share the tender I rotate between my other 3 summer only vehicles.
I have a 12v "Battery Tender"-brand unit.
I'll attach the plug in cables to each battery (fitted with O -rings on each post) so I won't have to use the alligator clips.
My restorer said it will work fine, but I should disconnect the two batteries.
So, I'll simply disconnect the bridge cable.

Sound correct?

Yup, as long as the circuit is open, nothing other than time will drain either one.

 

[Maverick1701]

Anyone out there ever tried charging both batteries while wired in series with a standard 6-12-24v battery charger?

I routinely charge both batteries (on my M38a1 and on my M35A2 when I still had it) with a 24v battery tender.
I've never had any issues with battery imbalances.

this is the model I use:

 

[Bill Nutting]

I routinely charge both batteries (on my M38a1 and on my M35A2 when I still had it) with a 24v battery tender.
I've never had any issues with battery imbalances.

this is the model I use:
View attachment 882997

I’ve been using these Battery Tenders for years. I had my M37 for twenty years and replaced the batteries once. This truck sat most of the time but the batteries were always ready to start the truck. I have a 24v Battery Tender installed in my M934. It also has a 12 v tender for the 12 v system I added for the “camper section”. It’s my opinion that a good battery tender will add years to the life of your batteries. I also have a battery disconnect switch on my MV’s. This way I know nothing will be draining the batteries when it’s not in use.

 

[ToddJK]

That seems like a great option. I'll have to look into one of those battery tenders.

 

[MarkM]

I've had luck with the smart chargers below. One amp charge and a minimal float charge when the battery is fully charge. I use these for my car trailer for a car with two batteries and two motorcycle batteries.

My trailer has a solar system (150w) and four mismatched car batteries. I wanted low draw float chargers because of the solar setup. Also had found a 60w inverter without a fan to power the chargers to keep the load down during the long New England winters.

Mark

https://www.amazon.com/gp/aw/d/B082VQJQJP?psc=1&ref=ppx_pop_mob_b_asin_title