Charging batteries hooked up in Parallel

[kenjenmo]

Hi...I have just installed 2 new deep cycle batteries for my trolling motor and hooked them up in parallel. I am curious about charging them. I have an older model BassPro 2 bank 5/5 charger that I was using before for my starter battery and single trolling motor battery. With my new setup of the batteries in parallel, can I put both charger lines on my trolling motor batteries, one set to one battery and the other set to the other? I figured the starter battery doesn't need to be charged as often because it gets charged while running the outboard and I could do that with my normal battery charge every now and then. Any help would be appreciated.

 

[Silvertip]

Re: Charging batteries hooked up in Parallel

Yes. And just so you know, yolu could attach both charger outputs to one battery and accomplish the same thing. It really doesn't matter. I'm just checking -- are you certain the batteries are connected in parallel and not series? People very often confuse the two and the results are very different.

 

[kenjenmo]

Re: Charging batteries hooked up in Parallel

Thanks for the response. Yes. They are in parallel. It's a 12 volt system neg to neg, pos to pos. Also, in researching on this forum, it seems that I could still just hook up one set of charger outputs to one of the batteries in the parallel setup since they are connected, the charger still only sees it as 1 big battery. If I did this, would it just take longer to charge?

 

[smokeonthewater]

Re: Charging batteries hooked up in Parallel

I don't know about your charger but the ones I have used, you can't use both leads on the same battery bank.... as soon as the positives are on the same circuit, the charger shuts down.... If your charger is like that you will need a switch between the pos terminals of the batts turned off when charging....... YES you can just charge both batts with one 5 amp lead but it may take a couple days to charge em if they are quite low.

 

[kenjenmo]

Re: Charging batteries hooked up in Parallel

Thanks for the info everyone. I really appreciate it.

 

[Skeeterbait]

Re: Charging batteries hooked up in Parallel

It you have a multi-bank smart charger that runs charging profiles and diagnostics on the battery and informs you of the battery status and any faults detected, then the only way for the charger to perform its job properly and let you know if one of the batteries has a problem is to charge the batteries disconnected from each other with it's on seperate charging bank. I have the same setup. I use two group 31 deep cycle batteries wired in parallel using 6AWG wire, pos to pos, neg to neg, to power a 12 volt trolling motor. I have a two bank charger with a bank connected to each battery. However I also used a Blue Sea 200 amp dual circuit switch to break the connection between the batteries before charging. I used 4 6AWG jumpers, two from one battery to the switch and two from the other battery to the switch. When the switch is turned, it opens both the pos and neg connections between the batteries. The charger then charges each battery seperately running its charge profile and diagnostics on each battery and telling me the status of each seperate battery. Once charged, I close the switch reconnecting the parallel link. If you do not break the link, you will not know for sure when one of the batteries goes bad, and you run the risk of overcharging a good battery trying to top off a bad battery.

 

[bruceb58]

Re: Charging batteries hooked up in Parallel

I don't know about your charger but the ones I have used, you can't use both leads on the same battery bank.

probably depends on the charger because my Guest 2 bank charger doesn't mind at all. Also, with an ACR that basically happens autmatically.

 

[bruceb58]

Re: Charging batteries hooked up in Parallel

If you do not break the link, you will not know for sure when one of the batteries goes bad, and you run the risk of overcharging a good battery trying to top off a bad battery.

Overcharging won't be the problem. If you have one bad battery in parallel with a good battery, the bad battery will hold down the voltage keeping the good battery from ever getting fully charged.

 

[kenjenmo]

Re: Charging batteries hooked up in Parallel

One of the leads on the charger is actually labeled, "Starter Battery" which makes me worry that it may be charging at a different rate than the trolling motor lead. The batteries are both brand new and exactly the same. I can't find my manual right now and can't find it online. They don't make the onboard charger anymore or at least it has been updated.