Can you charge batteries this way?

[Droptine300]

I have 5 batteries in my boat. 3 of the batteries are hooked together in series to make 36 volts for the trolling motor. I have two batteries in the back hooked in parallel. ( I hope i have stated this correctly?)

Currently I have a 3 bank charger hooked to each of the batteries in series. I think my charger is going bad and it is 8 years old.

My question is can I buy a 4 bank charger and run the 4th bank to one of the batteries in parallel?

Thanks,
Droptine

[hondo]

My question is can I buy a 4 bank charger and run the 4th bank to one of the batteries in parallel?


Yes, you can do that. The batteries connected in parallel will take twice as long to charge, and if one of the batteries is stronger than the other one the charger won't get an accurate reading on them and will want to overcharge the stronger battery while waiting for the weaker battery to get fully charged.

Have you considered getting two on-board chargers, a 3-bank and a 2-bank. Not sure if that's a good option for you or not.

[Hot Runr Guy]

Like Hondo says, the problem with charging batteries wired in parallel is that the charger sees them as 1 big 12volt battery. If you can swing it, get a 2-bank charger for the "house" set, but create a switch or disconnect of the positive-side jumper, to "break" the parallel connection. This way, when charging, the 2-bank charger sees 2 independent batteries, and will charge each of them as needed. All you really need is a simple battery disconnect like shown below, to achieve this break of the jumper used on the positive side.

[Droptine300]

Thanks much for the info guys. I think I will run a 3 and 2 bank charger with a parallel disconnect.

:)

Droptine

[PRD1]

Yes you can as far as charging the two parallel batteries with a single bank of the charger. It will take a while since the charge rate effectively will be half of the amperage for that bank so depending on how they are used it may not get fully charged in an overnight charge period.

I used a three bank charger with two banks to a set of parallel 24V batteries and they do charge independently even without a cutout switch. I was using an MinnKota 330 and if you check the manual it will state that it will charge batteries independently in spite of their being in a series or parallel configuration and it works fine.

[bob1]

When charging 2 batteries in a parallel connection, I believe when you only hook up one bank of the charger, the positive cable from the charger would go to the positive terminal of one battery and the negative cable to the negative terminal of the other battery!

Bob

[yarcraft91]

When charging 2 batteries in a parallel connection, I believe when you only hook up one bank of the charger, the positive cable from the charger would go to the positive terminal of one battery and the negative cable to the negative terminal of the other battery!

Bob

You can hook two or more banks from the charger to batteries wired in parallel to increase the charging rate. I do something very similar- a 2-bank Guest charger hooked to a single battery.

[Hot Runr Guy]

I was using an MinnKota 330 and if you check the manual it will state that it will charge batteries independently in spite of their being in a series or parallel configuration and it works fine.

Here is the response I got back from the Minn Kota Technical Service group when I asked how a parallel-wired pair of batteries could be independently charged.

I have not yet checked any of the manuals to see how they were written. I assure you that I will take a look and if that is how they are worded, I will check with my supervisor to see if that needs to be changed.
I can tell you that in parallel, the batteries would not be independently monitored. Because the batteries would be run down and recharged at the exact same rate, it is essentially the same thing. Technically however, they are not being independently monitored.

HRG