Pontoon Boat & Deck Boat Forum

I have a question on charging a dual battery setup. I topped my batteries off due to the excessive cranking my last trip out by unhooking the jumpers between the two batteries and charging them one at a time. I was wondering if you could charge them both at the same time with the jumpers hooked up? If so, how do you hook the charge cables? Positive side on one battery and negative on the other? Or will it work if you just hook to one battery and it feeds over? And I charged them on a fast charge, 20a, up to 75% and them the rest on a 10a charge. They're marine batteries and I didn't know if leaving them on the 20a charge the whole time would hurt. I know deep cycle batteries like a slow charge. Thanks in advance for all the help!

Im definitely interested in responses on this.

Please tell me your not starting with deep cycle batteries, they are not made for starter use, or do you have the combo type batteries ?

But the best would be to charge them one at a time usless you have a two bank charger and you need a smart charger that knows when to quit charging to make your batteries last a long time

Well maybe I goofed, they're marine batteries. I was thinking marine batteries were the same as deep cycle? Maybe not? But they are marine batteries, one Interstate and one Everstart (Walmart special). And I do have a smart charger. Money well spent compared to the older analog chargers.

I think the Deep Cycle battery will have DC and the Starting battery will have MS on the battery. But both would be marine batteries.

Does anyone have any thoughts on the OP's original question about charging them together, individually, etc.? Interesting questions. I'm also interested in the answers.

I would do them separate so both get a full charge and then charger shuts off, I have a three bank charger and it handles each one separately, so if one battery needs more time, it is the only one getting charged.

unless they are 100% identical batteries (highly unlikely), i'd charge them separately. you can charge them together, but you risk hurting one or both in the long run.

Better safe than sorry. It only takes a second to unhook a jumper, thanks.

dunny961, have you thought about installing a battery switch? Sure makes life with dual batteries a lot easier.

I use the MinnKota MK 220D On-Board Battery Charger (2 Banks, 10 Amps Per Bank) charger.

The two batteries connected are Wal Mart's EverStart 27DC-6 Marine Battery. I bought them both on the same day. They are only used to 'run stuff'. Not used to start battery.

I do not remove the jumper between batteries when charging. That's the beauty of this (and other) smart chargers.... Park the boat, plug in the charger, walk away.

Bryden24shp wrote:dunny961, have you thought about installing a battery switch? Sure makes life with dual batteries a lot easier.

I've got a battery switch that I keep on "2" most the time. The only time I put it on "1" is when we're anchored listening to the tunes. I'm just not sure which battery is #1. The closest to the switch or the futherest?

dunny961 wrote:

Bryden24shp wrote:dunny961, have you thought about installing a battery switch? Sure makes life with dual batteries a lot easier.

I've got a battery switch that I keep on "2" most the time. The only time I put it on "1" is when we're anchored listening to the tunes. I'm just not sure which battery is #1. The closest to the switch or the futherest?

Easy to trace it out, should be able to see the terminals and leads to the + posts of the batteries.

I have two batteries with Perko switch installed. Unless it's a really demanding day on the battery, I run the switch on one battery and alternate which battery I use. (Battery 1 today, Battery 2 tomorrow) As far as charging goes, I charge each battery separately if needed. An onboard two bank charger could be a good investment if you have high battery usage.

I have two batteries and use a Guest two battery charger. I plug it in and forget it. It automatically detects the type of each battery and charges each battery according to its individual need and then shuts down to maintenance level only kicking on if and when either battery falls below a certain level. I have used this with great success for over two years with the same two batteries without any problems. I highly recommend this product.