Battery Charger advice

[gman]

Hi all, I;ve got a 16' boat w/ a 40 h.p. Merc on it. With all the gadgets I've got running now (gps, fishfinder, am/fm radio, trolling motor, etc.) I think it's time to add another battery as the boat only has one right now.
My question: should I hook these up in parallel or designate one battery for the trolling motor and the other for cranking/accessories. From what I've read I should get a two bank charger to keep them up after use.
Will the motor charge the two batteries when I'm fishing? I'm guessing not as at trolling speed what juice is produced will be used by accessories.

Any advice would be appreciated as I'm on a budget and want to get it right the first time. My existing battery is a deep cell RV/Marine battery I think about 550 CCA.

Thanks in advance

[shadow7663]

Always designate 1 battery soley for the big motor on the boat. Use the second battery for all of your electronics and what not.

Use a battery Isolator also this will allow the big motor to charge both batteries when its running and will stop one battery from draining the other resulting in 2 dead batteries and you stuck on the lake.

You will want to get something to make sure the batteries stay charged up when the boat is not in use

[PARSON]

I have a similiar setup as you and I hooked mine up parallel but also hooked up to a switcher where I can use 1 for main motor 2 for acc. and three both. I can also charge either one, two or both. Go to your local marine store and tell them what you want to do and they will point you toward the right kind of switch :fish:

[TONGA]

I would not recommend charging more than the main battery with that little 40 merc.the charging system on that motor is designed to keep your main battery topped off not to charge dead batteries..asking it to charge 1 or 2 deep cycle batteries that have been drained from a days fishing with a trolling motor will be very hard on your stator!
I would say you can go ahead and run your gps,fishfinder,and even your radio of the main battery they do not pull to much juice but I would isolate the trolling motor and battery or batteries with an auxiliary plug in charger

[gman]

Would it be better to run a automotive type battery for the cranking motor? I know the deep cell battery would be better for the trolling motor.

I had a problem last year late in the season where as long as I was trolling the fishfinder and radios (am/fm, off shore) would work but when I took off on a plane to head somewhere else the radios, fishfinder would cut off. then when I knocked it back down to trolling speed the accessories would come back on by themself without having to turn them on, kinda like they went to sleep or something.

I've since checked out all wiring and all connections were good with no bad splices or anything. I just have to check alt. output when I can get it back in the water. I'm thinking either the alt. is going or all the trolling speed usage isn't charging the battery (deep cell I've got) enough to keep the accessories going at high rpm running and I need to go to a second battery and charging system for between outings.

Thanks all to the info so far it is appreciated.

[TONGA]

Yes you want to run a marine cranking battery for the motor and a deep cycle for the trolling motor.
I know if at all possible you want to keep your fish finder wiring away from the motor wiring to avoid RF noise getting to your fish-finder. as for them shutting off ? never had that one.