Onboard Charger and Battery Question need help fast

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honkytonker26

Cadet
Joined
Apr 3, 2007
Messages
18
I just bought a used bass boat and I am upgrading the batteries.

I bought a Bass Pro Shops onboard charger 30 amp 10/10/10.
I have a 12v trolling motor with 2 deep cycles batteries. That means I need to run them parallel right?

Someone also told me I only have to hook one deep cycle up to the onboard charger to charge both is that right. Should I have bought a 2 bank charger or can I still use the 3 bank?

last question: The boat came with one deep cycle battery (interstate) so I bought one Bass pro shops AGM maintenence free. I was also told I need to buy another Bass Pro Shops AGM to match the other one. Is that true?

I am leaving out friday morning and would really appreciate some quick help.
thanks,
Channing
 
Boatist

Boatist

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Apr 22, 2002
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4,552
Re: Onboard Charger and Battery Question need help fast

It is not clear to me if you have 2 batteries or 3. Sounds like you have 2.
If you do have two then a 2 bank charger would work good. One bank on your starting battery and one on your trolling battery. If you do add a 3rd battery then it needs to be the same size, type, and age as the other trolling motor battery.

If you add a third battery another option would to be have a starting battery and 2 trolling motor batteries but not wired in parallel. You would then need a switch to select which trolling motor battery you use. I like to wire this way for several reasons. When I use to fish Tournaments this is the way we wired them. We would run on one battery until the first sign of weakness then switch to the other battery for the rest of the day.

1: Trolling motor battery do no have to be same type, age and size when not wired in parallel..

2: If one of the batteries goes bad it does not affect the other battery. Wired in Parallel your batteries are only as good as the weakest one. also when you need to replace one you have to replace both.


If you end up with 3 batteries and the trolling motor batteries wired in Parallel then a 10 amp charger is not big enough in my opinion. If you ran all day and the batteries were discharged they would not recharge over night with 5 amps per battery. Example when we fished the tournament circuit we would pre fish on Saturday to find where the fish were and plan our fishing for the tournament on Sunday. We would go home early and charge both batteries with 2 15 amp charger. Even thou the batteries had less than half their normal use they would barely be fully charged at 4Am when time to leave for the blastoff.

Some will tell you the batteries will last much longer if wired in parallel than running one and then the other. I really did not see this when we tried it a couple of times. Also the batteries will be much lower state of charge before you notice it because each battery supplies half of the current so before the motor need more current to operate at the power level you need each battery will be a lot lower. I belive this does a lot of harm to the batteries that that should not be discharged 50 percent before recharging.
 
H

honkytonker26

Cadet
Joined
Apr 3, 2007
Messages
18
Re: Onboard Charger and Battery Question need help fast

I have a Pro Mariner 30 amp onboard charger. 3 banks 10/10/10
I have 2 deep cycle batteries and one cranking battery.
I have a 12v trolling motor.
I am trying to figure out the best way to hook it all up.

I have been told that in order for me to use 2 Deep Cycle batteries on a 12v troller I have to hook them up parallel.

I like the switch suggestion. What do you suggest?

I maybe overthinking all this, but I am about to leave for a 4 day fishing trip (vacation) and the last thing I need is to loose some good fishin' days working on this. I really appreciate your quick response...
Channing
 
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I/O WALDO

Petty Officer 1st Class
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Nov 16, 2005
Messages
320
Re: Onboard Charger and Battery Question need help fast

Parallel the two trollers,connect a charger output to each of the (3) batterys,install an "on-off switch between the start batt.and the troller bank(on the + batt cable #4 wire, also connect all the grounds together) . While underway have the switch "on" to charge the trollers & "off" when stopped to isolate the start batt.Then go fish!
 
I

I/O WALDO

Petty Officer 1st Class
Joined
Nov 16, 2005
Messages
320
Re: Onboard Charger and Battery Question need help fast

(" but see if you can understand how I have wired this up")In a picasso-ish sortta way! Long as the grounds are connected together(inc. the one from the charger),the troll bank + is isolated from the start batt +.Should work! I suggested a switch between the two bank's + wires to allow the alt. to charge the troll bank while underway butt not necessary if they hold up all day.
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Onboard Charger and Battery Question need help fast

The diagram you posted is very safe and is what a great majority of folks use. Unless you have a very high output alternator, the engine will not contribute much additional run time and you would need to make quite long runs to get that additional run time.
 
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