Another Battery Question

[Magnolia637]

I have (3) 12V batteries. One cranking battery and two batteries wired in series (i.e. 12 v output) for trolling motor. I want to install a 3 bank on board charger. My questions are: Do I need to disconect the trolling batteries from each other to charge the trolling batteries in the 12v configuration? If I decide to go with a 24v system (i'm thinking of getting a 24v trolling motor), do I need to disconect the trolling batteries from each other to charge? Is there a way to run 12v accessories in a 24v configuration - that is to say can I isolate 12v from the 24v system to run fish finder, lights, etc., instead of running them off the cranking battery. Any help would be much appreciated.

 

[5150abf]

Re: Another Battery Question

For a 24v troller you would run cables from both batteries to the troller btu if you hooked your lights ect to just one it would be 12v so yes you can do that, the boat is still 12 only the troller woould be 24.

To isolate batteries you would need a battery switch, available here at iboats, it lets you chose bank1, bank2, both or off.

Wait fir another reply just in case I am wrong but I am prety sure that is how it works.

 

[Bondo]

Re: Another Battery Question

and two batteries wired in series (i.e. 12 v output) for trolling motor.

Ayuh,... In Series is 24V.... Parallel is 12V...

 

[F_R]

Re: Another Battery Question

Ayuh,... In Series is 24V.... Parallel is 12V...

Yep, need to get the terminology correct. If there are two batteries wired for 12Volts, they are parallel, not series. But back to the question, no you don't have to disconnect the cables to charge them. Your charger will "see" the two batteries as one big 12V, just like your trolling motor does. The troller discharges them both at the same time and the charger will charge them both at the same time.

Now. putting them in SERIES produces 24 volts. Still no need to disconnect them to charge them, but if using a 12V charger, you have to connect the charger leads across one battery at a time (without disconnecting them). Then do the other one.

Yes, you can draw 12V from a 24V series hookup. Just connect your 12V load across one of the two batteries (like you did the charger). The 12V load will draw from that one battery and the 24V trolling motor will draw from both batteries. And yes, before you ask, the one supplying 12V accessories will discharge faster because of the extra load on it. And yes, before you ask, one charged 12V battery in series with one discharged 12V battery does not provide 24V. They both have to have a charge to provide 24V

 

[NYBo]

Re: Another Battery Question

Yep, battery switch plus appropriate charger is the way to go. Manually switching leads to get the job done increases the odds of making a hook-up mistake.

 

[Silvertip]

Re: Another Battery Question

You should decide first which system you will run "before" you buy an on-board charger. The reason for this decision is if you will use a 24 volt system for the troller, you can use a 3 bank charger. One output will connect directly to each of the three batteries and no switch is needed. The only time a battery switch is needed is if you intend to charge all of the batteries from the engine and even then, the 24 volt system presents a challenge since there is no convenient way to charge a 24 volt system from a 12 volt alternator without some way to disconnect the two batteries. If you wire the troller batteries in parallel to provide a 12 volts, you could get by with just a larger two-bank charger. The two batteries in parallel as was mentioned, appear to the single output as just one large battery. So figure out which way you want to go and then post back. I can help you with diagrams. The key here is not to "over engineer" this system which creates reliability issues due to many points of failure. As for running accessories off one of the troller batteries, that is unnecessary unless you have a large number of high current draw items like killer stereos or a half dozen livewell pumps and aerators. A good sized starting battery can easily handle most normal lighting and accessories and the engine will keep that battery topped off. Not true for the trollers which tend to get deeply discharged if you are a serious fisherperson.

 

[tpcowfish]

Re: Another Battery Question

You should decide first which system you will run "before" you buy an on-board charger. The reason for this decision is if you will use a 24 volt system for the troller, you can use a 3 bank charger. One output will connect directly to each of the three batteries and no switch is needed. The only time a battery switch is needed is if you intend to charge all of the batteries from the engine and even then, the 24 volt system presents a challenge since there is no convenient way to charge a 24 volt system from a 12 volt alternator without some way to disconnect the two batteries. If you wire the troller batteries in parallel to provide a 12 volts, you could get by with just a larger two-bank charger. The two batteries in parallel as was mentioned, appear to the single output as just one large battery. So figure out which way you want to go and then post back. I can help you with diagrams. The key here is not to "over engineer" this system which creates reliability issues due to many points of failure. As for running accessories off one of the troller batteries, that is unnecessary unless you have a large number of high current draw items like killer stereos or a half dozen livewell pumps and aerators. A good sized starting battery can easily handle most normal lighting and accessories and the engine will keep that battery topped off. Not true for the trollers which tend to get deeply discharged if you are a serious fisherperson.

Don't want to hi jack,but i too am going to 24 volt troller, have a 2 bank onboard charger, do you have to unhook batteries to charge?

 

[Silvertip]

Re: Another Battery Question

If your two-bank charger is dedicated to ONLY the troller batteries -- NO! You don't need to disconnect them. Connect one pair of outputs to each battery. You cannot tie the starting battery into this system. Actually you can but I prefer you not do that as the engine would then charge the starting battery and only one of the troller batteries. And if you connected the starting battery to the wrong troller battery you get smoke. So don't do this.

 

[Magnolia637]

Re: Another Battery Question

Thanks everyone and excuse my mistake, I do know the difference it was just late at night and well . . . I screwed up. As some of you will notice, since I,m new here, I posted this same question on two different boards - won't happen again. Silvertip, from reading your other posts I thought it would be O.K. to just hook up the three bank charger directly (two leads to each battery) but I wanted to make sure (if I decide to go with the 24v system). If so, I will be purchasing a 30 amp -10 amps to each battery- charger. I defintely don't want to over engineer the project. I have an inordinate fear of the cranking battery being low since I have a 1988 Johnson motor and Johnsons, in my experience, are notoriously cold natured when cranking. Anyway, I will go ahead and run the accessories off the cranking battery. Again, many thanks to everyone!!

 

[tpcowfish]

Re: Another Battery Question

If your two-bank charger is dedicated to ONLY the troller batteries -- NO! You don't need to disconnect them. Connect one pair of outputs to each battery. You cannot tie the starting battery into this system. Actually you can but I prefer you not do that as the engine would then charge the starting battery and only one of the troller batteries. And if you connected the starting battery to the wrong troller battery you get smoke. So don't do this.

Thanks Silvertip, I just don't wanna mess something up, and don't need a new charger, or hassle of un-hook, Thanks for the help Tim