One Bank, two Batteries

[Lund]

I have two batteries in the boat, one cranking and one for the trolling motor.

I just bought a one bank unit for the trolling motor.

Without going out and buying a 2 bank unit, can I wire the charger to a switch that is wired to each battery, and chose which one gets the charge?

It is a 6 amp charger, and was also wondering if running the wires from the front of the boat where the charger will be mounted to the back of the boat for the cranking motor will be a problem? (Boat is 17' long)

Thank you.

 

[Silvertip]

Re: One Bank, two Batteries

Yes it can be done! and No -- it's not a problem with distance provided the wire gauge is large enough to prevent too much voltage loss on the way to the start battery.

 

[bruceb58]

Re: One Bank, two Batteries

You could mount an ACR and it will turn on and connect both batteries to your charger when it is turned on or when your engine is running.

 

[Lund]

Re: One Bank, two Batteries

You could mount an ACR and it will turn on and connect both batteries to your charger when it is turned on or when your engine is running.

Sorry, what is an ACR?

 

[PondTunes]

Re: One Bank, two Batteries

An ACR is short for an automatic charging relay. Simply put it is a relay that automatically closes a connection to a second battery when a charging current is available. Once the charger is disconnected the connection is broken preventing the second or backup battery from draining the primary or starting battery.

Blue Sea Systems makes a kit that includes a battery switch that allows you to combine the batteries in case of an emergency. It's called the Add-A-Battery system and if you search the forums you should find multiple posts talking about this system.
http://bluesea.com/category/1/productline/docs/329' <--- Add-A-Battery system

However; this setup might not be exactly what you need...

An example wiring diagram would be:

This setup would automatically charge the starting battery (battery #1) and the trolling motor battery (battery #2) while underway provided your engine's charging system has the output to charge two batteries. It would also allow you to connect your charger to battery #2 and battery #1 would also receive charge.

It looks like you just want to make sure your starting battery is topped off after the trolling motor is charged. I really like the ACR setups but they may or may not be best for your situation.

Some considerations:
1) Your engine is supposed to keep the starting battery charged. Going to the trouble and expense of the above setup just to make sure the cranking battery is charged is probably not the best route.
2) If your engine is an outboard it may not have the output needed to keep two batteries charged (as it will be trying to do with the above setup) Check a shop manual on your make/model engine for its charging system limitations.

3) A simpler solution may be to install a 1-2-OFF-BOTH switch that would allow you to connect the batteries in parallel for charging (or to charge/crank with either battery). When you get ready to go out just switch to battery #1 and crank up and go. However; then you have to remember to switch off of the BOTH setting otherwise the trolling motor battery #2 can drain your cranking battery...

4) Another simple solution would be just a simple ON-OFF marine disconnect switch connected between the positives of both batteries. When you connect your charger you switch the switch to the ON position. When you remove the charger switch it back to OFF.. This setup isn't as versatile as the 1-2-OFF-BOTH style switch but would be simpler to set up.

5) Lastly you could look at a large high current relay that could be wired to a switch on your dash. Switching the switch to on would connect the batteries for charging and may be easier to remember.
http://bluesea.com/category/1/productline/8' <-- High current remote relay.

 

[Uraijit]

Re: One Bank, two Batteries

Just get something like this: "http://www.outerbanksoutfitters.com/product/196901516msk.htm"

 

[Boatist]

Re: One Bank, two Batteries

I charge both my batteries form a plug at the bow of the boat. I charge both batteries thru the same battery isolator that the engine 65 amp alternator uses. My battery charger I use most is a 10 automatic. Wire from the front of the boat to the stern mounted battery isolator is 12 guage.

I also have 12 volts from my truck's alternator to the trailer thru a 8 guage wire and a plug that I can connect a adapter to plug in the boat while going down the road. I really do not use it very much but can by just plugging in.

My boat is a 1980 21 foot runnabout

 

[BAYLINER185]

Re: One Bank, two Batteries

Yea I think all you really need is a battterie isolator. I put on on my 18 foot ski boat that Ive been using for fishing and use one battery for starting and one for the lights and other electrical accessoies we may plug in.

An isolator will make you a 2 bank system. bank one for starting and the number 2 banks for everything else on the boat. In your case the trolling motor.

You can get an isolator at any auto parts store. I got mine at Pep Boys.

Its easy to wire and its worked great for me. Before I had it my main battery died and we got stuck for a few hours till we got a jump for some college guys. With the isolator Ive never had to worry about power.

I also bought a cruser with a perko switch and no isolator and I have to switch from bank one to bank to to ALL when under way. I have to remember to use 1 for starting the motor then switch to ALL so both banks charge then switch to bank 2 when we ancor or stop somewhere. Im thinkinf of adding an isolator to this as well and just leaving the switch on ALL when underway and when I dock for the night then Ill switch to 2 just for added security that the boat is only running off bank 2. There are diagrams on here somewhere that show all this, I have seen then before but you really shouldnt need anything that tough, just a simple isolator will do.