batteries

my boat has a starting battery and two 12 volt trolling batteries wired for 12volts, all my electronics and etc come off the starting battery, i want to add a battery for the electronics and leave the starting battery by itself if i add a common and neg from starting battery to new battery will the engine then recharge both batteries

Re: batteries

Welcome to iboats!

Taking the trolling motor batteries out of the equation and you are adding a second battery to the boat. There are many threads on this topic (do a search) with good explanations of the advantages and disadvantages of the different ways of doing this. In most cases, a 1-2-Both-off battery switch is the recommendation.

Re: batteries

It appears to me you will end up with four batteries total. Not knowing what "electrics" you have makes it hard to tell if adding another battry is overkill. Next, there is no COM on a battery. Just + and -. Connecting + to + and - to - will make a parallel setup and yes the engine will charge both. But with that setup you are discharging both batteries at the same time regardless which one you have the electronics connected to. You didn't mention what engine you had either so just because the engine can keep the starting battery charged does not mean it can keep two batteries charged -- especially if either or both are deeply discharged. Regarding the trolling motor batteries -- are you sure you have them in parallel for 12 volts or series for 24 volts.

Re: batteries

Silvertip said:

It appears to me you will end up with four batteries total. Not knowing what "electrics" you have makes it hard to tell if adding another battry is overkill. Next, there is no COM on a battery. Just + and -. Connecting + to + and - to - will make a parallel setup and yes the engine will charge both. But with that setup you are discharging both batteries at the same time regardless which one you have the electronics connected to. You didn't mention what engine you had either so just because the engine can keep the starting battery charged does not mean it can keep two batteries charged -- especially if either or both are deeply discharged. Regarding the trolling motor batteries -- are you sure you have them in parallel for 12 volts or series for 24 volts.

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Thanks i have a 225 evenrude, the trolling motors are in parallel, i run electric anchors a gps a depth finder radio two live wells and two bait wells, its a 21ft starcraft pro elite 2000. should the parallel wireing i add be heavy enough to carry starting amps? should i put an isolation switch on it to prevent draining both batteries?

Re: batteries

Your objective is to protect the starting battery from being drained. Simply paralleling the added battery doubles the available current capacity but it does nothing to prevent discharging both of them. So yes -- you need to add a dual battery switch or if you don't want to be bothered with that, add an ACR (automatic charge relay). ACR's are wired so the primary battery (the start battery in your case) always gets charged first. When fully charged the acr switches charge current to the auxiliary/house battery. Unfortuanately, unless the ACR has a "combine" function, you couldn't start the engine from the house battery if that scenario every arose. A dual battery swtich allows running everything from BAT 1, BAT 2, or BOTH, charging BAT 1, BAT 2 or BOTH or starting the engine from BAT 1, BAT 2 or BOTH depending on what you have the switch set for. It also has an OFF position that kills everything. Dual battery switch installations are covered in detail in this forum. Use the search feature.

Re: batteries

Silvertip said:

Your objective is to protect the starting battery from being drained. Simply paralleling the added battery doubles the available current capacity but it does nothing to prevent discharging both of them. So yes -- you need to add a dual battery switch or if you don't want to be bothered with that, add an ACR (automatic charge relay). ACR's are wired so the primary battery (the start battery in your case) always gets charged first. When fully charged the acr switches charge current to the auxiliary/house battery. Unfortuanately, unless the ACR has a "combine" function, you couldn't start the engine from the house battery if that scenario every arose. A dual battery swtich allows running everything from BAT 1, BAT 2, or BOTH, charging BAT 1, BAT 2 or BOTH or starting the engine from BAT 1, BAT 2 or BOTH depending on what you have the switch set for. It also has an OFF position that kills everything. Dual battery switch installations are covered in detail in this forum. Use the search feature.

Click to expand...

thanks alot