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TR4321

Number of chargers for three batteries

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I have one starter battery and two trolling motor batteries.  Do I need 1) a three bank charger or 2) a two bank charger for the two trolling batteries and a separate single bank charger for the starter battery?

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Your cranking battery should charge from the alternator so theoretically a 2 bank charger would work. This is what I have but I find myself charging the cranking battery often as well since I’m not on the big motor long enough to get the voltage back up full. 

 

I will eventually change all of this when I buy a new TM. 

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Chargers have settings on some and self detect on others for what type of battery you have.  The charging profile has a big impact on how long, and how good of charge you get.  If it were me i would have one onboard for the TM batteries and one regular not mounted for your cranking battery.  This can also be used for your cars and other batteries around the house.  Be very careful in which you choose for the onboard as once you pick the one, you should verify what batteries it is compatible with when and if you change the TM batteries later.  Lead acid and AGM have different charging profiles to maximise the life of the battery and how well it maximises the charge.  The homework will pay big dividends in your wallet and time on the water.

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I have been using a battery tender trickle charger on my cranking battery while off the water and a two bank charger for my trolling batteries.  Seems to work fine for me so far.  Never had an issue starting the boat using this method.

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2 hours ago, TR4321 said:

I have one starter battery and two trolling motor batteries.  Do I need 1) a three bank charger or 2) a two bank charger for the two trolling batteries and a separate single bank charger for the starter battery?

It is simple 3 batteries/3 bank charger.

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Obviously, a 3 bank charger would be best. On my boat, the two trolling motor batteries are in the center of the boat and the starting battery is in the back. Wiring would have been a challenge so I used one two bank charger and a separate single charger for the starting battery.

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3 hours ago, Jig Man said:

It is simple 3 batteries/3 bank charger.

X2

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I just charge all 3 of mine with one small charger that gets up to 3 amps. If one of them gets down below 9 or 8 volts I have one of the big battery chargers on wheels that has 2,10, 40, and 200 amp settings. So if I needed to I could defribulate one of the batteries from dead to hot very quickly. With eye protection of course 

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One bank for each battery. A single 3 bank charger would be the simplest solution

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For a couple years I had the same setup, 2 TM batteries and 1 cranking. I only used a 2 bank onboard charger for the TM batteries and let the alternator do the rest for the cranking. I never felt overly comfortable with this although I never had issues. I upgraded this season to a 3 bank and prefer it way more. That extra peace of mind on the water is worth it. 

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Three batteries and a three bank charger mentioned above is ideal but three bank chargers cost more than I want to spend right now but one day I'll spring for one.

 

I have an all electric Lowe with three batteries. Two batteries for the TM and one for my instruments, lights, bilge pump etc. I leave the two for the TM on a dual "Battery Tender" the other is always disconnected and I use the battery tender once every couple of weeks to make sure it's topped off. For now it's working OK.

 

 

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three banks, 15 amps per bank,... one night, all 3 batteries from dead to fresh.  Ever go away for a week to fish?

 Trust me the extra money up front is worth it

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On September 3, 2018 at 9:53 AM, TR4321 said:

I have one starter battery and two trolling motor batteries.  Do I need 1) a three bank charger or 2) a two bank charger for the two trolling batteries and a separate single bank charger for the starter battery?

What you maybe missing with a good onboard charger is each bank is independ and charges each battery separately, then shuts down when completed into maintenance mode. The initial cost for the basic onboard charger is the major part, each bank adds more cost. For example The 2 bank charger may cost $130, a 3 bank $160 or $30 more. If you know you need a 3 bank charger, don't buy a 2 bank and later upgrade to a 3 bank, your cost would $130 + $160 = $290, better off spending $160 to start with.

If you batteries are in different locations simply run a wire to wherever the battery is located from the charger.

Tom

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Unless you make long uninterrupted runs on you big motor you cannot count on it to charge your cranking batter adequately.

 

 

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