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Old 23-05-2015, 04:58   #1
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Split Battery Bank

The boat is short things are tiight. Using(2) Trojan T105 GC2 Flooded 6v in series yielding 225ah instead of 160 ah before. It fits nicely in the port case under the panel and switch. I need new cables. Using 2awg.
I have added a group 24 battery case to the starboard side for the start battery. Which has been a 2000 west marine gel cel. It has 350 cca but voltage is getting lower 12.45v. It still starts the 3ym30 yanmar but I think it is time to replace it. - Could it screw up the starter?

A decent lead acid 12v costs about $125. Perhaps I should just get two more T105 6v in series with another 225ah if I have the room?

If I can fit this should I put the two separate banks together as one? It would be more effective in use, but I would have to start the engine with it. I read that the cables should be the same length. How much does that matter?

For emergency starting I would get one of those heavier 120v plugin with battery and jumper cables and store it in a locker for emergency start. The second bank would be unused. Normally I would start using my housr bank. Would that be okay for these (2) T105 225ah 6v in series + another 225ah (2) T105 in series setup on the other side of the boat (with the two sides wired in parallel)?
Would starting engine be ok?
Would uneven cable lengths be critical? All 2 awg.
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Old 23-05-2015, 06:00   #2
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Re: Split Battery Bank

Several possibilities here, depending on:

1. your intended use of the boat;
2. your present charging systems (battery charger, alternator, etc.); and
3. your budget.

I understand things are tight and the boat is small.

How do you charge the batteries now (be specific)?

Are you mostly in a marina or on a mooring?

What are your cruising plans?

Bill
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Old 24-05-2015, 04:38   #3
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Re: Split Battery Bank

Good questions Bill. We are on a mooring near the channel. I like to leave amazonia mirimar anchor light on. I have a 14 watt powerstrp pv solar flexible panel which will be connected to a genasun gv-10 ( room to add panels up to 140w. Controller is necessary even with 14w.

The other source of power is rebuilt Balmar 90-65 and a Ballmar ARS-5 now set on flooded.

Cruising is one ans two weeks to maine cape cod long island and possibly south. Would like to go for longer periods.

We have 6cu ft ref Ozifridge w danfoss and large evap. Box has 2" insulation and we've added 1/4 " foam and we freeze the milk and oj when we load sometimes add ice. Takes 36ah startup the fridge then 18ah per day. Worst case day is moror out 1/2 hour and motor in when we run ref on full with water exchanger going. Sometimes worse is motoring long day as enfine gets hot and ref is adjacent. Need to put 1"-2" inches of insulation next to that side but have some concern about fire protection. Draws 5-6-7 amp depending on power available. Engine on =7a runs 5hr initially. Then about 18ah every 24hr.


We have old autohelm radar rl9
And handheld chart gps. Wish to replace with broadband radar and opencpn with ais.













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Old 24-05-2015, 04:46   #4
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Re: Split Battery Bank

Ps fitting the alt and bat temp sensors today. Have a fan we turn on in engine compartment to draw out hot air. At some point we ca get a new 125amp balmar alt after I fit the second bank of 6v t105?

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Old 24-05-2015, 04:48   #5
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Re: Split Battery Bank

We try to make improvements yearly this year I installed new groco ibv + ibvf seacocks. What a difference.

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Old 24-05-2015, 04:52   #6
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Re: Split Battery Bank

2yr old Yanmar 3ym30.

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Old 24-05-2015, 06:58   #7
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Re: Split Battery Bank

OK. I think I've got the picture. The details really help. Thank you.

Given your setup and cruising plans and equipment upgrade plans, I think a house bank of 4 T-105s would be appropriate. And, yes, you should run them as ONE single bank, even if they have to be separated. Mine are, and have been for 20+ years!

AWG 2 is too light, IMHO, to connect the two banks. I'd use AWG 1/0, and keep the runs as short as possible. Terminations are extremely important. Make sure the lugs are fitted with a quality crimper, and that you use heavy adhesive heat shrink over the ends. As usual, make sure ALL connections are clean and tight.

I'd recommend a separate start battery, maintained by an EchoCharge. That's worked for me and dozens of my customers for many years. Here's how you may wish to connect them.

Sorry...gotta run. More later if you need it.

Bill
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