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Old 08-08-2017, 12:40   #1
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Location: Bainbridge Island, WA
Boat: Hallberg Rassy 39
Posts: 73
Parallel wiring question

My boat has 6 105AH 12V batteries, 5 for the house and 1 for starting. The old batteries were gel cell and I replaced the house bank with 5 new Lifeline AGM's. The start battery tested OK, but I have a newer lead acid battery that I installed for the starter. There is a small DC to DC charger between the the house bank and starter battery. The new house bank battery posts are in different positions compared to the old bank, so I attached the main positive and main neg on different batteries than before, so not at opposite ends of the bank. I recently noticed a more rapid loss of amp hours than expected and rather long charge times. My question is do the main leads have to be connected to opposite ends of the parallel bank or can they be connected to other terminals on the pos or neg side? Also, does the start battery need to be the same as the house bank when using a DC to DC charger? The old batteries were all the same for house and start.
Thanks in advance for any help!
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Old 08-08-2017, 15:43   #2
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Re: Parallel wiring question

The load wires should be at the same posts as the charging ones.

Understand this:
http://www.smartgauge.co.uk/batt_con.html
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Old 10-08-2017, 08:44   #3
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Re: Parallel wiring question

The difference would be unoticeable by you using them. Maybe slight difference in how long the bank lasts. (Years later)


The only way you can lose more amp hours is by using more power..., Which of course will take longer to charge. Do you have a battery monitor?
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Old 11-08-2017, 09:36   #4
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Re: Parallel wiring question

"The load wires should be at the same posts as the charging ones."

According to Nigel Calder's book "Boatowners Mechanical and Electrical Manual 4/E" (which is now part of my boat library), connecting the charger at opposite ends of the bank as the loads is better than connecting at the same end. "This will create some degree of separation btw charging and distribution circuits, which will help keep unwanted voltage spikes and interference out of the distribution circuits (in effect, the batteries act like a filter)."

Next project: rewire the bank to these specs and see if performance increases.
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Old 11-08-2017, 09:40   #5
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Re: Parallel wiring question

Quote:
Originally Posted by smac999 View Post
The difference would be unoticeable by you using them. Maybe slight difference in how long the bank lasts. (Years later)


The only way you can lose more amp hours is by using more power..., Which of course will take longer to charge. Do you have a battery monitor?
I do have a battery monitor. It's pretty basic and only shows AH used, voltage and amps going in/out.
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