Building 450-Ampere-hour House Battery Bank

Electrical and electronic topics for small boats
peterd
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Joined: Mon Nov 23, 2015 9:25 am

Building 450-Ampere-hour House Battery Bank

Postby peterd » Tue Mar 21, 2017 12:54 pm

I'm trying to build a house bank of batteries in a small boat where space is very limited. I'd like to use two Trojan T-105 6-Volt batteries each having 225-Ampere hour at 20-hour [discharge rate]. The problem is I'd like to have both a 12-Volt system with only the two batteries with the combined 450-Ampere-hour. Whether they're wired in series, parallel, or series-parallel it seems impossible to achieve.

Is there a converter that would make the two 6-Volt batteries into a 12-Volt unit yet allow the combined 450-Ampere-hour?

Or am I dreaming?

jimh
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Re: Building 450-Ampere-hour House Battery Bank

Postby jimh » Tue Mar 21, 2017 2:34 pm

The Ampere-hour rating of batteries does not add when in series.

When batteries are in parallel their Ampere-hour rating is additive.

When two 6-Volt batteries of 225-Ampere-hour are in series they make a 12-Volt battery of 225-Ampere hour.

The only device that can be connected to two 6-Volt 225-Ampere-hour batteries in series to make a 450-Ampere-hour battery is two more of the 6-Volt 225-Ampere-hour batteries in series connected in parallel to the first two.

peterd
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Joined: Mon Nov 23, 2015 9:25 am

Re: Building 450-Ampere-hour House Battery Bank

Postby peterd » Wed Mar 22, 2017 9:11 am

Thanks Jim, I didn't think it would work even with a convertor.
I'll search for a single 12 volt with the highest Ah I can find with the same footprint as the two 6 Volts

jimh
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Re: Building 450-Ampere-hour House Battery Bank

Postby jimh » Wed Mar 22, 2017 11:50 am

I anticipate your search for a single 12-Volt battery with a rating of 450-Ampere-hours will be unsuccessful.

One alternative might be the ODYSSEY PC1800-FT. It is rated for 214-Ampere-hours, and it weighs 133-lbs. The battery case is much larger than most batteries. Two of these in parallel would give you 428-Ampere-hours. You can find the dimensions and other specifications at

http://www.odysseybattery.com/marine_battery_specs.aspx

In a single case, you might consider the ROLLS 12 CS 11P, which weighs 272-lbs and would provide 357-Ampere-hours. For details see

http://www.rollsbattery.com/wp-content/uploads/batteries/12CS11P.pdf

If space and weight are important, you should consider Lithium-Ion batteries. However, be prepared to spend thousands of dollars and to purchase a dedicated battery management system to regulate charging and discharging. For example, a 12-Volt 450-Ampere-hour Lithium Ion battery system is available at an introductory price of $5,477. See more at:

http://www.bruceschwab.com/uploads/ope-li3-intro-price-ope-1.pdf

jimh
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Re: Voltage Convertors

Postby jimh » Wed Mar 22, 2017 12:07 pm

peterd wrote:...I didn't think it would work even with a convertor.


A voltage "convertor" can only lose power, never create power.

jimh
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Re: Building 450-Ampere-hour House Battery Bank

Postby jimh » Sun Mar 26, 2017 9:39 am

The least expensive approach to assembly of a large Ampere-hour house battery bank is probably to use two 6-Volt batteries in series, and to use relatively inexpensive flooded cell lead-acid batteries. These batteries are often targeted for use in golf carts.

I found literature from battery manufacturer TROJAN to be very informative. See

https://www.thesolarbiz.com/media/catal ... _Guide.pdf

peterd
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Re: Building 450-Ampere-hour House Battery Bank

Postby peterd » Wed Mar 29, 2017 9:14 am

Thanks for for the Trojan link Jim.

Rolls Surette have nice 6 volt battery. I like the weight, the dimensions and the 230 Ah. The 6 FS 230
http://www.rollsbattery.com/wp-content/ ... 6FS230.pdf

I've noticed on a number of cruising sites the Trojan T-105 PLUS 6V Deep Cycle Golf Cart Battery is still very popular

Both have attractive pricing compared to most

I appreciate your input