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Old 26-09-2014, 06:23   #1
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Installed Battery Capacity

I fight the urge to increase my battery capacity all the time. I don't know why it even occurs to me to do this since I normally am above 80% SOC at worst and mostly above 90% SOC. Even a couple of years ago when I was trying track down battery charging problems my house bank was above 50% so it isn't like I don't have enough capacity. So maybe this just a misplaced "bigger is better" thing.

But I wonder how my battery capacity compares. So on my 43' cruising type boat I have 460AH rated house batteries, and this has been more than enough.

How about everyone else (do the poll also please) (never mind as I didn't click the poll box and apparently can not add via edit)

This is rated AH, not usable AH.
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Old 26-09-2014, 06:25   #2
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Re: Installed Battery Capacity

I have a lot of urges too , I keep them in check by reading dull technical spec sheets, never fails to work.

dave
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Old 26-09-2014, 06:38   #3
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Re: Installed Battery Capacity

I'm low end - 150 AH

And I don't worry about fighting the urges...
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Old 26-09-2014, 06:44   #4
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Re: Installed Battery Capacity

IMHO the real question should be:

What is your actual installed amp hour capacity now not what was it is rated for when new...? Far too few boaters physically test their banks to know this number and this leads to erroneous assumptions of capacity and batteries that tend to cliff dive later in life....

Approx 90% of the batteries that run through my shop, for physical capacity testing, are not even at 85% of their rated capacity let alone 100%.

This I can only assume is why batteries tend to do okay for a few years then fall off a cliff... If more boaters tested capacity, and then adjusted usable capacity down, as the batteries aged, I suspect we would see average bank life move up....

I see far to many owners with four or five year old banks and an Ah counter still programmed for the "as new" Ah capacity....

Me, I am 400Ah's & 130 pounds of battery bank on a 36 footer, and 80% of it is fully usable capacity, not 35%...
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Old 26-09-2014, 11:33   #5
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Re: Installed Battery Capacity

Quote:
Originally Posted by sailorboy1 View Post

But I wonder how my battery capacity compares. So on my 43' cruising type boat I have 460AH rated house batteries, and this has been more than enough.

How about everyone else

This is rated AH, not usable AH.

42' boat, 600 Ah capacity (when new) divided into two separate start/house/bridge banks. (Doesn't count separate genset strating battery.)

Sufficient so far (and we rarely stress either bank), charging 2x/day as we do breakfast and dinner cooking.

Our starboard bank takes the bigger hit -- with bridge electronics -- so my intention is to slightly increase that bank when we eventually need new batteries on that side. Partly influenced by having enough physical space to increase that footprint a bit... otherwise, I'd leave well enough alone.

-Chris
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Old 26-09-2014, 11:41   #6
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Re: Installed Battery Capacity

22' = 80 Ah
33' = 420 Ah
48' = 980 Ah
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Old 26-09-2014, 11:48   #7
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Re: Installed Battery Capacity

We have some 100 Ah in a small boat. It is well enough. She came with 240 Ah.

I consider 400 to 600 Ah about the norm for most mid size boats.

As long as you have enough charging capacity to easily fill up the tank, there is no upper limit other than the weight.

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Old 26-09-2014, 11:53   #8
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Re: Installed Battery Capacity

The battery capacity, in addition to what Maine Sail wrote, has to be compared to your daily energy budget and anticipated boat use (marina hopper all the way to anchor out), otherwise the question is meaningless.

A single 90 ah house bank survived in my Catalina 25 for 12 years (size wise), outboard engine, no alternator. No fridge, small ap, rarely used depthsounder, Loran C later on. Mostly daysails, some coastal cruises with ability to plug in every two days.

On our C34, we do anchor out almost every time we go out, has a fridge with a daily use of 100-120 ah. With a 390 ah house bank, 100 ah alternator with external regulator.
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Old 26-09-2014, 11:54   #9
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Re: Installed Battery Capacity

Mine has been upgraded to six 125Ah 12V batteries. This works well for my purposes.

Mine is set w/ one dedicated to starting the generator.

Yes, batteries degrade over time and usage. Factor 5-10% Ah capacity loss per year.
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Old 26-09-2014, 12:44   #10
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Re: Installed Battery Capacity

625, but they are pretty much shot, no idea of real capacity, I'm nursing them until I can do better, really considering a LIFE-PO bank, but really don't know where to start and the threads, sort of like the anchor threads get way too involved
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Old 26-09-2014, 13:02   #11
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Re: Installed Battery Capacity

230 AH (12V) House.

Small Fridge + lights uses less than 50A per day.

Good enough for me.
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Old 26-09-2014, 13:10   #12
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Re: Installed Battery Capacity

Oh man... I forgot about the 32" boat....

8 x AA = 8.4 Ah @ 500ma... But it should be noted that cruising times are limited to two to three 3-4 hour passages because rudder and sheet controls are fully electric...

I find it easiest and fairly economical to simply change out the entire house bank when they become depleted...
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Old 26-09-2014, 13:19   #13
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Re: Installed Battery Capacity

Happy: maybe you should consider NiMH for the 32" boat. I'd think they're sold everywhere parts are for said same boat.

My C30 - 230Ah + a 80Ah reserve battery. Small fridge, AP. 160W solar + 50A alternator on the wheezy A4 (and no way will it ever output 50A). Plugged into shore power except when at Catalina or on a day sail. It's plenty. Can be off shore power indefinitely as long as its sunny.
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Old 26-09-2014, 13:40   #14
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Re: Installed Battery Capacity

We have as follows:

House bank = 4 x 4d gels @ 215Ah each. But we run 24V house system. Does that count as 430Ah or 860Ah?

Yanmar starting 1x4d @ ~185Ah

FP Genset starting 1x4d @ ~185Ah

4 x Group 31 @ 125Ah each for Windlass and Bow Thruster (again, 24V -- runs off same 150A alternator/100A charger as house)

1 x Group 27 @ 90Ah for 12V electronics/vhf/some lights -- (I'm not sure whether to count this as "house" since it powers some typical "house" functions)
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Old 26-09-2014, 14:07   #15
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Re: Installed Battery Capacity

Quote:
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We have as follows:

House bank = 4 x 4d gels @ 215Ah each. But we run 24V house system. Does that count as 430Ah or 860Ah?
You don't know?????????? I could just tell you, but I'm not and hope you look it up.
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