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house battery Q:

Old 10-12-2008, 04:25 AM
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Default house battery Q:

Hello all,I know I have my work cut out for me and a lot more reading to do but I was wondering if someone could point me in the right direction.I'm triing to figure out what size house battery I need.Q:How do I find out how many amps my electronics draw per hour(is that what I should be looking for)?and Q:How many amps is my alternator putting out per hour(is this the right Q to be asking)?and Q:Should I hook up a battery charger at the dock?Thanks for any advice ;? ;?
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Old 10-12-2008, 07:03 AM
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Default Re: house battery Q:

In my opinion, you should do a "amp hour" survey of all your systems on your boat. I took every device and using spec sheets and even catalog pages determined the amp usage then calculated what my needs are for house batteries.

For example; I wanted to keep my radar and fish finder on while anchored or drifting but I was nervous about running them on my starting battery. So I determined that my fish finder used 1.01 amps per hour and my radar used 3.50 while active. So I knew I could run those devices for eight hours without worry. With totals of 28 amps for the radar (active) and 8.08 amps for the fish finder. That's 36.08 amps used in 8 hours on my 115 amp hour house battery with a total percentage of 31.37% of power used on that battery. Cool.

I have all this data in a spreadsheet which allows me to calculate usage for different lengths of time or items used only at night etc... I have two 115 amp hour house batteries. My wife thinks I've lost my mind.

I installed a three bank Pro Mariner battery charger that charges my house batteries when I get back home.

I hope this helps.

Dave
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Old 10-12-2008, 07:35 AM
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Default Re: house battery Q:

Well, you can do a lot of calculations if you want to, but my recommendation is that you install the largest battery or batteries that will fit (within reason). You cannot have too much power available. Use deep cycle batteries for your house bank. Connect all your electronics and lighting to it with a master switch and proper circuit protection.

It doesn't matter how many amps your alternator puts out unless you are trying to run very large loads (such as an airconditioning system) from your batteries.

Buy a "battery combiner" to keep both your starting and house batteries charged.

Charging at the dock is a good idea also.
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Old 10-12-2008, 10:35 AM
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Default Re: house battery Q:

Despite the excellent advise on calculating required capacity, the limitations are usually space and convenience of access. I would decide where the battery is going to go, how much weight you can lift and put in the space, and then get the biggest battery you can.

If it is too small you gave it your best shot and may have to find space to add another battery in parallel.

If it is too large you will extend the battery life by as much as 10 times. Matching a battery to JUST the capacity you need will only give you a short life due to depth of discharge. As a rule of thumb, for maximum life the battery should be discharged no more than 50%. For every 10% discharge below that you halve the life. So, for example, 6 years at 50%, 3 years at 60%, 18 months at 70%, 9 months at 80%, 18 weeks at 90%, 9 weeks at full discharge, 1 trip at more than full discharge.
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Old 10-12-2008, 04:12 PM
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Default RE: house battery Q:

Thanks dpowell,rwidman and yandina.Thats just the kind of addvice I was looking for.
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Old 11-25-2008, 04:32 PM
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Default Re: house battery Q:

yandina - 10/12/2008 12:35 PM Despite the excellent advise on calculating required capacity, the limitations are usually space and convenience of access. I would decide where the battery is going to go, how much weight you can lift and put in the space, and then get the biggest battery you can. If it is too small you gave it your best shot and may have to find space to add another battery in parallel. If it is too large you will extend the battery life by as much as 10 times. Matching a battery to JUST the capacity you need will only give you a short life due to depth of discharge. As a rule of thumb, for maximum life the battery should be discharged no more than 50%. For every 10% discharge below that you halve the life. So, for example, 6 years at 50%, 3 years at 60%, 18 months at 70%, 9 months at 80%, 18 weeks at 90%, 9 weeks at full discharge, 1 trip at more than full discharge.
yandina (an amateur tech working out of his garage) unjustly blasting BOE (a long time supporter of THT) is an absoluteCROCK!!!

http://www.thehulltruth.com/forums/thread-view.asp?tid=223800&start=1

yandina =
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Old 11-28-2008, 05:05 PM
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Default Re: house battery Q:

Jim Z - 11/25/2008 6:32 PM



yandina - 10/12/2008 12:35 PM Despite the excellent advise on calculating required capacity, the limitations are usually space and convenience of access. I would decide where the battery is going to go, how much weight you can lift and put in the space, and then get the biggest battery you can. If it is too small you gave it your best shot and may have to find space to add another battery in parallel. If it is too large you will extend the battery life by as much as 10 times. Matching a battery to JUST the capacity you need will only give you a short life due to depth of discharge. As a rule of thumb, for maximum life the battery should be discharged no more than 50%. For every 10% discharge below that you halve the life. So, for example, 6 years at 50%, 3 years at 60%, 18 months at 70%, 9 months at 80%, 18 weeks at 90%, 9 weeks at full discharge, 1 trip at more than full discharge.
yandina (an amateur tech working out of his garage) unjustly blasting BOE (a long time supporter of THT) is an absolute CROCK!!!

http://www.thehulltruth.com/forums/thread-view.asp?tid=223800&start=1

yandina =
I don't think your description of yandina as "an amateur tech working out of his garage" is correct and any problem between that company and "BOE (a long time supporter of THT) " is irrelevant as far as technical advice is concerned. Yandina's advice is good sound advice. It's not a popularity contest.
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Old 11-28-2008, 05:37 PM
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Default Re: house battery Q:

Forget the calculations. Go measure the location you have to mount a battery. Take those measurements to the nearest distributor of AGM batteries, and pruchase yourself the LARGEST, AGM battery that will fit the space.

Done. Your welcome.
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Old 11-28-2008, 05:39 PM
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Default Re: house battery Q:

Birdman - 11/28/2008 7:37 PM

Forget the calculations. Go measure the location you have to mount a battery. Take those measurements to the nearest distributor of AGM batteries, and pruchase yourself the LARGEST, AGM battery that will fit the space.

Done. Your welcome.
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Old 11-28-2008, 05:43 PM
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Default Re: house battery Q:

Too bad, I have 2 Group 31 AGM new, for sale. They are approx 75 lbs each, so you need to know where to mont them for the best weight distribution.
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Old 11-29-2008, 06:16 AM
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Default Re: house battery Q:

Dittoes to birdman, if you use an agm, you do away with difficulties like venting gases, and corrosive effects. And size does count.

mattie
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