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Author Topic: What i can take out of my battery  (Read 2906 times)
chris1000
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« on: August 28, 2008, 05:28:35 PM »

Hello everyone
i have read through lots of your posts and my head is sore Huh
could someone tell me when working out the total load dose it make a difference if its run through a inverter, i have seen the calculation if you have 12v lights ( eg 60w @12volt is 5amp so i could run this for 2 hours on a 100AH battery which would take 10% of is charge)  my battery is 170AH volvo truck battery it has been stood around in my garage for abit it is on charge at the min on a bike charger (yes its taking ages no supprise there then!!! ) i will teset it when its done to see if its any good.
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martin
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« Reply #1 on: August 28, 2008, 05:42:20 PM »

the following is a cut and paste from another thread where someone had a large forklift battery, but the maths is all the same! Roll Eyes
If you take the "10%" rule pretty seriously you won't go far wrong - with 1000 amps of battery, you can draw 100 amp/hrs without stressing it  at all, which would enable you for instance to run a tv, computer, radio, and energy saving bulbs for a day without any problems (bearing in mind you need to replenish each day what you've taken out).
Biggest mistake is buying a thumping great 2kw inverter, and trying to run fridges, deep freezers and washing machines off the bank........unless you've got a seriously big bank, a hefty turbine, and a few kw of pv panels, I'd go for a "only use electricity where nothing else can do the job" philosophy - that way you can survive well off a relatively small and affordable system.
(I've done the sums for people who want to run a fridge freezer off pv panels - just to do that can mean you need to spend another 5,000 on the system just to make up the ginormous gobbets of power they consume)
To expand on the "10%" draw thing -
A brand new el cheapo leisure battery is probably rated at something like "200 cycles to 50% DOD" - in simple terms, that means you can discharge half it's capacity 200 times before it'll keel over stone dead, and roughly pro rata (DOD is depth of discharge) Cool
SO, if you were a plonker, and bought a brand new caravan battery, and used it every day, and used 50% of it's charge, in about 7 months time, you'd be buying a new battery..............if you used 10%, it would probably last 5 times as long (around 3 years).
If you have a "truck" battery, they're not really designed for renewables use, so I'd suggest treat it as a 170w "caravan" battery Wink
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martin
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« Reply #2 on: August 28, 2008, 05:46:37 PM »

ps, if you have a flattish battery that hasn't had a lot of use, charge the living daylights out of it - if you can get hold of a "good" car charger, it's better than nothing, ideally you want something that'll give it an "equalisation" charge - circa 15 volts, and let it have a good "bubble" to clear the sulphation. If you need a car charger, they can often be picked up dirt cheap at boot sales! Wink
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chris1000
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« Reply #3 on: August 28, 2008, 06:02:59 PM »

so you think it would be i good idea to get a new battery.
i will use it to run lights and see how it goes on.
i have seen these on ebay i was going to by two of them do you think they are any good??http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=270263197735&ssPageName=STRK:MEWA:IT&ih=017
many thanks chris
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martin
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« Reply #4 on: August 28, 2008, 06:15:50 PM »

I honestly don't know Chris - they're "amorphous" panels by the look of them, they may be good, they may be typical Fleabay Undecided
If you've got the battery already, try using it fairly gently (you've got nothing to lose) - I'd suggest a couple of Navitron's 20w panels for around the same cost as the Fleabay jobs (we KNOW they're good, and from a reputable company that will give you a decent after sales service), and a 15 controller........then just "get the feel" of using a pv system - once you have, THEN lash out more serious money when you have more of an idea of what you actually need!
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chris1000
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« Reply #5 on: August 28, 2008, 06:24:37 PM »

cheers for your advice martin Smiley
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