mwg
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Registered: 19th Feb 04
Location: South Lakes
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I've just got a grinder that runs off a 12v battery by connecting to the battery terminals like on a car. So I need a battery! Really don't have a clue how big it'll need to be. Cheaper the better I guess.
Car battery is the obvious answer but they're a bit heavy to move around and not sure how it'd cope with being run down and charged up? I don't have a much of clue whats best so any help would be good thanks.
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Bart
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Registered: 19th Aug 02
Location: Midsomer Norton, Bristol Avon
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well you need to know roughly the power consumption of the grinder.
a smallish 14Ah (amp hour) battery will give you around 9 hours of a device drawing around 1 amp.
A 14Ah battery is about 1/3 the size of a car battery.
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Jakey
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Registered: 4th Jun 07
Location: Sandbach
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No idea what kind of spec you might need but what about a motorbike battery?
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Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
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Leisure battery will respond better to being charged and fully discharged but they're more money.
Would a 14Ah battery not give 14 hours of 1A? Or are you not going to total discharge?
Need the wattage of the grinder really.
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mwg
Member
Registered: 19th Feb 04
Location: South Lakes
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I can't find anything about the power consumption of it.
This is the grinder http://granberg.com/product/precision-grinder
It'll only be used once a week for maybe 10 or 20 minutes so probably don't need anything heavy duty. Be nice to have something small enough so I can use it out in the woods or in the workshop. It's only a small portable thing
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Bart
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Registered: 19th Aug 02
Location: Midsomer Norton, Bristol Avon
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quote:
Originally posted by Ian
Would a 14Ah battery not give 14 hours of 1A? Or are you not going to total discharge?
No, I think you have to times it by power factor, around 0.7 off the top of my head.
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Dom
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Registered: 13th Sep 03
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Use a multimeter and find out the power draw; then you can work out on what size battery you need.
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Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
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Power factor is 1 for DC.
Even if that was 200watts which is quite a bit for a 12v device of that size, that about 15A depending on the state of charge of the battery. You'd get a good few hours out of a car battery.
http://www.ebay.co.uk/itm/190392721584
Thats 12Ah so would give you an hour at 160 watts give or take.
They've got other sizes as well but that should be up to the job. Do need the grinder specs to make sure but its not massive.
You can charge that using a car battery charger.
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Jamie Walby
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Registered: 15th Nov 04
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I sell 12v 7Ah sealed lead acid batteries for £19.
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Jamie Walby
Member
Registered: 15th Nov 04
User status: Offline
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12v Battery
Expensive to post though
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Bart
Member
Registered: 19th Aug 02
Location: Midsomer Norton, Bristol Avon
User status: Offline
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sorry, the 0.7 is a discharge rate.
Search for any battery life calculator and it will include this in the calculations
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