# 12V Car Battery Tester

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#### vince123123

##### Guest
Hi everyone, hope someone can point me in the right direction.

I hope to have real life and accurate input for this one, because I won't have a chance to test out the inputs.

In ICT, we draw out 12V car batteries for use in operations. We may take up to around 20 or so of these.

I need a method for testing whether these batteries are fully charged; so that the battery store will not give me half charged duds which fail when we are out in the field. They always claim "all are charged", but real life experiences show otherwise.

Is there a "meter" of some sort that can test capacity of a 12V battery that we can buy? Is this suitable?

Or what I actually need is just a multimeter (which I do have). If so, what voltage ranges would mean the battery is full, and what means its half full/empty?

I also note from the ebay pic that it may be just a voltmeter - but I was confused to see that the meter reads 10.5V to 12.5V as good, but 12.5V to 13.5V as weak and 13.5V to 15V as OK.

Urgent input would be appreciated.

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Anyone knows?

#### Cursor

##### New Member
To me, that just look like normal Volt meter to me.
And the 10.5V-12.5V - is refering that the battery is in good condition.
12.5V to 13.5V as weak, if you look futher down the meter screen, the bottom part is saying charging system. So it is measuring either the charger itself or the battery during charging. If charger is only delivering 12.5 to 13.5V, it is a consider a weak charger for a 12V battery.
Normally the charging voltage for a 12V battery is 13.5V to 15V, which is indicated as OK in the meter.
Anyway, if you measure the battery that had been on the shelf for a couple of days and still measure above 12.5V the battery are almost close to 85% capacity liao.

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#### vince123123

##### Guest
Thanks Cursor and Big Kahuna - I'll read the reference.

Cursor: Does this mean I can use a normal voltmeter to test whether a 12V battery is charged? So long as it reads above 12.5V I can accept from the battery store? I've read online about testing voltage under a load and no load - does this make a difference?

I think I now know - the "charging system" part is intended to test the alternator in the car....to see if it is working well enough to charge the battery. I don't require this feature, merely need to test the battery itself.

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#### vince123123

##### Guest
Big Kahuna, 9.12 says:

9.12. How Long Will a Deep Cycle Battery Last On a Single Charge?

Is this the correct one?

#### Big Kahuna

##### Senior Member
Big Kahuna, 9.12 says:

9.12. How Long Will a Deep Cycle Battery Last On a Single Charge?

Is this the correct one?
Yes if how long the bat can last you're after......but don't ask me how to calculate as I flung my math in high schewl :lovegrin:

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#### vince123123

##### Guest
Oh no actually I was trying to ask how can we test a battery to determine how fully charged it is.

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