Hi,
I was just checking a battery I have and it says it has 10.55v on the multimeter is that enough to crank a car ?
or does it need a charge ... I was thinking if I put it back in the car and take it for a drive the alterntor might bump it up a bit or is the alternator more of maintaining instead of charging ?
Thanks
10.55v means that one cell is kaput. It may still have enough go to start the car. Try it, a half hour run should be enough to find out whether it will take a charge or not, probably the battery is past it though.
The alternator is more than capable as a recharger, that is its job!
Hmm thanks for that info Mrcheerful. Its a 9/10 month old VARTA calcium battery. The door light somehow stayed on in my car which overnight drained the battery so leaving me with no power. I later found out at the garage the something in my door lock module went doolally and caused the light to stay on permanently. I had another battery kicking about which I used which got the car started up fine and have been using it since. But I thought I paid £65 for this battery it must be salvageable with a charge or something. So am looking at buying a charger that I found on the argos website
When I checked the battery with a multimeter when I first noticed I had no power to my car which was when I tried to open it with the remote central looking remote saw no door led. Got in tried to start it and nothing. So I put a multimeter across the battery which read 0. Today I thought I'd double check it and its coming up at 10.55v and has been sitting my stock cipboard for about a 9 days. What I was hoping was that if I charge it with the above charger I'll get it back at 12v +
What do you reckon ?
To add its a : VARTA blue dynamic battery 12V 44Ah
Surely you can get near any open circuit voltage depending on the state of charge? But if that is the open circuit voltage it's pretty well flat -
10.8 is regarded as the minimum.
Possible if a cell is faulty but can still pass enough current from the other good ones - but I wouldn't bet on it.
Sometimes a higher voltage (not current) than the alternator can give can partially resurrect a knackered battery. But I wouldn't bet on it. ;-)
My mate was warned when purchasing a new alternator for an old mini that something (diodes or voltage regulator I guess) couldn't take the current drawn by a totally flat battery, and that the alternator would die if he tried...
(Which could well explain how the original alternator failed!)
You could try charging it, if it has only gone flat due to the door light being left on. You might be lucky.
Someone less honest might keep quiet about the door light, and get it replaced under guarantee. Saying it just stopped working for no apparent reason. Not that I'm suggesting you would do that of course. :-) Mike.
generally it is almost 2.2 volts per cell (12.5 -12.7 is full charge), so
10.55 would point to one cell contributing nothing at all. 12.3 or so is flat.
:)
In which case you take it back & complain, almost any old mini could sink more current than the alternator could supply.
12.3v flat? No.
That's patently rubbish. Flat batteries are a fact of life - if they could damage the alternator it is not fit for the purpose.
Perhaps, but it was a mini...
yes. (assuming it is a good battery, physically)
It depends on how "flat" is defined, surely?
12.3v means there is some charge in the battery; it doesn't necessarily mean there's enough to start the car.Chris
the 12.3 figure is the one given by a very espensive electronic battery tester by TIF instruments, 12.3:needs recharge, 12.4:50 percent,
12.5:75percent, 12.6 - 12.7 is fully charged, anything over is a surface charge which should be lost before rechecking. Over the last 20 years or so I have found this to be very accurate on all car type batteries, it can then load the battery according to capacity and give a guide to condition, also very easy to use to check voltage drop under load on battery connections, leads, earths etc.
Don't care how expensive a tester it is - open circuit voltage only gives a *very* rough guide to state of discharge. The only accurate way is to measure the SG. And 'needs recharge' isn't the same as being flat.
the tester is to measure the state of the battery, the second stage of testing is irrelevant if the first stage shows it needs a charge.
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