what voltage should a battery show on a multimeter?

smarjoram · smarjoram's Garage

I've been having some starting problems this winter.

I gave the battery a charge - haven't reinstalled it yet.

When charged it read 12.57V and since then it's been losing 0.1V each day and this morning I tested it and it had lost a whole volt! - it now reads 11.4V

Is it going to level out at a reasonable charge? Has it gone too low already? Is it time for a new battery?

Thanks for any advice.

Stefan

Zendalar · 01-10-2003, 01:23 AM

Without load, it should hold the charge for longer time. Is the battery maintenance free? If not have you checked the electrolytes (added distilled water)

nick-moss · nick-moss's Garage

Hi Stefan

The battery should hold 12.5V for several weeks. Does the battery loose it's voltage if it's diconnected from the car? If so, the battery is due for replacement (by the way how old is it?) If not, there is a drain in the electrical system, I would suspect the alarm or possibly the radio. You may need an auto electrician to trace anything else!

RoninLB · 01-10-2003, 01:30 AM

what I do to check voltage after a full or trickle charge is turn lights on for a few seconds to remove a distorting surface charge.. then I get a clearer picture.. kinda like cleaning eyeglasses, LOL...............Ron

smarjoram · smarjoram's Garage

Thanks alot for the speedy replies...

The battery has been sitting in my house - not connected to anything. It's difficult to say how old it is but it's maintenance free and looks like quite a good one.

The voltage now is close to what it was when I removed it from the car because it wouldn't start. It looks like I might have to get a new one then.

How would I measure how much power the alarm is using? (or how much power is being used when I leave the car) Everything was going fine untill I had that fitted.

Roy M · 01-10-2003, 02:03 AM

Stefan

Disconnect your -ve post and put a multimeter between the disconnected post and the battery - you should get a drain but it should be in the 200 ma range (rough guess) If it's more than that pull the alarm fuse and see if it drops.

Could well be just a bad battery though - take it to anybody that sells them and have it load tested - a decent battery is less than the price of a tank of fuel and is well worth it.

Cheers

RoninLB · 01-10-2003, 02:06 AM

Quote:

Originally posted by smarjoram
it's maintenance free and looks like quite a good one.

(or how much power is being used when I leave the car) .

not clear on what battery you have, but a gel battery has a technique to revive them.. do a search on their site.. and a dig volt meter is used to measure acurate voltage system draw at shut down.. you can measure total system draw and individual circuits.. it's easy ...................Ron

Zendalar · 01-10-2003, 02:06 AM

You could try and get the battery tested. At least here Finland they don't charge anything for it. Besides new batteries won't cost more much more than 50$ (could be less)

smarjoram · smarjoram's Garage

So it's not worth paying £60 ($100) for the Bosch Silver ones at type-911 then.

Any recommendations on which battery to go for in the UK?

Zendalar · 01-10-2003, 02:54 AM

Well, I bought Varta battery (65Ah) which had pretty much the same outer dimensions than one I had before for 50$

Last week I changed that battery to my "winter" car. This morning it was -30 celsius outside. I started my car with that battery and my car was without block heater whole last night. Lets just say that there was enough power in this battery.

When buying a battery, buy "decent" battery, just don't buy those with no-name.