Battery Seems Dead, But Showing 12V?

[Goliath 94]

I have a strange problem with the battery on the 104.

 

It is showing 12.4v using the multimeter on the terminals, it shows the same on the starter and earth point so battery connections are good. However it won't turn the car over, it managed one really slow turn when I tried it just now.

 

Any ideas what the problem is? In my mind 12.4v should be enough to turn over for several seconds at least. When jump leads are connected (showing ~14v) it will turn over fine, as it should with a fully charged battery.

 

So is the battery dead? Or does it need some distilled water?

[EdCherry 34 1 Cars]

Sure its not the starter or the wiring rather than the battery?

[Anthony 1,003]

Is the connection between the battery and the terminals good?

 

If this is poor, it can look fine until you try and crank the engine over, whereby it can't pass sufficient current and won't crank. Putting jump leads on gets around the issue, as you're putting the jump leads straight on the terminals, thus making a good circuit to the battery on the jump start car.

 

12.4v is a bit low for a good battery though - should really be 12.7v, so might be that one of the cells is on the way out which of course won't help.

[Alastairh 47]

What is the voltage as you trigger the starter?

[Daviewonder 533 3 Cars]

My battery was doing the same when I had a dodgy cell.

[Goliath 94]

Sure its not the starter or the wiring rather than the battery?

 

That was my first thought but the fact it seems to work fine with jump leads connected ruled this out in my mind!

 

Is the connection between the battery and the terminals good?

 

If this is poor, it can look fine until you try and crank the engine over, whereby it can't pass sufficient current and won't crank. Putting jump leads on gets around the issue, as you're putting the jump leads straight on the terminals, thus making a good circuit to the battery on the jump start car.

 

12.4v is a bit low for a good battery though - should really be 12.7v, so might be that one of the cells is on the way out which of course won't help.

 

I see what you mean, basically a dodgy terminal connection could still show 12v at the starter but can't deliver the 'ampage' when put under load? I will go see if my multimeter has an 'ampage' setting!

 

I did clean up the terminals just yesterday so will be a bit miffed if that is the problem!

[Anthony 1,003]

I see what you mean, basically a dodgy terminal connection could still show 12v at the starter but can't deliver the 'ampage' when put under load? I will go see if my multimeter has an 'ampage' setting!

No! Don't do this - there is no way a multimeter will pass sufficient amps to crank the starter and you'll just kill the meter (or pop the fuse if you're lucky)

 

Do you not have another battery kicking around that you could try? As said. 12.4v is a bit on the low side for a healthy battery.

[Obey_R 23]

A battery can still show 12-13volts but have no CCA (cold cranking amps) which is the power it has to turn the starter. If you can get it to a motorfactor and get them to test it, they can show you the CCA.

[Goliath 94]

No! Don't do this - there is no way a multimeter will pass sufficient amps to crank the starter and you'll just kill the meter (or pop the fuse if you're lucky)

 

Do you not have another battery kicking around that you could try? As said. 12.4v is a bit on the low side for a healthy battery.

 

I don't think I worded it correctly, I meant to say I will go and see if I can measure what amps the battery is showing, if that is possible with my multimeter. I wasn't going to try and bridge the battery to the started or anything!

 

The battery I am using is my spare, the one that came with the car is completely flat (not sure if dead) and I have no way or charging (have asked for a battery charger for xmas!), the neighbours get a little peeved if I leave the car running all night with a battery hooked up with the jump leads to charge it!

 

I did have a brand new battery but some pikey nicked it!

 

A battery can still show 12-13volts but have no CCA (cold cranking amps) which is the power it has to turn the starter. If you can get it to a motorfactor and get them to test it, they can show you the CCA.

 

Ok thanks, will take both batteries to my local and see if they can help.

[jackherer 543]

You were perfectly clear and Anthony understood what you meant. To measure amps with a multimeter you need to put it in series with the load, so you would take the battery terminal off and bridge the gap between the terminal and the battery post with the meter, I'm sure you can see why that would be a bad idea, the multimeter leads alone would melt if you tried to put the starters amperage through them but long before that the meter would be toast (or just a blown fuse if you are lucky).

 

If you really want to measure the current of a starter you need some sort of clamp meter that goes around the cable you are measuring.

 

But all you need to do is answer Alastairs question (What is the voltage as you trigger the starter?) as voltage drop will tell you all you need to know about current flow without actually measuring it directly.

[cheesegrater 43 1 Cars]

I don't think I worded it correctly, I meant to say I will go and see if I can measure what amps the battery is showing, if that is possible with my multimeter. I wasn't going to try and bridge the battery to the started or anything!

 

The battery I am using is my spare, the one that came with the car is completely flat (not sure if dead) and I have no way or charging (have asked for a battery charger for xmas!), the neighbours get a little peeved if I leave the car running all night with a battery hooked up with the jump leads to charge it!

 

I did have a brand new battery but some pikey nicked it!

 

 

 

Ok thanks, will take both batteries to my local and see if they can help.

Voltage is measured in parallel and current in series so you'd have to stick your probes on the battery and then your + lead which as you can tell isn't going to end nicely. If you have an amp clamp then you would be able to measure the current draw.

[Cameron 16]

What is the voltage as you trigger the starter?

 

Why has everyone just ignored this post!? This should be the second step of battery fault finding, surely everyone knows that?

 

1 - connect multimeter to battery

2 - observe voltage when cranking

 

Unless your battery is absolutely dead it will pretty much always show around the 11-12V mark when sitting idle (ignition etc off) so it's not an indication of battery charge. When you go to turn the engine over the voltage will plummet, and you typically need at least 9V when cranking to start the engine.

 

Don't waste your time (and multimeter) checking current, or anything else for that matter, until you've checked the cranking voltage.

[pug_ham 244 3 Cars]

As already suggested, get the battery properly load drop tested & I expect you'll find it has a dead cell & fails when you put the cranking load on it.

 

g

[jackherer 543]

Why has everyone just ignored this post!?

 

Why have you ignored my post?

 

But all you need to do is answer Alastairs question (What is the voltage as you trigger the starter?) as voltage drop will tell you all you need to know about current flow without actually measuring it directly.

 

I agree it is odd that most people are ignoring it

[Cameron 16]

I did spot yours, but it was buried in the middle of a big discussion on testing cranking amps so felt it necessary to reiterate. With any luck people who skim this thread for replies won't miss my one and spend their afternoon killing multimeters.

[MrMemzi 12]

Id left my 205 for around a month (removed battery obv). I fired her up again today and had a sticky starter and alternator! Seemed like the battery was dead as it wasnt turning at all. But with the magic power of an angry key turn it started. So maybe you need an angry key turn