Is my battery kaput?

[swee'pea99]

Ok, so 24 hours on from 11.13v, having done nothing but sit by the kerb, it's now on 10.39. Summat's awry...

I'm pretty sure it's not the alternator. The battery does charge up while it's being driven: my wife had to boost-start it before a half hour trip at the weekend, but not before the drive back. And the multimeter reading when the car's actually running is 14.73v. It just seems to be unable to maintain any kind of charge. And no, there's nothing obvious like a glove box light on.

If the charging circuit is working okay, and the car is only used occasionally, you could make sure the battery is fully charged and then disconnect it (assuming it won't cause problems with radio security codes or whatever) and then see if the car starts when you reconnect it a few days later. If so, the car is somehow draining the battery. If not, the battery is not holding charge and needs replacing.

I like it! Simple but effective! I shall try that when the timing works (my wife needs the car quite often at this time of year).

I think for the moment I'm going to wait till the solar panel and controller turn up, charge the battery, fit them, and pray. After that, who knows....?

 

[Gwylan]

Stick this in the circuit. But make sure you don't isolate the solar panel too
Ask why I might know this

https://www.ebay.co.uk/itm/36452597...dTVsK_rRQC&var=&widget_ver=artemis&media=COPY

 

[Cycleops]

I don't know what you think a solar panel will do.
Get a good auto electrician who can sniff out the problem as it's quite clear something is causing the battery to drain.

 

[CXRAndy]

It's most likely the battery is duff. As described, charge the battery off the car. Disconnect the charger,

It should hold 12.6 Volts after several days upto a week, easily. If it drops below 12.6 in that time battery is dead

 

[swee'pea99]

Stick this in the circuit. But make sure you don't isolate the solar panel too
Ask why I might know this

https://www.ebay.co.uk/itm/36452597...dTVsK_rRQC&var=&widget_ver=artemis&media=COPY

I've never heard of such a thing! Ok, so if I'm reading this right, if it turns out that there is some kind of parasitic drain (ie, if I disconnect a fully charged battery, it's still fully charged two days later), then I can effectively ringfence whatever that problem is by using one of these to disconnect the battery every time I leave the car, then reconnect when I need it. Is that right?

 

[swee'pea99]

I don't know what you think a solar panel will do.
Get a good auto electrician who can sniff out the problem as it's quite clear something is causing the battery to drain.

I'm sort of more-hoping-than-expecting that the charger will in effect counterbalance the drain, hopefully to an extent that keeps the battery usable.

I did take it to an auto electrician one time. I've no idea whether he was good - how would I tell? - but he came recommended on local forums, so...

Anyway, he did a full check, after he which he explained to me at some length and with the help of his multimeter how he knew that there was no parasitic drain. Needless to say, I understood none of it, but he seemed pretty adamant.

I did read somewhere

Carefully use the ampere mode in the multimeter by selecting correct probe cables and selector knob. Disconnect the car's negative terminal. Now bridge the multimeter wires between the negative battery node and the disconnected terminal. Note down the ampere passing thru multimeter. If it is approximately 0.05Amp then there is no parasitic draw. Otherwise, if it is above this value there is certainly an error in some circuit.

Does that sound right?

 

[CXRAndy]

I'm sort of more-hoping-than-expecting that the charger will in effect counterbalance the drain, hopefully to an extent that keeps the battery usable.

I did take it to an auto electrician one time. I've no idea whether he was good - how would I tell? - but he came recommended on local forums, so...

Anyway, he did a full check, after he which he explained to me at some length and with the help of his multimeter how he knew that there was no parasitic drain. Needless to say, I understood none of it, but he seemed pretty adamant.

I did read somewhere

Carefully use the ampere mode in the multimeter by selecting correct probe cables and selector knob. Disconnect the car's negative terminal. Now bridge the multimeter wires between the negative battery node and the disconnected terminal. Note down the ampere passing thru multimeter. If it is approximately 0.05Amp then there is no parasitic draw. Otherwise, if it is above this value there is certainly an error in some circuit.

Does that sound right?

I said earlier, it varies from vehicle to vehicle, less than 30 mA (0.03A) is normal.

10mA (0.01A) is perfect conditions

 

[MrGrumpy]

Ok, so 24 hours on from 11.13v, having done nothing but sit by the kerb, it's now on 10.39. Summat's awry...

I'm pretty sure it's not the alternator. The battery does charge up while it's being driven: my wife had to boost-start it before a half hour trip at the weekend, but not before the drive back. And the multimeter reading when the car's actually running is 14.73v. It just seems to be unable to maintain any kind of charge. And no, there's nothing obvious like a glove box light on.



I like it! Simple but effective! I shall try that when the timing works (my wife needs the car quite often at this time of year).

I think for the moment I'm going to wait till the solar panel and controller turn up, charge the battery, fit them, and pray. After that, who knows....?

Battery is shot ! You’re getting 14.0 odds when the engine is running so your alternator is all good . It’s just not holding the charge as cells kaput . New battery time .

 

[Gwylan]

I've never heard of such a thing! Ok, so if I'm reading this right, if it turns out that there is some kind of parasitic drain (ie, if I disconnect a fully charged battery, it's still fully charged two days later), then I can effectively ringfence whatever that problem is by using one of these to disconnect the battery every time I leave the car, then reconnect when I need it. Is that right?

In principle yes, but I'm not a car electrician.
Will mean that you have to reset the clock and maybe the radio. Might impact any anti theft.
But the car will be immobilised for sure.

 

[swee'pea99]

10.39 this morning, which means it hasn't dropped at all overnight. Which seems kind of odd..

Putting that to one side, I tried measuring the amps, as per "the multimeter wires between the negative battery node and the disconnected terminal", above.

Using these settings/connections...

...I got readings fluctuating between about 0.07 and 0.13.

First things first - was the multimeter set up properly? Ie, can I trust these readings?

If so, it seems clear that there is some kind of drain going on. It does seem odd to me at least that it should give such an inconsistent reading - between 0.7 & 0.13 is quite a disparity - but either way, assuming the MM is set up right and those are accurate readings, I clearly do have a problem.

Any thoughts much appreciated. (For the moment I've removed it for a recharge - 'er indores is going to need it at the weekend.)

Oh incidentally, I remembered to check the date stamp: July '22...so not even 18 months old yet.

 

[Fastpedaller]

Ere - have you nicked my meter!
10.39 is I guess the time of day rather than the voltage?

 

[presta]

...I got readings fluctuating between about 0.07 and 0.13.

You're on the 20mA range with the lead plugged into the 10A socket, I think you'll find it's not reading correctly.

 

[swee'pea99]

Should the lead be plugged into the middle 'ole? Is the 20mA setting right? Forgive the dumb questions but I'm feeling my way here, as you'll have gathered .

In other news, I took the battery out on Thursday and recharged it, since when I've been keeping an eye to see what if anything will happen to the charge with the battery left entirely to its own devices - no connections, no nothing. With the upshot:

6pm (immediately post-charge) 13.63

Now I always assume that I can't get a good reading till it's calmed down a bit after all the tizzy of a charge, so I left it for a while, then got:

7pm - 13.34
10.30 - 13.28
12.30 - 13.26

next day:

11am - 13.19
2pm - 13.16
10pm - 13.14

This morning:

10am - 13.10

So, in c36 hours it's come down from 13.34 to 13.10, without any connection to anything. Would that suggest a battery in good health? Or a battery flaw? Or doesn't it tell anything?

Thanks for your thoughts.

 

[CXRAndy]

Should the lead be plugged into the middle 'ole? Is the 20mA setting right? Forgive the dumb questions but I'm feeling my way here, as you'll have gathered .

In other news, I took the battery out on Thursday and recharged it, since when I've been keeping an eye to see what if anything will happen to the charge with the battery left entirely to its own devices - no connections, no nothing. With the upshot:

6pm (immediately post-charge) 13.63

Now I always assume that I can't get a good reading till it's calmed down a bit after all the tizzy of a charge, so I left it for a while, then got:

7pm - 13.34
10.30 - 13.28
12.30 - 13.26

next day:

11am - 13.19
2pm - 13.16
10pm - 13.14

This morning:

10am - 13.10

So, in c36 hours it's come down from 13.34 to 13.10, without any connection to anything. Would that suggest a battery in good health? Or a battery flaw? Or doesn't it tell anything?

Thanks for your thoughts.

The only true way to say if a battery is ok, is to do a load test, putting the battery under heavy load. It should be able to put out nearly the cold cranking amps(CCA-written on battery)) for a short period.

However a battery that stays above 12.6V for a long period would be a good indication of being good. The battery will fall away from above 13V because that is peak voltage charge. Nominal is 12.6V. If its still above 12.6V for a few days and it spins the engine over quickly when you re install it-good battery.

Sluggish turnover indicates worn battery.

Be very careful when measuring inline current with a simple meter that requires correct lead position for low amperage readings. Cars can draw several amps for a short period whilst going into sleep mode. If you have you meter set on the wrong scale it could either blow a fuse(in the meter) or fry the meter.
Never test in line current when the car is running or about to be started, many, many tens to hundreds of Amps can be drawn and will literally set your little meter on fire.

The only way to measure high Amps safely is to use an Amp clamp.

 

[presta]

Should the lead be plugged into the middle 'ole? Is the 20mA setting right? Forgive the dumb questions but I'm feeling my way here, as you'll have gathered .

Red lead in the left hole for the 10A range, middle hole for everything else. If you value your meter you'll start with the 10A range first until you know the current is below 200mA. If for any reason you see it's several amps, pay heed to the 10s time limit.