12 replies to this topic

[dreadster]

Hi Everyone

The battery on my 96 SPI is going flat after a couple of days standing. I have had a multimeter on the battery and there is a 40 milliamp drain. I removed the fuses one by one to narrow down the issue. I have the 24 black fuse box and when I remove fuse 7 the drain drops to almost zero.

I have looked up what this fuse is for and the manual says "headlight flasher, horn, anti-theft alarm'. Surely the alarm shouldn't be draining that much from the battery?

I have done some research online and most stuff says that 0-15 milliamps is about standard, over 25 is unacceptable.

Any one any ideas/thoughts?

Cheers
Darren

[mini13]

that sounds about right for an alarm,

at that drain you should get a good couple of weeks before it starts getting low.

[tiger99]

I agree. 40mA times 24 hours is 0.96AH, and your battery might be around 40AH, depending on type, so it would only be half drained in 20 days. Certainly good for starting for a couple of weeks, even if the battery has lost a bit of its capacity.

I suggest that you connect the multimeter and watch it for a couple of minutes to see if the alarm might be drawing the occasional peak of higher current.

[dreadster]

Thanks for the info guys. I have tried leaving the multimeter connected for a while and if anything it slightly drops down every now and again.

I wonder if the alternator is not working to its full capacity, so the battery is getting run down when I use it. I will give this a test next.

[mini13]

yep measure the voltage across the battery, if your seeing high 13's to low 14's then its charging,

at that point let the battery flat out a bit (if it isnt already) dis connect the battery and put it on a battery charger with a meter and see what current it takes.

somtimes you get batterys that just dont want to take a charge, ie if you leave them on charge they'll charge up gradually,

[4V8s]

either that or your battery has gone duff. As others said, 40ma drain is normal. measure voltage accross battery when running, if over 13-13.5v, especially with a little revs, then alernator is likely OK. If the battery wont hod charge, or after stopping the car after a good run the battery voltage is well below 12.6v (fully charged) say an hour later, then id say you haave a duff battery.

[KernowCooper]

13.7-14.2v is the normal voltage regulator setting, and 12.65v if fully charged

[dreadster]

Just done a test on the battery to see if its charging.

Reading with the car off was 12.7

With Engine running it was 13.9 regardless of RPM

If I turn on the headlights it dropped to 13.5. With the radio, lights and fan it was 13.2.

I could also actually hear a noise coming from the alternator when I turned on the lights etc. Are these readings too low?

[KernowCooper]

Alternators noise when under load which could be the fan belt in the pulleys unless its a bearing under load ?, 13.9v is within the limits of a regulator and the more you turn on the lower the voltage will be and 13.2/13.5v is still charging the battery under a high current drain.

[Oggyp]

Sorry can you confirm 0.400 amp or 0.040 amp? if its 0.400 amp then it certainly isnt ok!

[dreadster]

Alternators noise when under load which could be the fan belt in the pulleys unless its a bearing under load ?, 13.9v is within the limits of a regulator and the more you turn on the lower the voltage will be and 13.2/13.5v is still charging the battery under a high current drain.

So the drain is too small to flat the battery in a couple of days and the alternator is charging the battery when in use. Might be a duff battery then, I will keep an eye on that.

Its just annoying as its a weekend car and if I leave it 5/6 days its completely flat. I do have a trickle charger I can use though to keep it topped up. At least through this process I have learnt a bit. Thanks for the help

Sorry can you confirm 0.400 amp or 0.040 amp? if its 0.400 amp then it certainly isnt ok!

Its defo 0.04 amps, not 0.4 amps. If I put the interior light on it goes up to 0.08 amps. This all seems correct/normal.

Edited by dreadster, 10 February 2013 - 04:18 PM.

[tiger99]

There is something wrong with your measurements, because an interior light is usually 2.2 watts, which is 0.18A, or 6 watts, which is 0.5A.

[dreadster]

There is something wrong with your measurements, because an interior light is usually 2.2 watts, which is 0.18A, or 6 watts, which is 0.5A.

Sorry, I meant 0.80 amp with interior light on. I'm new to all this so learning as I go.

Here are photos of my test.

Everything switched off:



Interior Light on: