Battery drying out

[newsh]

Recent topic ;-)

For anyone needing a switched power feed for the "Acc" connection on the head unit.

There is a thin red wire on the back of the ignition switch that gives 12V as soon as the key is turned and stays powered up until the key is removed completely.

[Billman]

Recent topic ;-)

[Billman]

I did it. It was very easy! Thanks!

The total current draw dropped from 0.1A to 0.08.

Is this value acceptable? I think I can't do anything more except removing the radio.

It has 0.06A draw by itself and the rest of the car (incl. alarm system) draws the remaining 0.02A.

[newsh]

Have you definitely got the switched and unswitched the right way round? It doesn't seem to have dropped enough.

[Billman]

Yes definitely. The permanent is clearly marked. Even if I measure the current on the fuse of the permanent line I see 0.06.

[driftin jo]

You don't want more than .05 Max preferably 0.03 mine is 0.035

[Billman]

I must connect another radio maybe to see what is it drawing. I can't find any other solution....

[newsh]

Yes, I think mine is 40mA

[driftin jo]

Yes, I think mine is 4mA

Surely you mean 40mA

[driftin jo]

The other thing to note is that when testing cars for current drain you must wait for them to go to sleep, a lot of cars keep things live such as electric windows , sunroof etc for 2 mins after the key is removed and some other things like after market alarms and stereos may also drain for a few minutes before settling off to sleep properly . Last year I tested a mates golf for battery drain and when the doors were locked and the alarm armed it would drain 0.2 A (200mA) for ~ 2 mins and then it would drop back to ~50mA when it went to sleep.
I have heard of some car systems (not S2) that you needed to leave for 40 minutes before you could
see the proper resting current drain.

Its also worth noting that if you have had you charge you battery from dead more than a few times it will have lost a huge amount of it's stated capacity.
Car batteries are not designed to be drained low at all and every time they are drained completely you loose about 5-7 % of there capacity.

[Billman]

I have a new battery now...gonna make a measument of total current flow with ign off for over an hour. I dont think though that these older cars will need more than a couple of minutes to show the correct drain.

[newsh]

Surely you mean 40mA

Er yus I did Guv


And you're correct, if I sit in he car with the meter in line with the battery lead I think I see 80-100mA, then if I lock the doors by pushing one of the buttons down, about a minute or 2 later there's a click and the current drops to 40mA.