Electrical issue

[Cooper1275]

Hi guys,

Hoping someone with a bit more knowledge on this can give me some insight.

The battery on my mini started draining flat in between weekend drives (so 5-7 days) a few weeks ago, something it had never done before.

I checked that it was being charged correctly and that alternator was working, all good there.

had the battery tested and there was a weak cell so replaced it with a brand new Willard.

Thought I had it solved, but same problem.

So far I have checked that there isn't anything obvious draining the battery and now running out of ideas.

is it possible that a defective relay could cause this? looks to me like the relay for the hooter (and wipers?) is not working because fuses are not blown and hooter/wipers have stopped working but not sure I see how that would drain the battery if the  hooter/wipers aren't operating?

Another option that Google suggests is that the main positive cable from the battery to the solenoid is earthing on the body from wear and tear somewhere (often in the bend up into the engine bay apparently) in my mind that would cause a dead short and heat/sparks though...will check that tonight too for the record.

Any other tips on what to check?

Regards, Craig

[Tiaan]

The alternator can also drain the battery if it stays on (energized).
Then the coils in the alternator keep on draining power from the battery.

[Cooper1275]

The alternator can also drain the battery if it stays on (energized).
Then the coils in the alternator keep on draining power from the battery.

Thanks Tiaan,

I will check out that possibility too.

[Leykor]

Hi, please someone correct me if I'm wrong. I would get hold of a electrical multimeter, set it to measure small current. Connect it between the battery and positive cable and see what current is flowing.
If there is current is means the battery is draining. I would then remove 1 fuse at a time and find which circuit is causing the drain.

Cheers

[Boyscout]

Leykor. That is exactly what I would do.

[Tiaan]

That is correct yes.

http://www.wikihow.com/Find-a-Parasitic-Battery-Drain (Ignore the ECU sleep mode thing, a Mini doesn't have an ECU)

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Also, I don't know if you have done it already, but to give the battery a better charge voltage, run a battery cable directly from the battery negative (connecting together with the original negative wire on the battery clamp) underneath the car up to the alternator mounting on the engine block.
This will give a direct charge wire for the battery so the charge doesn't have to travel through the car's body to reach the battery.

[Cooper1275]

Hi, please someone correct me if I'm wrong. I would get hold of a electrical multimeter, set it to measure small current. Connect it between the battery and positive cable and see what current is flowing.
If there is current is means the battery is draining. I would then remove 1 fuse at a time and find which circuit is causing the drain.

Cheers

A very logical comment, except that my car is a '63 and only has the two fuse box

I am replacing relays today get the hooter/wiper working and then will test if there is still drain in which case it is likely a faulty alternator.

[Leykor]

Same would still apply, I.e. measure current draw and remove components until u find the fault. The components could be a fuse or a wire being pulled off the alternator etc.

[Tiaan]

Do the whole exercise first and see if there is a parasitic battery power drain.
If there is then disconnect all the wires on the alternator.
If it still exist then start pulling the relays and fuses out.
If you still can't find the culprit, then search for the main point where all the positive wires for all the connections come together and disconnect it there wire for wire till the power drain drops. The wire that made it drop must then be traced to see what it is.
Also disconnect your ignition coil, if it stays power on it can also drain a battery as it stays charged.

[Cooper1275]

Do the whole exercise first and see if there is a parasitic battery power drain.
If there is then disconnect all the wires on the alternator.
If it still exist then start pulling the relays and fuses out.
If you still can't find the culprit, then search for the main point where all the positive wires for all the connections come together and disconnect it there wire for wire till the power drain drops.  The wire that made it drop must then be traced to see what it is.
Also disconnect your ignition coil, if it stays power on it can also drain a battery as it stays charged.

perfect. Thanks!

Really appreciate the help and advice guys.