Reply to: Any diy car mechanics here?

[Uncle Albert]

Bit crude but would do the job.

https://www.ebay.co.uk/itm/264539496409

That's what I use on my "summer" car. It's quite happy spending 6 months of the year with no battery power. It's a 27 year old car though.

[woody1]

My 97 Corolla had a permanent drain of 600mA with everything "off". So I designed a thing that charged the battery back to 13.8V when it had droped to 12.8V or so, mostly so I didn't have to figure out what was actually wrong with the thing.

It worked well for years until the battery eventually died.

14Ah per day. It would have been touch and go leaving that at an airport if you went on holiday, even for a long weekend.

[DoctorStrangelove]

Modern cars I'd agree. A 2007 Audi? I doubt it. Hardly bristling with high end tech. I'd expect you could leave that for weeks and shouldn't have a problem.

My 97 Corolla had a permanent drain of 600mA with everything "off". So I designed a thing that charged the battery back to 13.8V when it had droped to 12.8V or so, mostly so I didn't have to figure out what was actually wrong with the thing.

It worked well for years until the battery eventually died.

[woody1]

Out of curiosity, I put the trickle charger on a mains power meter. It's drawing 2W, which works out at 2*24*365/1000 = 17 units/year, which @34p/unit is £6/year.

For six quid a year, I think I'll stick with what's been working for over 10 years.

[ladymuck]

Modern cars I'd agree. A 2007 Audi? I doubt it. Hardly bristling with high end tech. I'd expect you could leave that for weeks and shouldn't have a problem.

This is why I like my old banger. Just enough electronics to be functional.

[northernladuk]

Some cars don't appreciate being without power for several days - radios and other bits of electronics may be OK for a couple of days, but might get upset if left much longer.

Modern cars I'd agree. A 2007 Audi? I doubt it. Hardly bristling with high end tech. I'd expect you could leave that for weeks and shouldn't have a problem.

[woody1]

Some cars don't appreciate being without power for several days - radios and other bits of electronics may be OK for a couple of days, but might get upset if left much longer.

True.

The other slight snag with my car is the battery is in the boot, and the boot can only be opened electrically (key fob or switch on driver's door), so I'd have to clamber over the rear seats to switch the battery back on.

[WTFH]

Bit crude but would do the job.

https://www.ebay.co.uk/itm/264539496409

Some cars don't appreciate being without power for several days - radios and other bits of electronics may be OK for a couple of days, but might get upset if left much longer.

[woody1]

Bit crude but would do the job.

https://www.ebay.co.uk/itm/264539496409

[woody1]

Next test to do to find the drain is to remove the fuses one at a time, and find out removing which one stops the drain.
Then trace what is connected to that.

The other thing you can get, rather than plugging in a charger, is an AA solar panel charger (if your car is parked somewhere that you can get sunlight): https://www.amazon.co.uk/AA-50601146.../dp/B00AC1LLQY

Don't go for other brands or models, this one works. Plug it in to your EOBD port and leave the panel on your dashboard, or clip it to your battery if that is easier.

Yes I guess I ought to try and get to the bottom of it.

I tried a solar panel many years ago, and it just about kept the battery charged in the summer but not over the winter. Obviously it would stand a better chance if I could get the drain down.

I suppose the other option would be a massive switch* between the battery and the car, so I can disconnect it when I'm not using it.

*and it would need to be massive to cope with the 200A draw from the starter!

[WTFH]

Next test to do to find the drain is to remove the fuses one at a time, and find out removing which one stops the drain.
Then trace what is connected to that.

The other thing you can get, rather than plugging in a charger, is an AA solar panel charger (if your car is parked somewhere that you can get sunlight): https://www.amazon.co.uk/AA-50601146.../dp/B00AC1LLQY

Don't go for other brands or models, this one works. Plug it in to your EOBD port and leave the panel on your dashboard, or clip it to your battery if that is easier.

[woody1]

Do you turn the radio/CD OFF before you get out of the car, or does it automatically come on when you start the car?

I never use it; it's always turned off.

From what I've read, on newer cars, the normal parasitic drain is about 50-85mA. However, even 50mA adds up if a car is stood for a long time:

1 week = 7 * 24 * 0.05 = 8.4Ah
2 weeks = 16.8Ah
4 weeks = 33.6Ah

-------------

Starter motors draw about 200A and, if cranking takes 5 secs, then that's
200 * 5 / 3600 = 0.28Ah

A parasitic drain of 50mA over 24 hours is four times as much!
0.05 * 24 = 1.2Ah

[WTFH]

An old CTEK one.

What's ICE? Of the others, only alarm/immobiliser.

I've had this parasitic drain pretty much since I got the car 14 years ago, and I've just learned to live with it. If I used the car more regularly I doubt I'd even be aware of it.

It's ok if I leave the car off the trickle charger for a week, but much longer than 10 days and I'll probably have trouble starting it. And of course it's not good to let lead acid batteries run down.

Do you turn the radio/CD OFF before you get out of the car, or does it automatically come on when you start the car?

[woody1]

ICE in this context would be "in-car entertainment"

It's quite common for an old stereo to develop a cabling issue over time and generate a low level drain.

In which case, yes, it's got a radio/CD player.

[ladymuck]

ICE in this context would be "in-car entertainment"

It's quite common for an old stereo to develop a cabling issue over time and generate a low level drain.