battery losing charge

[280bod]

Anyone know how to check why a battery would be losing its charge.
Seems to charge OK with accumate and hold charge out of the car.
If charged can start and run engine and be showing full voltage, but then will be dead after about a week when left fitted in the car.
Might be time for new battery but would like to check if any other problem thats draining it first before buying one.
Thanks

[jmorgan]

Me personally, with everything turned off and sure what you are doing, put an ammeter in circuit with the battery. Some draw expected for clocks and alarms etc. Over a certain amount and its pull fuses time to see what circuit is drawing current.

Also, is there a charge going in? Does the voltage rise when the engine starts? Think mine does around 14 volts on tickover. That is a volt meter properly applied.

Usual caveat, careful what you are doing around the battery etc, not sure, get someone who does. Not meaning to teach the egg sucking and all that but it is sort of straight forward.

OH, and can you disconnect everything without affecting equipment in the car? Radio codes and all that.

[dwgriffith]

Had this on the 350i once, boot wasn't shut fully so the interior boot lights were on for a week, this was enough to drain the battery.

[Waynester]

As above ^ try and ensure nothing is on drawing current that shouldn't be.

It might just be a dodgy battery though. Had one of them myself. Bought a new one and no problems.

[eesbad]

Had one the other week - I brushed past the silly interior light under the dash when I was turning my fans off (manual override switch) after a Sunday hoon, and turned it on. Didn't see as it was a bright sunny day... Two days later - flat battery! Have removed the bulb now!

[tempus]

As our toys get older electrical gremlins get more common,one way round it is to fit a battery isolator switch,this has a few plus points,can check if there is any battery drain,car does not set on fire,thieves are thwarted,cost very little,one day i will get round to it,but not today,the sun is out! Tempus

[leorest]

Are there any old immobilisers/alarms or remnants thereof?

[Grady]

My wedge came with one of those little battery disconnects that clamp on the post and has a black thumb screw for loosening and breaking the connection. (They are advertised all over.)

Don't know if it was mine or if it a general thing but I had nothing but problems with it losing the connection. I tightened it, copper coated it, etc. and finally binned it.

If I had to do it again, I'd look for a marine or RV cut-off switch.

[Terence]

When I bought my 350i it had just had a new battery because the previous one kept going flat. I used to keep the car outside and if the weather was wet the new battery would be flat in a couple of days. I put the vehicle on a ramp for a general checkover and noticed that the relatively new stainless manifold looked as if it was touching the main live terminal on the rear of the starter motor. Obviously it was not actually touching but you would have had a job to get a fag paper between the terminal and manifold. I shortened the the threaded terminal to give a couple of mm clearance and that seemed to cure the problem. I think what was happening was when it rained the water that collects in the battery tray area was running down onto the manifold then down the pipe till it bridged the gap to the starter. Bit of an unusual one this but I though I would share as I have been absent for a while. T

[280bod]

Thanks guys, never really got on with car electrics but theres a few things I can check there

[honestjohntoo]

280bod said:

Thanks guys, never really got on with car electrics but theres a few things I can check there

If there is no current drain as explained already then your battery is shot. Read all about it and how to test for probs here:

http://www.vintagemodelairplane.com/pages/Download...

Then buy the best one you can afford.

[jeff m]

Fully charge battery, leave for three hours, then use a load tester.

[dickymint]

Could also be the diode pack gone tits up in the alternator. This will allow "reverse" current flow and drain your battery. Sometimes you can tell if this is happening when the ignition light stays on (dimly) with the ignition off.

[rev-erend]

Also check the headlight motors are cold .. if one is warm then it's still running ..

[Jon S]

Just a thought, cos it happened to me. I had a problem with my headlight motors, so I wound the pods up manually and took the fuses out, so I could still use the car. A week later the battery was flat. Never had a problem with it before. So checked no lights were on in the boot etc, and charged the battery up and another week later it was flat again. Thought the battery was knackered so bought a new one. A week later the new battery was flat as well. Eventually when I fixed the lights and retracted the headlight pods, the problem went away. The car can be left for a few weeks and still start with no problems. There must be a limiter switch or something on the headlights that was draining the battery even though the fuses were removed. weird!

[General Zod]

This seems like an appropriate thread in which to ask this question.

Noticed me battery has been draining a bit recently, so was doing a few checks.

Why do my headlights come on when the ignition isn't on? I suspect they are the cause. Something isn't fully off when then ignition is off

[mrzigazaga]

Hi Rory....

I have had to remove the bulbs from my interior lights as the ones I had under the 280i dash kept getting knocked by my knee and then I would cover the car for a couple of days and then come out to a dead car...The ones on the 350i were staying on as the pins that turn them off when the door was closed were not being pushed in enough....Partly because the cover on the large metal insert that it rests against had come off...Other than that alarms can kill the battery...


Ziga

[v8s4me]

I have exactly this problem at the moment! And...

Jon S said:

............I had a problem with my headlight motors ...

One of my pods is sticking and not fully retracting. So could this be coincidence, or would the pod motor continue to draw power if it hasn't seated fully?

Jon S said:

...........so I wound the pods up manually ...

How does one do that?

I have a current tester and tomorrow's job is to attach it to each circuit in turn (with the ignition off) and see if any of the circuits are drawing current. I've got an inkling the instruments are connected to a permanent live so that might be the culprit.

[adam quantrill]

I once had the headlamp problem but definitely a one-off. Luckily it was at night and I had only left the car a half hour or so. It wouldn't turn over right away but after fixing the lamps I left it 15 minutes and then there was just enough juice to fire her up.

Motto - always park on a hill!

[General Zod]

mrzigazaga said:

Hi Rory....
I have had to remove the bulbs from my interior lights as the ones I had under the 280i dash kept getting knocked by my knee and then I would cover the car for a couple of days and then come out to a dead car...The ones on the 350i were staying on as the pins that turn them off when the door was closed were not being pushed in enough....Partly because the cover on the large metal insert that it rests against had come off...Other than that alarms can kill the battery...
Ziga

Cheers Mark. I did suspect those wee buggers too, but they are behaving which is good.

Are your headlights supposed to come on when the key isn't even in the ignition? I think they are the culprit, also because to get them on you have to flick the switch on, then off, then on again. Maybe to get them off I have to switch them off, then on, then off again! I'll try this. If it works I'll just do it- I call this "Character".