Battery draining overnight

bman

Hi,

I have a 95 Lancer that is draining the battery when left sitting overnight. I have tried replacing the battery with batteries from other cars but this doesn't solve it. I checked what power it is using when the car is off (including lights, etc.) using an ammeter and found that it is drawing 10mA. This seems pretty normal from what I've read. By removing fuses I have found that this 10mA is mostly taken by the clock. Even at 10mA it should still take weeks or longer for the battery to drain.

Also, when I jump start it, then drive it for a bit, turn it off and then start it again it has no problem. So the problem is unlikely to be the alternator.

Anyone have any suggestions as to what else to look for? Any help would be greatly appreciated.

Gumbo

i would of said a problem with the battery cells and that the battery needs to be replaced, but if you have tried it with different batteries then thats no use.

you could put the battery in the house overnight on a charge and then stick it back in the car and see if it still drains overnight while in the car.

if it starts the next morning no probs then you know that the battery wasnt receiving a charge in the first place.

crosstownk

It sounds like you may have a problem with your alternator. Have it checked. You have used various batteries - so the battery is not the problem. The 10mA drain does not indicate a significant current draw. Check the voltage at the battery terminals when the engine is running.

bman

Cheers for the reply. Can't be the battery. Have tried multiple different batteries (all either fully charged or close to it) and none of them have managed to start the car the next day. None of these batteries have problems starting the other cars at the house (before their overnight stay with the Lancer obviously).

bman

crosstownk wrote: »

It sounds like you may have a problem with your alternator. Have it checked. You have used various batteries - so the battery is not the problem. The 10mA drain does not indicate a significant current draw. Check the voltage at the battery terminals when the engine is running.

Here's rough estimates (analog, not digital readout on voltmeter!).

Voltage across battery when turned off: 12.5 - 13V
when turned on: 14V

crosstownk

bman wrote: »

Here's rough estimates (analog, not digital readout on voltmeter!).

Voltage across battery when turned off: 12.5 - 13V
when turned on: 14V

Hmmm.....Sounds like the alternator is functioning to some extent. It might be an idea to check all your connections between the battery and the earths. Especially the earths. Remove them all and clean the surfaces and then retighten them. A bad/poor connection may cause the problem. Remember that it requires a lot more current to start a cold engine.

EDIT: Also check all starter motor connections - it could be that the starter is not getting enough current.

BrianD3

Have you checked the charge in the battery the following morning? Or are you assuming that the battery has been discharged because the car won't start?

If it's the latter perhaps the slight drain on the battery overnight + a cold engine in the morning + a tired starter motor is enough to prevent the car from starting.

edit: crosstown said it already

Steve

I had this problem - charging fine, atlernator fine yet went flat over the weekend. Bought a new battery and same thing happened.

Turned out the boot courtesy light was staying on and draining it.

crosstownk

stevec wrote: »

Turned out the boot courtesy light was staying on and draining it.

Fine. But OP only has a 10mA drain. A boot light would have a bigger drain than that.

Steve

crosstownk wrote: »

Fine. But OP only has a 10mA drain. A boot light would have a bigger drain than that.

Yeah you're right.

10mA sounds a bit low tbh, ice on standby + clock + ecu + alarm should draw more than that.

bman, can you explain how you measured the current.

It could also be a bad lock solenoid which doesn't fully close and turn off.
This might not be apparent while the measurement is being taken as the car is unlocked.

bman

crosstownk wrote: »

Hmmm.....Sounds like the alternator is functioning to some extent. It might be an idea to check all your connections between the battery and the earths. Especially the earths. Remove them all and clean the surfaces and then retighten them. A bad/poor connection may cause the problem. Remember that it requires a lot more current to start a cold engine.

EDIT: Also check all starter motor connections - it could be that the starter is not getting enough current.

I haven't explained the situation fully. The car is not currently been run every day since it isn't insured yet and is awaiting NCT. The engine has always been cold when the charged battery is placed in it. And it then starts without a problem. The problem occurs when the car is left sitting idle for a decent length of time.

BrianD3 wrote: »

Have you checked the charge in the battery the following morning? Or are you assuming that the battery has been discharged because the car won't start?

If it's the latter perhaps the slight drain on the battery overnight + a cold engine in the morning + a tired starter motor is enough to prevent the car from starting.

edit: crosstown said it already

It definitely isn't a slight drain. The battery will not start any car once it has been left sitting in the Lancer. It must be jump started and charged before it will start any car again.

Doubt there's a problem with the starter motor. The car has no trouble starting once the battery is charged.

Thanks for all the suggestions so far. It really has me confused as to what it could be.

Steve

bman wrote: »

The problem occurs when the car is left sitting idle for a decent length of time.

A day?, a week?, 2 weeks? how long are you talking about.

bman

stevec wrote: »

Yeah you're right.

10mA sounds a bit low tbh, ice on standby + clock + ecu + alarm should draw more than that.

bman, can you explain how you measured the current.

It could also be a bad lock solenoid which doesn't fully close and turn off.
This might not be apparent while the measurement is being taken as the car is unlocked.

Car has no ice (pretty much) and no alarm.

Measured current by disconnecting the negative terminal off the battery and placing the probes from the negative cable to the positive battery terminal (which still had the positive cable attached).

How would I go about checking a "bad lock solenoid"?

bman

stevec wrote: »

A day?, a week?, 2 weeks? how long are you talking about.

I've seen it run down a battery in slightly over 24 hours.

But I only work on the car at weekends so I've only seen this happen once. Have another "full" battery in it tonight and am gonna see if it's dead in the morning.

Steve

bman wrote: »

How would I go about checking a "bad lock solenoid"?

OK, as you've no alarm, just do the same test and lock the car (with the key or fob) as normal - see does the current rise.

The battery AH rating means it should supply X amps for Y hours. e.g. 40AH means 40 amps for 1 hour -or- 40mA for 1000hrs so a small drain shouldn't kill the battery. The only reasons can be a dud battery or something draining it that you're not seeing overnight after you lock it.

Steve

bman wrote: »

Car has no ice (pretty much) and no alarm.

Measured current by disconnecting the negative terminal off the battery and placing the probes from the negative cable to the positive battery terminal (which still had the positive cable attached).

Just re-read that.

The way to measure drain is disconnect the negative (-) from the battery, then connect the multimeter as follows:
Put meter in current measurement mode - make sure the leads are in correct plugs(black in common, red in current - not voltage)
red (+) lead to the disconected negative lead. black (-) to the battery negative.

10-10-20

Given that the battery is likely to be ~50A and the drain is occuring overnight (~10 hours), that's a draw of ~4.5 amp-hours (50A/10h with some residual), or 54 watts. 54 watts will create significant amounts of heat - enough to burn a hand on a surface as large as the palm of your hand.
You could try searching for that source of heat (from the radio, ecu etc...).

Your reading of 10mA is wildly out. You need to re-measure with the car locked up for the night - the same as you do every other night. Just be careful with the multimeter - some only measure up to an amp on one of the input/settings so you may damage it or blow the fuse with anything higher. See if you have a 10A input and use that.

You may find that this load only appears a little while after the locks are closed, so be patient.
But, to put it to you this way, significant amounts of battery power don't dissapear just like that without reason!