Parasitic battery drain V50
 

Hi guys

Looking for suggestions on potential cause.

Story starts whilst at work car alarm goes off (parker for 4 hours), tries to unlock and wouldn’t unlock at first, then it did, tried to start car got a multitude of dash light in different orders, turned it off and various things stayed on headlights (half brightness) plus other bits.

Voltmeter showing 7 volts, jumped started car (battery 7months old)

Had several bouts of this now, not enough juice in it to even bump start it, alarm service message seen on dash, so pulled fuse, and still flattening battery, disconnected powersounder, still flatteneing battery, going to replace battery in this, this weekend and replug in see if that resolves the issue (but I doubt it)

Tried measuring amp draw without success, funny readings but I did notice the 2 small green leds on where the courtesy light buttons are located when everything should be off.

if you are able to measure current and voltage then start simple. What's the voltage across battery with everything off (7v?) in which case the battery is toast, could try recharging but at 7v I don't see it recovering. Next, with engine on, what is the voltage across battery... I think 14.4-15v should be expected if the alternator is working efficiently. On these cars I don't know if they have a variable recharge so you may need to check the voltage across the alternator to know for sure it's good.

Then, figure out what the actual drain is, you need to measure the current across the battery with everything off. Id do this with, and without the alarm fuse in place. Maybe someone on here can tell you the normal 'minimal' current draw on a car with everything as it should be and car off. This might give you a clue, if yours is a lot higher. I had this problem on an old VW, and by doing this I figured out the stereo was in 'standby' not off, because it hadn't been wired correctly off a switched live.

since the alarms go bad on these cars my first thought was the alarm system, but I'd be guessing. Best to methodically test things rather than guessing..

when measuring current draw, you can sequentially remove fuses to try to isolate the circuit pulling current...

Why is it grammar goes out the window when posting from a phone!

Just read my own post back and thought good god!

I was rushing it as I was heading in to football.

Anyways, think my multimeter is up the spout as it was showing 20 volts across the battery (including the missus’s toyota) so cant confirm any readings I’ve already taken.

Well, before I go a buy another multimeter I’ll replace this battery in the alarms powersounder, already inspected the internal fuse box clean and dry and inspected the engine ecu also clean and dry (btw what a daft spot for an ecu)

But I did see the ecu loom resting on the gearbox and has worn the protective sheath away, couldn’t see if any cables damaged so insulated it for now, might revisit if it’s still draining after replacing alarm battery.

Buy a multimeter and check the cars main battery and alternator before spending time and effort elsewhere. If you doing the alarm anyway great, but I'd want to know for sure before making changes... sounds like a short jn the loom is possible :-/

Well, garage round the corner checked alt charge and came back ok, but

Been driving round with my voltmeter inside and think I’ve spotted something, first 2 minutes of starting the car meter is showing 14.5 volts after 2 minutes meter shows 13.1 and stays there, if i then switch on heated seats, rear screen, lights etc it drops down to 12.8.


Think the alternator is goosed

hmmm could be, but i think there is a variable charging on these cars. It may depend where you measure it, If the battery charge is good, it may deliberately drop voltage from 14.5 to a maintenance charge after a time. This was the point I wasn't 100% sure about. Maybe someone smarter than me can confirm?

the best way to find parasitic drain is across battery, with car off. check current. Then slowly remove fuses of suspect circuits and see which one makes it change.

I never had any weird alarm symptons but I did used to have a parasitic drain on my battery, it was due to a black box fitted 3 years previously. After I found where it was and ripped it out there hasn't been a problem since.

Thanks for taking the time to respond lockstock and statusred

Not aware of any blackbox fitted, I think I would of found one as I’ve been inside and everywhere in it.

Fitted a new alternator, still does pretty much the same voltage wise first 2 minutes of running voltage is as expected 14.7 then drops to 13.3 volts at the battery.

Picked up a new multimeter, when i measure the current it starts at 1.2 then drops after 30secs to .66 then .12 for 30 secs then 0.00

Alarm sounder still currently disconnected

Not seeing any eureka moment at the minute where I think I’ve nailed it, the green lights are still on, are other v50s always on with this?

Are these on because alarm disconnected?