Thread: Slow drain on main battery

Originally Posted by streaky

My 4.6 Efi Discovery has twin Optima batteries but recently the main starter battery keeps going flat. I thought it was just the age of the battery so replaced it with a new one.
It still keeps going flat though. I jump start the car and take it for a drive and alls well for a few days but if i leave the car for a week or more it's flat as a pancake again.

The auxillery battery stays charged for ages because it's isolated from the main battery when the engines not running. I have the Piranha DB180S system.

Whats the best way to check for a slow drain on a battery?


Thx guys.

S

Temporairly fit an ammeter (multimeter set to 10 amps first) between the positive battery terminal and the battery cable. Remove every fuse, one by one, until the current draw drops. Or fit a trickle charger, either mains powered or solar depending on where your vehicle is stored.

I would also check your connections to the main battery first. If it is not being charged correctly, it will go down very quickly without much to drain it.

Just had this on my wifes 90. It was the alternator. I suspect the diode pack has gone. Put a multi meter across the battery and see if the voltage is dropping (wifes was and you could see it quickly). When I spotted the voltage dropping I disconnected the alternator, re-connected the battery and put the multi meter across the battery again. No voltage drop which proved it was the alternator. It was much quicker than removing the fuses one by one. If you still see a voltage drop after disconnecting the alternator then it's a case of removing the fuses one by one as suggested by Bee uty.

HTH

Ivan

Had the same problem with my 90
And
I also have a yellow top optima for the main battery

But also don't use it that much does not help

I have ended up putting a battery cut of on the main battery and when I am going to the leave the car for more than a few days I turn it off. Did not cost much and took no time at all to do it

But will have to go back and check the alternator after all there is not that much electrical in a 90 to drain the battery :-)


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I too have this problem with my disco not sure why leave it a week and it wont start again red top starter and yellow top second.

red top is due for a change and we do have a small draw on the battery (which one would assume is the clock) but its a bit more of a draw than the clock and the clock should not make a car start after 4 days

Electric brake controller for trailer brakes was draining my battery. Been good since I disconnected it and its easy to plug it again if needed.

I have a feeling mine might be the battery Leval indicator for both batteries running them down as that is on all the time . Sort of ironic really

But got the next couple of weeks off so play with both of the defenders and giving them both a full service and full oil change of all oils.

Ali


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Here's the latest.
After a few hours drive I reached the campsite. Turned off the engine and could hear an almighty whistle coming from under the bonnet.
Closer inspection found the Yellow top has a type of porus vent that was making the whistling....pretty loud it was too!

One chap made comment that the Piranha DB180S might be over charging the battery. I put a meter on and got 12.8v at the battery without the engine running.

Could his theory have any merit?

Thx.