Thread: 24 Hour Battery drain D2a HSE V8

Just to update the thread,
Grabbed the tester today and probed my heart out -

the only fuse that is getting any residual voltage use is F20 - and is consuming around 2.6MV
I thought there was a reading from the Passenger seat circuit - but a couple of ID-10-T errors on my behalf sorted that out!

The real surprise (well not really) was the Alternator Diode test
Getting readings
Neg to Terminal and Pos to ground = 127 (should be 500 - 800 apparently)
Neg to Ground and Pos to Terminal = 169 (Should be zero apparently)

So short story long - looks like a replacement Alternator is on the cards!
So off to RoverLord again - look out Mario!
M@

Originally Posted by D2Matt

the only fuse that is getting any residual voltage use is F20 - and is consuming around 2.6MV

i think you've done something wrong here. with current draw, your testing for maps, not volts.

Originally Posted by D2Matt

The real surprise (well not really) was the Alternator Diode test
Getting readings
Neg to Terminal and Pos to ground = 127 (should be 500 - 800 apparently)
Neg to Ground and Pos to Terminal = 169 (Should be zero apparently)

before you spend your money. I'm not even sure what you have tested for here


also a test for stray voltage should be done.

Originally Posted by johntins

If only it were that simple.... I have now got an ammeter that has a blade fuse connector so I can plug it into each individual fuse holder, one at a time. It hasn't helped. This is on a D1, not 2, but the principle is surely the same. Mine shows draw on two fuses, from memory 16 and 18, but if I pull those two I still have a dead battery in around 24 hours. If Im leave the switch on that connects the two batteries together I will have two dead batteries in the same time.

This isn't it, but it's similar
12V Automotive Current Tester with Mini Blade Connector - TENMA | CPC

it means you have a drain before the final circuits which are through the fuses and the most suspect in this case is the alternator cos if only one p/n junction is shot within the rectifier pack(which has 8 in it) the alternator will still give you normal charging voltage but there will be a drain ... remove maxi fuse MF1(100A) and see drain there

Thanks Eevo,

I followed this you tube video series (both one and two) to check Alternator - it shows in this one the diode test I did to get readings

How To Test an Alternator Part 2. Rectifier, Diode Pack, Parasitic Battery Drain - YouTube

Then to double check I disconnected the Alternator for two days and battery was still fully charged, so kind of thinking that is reason enough to replace it, if not at least I have a new Alternator!

The Drain test I did was in this video, beginning shows the drain test - second half shows the method I followed to check the fuses

How to identify and locate a parasitic drain - YouTube

The overall battery drain doing this test was around 0.8 - 0.9 Amps after 1 hour to let it go to sleep
The volt readings above were probing the fuses after this

I should have clarified all that in the previous post, but now there are a couple of links for others to use if they need to

M@

OK a little further down the track on this one

Replaced Alternator with one that had operating diodes, slowed down drain considerably, but still present

Caved in and took it to an Auto Elect -
Looked promising when they found a pretty constant drain - traced it back to DVD player - unplugged that and drain dropped down to a constant 60 Milli Amps
which he said will still drain battery in about 4 or 5 days

He said about 40 Milli Amps disappeared when he pulled one of the relays (near the front of the under bonnet fuse box) out - leaving about 20 Milli Amps which he believes is the clock etc

Does that sound about right?

OH and by the way - his suggestion to fix the ongoing battery drain either drive it more often or fit a battery isolation switch!

I am going to go and pick it up ask him to point out exactly which relay has the 40 Milli Amp drain and have to do some more research
M@

60 milliamperes constant load is a discharge of 1.44 amp hours per day (24 hours). Not sure what brand/capacity of starter battery you are running, but doesn't seem enough to kill a battery in a few days.

Its only a 0.6 Watt power draw.

This load will be offset by a trickle charger running at greater than 0.6 Watts. Or a >2 watt solar panel (assuming 8 hours of sunshine a day).

Thanks I thought his threat of discharge in 4 - 5 days was pretty severe - given I thought 60 Milli Amps was a tiny little amount - I might get it back and see how it goes for a week or so

I have a brand new Batty with 850cca (will get details shortly)
M@

If 60mA is killing your battery in few days that battery is FUBAR without any doubt, or it's not a starter battery, maybe deep cycle and you make short rides so it's not able to get recharged, a proper starter battery should be able to start the engine after 1 month without probs(provided it's not cold outside)