Thread: Power Drain Logging

Originally Posted by Mk1_Oz

My lads 2003 D2 HSE has been experiencing some electrical wierdness for some months now. The alarm has sounded for no reason, the battery has gone flat multiple times and the dash lights up like a Christmas tree. I have had the batteries checked out (twice), charged them well, changed the dual battery isolator, checked the alternator output including an AC ripple test. Checked what earths I could find. Done a parasitic drain test (<0.4A and often in the mA range). Been quite thorough.

Last afternoon the alarm sounded. The car started fine. Turned it off but left it unlocked. The next day I tried to start it but the battery was flat and would not turn the engine over. The doors would not lock. I put the battery on charge using a decent CTek charger.

My suspicion is that although the car goes to sleep properly (and therefore has a mA range draw) at times (and quite randomly) something is starting the draw power and flatten the battery. Once the battery is low all sorts of electrical wierdness occurs due to the various computers and modules not getting sufficient voltage/power. I also suspect that the alarm sounding is due to it getting so flat that the alarm system believes the battery has been disconnected.


Getting to my specific question................

Is there a way to log power draw over an expended period of time? Has anybody come up with a smart way to do this? I was thinking of using an Arduino data logger somehow.

Sounds weird, but on my RRC TD5 conversion, the main ECU was not quite always going to sleep and would sometimes flatten the battery overnight. Don't know what he did, but an electrically inclined mechanic finally traced it through and fixed it. Might help?

You don't live near a shopping centre by any chance, or a neighbor has one of those outdoor weather stations?
The alarms can be set off and /or the car immobilized by a sliding door sensor, or several other types of RF interference.
Mine has needed the Microsoft reboot ( lock doors /unlock doors start) several times at my local shopping centre before it will start.
I met a bloke on the ferry to Kangaroo Island whose D2 would not start and we replaced the batteries in his fob, and pushed it to the other end of the car park. It still had to be pushed onto the ferry but started fine the other end.
So check your neighbours for weather stations. I hope you don't have one as that would be self inflicted pain. There was a bloke in WA with a 38A some years back who was advised to build a Faraday Cage around it.
Regards Philip A

No weather stations but it is parked next to the garage infra-red sensor. However, this battery flattening has occurred in a more remote (RF isolated) area too.

When this one doesn't start it is generally more that the starter clicks but doesn't have the power to turn the motor over rather than there being some internal electrical inter-lock stopping it.

Today I locked it a number of times and after 30 seconds or so the power draw dropped from 1.5A to 0.04A so it was going to sleep properly on those ocassions. Maybe I need to monitor whether it properly sleeps EVERY time. The only way to do that will be to lock and unlock many many times. grrrrrr

[QUOTE=Mk1_Oz;2715379Is there a way to log power draw over an expended period of time? Has anybody come up with a smart way to do this? I was thinking of using an Arduino data logger somehow.[/QUOTE]
This might do the trick: IP67 True RMS Autoranging Cat IV DMM with Wireless USB Interface | Jaycar Electronics , in conjunction with a laptop or tablet? Probably many other similar options.

Or could you not hook up your multimeter for parasitic currents (I presume you are putting it in series between the (disconnected) negative lead and the battery negative terminal?), running the leads out under the bonnet, close the bonnet, lock the car and then come and check the current reading regularly, for as long a period as possible between using the vehicle?

Leo. Your suggestion would work however I have found a $9.95 solution in an ACS712 hall effect current meter. I will connect the meter to an Arduino board and a data logging shield and let it sit writing readings to an SD card for 2 or 3 days then see what I get (yes in series with bat -ve cable running out of the bonnet). If I can establish that there is some random parasitic drain then I can move the monitor to individual fuses until I find the culprit. Then it's a case of doing the same on the various components that come from those fuses to isolate the issue.

Will not be a quick process but unless I get lucky and see the parasitic drain when I just happen to have the multimeter on the car then I have no option.

The alarm system is my first suspicion. Does anybody know how the battery backed-up sounder charges? I assume it has some sort of a battery in it that needs charging (doubt if it is capacitors)? Maybe that battery has failed and is drawing alot.

My D2 would drain the battery if I left it unlocked with the key in it, (key turned to the off posn).
99 Model, Manual with ACE. Took about 8 hours but would do it without fail.
If the key was out then would be OK. Did a drain test and no immediate difference, I recall my drain being in the 300mA region.
Didn't do any further testing.

Would be interested to see your arduino data logging thing once you got it going?

Cheers Glen

I can leave the key in my D2a unlocked for weeks at a time and I have absolutely NO problem starting Her

I dont think the car sleeps until the key is removed. I was seeing drain of 1.5A with the key in the ignition, unlocked.

Have ordered teh parts I need which should be here in a week. Should have answers soon.......