Battery drain current draw testing

[mjheathcote]

All this talk of batteries and possible tracker battery drain issues, I thought I would do a little experiment.
My car has been parked up in my garage unused for a few weeks on a maintenance battery charger, without the alarm being set. As the boot lid is not quite closed, the boot light has timed out, in other words, I can open the boot to gain access to the battery with no electrical services being activated.
Therefore I unplugged the charger, and using a digital multimeter I connected one lead to the negative pole of the battery, the other to ground on the body. I then switched off the battery isolator so any electical load would then flow through the multimeter. It's important to connect the multimeter first, so not to disconnect the car from the battery and cause a 'system reboot' when connecting the multimeter...the current draw then might exceed the rating of your multimeter if not fused.
The result was a current flow rising and falling between 0.09 amps and 0.12 amps, or if you like a maximum draw equating to 1.5 watts approximately. I repeated with another multimeter and obtained the same results.
I don't think I have a problem with a tracker with such low current draw, the fluctuation could be due to the clock maybe, it did appear to rise and fall every second.
It would be interesting to know the results of other cars, and then maybe if a higher current draw is present, this could be due to a tracker problem.
Cheers
Mike

 

[ZAM400209]

that's very interesting- I've never read of anyone else making a measurement like that.

What I would say to you, is that alot of multimeters, particularly on DC current scaling, having relatively slow sample frequencies. If, as you say, the current changed every second I would wonder if that wasn't the 'meter doing the best it can to display a reading faster than it' sample frequency.

The tracker is unlikely to be hooking up (to network) every other second, I would say it's probably trying every 20 minutes...

JimP

 

[mjheathcote]

What I did do before hooking up to the car, was to use the same multimeter through my 5w filament test bulb, and that measured a solid unchanging 0.33 amp draw, so it does appear that there is a slight fluctuating current draw through the car, not an issue with the multimeter.

 

[Emtee]

Can't say with any certainty how the tracker works in relation to the Navtrak network, but when mine was active, it was transmitting far more frequently than every 20 minutes, indeed I tested it to measure the response time and they were on the phone to me within a minute of the car moving. The tracker may be sending a location signal irrespective of whether anyone at the Navtrak office is taking any notice, and I can quite believe this could be every few seconds.

 

[mjheathcote]

Even though my current draw is only 0.12 amps, if you work it out, the battery would be flat in just over 3 weeks without a battery conditioner fitted.
If you have a multimeter with DC current measurement, post up your current draw, alarm off, and boot light off (it times out)
Cheers
Mike