Battery current at rest

[PeterN]

Hi Paul

Thank you very much for that, just the information I needed, I will make a note of it in the manual. I obviously have a fault on both cars, I will start by checking for alternator leakage as I have come across that before.

Thanks again

Peter

[PhillipM]

That suggests an 096, (75Ah) battery should still have 50% capacity after 750 hours or about a month at a 50mA discharge rate.
Obviously the chances of it still starting the car will vary according to temperature, but 3 - 4 weeks in the summer shouldn't be a problem.

To be fair my bro's current 110 HDi doesn't seem to be able to manage a week, but his previous 3 406's and both of mine never had any issues.

To be honest a lead-acid at 50% capacity will generally struggle to start a car no matter what the weather - the voltage drop at that kind of charge level is much higher than when you put it under load at higher charges.

[PeterN]

I tested my car again today, the current draw was over an amp at first then dropped to 600ma, I disconnected the alternator and it made no difference but when I looked at the meter again it had dropped to 96ma, I reset it and checked again sometime later, still 96ma, not what it should be but considerably better than before and the car started instantly although it had not been used for nearly a week.

The only theory I have is that the car was damp, it doesn't get used much and I could see condensation on the inside of the windows but its dried out this week. It was damp that led to the ruin of my first 406, mechanically it was fine at 246k miles but it went into permanent lockout after it was left damp for sometime. This doesn't account for the excess current on my wife's car which is used most days - perhaps that is the alternator.

Peter

[rwb]

Maybe it is better to connect the multimeter first, then disconnect the battery. In this way, the current is never really cut, but just re-routed via the multimeter.

After measuring, reconnect the battery first, then disconnect the multimeter.

This procedure will save you from having a disconnected battery altogether, which seems to give a chance of damaging the electronics (inside the BSI box). I read various postings indicating that even if the 3-minutes procedure is followed, the BSI has a possibility of losing its memory.

I was wondering whether something like this should be possible.
(Please excuse the slight hijack; following with interest as we have a 307cc that's dead after a couple of days.)

The trick to it will be connecting the multimeter to the battery terminal before removing the cable from the car. Any more specific tips?

Maybe
https://www.ebay.co.uk/itm/272971602863
or
https://www.ebay.co.uk/itm/192187556199
could be clipped on underneath the car terminal after it is unclipped and before it is removed?

[frog]

Sure, if it fits underneath the car terminal. If there is not enough space you might use a piece of solid copper wire that you wrap firmly around the battery pole underneath the terminal. You could then tighten the wire by twisting its ends with a set of pliers. The twised wire ends can be used to clip a small crocodile clip onto.

Use the resistor measurement function (Ohm) of the multimeter first to check if there is firm contact between the copper wire and the battery pole.

Be careful to use only tools (pliers) with insulated grips. The voltage of the car battery is low, you can touch it safely. But a car battery can deliver enormous currents. When the + and - pole are connected e.g. via a metal tool, it will go red hot!