when it sparks, when battery is reconnected

[shogun]

I have a question to the electric experts.
I have read several times, that when reconnecting a battery cable and it sparks, that shows there is a problem with power drain or ground cables.

Here something I copied from a Chevy board:

"If there is a spark there is current draw. Use a test light, you can make one or buy one. Use a side marker of tail light with the connector. Disconnect the + battery cable and hook the two wires from the the light between the battery terminal and the cable. Start pulling fuses and disconnecting wires until the light goes out. When the light goes out you found the short."

Maybe some others can comment on this.
When I connect the battery on my grey 750 I have no sparks, but on the Highline it sparks a bit.
The grey one is my daily driver, no problem at all with power drain, the Highline is still under reconstruction and I can't say of any battery problems at the moment as the battery is always on a trickle charger.

[Kalevera]

Erich, I think in most cases the "short" will be the GM/RM sending current to the interior lights because a door is open. The principle makes a lot of sense, though. Don't forget about other inherent draws on the system - radio memory and the like.

[shogun]

That is right, but the general question is: does a spark when reconnecting a battery point to some problems or not?
Copied more:

You definitely don't want sparks when connecting battery cables! I agree with Don that there must be a parasitic load on the 12 volt system
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If you have large sparks when you reconnect a battery (with the ignition off), then you have a short somewhere OR you have accessories (like a clock, radio, amplifier, headlights) that are drawing current with the ignition off. If you have big sparks, you probably have a short or something.

When you use jumper cables to connect a live battery to a dead battery, there are sparks because there is a large voltage potential between a live battery and a dead battery.
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Interesting subject.
If that is really true, that a (large) spark points to something wrong in the system, that would be a great help.

Of course, always under condition that the battery is disconnected/connected correctly.

[DaveVoorhis]

While the size of the spark might be a rough indicator, a measure of actual continuous current draw is better. If I get a chance this weekend, I'll measure the normal current draw under an all-systems-off condition. Some current draw is to be expected from parasitic resistance and the alarm. I'd expect it to be relatively high when the battery is first connected, as capacitors charge and systems initialise.

[shogun]

According to this link 30-40 mA is o.k. (from Bill R.)
http://www.bimmernut.com/~billr/images/switch.jpg

But you have to wait 16 minutes I once read, after locking the doors, because when you open the door, already the GM is on standby.
So open the rear window (if the battery is under rear seat), lock the doors, wait 16 minutes, then use the multimeter you have attached before.

[genphreak]

According to this link 30-40 mA is o.k. (from Bill R.)
http://www.bimmernut.com/~billr/images/switch.jpg (http://www.bimmernut.com/%7Ebillr/images/switch.jpg)

But you have to wait 16 minutes I once read, after locking the doors, because when you open the door, already the GM is on standby.
So open the rear window (if the battery is under rear seat), lock the doors, wait 16 minutes, then use the multimeter you have attached before. Also beware of aftermarket amplifiers... they will also consume 30-40mA or so in their standby/remote-on circuits. Perhaps the car's draw is partly the stock amplifier... who knows. Drain is bad, all cars need a solar panel to help the battery against fouling its plates, especially if leaving them for a while without running

[Ross]

Both of the 750s I've owned had some parasitic draw. Parking one for say a month was a gauranteed dead battery. Never bothered to diagnose a fault, just attributed it to all the electronics.