drain on main battery

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davi saunders about 5 months ago

I have a 1999 Nissan patrol with a Redarc system already installed when I purchased the car.

Soon after I noticed that the the earth lead on the secondary battery was seated on the plastic of the radiator overflow - so I am wondering what else the previous guy might have done .......

The problem is that the main battery will drain flat in about 6 days. The secondary battery remains at 12.6v. I don't have any other equipment such as a fridge connected to either battery. The only things connected to the main are fog lamps & a cable for spot lights which were removed prior to me obtaining the vehicle. These shouldn't be drawing when the engine is off.

The car does have an engine immobiliser.
I notice that when turning off the engine the voltage on the main drops to 12.0v within 10 minutes.

Connecting a multimeter to the earth lead and the -ve terminal on the main, it is drawing 0.1A. The auto electrician showed me this.

I have been told that the isolator only separates the two batteries, so if something is draining the main, it could still go flat.

Is it simply that the system has somehow been installed backwards ? (given that the secondary remains at 12.6v)

If anyone has any ideas they would be appreciated.
Thanks for your help in advance.

Dylan @ REDARC

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Hi Dave,
Firstly thanks for your forum post.

It's definitely not a good idea to have the ground connection for your secondary battery through the plastic brackets on the radiator. Metal to metal, with as much contact area as possible is always best.

Your battery going flat so quickly with only the immobiliser, possibly a stereo? and the solenoid standby current (7.5mA old model), it seems like the battery may be faulty.

My suggestion is to go to another auto electrician and get them to check the battery and the entire system.

You are completely correct when you say "I have been told that the isolator only separates the two batteries, so if something is draining the main, it could still go flat", which is why people generally have any major, non-essential loads drawn from the second battery. Your system is not installed backwards, it's simply that you do not have any loads drawn from the second battery.

If you have any further queries i'll be happy to answer as soon as i can.