Split charge Relay and power drain

**slarty** · 11-03-2003, 02:15 PM

Originally Posted by shakes

most 'ignition' inputs need 12v to trigger. sounds to me like that's the culprit

Nice one I'll find a new input ...hmm

**shakes** · 11-03-2003, 02:44 PM

what is the part number for your relay? just curious

**slarty** · 11-03-2003, 03:16 PM

LUCAS 33RA associated documents XXB464

I'm going to try and work on it next weekend... the keyboard drain is enough to drain the battery overnight... I think I need some kind of intelligent circuit here. time to start searching the forum

**meddler** · 11-03-2003, 07:12 PM

as Shakes said, you need 12V across the relay to get the relay to click (probably about 8V min). Getting 12V from the ignition on from your head unit should be enough to make the relay change contacts. Make sure the other side of the coil for the relay is going to ground. The relay is definately the problem, either the realy itself or the wiring for the coil in the relay (terminals 85 and 86)

**slarty** · 11-04-2003, 06:01 AM

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Originally Posted by meddler

as Shakes said, you need 12V across the relay to get the relay to click (probably about 8V min). Getting 12V from the ignition on from your head unit should be enough to make the relay change contacts. Make sure the other side of the coil for the relay is going to ground. The relay is definately the problem, either the realy itself or the wiring for the coil in the relay (terminals 85 and 86)

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When the 12v comes from IGN on is it a perminent on and therefore a perminent signal to the regulator to charge the second battery. so when Ignition is off the relay disconects on allowing the rear battery to discharge. Excuse the basic theorising, I'm clearing this up in my head.

**meddler** · 11-04-2003, 08:24 AM

Originally Posted by slarty

When the 12v comes from IGN on is it a perminent on and therefore a perminent signal to the regulator to charge the second battery. so when Ignition is off the relay disconects on allowing the rear battery to discharge. Excuse the basic theorising, I'm clearing this up in my head.

Correct. When you have the ignition switched on it will give a permanent 12V to switch the contacts of the relay and the second battery is connected to the main battery. This happens even with the engine off, remember ignition on doesn't necessarily mean engine running. You should be carefull of this because you can flatten both batteries if the alternator is not charging both batteries (engine off condition).
When the ignition is switched off, the second battery is isolated from the main battery and the rear battery will discharge.

I know this is a little confusing, but hopefully this has helped. if not, I have probably not explained it very well

**shakes** · 11-04-2003, 09:16 AM

you want your ignition signal to only be 'on' (12v) when the ignition is on (car running or in accessory position). It should be 0v (or close) when the car is off and ignition is not in accessory.

**slarty** · 11-04-2003, 09:55 AM

Originally Posted by shakes

you want your ignition signal to only be 'on' (12v) when the ignition is on (car running or in accessory position). It should be 0v (or close) when the car is off and ignition is not in accessory.

Thanks both, It your explainations were great. It is how I thought it should be, I'll stick a muultimeter on the ignition cable as soon as the car is back