Thread: Dual battery connection

Hi

Thought I might share my 2nd battery controller install in the L322. I actually decided to use a 200amp solenoid switched by ignition instead of a voltage sensitive type controller because I run an electric (boat trailer) winch of the same Andersen plug that is used to charge the battery located in the camper – I don’t have a 2nd battery on board (as mentioned else where there’s a perfect spot for one under the loadspace floor), if I did have one there, Drivesafe’s new product would be perfect, as I think if the battery is mounted in the car (permanently) you need voltage sensing – not just a solenoid. Anyway the type of controller is not important for this info to be used.

I’ve connected into the rear fuse box. I’ve read that this is not to be done but after heaps of research I fail to see why, so I thought I’ll do it, test, test, and test. If it doesn’t work or causes problems then I’ll start again. I think some people fall down on a poor earth.

In the attached pic, the solenoid is seen in the bottom right of shot, bolted in place. I’ve run an 8mm2 wire from the spare outlet plug indicated by the yellow arrow to the solenoid, which is protected by the new 40amp fuse indicated by white arrow. Acording to RAVE these empty fuse and socket is not used in any model. The wire is routed inside split tube behind the fuse box bracket only to keep it out of the way. From the solenoid to the Andersen plug (and on the trailer) I’ve run 13mm2 (6b&s) cable to limit loss over the long run. The Andersen plug – hence the 2nd battery – is earthed at a newly created (in stainless) point near the towbar.

Test. The camper has a 110AH deep cycle battery. I ran a 60L Evacool fridge and a 16w fluro for 24hrs to run it down a bit. Plugged into the back of the car and attempted to get a reading of amps going to the 2nd battery, unfortunately my Multimeter can only measure 20amps and reported an out of range error at idle (and blew the internal fuse). Then went for a 30min drive. When back at home recorded 5-7 amps at idle going to the battery, voltage at the Camper battery was 14.1v and steady with car idling. Then turned on some electrical load that draws from the rear fuse box, rear screen heater, rear AC blower, plugged laptop in cig lighter, and raised and lowered the suspension to get the compressor running. Only drop in voltage (at camper) was when the air compressor was running but it still remained above 13.8 and I expect with more engine RPM that would be higher.

No ECU errors were logged.

So at this stage I’ll say its all good, but will monitor during usage.

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Originally Posted by harlie

Hi

Thought I might share my 2nd battery controller install in the L322. I actually decided to use a 200amp solenoid switched by ignition instead of a voltage sensitive type controller because I run an electric (boat trailer) winch of the same Andersen plug that is used to charge the battery located in the camper – I don’t have a 2nd battery on board (as mentioned else where there’s a perfect spot for one under the loadspace floor), if I did have one there, Drivesafe’s new product would be perfect, as I think if the battery is mounted in the car (permanently) you need voltage sensing – not just a solenoid. Anyway the type of controller is not important for this info to be used.

I’ve connected into the rear fuse box. I’ve read that this is not to be done but after heaps of research I fail to see why, so I thought I’ll do it, test, test, and test. If it doesn’t work or causes problems then I’ll start again. I think some people fall down on a poor earth.

In the attached pic, the solenoid is seen in the bottom right of shot, bolted in place. I’ve run an 8mm2 wire from the spare outlet plug indicated by the yellow arrow to the solenoid, which is protected by the new 40amp fuse indicated by white arrow. Acording to RAVE these empty fuse and socket is not used in any model. The wire is routed inside split tube behind the fuse box bracket only to keep it out of the way. From the solenoid to the Andersen plug (and on the trailer) I’ve run 13mm2 (6b&s) cable to limit loss over the long run. The Andersen plug – hence the 2nd battery – is earthed at a newly created (in stainless) point near the towbar.

Test. The camper has a 110AH deep cycle battery. I ran a 60L Evacool fridge and a 16w fluro for 24hrs to run it down a bit. Plugged into the back of the car and attempted to get a reading of amps going to the 2nd battery, unfortunately my Multimeter can only measure 20amps and reported an out of range error at idle (and blew the internal fuse). Then went for a 30min drive. When back at home recorded 5-7 amps at idle going to the battery, voltage at the Camper battery was 14.1v and steady with car idling. Then turned on some electrical load that draws from the rear fuse box, rear screen heater, rear AC blower, plugged laptop in cig lighter, and raised and lowered the suspension to get the compressor running. Only drop in voltage (at camper) was when the air compressor was running but it still remained above 13.8 and I expect with more engine RPM that would be higher.

No ECU errors were logged.

So at this stage I’ll say its all good, but will monitor during usage.

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Thank you. Just what I needed to know! Installing 2nd battery in the rear of my 2003 G4 RR