Reverse charging

**Pedro_The_Swift** · 2nd September 2014, 08:38 AM

Nearly everyone that tows something you can sleep in has an Anderson plug on the back so you can charge batteries off the cars alternator. In our case we have 300 (soon to be over 400) watts of solar panel on the caravan roof to charge the house bats so we never connect it. With our latest D2 lack of charging adventure I wondered if we could just plug it in and reverse charge the car bats. ..
No.
It would appear the cable to the Anderson plug is taken from the D2 fuse box and is limited to one direction

.
Took me a while to work that out---.

I dismantled the plug and attached jumper leads direct to the battery. Not very elegant but works like a charm

**PhilipA** · 2nd September 2014, 11:13 AM

Is the tapping after an ignition controlled relay rather than a dual battery controller? That is the only reason that I could think of to do that, so that the caravan is disconnected with ignition off. Are you sure that there is not a dual battery controller just tapped into the fuse box input? that is an easy place to tap.

The usual way to do it is to have a dual battery controller which connects the batteries until a preset low voltage is reached sensed at the starting battery .
In that case if you go below the starting battery's drop out voltage it won't work, however my battery controller (ABR Sidewinder) has a switch to connect the batteries .

I don't know why as it is hard to conceive of a situation that you will have a full aux but flat starting battery. Maybe dead starting battery?

However that would address your situation and I think Drivesafe's controller has that feature.

Regards Philip A

**Pedro_The_Swift** · 3rd September 2014, 06:49 AM

It was on there when I bought it Phillip,, no noticeable controller anywhere,,powered at all times,,
it just wont accept a reverse change.

**PhilipA** · 3rd September 2014, 07:46 AM

It was on there
when I bought it Phillip,, no noticeable controller anywhere,,powered at all
times,,
it just wont accept a reverse change

Then I suggest that you buy a dual battery controller with the facility to "connect both" regardless of state of charge.
Regards Philip A

**austastar** · 3rd September 2014, 03:58 PM

Hi,
If it wont accept a reverse charge when the vehicle battery is full, and ypu cant find a controller, it may be the original install is using a diode some where in the line.
I would remove it and go to a direct connection controlled by a voltage sensitive relay.
Why?
There is always a Voltage drop across a diode, which will inhibit fully charging your second battery.
Have a look at the Traxide dual battery controller or similar.
I'm very happy with mine.
Cheers

**Pedro_The_Swift** · 4th September 2014, 07:37 AM

All I'll end up doing is buying an El cheapo set of jumper leads and putting an Anderson plug on one end.
Or get my charging system checked.... again
This whole post was mainly about letting others know that
A. You can charge the tug off your panels
B. It may not work because of this reason

**cewilson** · 5th September 2014, 08:33 PM

Been doing this for years, and love the options I have available. I have solar panels on the trailer which charge the 2 deep cycle batteries, but they can also charge the Defender's battery if needed.

Also have the generator that can charge either the trailer or Defender's batteries through the Anderson plugs.

Lastly the vehicle can also charge all of the batteries, although a 40 amp alternator in a 200tdi Defender is limited in its capabilities.

I no longer run a 2nd battery in the Defender as the whole back of the vehicle runs from the trailers batteries when connected, or the vehicle itself when running. Different way but works for us.

Cheers
Chris

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