Anyone able to explain this Defender Wiring to me?

[traxx]

I bought this highly modified Defender a few months back.
Now I'm having all sorts of flat battery problems

I've asked a few people about the wiring of this second battery but know one knows about it - and I clearly don't have a manual

Anyone help me?
At its simplest when the main battery is flat how do I start the car from the second battery?

[Geordie boy]

When you say highly modified, does it have alot of electrical extras fitted? The 2nd battery may just be for running these items from? If your having battery problems then it is likely that these items are draining the batterys aswell and you could have a problem with that box that is for the "dual battery management"

I'd think a local car audio place would be able to help as alot of large stereo install cars can run several batteries

[Dave^]

As already mentioned, the second battery should be an auxillary, for the winch/spots/compressor/toaster/etc...

This should be setup to protect the main battery so you will always be able to start the engine after using the winch etc...



Eta - google dual battery install... There a guide at the top, and if you do an immage search, a few diagrams too...

Hth....

Edited by Dave^ on Sunday 19th September 21:29

[Dave^]

eta - fking mobile site error!

Edited by Dave^ on Sunday 19th September 21:33

[GKP]

Piranha clicky

[anonymous-user]

traxx said:

At its simplest when the main battery is flat how do I start the car from the second battery?

You might not be able to.
Depending on the spec of that little box of tricks, both batteries will recharge when the vehicle is running, then when the ignition is turned off the aux battery is isolated so that any use of the electrical accessories that it powers won't drain the main battery, so the main gets left well alone for starting the car.
Some systems do allow a sort of "manual overide" to facilitate vehicle starting using the aux battery should the main be flat, but then a lot of aux batts are intended to give a low amp long-lasting current instead of the massive but quick mega-oomphs required to start the car. It might be that the way your system has been installed doesn't allow for using the aux battery to supplement a dead main batt.
In terms of the actual fault (if there is one), it might be that the charging relay within the Box of Tricks has failed closed, so the batteries are effectively wired in a permanently parallel state as they would be if the engine was running (and thus charging them).
A less complex way of doing business is to wire the batteries in parallel with just a plain ol' battery master switch between the two. Keeps 'em totally isolated day to day, then if the aux has seen a lot of use, flick the switch at the start of the next long run and charge it up again. It's more of a twin battery set-up than an aux battery set-up and takes back control from a lickle black box of 99p resistors to which you have no access.