Thread: 2nd battery location??

Originally Posted by p38arover

Like this?

Hi Ron,

I notice your wires coming out and ducking under the carpet and into the subwoofer area.

I was wondering where you picked up the feed from, did you run a wire to the front or did you pick something up a bit closer?

Regards
Steve

Steve, I think you'd really only want to run a dedicated charge wire from the main battery. With mine i'm only running a fridge and lights etc, but when you start the car the next morning, and main battery will dump as many amps as it sees fit into the second battery to equalize the voltages.

Got my second battery in just before easter.
Managed to get it into the back, though my spare wheel arch...? has been cut out, and a floor put in with the gas tank mounted in it's spot - now on the outside of the car.
There's a 140A circuit breaker right next to the main battery, with a 2AWG running along the top of the chassis through a waterproof gland into the rear.
The Negative goes from the second battery to the chassis - wasn't quite sure about this, but was assured by an auto elec that it's fine.

I have seen three options mentioned;

1) Pick up from the BECM, which when i looked closely has 3 different 60A feeds running to it. Although physically convenient, i am a little leery of connecting anything non-standard to the BECM

2) Run a wire from the battery through the firewall. Using either Ron B's "drill the grommet" method, or another method i saw uses a spare hole which takes the clutch cable on the manuals.

Then the wire can be run behind the trims and through the existing channels pretty easily apparently.

3) Hoges and others method of running it along the chassis and in through the rear floor / spare tyre area.

I think 3 may be the easiest and best, as long as the cable can be kept out of harms way.

I am thinking of using a variation on the circuits here, Second Battery for P38A

I am going to use a 100AMP Schottky diode (which has 1/2 the voltage drop of a normal diode) to prevent reverse current flow, and use a relay controlled by the ignition hooked up to a Projecta DC20 charger and a fat AGM battery.

This second battery will essentially be isolated from the vehicle electrics except when the vehicle is running. I am thinking of using a changeover relay, so when the feed from the rangie is not connected, a different charging source could be hooked up, such as solar or a 12V power supply etc

Steve

I've run my feed from the battery, along the chassis (in conjute) up the grommet at the rear and into the rear quarter.

Ive used a Traxide SC80 and a 50amp circuit breaker at either end, with an Anderson plug in the rear attached to the aux battery cables, and a switch run off the earth on the smart charger which is positioned on the dash so I can turn the voltage feed on or off at will.

No discharge issues from me!

It took 6m of battery cable to get there, no trimming whatsoever.

I personally feel that's the best way too, in conduit under the car. Sometimes those maxi fuses are running close to full capacity anyway; and 60 amp may not be enough if one of the batteries are dead, and the other is full. Dad's car caught fire after he started the car with a low second battery and a very large new main battery on 50 amp cable.
Just don't feel comfortable with a large cable going through the cabin - even if it is protected by a relay etc.

Regarding the Diode, will you still be able to start off the second battery?

Originally Posted by benji

Regarding the Diode, will you still be able to start off the second battery?

Hey Benji

No i won't and I am planning on using an AGM battery as well, which is not much use as a starting battery.

If I wanted a second battery as a backup start battery, I would go the Hoges way and get them both under the bonnet

Steve

How did Hoges manage to get 2 batteries under the bonnet?

Gary

Originally Posted by mtb_gary

How did Hoges manage to get 2 batteries under the bonnet?

Gary

I used the spare compartment space behind the existing battery to house one of Drivesafe's magic Traxide SCR80 gizmos. This in turn charged two deep cell batteries connected (and used) in parallel in a camper trailer...