Adding 2nd battery to rear of 5 seater

[walker]

Due to a lot of problems with heat destroying 2nd batteries under the bonnet I decided to mount my second battery in cargo box at the rear of the Disco.
To do this you have to make sure the battery is less than 170mm wide and it is a fully sealed type battery.

1.

Remove cover of rear cargo box. By hitting hard with hand from behind the cover just clips out. (fairly tight the first time).
Then I used an angle grinder (what can't you do with one of these   ) to make to slots in the base the same width as the battery.

2.  



Thread a strap through the holes. This strap (just a small luggage strap or ratchet strap) will be used to fold the battery in place.

3.
Run wiring as per the dual battery controllers instructions. Many are different but they all have this in common.
Run an 8 guage wire from front battery to battery controller in rear. This is easiest done by first putting the wire in conduit then running under the car following the chasis from front to back.
Next run an earth from the rear battery down to the chasis. Ensure you remove all paint from chasis before bolting on lug and then spray with paint after bolting on lug to stop rust.

4.

At the rear there was a hole already in the floor of the car through wich I could pass the wires. This brought the wires up into the area to the right of the rear cargo box which is accessed via the vent. A hole is then drilled between the 2 spaces to pass the wires

5.


Wire in any accessories you need to rear battery & replace front panel of cargo box.

[Slunnie]

Such a good mod Adam. Is that the duel battery control box in with the battery, or is that still under the bonnet?

[walker]

The battery controller is in the back. That is it above to the right of the battery. To the left is a 6 way fuse box.

[Sniegy]

Nice job Adam,
One suggestion that i could make is that u make a false floor to sit above the battery cotroller or repostion the controller & fuse block to sit next to the battery in the side section giving u more depth in the bin? Just a thought as we all use these bins to store stuff in.
Another question is do u get gases inside the cabin? maybe u could install a fan in the section, where your wiring comes from. This is where the vehicle vents it own cabin air as well through a set of flaps basically just behind the battery to the right.

[walker]

Hi Pete,
            Yes I will make some type of false floor....but not yet  :roll:  I have just been trying to get it finished for Christmas holidays and have run out of time.

I dont think that it vents any gasses as it is a fully sealed type battery. Maybe someone else could let me know about this.

Adam,
I love it. I'm going to give this a try. It will fit in well with the mods I have already made to get power to the rear of the vehicle and I already have holes in the storage box from my old HF install.

Thanks for posting it.

Which battery controller is that you have used?

I think all batteries can vent, even the sealed ones if the environmental conditions are right.

How about getting some of those d-bolts used as tie down points in the floor of the Discovery and using them to secure the battery instead of just relying on the plastic bin?

Andrew

[walker]

I used a battery controller from my local auto electician. He reckons it is identical to the Piranah one but it only cost $135 instead of $270. I guess this is further proof that the 4wd shops are really making a killing on all us poor suckers.

I thought about mounting the battery in other ways but this was the simplist (is that a word) way and I'm sure it will be strong enough. The battery is a real snug fit on its own and does not move around even without a tie down.

[walker]

Ok, due to popular demand here is the

"REAR BATTERY MOUNT MK2"

Up grades include stronger mounting & a false floor (roof).

1. I widened the original slots I put in the bottom of the bins so that I could mount a steel tube frame with base plates. I drilled directly through the floor then mounted the frame with 1/4" bolts, washers & nylocks.

2. I then removed the frame and repeated step 1 because I had not made the frame high enough  :roll:  :cry:  

3. I wired up the batteries and moved the battery controller & fuse box below the top of the frame.

4. I managed to slide a piece of 25mm ply under the bottom of the storage box. There is a 25mm gap between the bottom of the storage box & the floor and the ply supports the weight of the battery so the base of the storage box wont crack.

5. I then wedged (hit real hard with a hammer) a piece of wood between the top of the battery & the frame. This wedges in the battery tight & it will not move.

6. I cut to shape a piece of ply which was screwed to the top of the frame and forms a flase bottom.

Another neat mod Adam.  Hope you dont get too much voltage drop to charge it seeing it is so far from alternator.

Regards
Grasshopper

[walker]

I hope its OK. The auto electician said charging current should never be much more than 30-40A max and I have run 8 guage (or was it 6 guage) which was rated for 120A . I figured overcompensating on the cable should make up for voltage drop.

Adam,
Excellent work.
8G cable will be fine for charging. You would only need some larger 4G if you wanted to start or winch from it.
Andrew
I am really keen to know the brand of the isolator you are using.

Hi Walker, could I make one suggestion. The isolator that you are using, like most, is voltage sensitive and as such, when the rear battery is below the cut out voltage level, when you start your vehicle the voltage on one side of the isolator will rise above the cut in level and the isolator will switch on. This is where a problem will arise. The load put on the cable between the two batteries will cause a voltage drop to occur on the rear end of the cable and if the rear battery is low enough, the isolator will switch off.
Now that the load is removed, the voltage in the cable rises back above the cut in level and the isolator switches on again and the load is back on the cable so the voltage drops again, so on and so on.
You have a Catch 22 situation. Besides dramatically increasing the time it will take to charge the rear battery, as you can imagine, this constant switching on and off could be very detrimental to your electric's.
There is a quick and easy way around this. Simply move the isolator to the other end of the cable, up at the front of the disco.
Cheers

[walker]

Hmmm. I will have to look into that a bit more. I am an electrician so maybe it is some of your terminology that I am not getting straight. Load does not cause voltage drop. Cable size & length will cause voltage drop. However I have used a much larger cable than necessary to cope with any voltage drop.

However I will measure the currant & the rear end of the cable when the secondary battery is low and see what I get. Normally the charging current to the battery is only about 30A peaking at maybe 40A. The cable I hae run is rated to 120A.

The only reason the isolator is at the back is to keep it in a safe dry place and anyone who has seen how I drive will no under the bonnet is never safe nor dry  :twisted: