Cable from front to rear for Battery box

Gemaskerde Tuinvurk · Fri Jan 27, 2012 8:23 am

I've decided to go the battery box route, rather than the 2nd battery in the engine bay. (there are various reasons - e.g. space not such a big issue currently, and would like to use fridge / lights / etc when not close to the vehicle)

My question relates to the wiring I need done to the car, and some of the battery box wiring.

Based on all the reading I've done, I've come to the following conclusion:

cable thickness for LWB between batteries should be 16mm
will use 50amp in-line fuse close to the main battery
will be using the 50amp brad harrison connectors at the rear
will make a 'lead' of about 2m to connect the battery box to the connector at the back - will be using 16mm cable for that as well.
QUESTION: I want to install a second fuse close to the battery box. Should I do this close to the car connector in the cable running from the main battery? Or should I install it in the 'lead' I'm making? Or should I install it in the short piece of wire that runs from the battery box connector to the battery in the box?
will add fuses to the positive cables of all the connectors I'm adding to the battery box. QUESTION: Any recommendation on the amp rating of these fuses? (connectors are hellas, 12V and brad harrison for the fridge)

any help would be greatly appreciated

4ePajero · Fri Jan 27, 2012 8:52 am

Save yourself a lot of hassle and use a DC-DC charger.

No solenoids
Thin cables / wires
Intelligent charging (proper charging for a deep cycle battery)

Gemaskerde Tuinvurk · Fri Jan 27, 2012 10:56 pm

I would... but COST! DC to DC is for later.

I will be removing the battery box when not camping/on vacation, so I can trickle charge otherwise at home.

I'm going to measure the voltage at the battery to check if its above 14.1 (or ideally above 14.3). This should mean that hopefully with the voltage drop I would be able to charge the aux battery to almost 100%.

Gemaskerde Tuinvurk · Sat Jan 28, 2012 6:35 pm

well, good news and bad news...

startup is at around 14.3 - 14.4V... but after 30 minutes drive it drops down to 13.9V.

I did however switch on both aircons on full blast, and still it remained at 13.9V (before and after aircons), so I believe this is just the rate at which the regulator keeps it?

Any chance of adjusting the way the regulator works?

HBannink · Sat Jan 28, 2012 11:02 pm

Your start up voltages are fine and the drop shows that everything is working the way it is supposed to.

The high voltage at start is because you have drained from the battery by starting the vehicle and the alternator is pumping out more to replace that loss. the aircons draw less power than the alternator can generate and when the start power has been replaced the voltage drops and will do even more so if the aircons are switched off

Gemaskerde Tuinvurk · Sat Jan 28, 2012 11:16 pm

but I wont be able to fully charge the deep cycle with 13.9V

paw_by_paw · Sun Jan 29, 2012 6:05 pm

Hi Karl,
I found this on the net somewhere hope it helps for you.
I am also going the box way - later.

BatteryMate Isolater.pdf: (131.2 KiB) Downloaded 176 times

BatteryMate Isolater.pdf: (131.2 KiB) Downloaded 176 times

BatteryMate Isolater.pdf: (131.2 KiB) Downloaded 176 times

BatteryMate Isolater.pdf: (131.2 KiB) Downloaded 176 times

: Redarc%20car%20rear%20mount%202mega%20(Small).gif (14.87 KiB) Viewed 2405 times

Formula For Determining Inverter Size and 12v Fridge Freezers.docx: (16.79 KiB) Downloaded 122 times

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: Redarc%20car%20rear%20mount%202mega%20(Small).gif (14.87 KiB) Viewed 2405 times

Gemaskerde Tuinvurk · Sun Jan 29, 2012 10:15 pm

oh wow, thank!

Funny how some guys swear by negative to the chassis, while others disagree totally.

personally, I wont do the negative to chassis. Just seems to increase risk of a short somewhere, with no fuse to stop it.

CATS · Mon Jan 30, 2012 9:10 am

4ePajero wrote:Save yourself a lot of hassle and use a DC-DC charger.
No solenoids
Thin cables / wires
Intelligent charging (proper charging for a deep cycle battery)

I agree with oom 4E. After having had a solenoid National Luna now for many years and recently adding a DC-DC charger to my setup I can confirm that it really is what they all say it is. I have even been running my fridge in the back all the time even when just driving to work and back and the DC-DC charger pushes sufficient punch to keep it all topped up and still keeping some cooldrinks cold in the back. My solenoid system could never manage to do this and was drained after a few days when used like this.

CATS

Gemaskerde Tuinvurk · Mon Jan 30, 2012 10:25 am

CATS wrote:
I agree with oom 4E. After having had a solenoid National Luna now for many years and recently adding a DC-DC charger to my setup I can confirm that it really is what they all say it is. I have even been running my fridge in the back all the time even when just driving to work and back and the DC-DC charger pushes sufficient punch to keep it all topped up and still keeping some cooldrinks cold in the back. My solenoid system could never manage to do this and was drained after a few days when used like this.

CATS

Ok, ok... But maybe I don't fully understand the capabilities...

Where do you put the charger? In the rear with the batteries?

No need for solenoid then? Cable to rear is permanently connected to charger?

Cable thickness no longer an issue? Surely if you have more voltage drop the charger will take longer to charge?

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