View Full Version : Adding A 2nd Battery and Split Charge System


Blade
29-10-2003, 09:54 PM
Bit of a guide here, for anyone looking to re-enforce their power system, by adding a second battery in the boot



Firstly, what you'll need:-

4AWG Cabling - Enough to run from the front battery, to the boot (Minimum- larger, 0AWG for example, will carry the voltage, and keep it higher)

Smaller guage cabling, to carry switching current

2X Fuseholders, and fuses

Split Charging Relay - Not available from Maplins anymore, but available from CAD/Autoleads etc.

Second Battery, ideally suited to Deep-Cycle applications, larger capacity is preferable

Battery Terminals, to connect large cabling to Rear Battery

Assorted Connectors, for connection to relay/ground-point/front battery



Instruction:-

[list=1]
Fuse this cabling, within 18" of the front battery, before it enters the cars firewall, and before the split charge relay
Use suitable connectors to attatch the 4AWG cabling to either of the Large connections on the split charge relay
Use a smaller size cabling, and run a length to an ignition-live source within the vehicle. This may be your fuel pump, or more commonly, the +ve connection of your altenator. This results in the relay being actuated, when the vehicles engine is running
This ignition live source should be connected to the input of the split charge relay
Using the same smaller cable as the input connection, connect the output connection of the Relay, to a suitable ground source
Secure the relay in a safe, but accessable position, under the dashboard, or engine bay will be suitable
Next step is to connect to the rear battery, use a length of 4AWG, from the non-used large connector of the split charge relay, to the +ve terminal of rear battery
Be sure to fuse this cable a few inches before it reaches the +ve terminal of the rear battery
Run another length of 4AWG from the -ve terminal of the rear battery, to a suitable grounding point in the boot
Power on the engine, checking the voltage at the relay, to be sure it is being powered on as required, and the batterys are being joined together by ther relay while the engine is running. You should hear a click from the relay, as it actuates
A circuit breaker, along the cable joining both batteries is optional, but will give you an extra bit of control, allowing you to disconnect front and rear batteries as required
[/list=1]

In addition to these steps, it is also reccomended that you uprate the "Big 3" connections in your engine bay. That is:-

-ve battery to chassis
+ve altenator to +ve battery
-ve engine to chassis


Overall, this should give a tremendous improvement- Voltage levels to amps will be improved, allowing them to produce higher power levels, voltage drop from large cable lengths should be reduced, and the risk of flattening your front battery through playing for long periods while stationary should be removed aswell

http://www.talkaudio.co.uk/photopost/data/504/3164split.gif

Hope that helps

Rich

Boxer_IVE
30-10-2003, 07:51 PM
Originally posted by Blade
Use a smaller size cabling, and run a length to an ignition-live source within the vehicle. This may be your fuel pump, or more commonly, the +ve connection of your altenator. This results in the relay being actuated, when the vehicles engine is running


I would suggest only connecting the signal wire to the alternator's output to the charge indicator light. This ensures that the relay only ever operates when the engine is running. If you connect to a switched live, the relay will activate as soon as the ignition is turned on, but not when the engine is running, and could lead massive current draws on your main battery if the secondary one is flat.

Boxer_IVE
30-10-2003, 10:11 PM
http://www.kampenwagen.co.uk/images/Split_charge_relay.gif

Note: If you connect to the +ve terminal on the alternator (labelled B+ on the diagram), the split charge relay will always be on!

Oh, and ignore the 10A fuses - fit as big a fuse as you require with your wiring, this pic is lifted of a camper van site! :)