27/03/08 - Split Charge

So having installed the physical bits of the winch, I now need a split charge system to run the two batteries. The winch is connected to the second battery in the boot and the main battery runs the normal car systems. A split charge relay connects the two batteries together, but only when the charging situation is good. The relay takes a feed from the alternator and when it is "good" it connects the batteries together. There are many types of split charge relays around but many are only suitable for low current applications such as caravan systems.

The relay below is rated at 200Amps continuous which means it can cope with high currents between the two battery systems when they are connected together.

 

The diagram below shows the overall wiring diagram, click on it for more detail.

Looking at the picture you will notice that the split charge relay is not connected to the alternator output, this is because the Jimny manual has in big capital letters the comment that no load of any sort should be applied to the Alternator "Bulb" connector.

Therefore I have built a small box which takes the alternator output and feeds it to a small, high impedance relay which then feeds the split charge relay. This has both the advantage of protecting the Alternator and permitting me to put in some other switch options.

The diagram below (click for more detail) shows the arrangement. In switch position "1" Twelve volts is fed directly to the switch charge relay, forcing the two batteries together - this is the equivalent of a set of jumpleads and will help should the main battery ever need a jump start. A red LED and buzzer warn when the switch is in this position.

Switch position "2" connects the output of the alternator "Bulb" setting to the split charge relay. This means the batteries are only connected when the engine is running and charging - this is the normal position and a green LED shows when this is active.

The third position disconnects the two systems, isolating the batteries from each other. A red LED warns of this position.

All the parts were purchased from Maplin electronics www.maplin.co.uk. It should be noted that the LED's are special "12 volt" LEDS that do not need a current limiting resistor, if you use any other type of LED you WILL need to put in resistors. Also the relay I have specified is POLARISED - this means it will only work when the coil connections are the correct way around. This is not mentioned in the Maplin specification and caused me a lot of head scratching!

Parts List:

• Green 12v LED - CJ69A (1 off)
• Red 12v LED - CJ70M (2 off)
• High Impedance 12Volt Relay - N17AW
• 4 pole 3 Way Rotary switch - FF76H
• 12volt Buzzer - FL40T
• Case 50x50x20- N53FK
• Knob - FE76H

So now I have a winch, dashboard winch control switches, twin batteries and a spit charge system - so thats about it for now!

However, the more observant of you will have noticed the solar charger panel in the main circuit diagram. This is a cheap panel mounted in the rear window and connected to the rear battery. This provides a trickle charge to the rear battery when its sunny, whilst this is never going to properly charge a winch battery it will help keep it healthy,