Durite split charge question?

Sneaky Pete

Member
Joined
26 Nov 2009
Messages
826
Location
In the shadows of Faslane.
I am about to fit a split charging system into my boat. The alternator output is 55amps the Durite split charger is rated at 140amps. The circuit requires a fuse either side of the split charge unit. Question is this would 10mm² cable rated at 110amps be alright and what fuse rating should be used either side of the terminals for this circuit it is my intention to use two midi fuse and holder?
 

Alpha22

Active member
Joined
22 Sep 2003
Messages
1,400
Location
Cambridgeshire
Save yourself a lot of grief later on and simply fit a Voltage Sense Relay or VSR. The contacts on the Durite relay will get pitted and it will start to fail.

To answer your question..... think about the max current it may take when charging from flat.... your fuses need to be bigger than that, but not much. 60A would probably be suitable.
 

VicS

Well-known member
Joined
13 Jul 2002
Messages
48,089
I am about to fit a split charging system into my boat. The alternator output is 55amps the Durite split charger is rated at 140amps. The circuit requires a fuse either side of the split charge unit. Question is this would 10mm² cable rated at 110amps be alright and what fuse rating should be used either side of the terminals for this circuit it is my intention to use two midi fuse and holder?

I take it this is a Durite voltage sensitive relay (VSR) ( http://www.split-charge-relays.co.uk/contents/en-uk/d84_vsr--split-charge-relay_kit.html )


The fuses should be rated at more than the maximum anticipated current ( 55 amps ) but less than the safe working rating of the cable ( 100amps ?). 60 or 70 amps will be fine

The fuses should be located as close to the battery + connections as possible so that they protect the wiring from the very large current that could flow from the batteries in the event of a short circuit.

BUT

if the cables runs ( total from alternator to relay + relay to battery) are long your 10mm² cable may result in excessive voltage drop, although safe enough

It'll be Ok up to around 7 or 8 ft but for 10ft I'd use 15mm² and for 15 ft 20mm². However these are generous as you will not likely be drawing 55 amps continuously for long periods unless you have some very large batteries.

That's the reason you see 3 metre and 5 metre fitting kits offered with the relay.

( I am not including the negative cable run in the calculations because I assume it is a very heavy cable capable of carrying starter motor current and there fore causing negligible volts drop at 55 amps)
 
Last edited:
Top