fred22 Posted March 19, 2012 Share Posted March 19, 2012 Hi, I am sure this has been covered before but I cannot find it. What size wire should I be using to connect the battery (85amp) to the battery charger? If I decide to up the battery to 110 amp will the same size wire cope? Link to comment Share on other sites More sharing options...
Guest Tracker Posted March 19, 2012 Share Posted March 19, 2012 The battery cables will never have to carry 85 or 110 amps as their current carrying capacity requirements are established by the higher of the maximum discharge rate if all the appliances and lights are on and the input from the various individual, or combined if they can work together, charging source(s) such as engine alternator (about 10 amps usually, but I allow for 20), on board charger (not sure but I think about 5 ish amps?) and solar panel (an 80 watt panel = 7 amps). On that basis I generally use cable capable of carrying 30 amps because it helps reduce voltage loss and does not cost that much more than lower amp cable. Don't forget fuses and its better to buy decent quality fuse holders, connections and fuses than some of the cheap and nasty crud as sold by many motor factors ! If in doubt don't risk it - consult a competent auto electrician better than a non functioning system - or worse - a fire. Link to comment Share on other sites More sharing options...
lennyhb Posted March 19, 2012 Share Posted March 19, 2012 I agree with Rich but I would go for a bit heavier cable as I've clocked our gel batteries charging at 44 amps on engine start up when they have been a bit low. Link to comment Share on other sites More sharing options...
Brambles Posted March 19, 2012 Share Posted March 19, 2012 fred22 - 2012-03-19 7:45 PM Hi, I am sure this has been covered before but I cannot find it. What size wire should I be using to connect the battery (85amp) to the battery charger? If I decide to up the battery to 110 amp will the same size wire cope? Others have answered this as if charging from alternator. Can you comfirm this is purely the cable from the Charger to the Battery? Also what is the max current output of your charger, then I can work out what size cable you need - properly. Making the assumption of a max 3 meter run of cable, and 16 amp charger you need minimum 2.5mm squared cross section. If you are over 3 metres then 4mm squared cross section is more suitable. In the case of charging from the alternator via the slave relays, it is fair enough saying it charges at 10 Amps, what happens if a cell goes short circuit or indeed you just switch everything on with engine running and draw a heavy load, such as a diesel heater firing up. You need a cable able to cope with the fuse fitted. Normally this is 30 or 40 Amps, so the cable needs to be at least 6mm cross section and able to carry 40 Amps. I have based figures on using standard un tinned cable and normal PVC insulation as this is often what people buy in the aftermarket. Link to comment Share on other sites More sharing options...
fred22 Posted March 20, 2012 Author Share Posted March 20, 2012 Yes the leads I am looking for are the ones solely from the charger to the battery. Since posting my original question I have, today,been able to obtain an instruction manual for my charger. It recommends wire of a min size of 2 mm sq to cope with the 7.5 amps produced. Many thanks to all those who responded to my post. Link to comment Share on other sites More sharing options...
Brambles Posted March 20, 2012 Share Posted March 20, 2012 At 7.5 Amps you can actually get away with 1mm Squared, but volt drop is just over the recommended and so 2mm Squared (2.5mm Squared is te net stamdard size is desireable.) 7.5 Amps is not very powerful charger if you are using a lot of power such as lights and an extractor or heater fan, or 12 volt TV. You will then start drawing power from the battery. If you increase the size of batteries then it might also be worth considering investing in a 12 or 16 Amp charger/powersupply. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.