Monday, Jun 06, 2016 at 13:01
Again we get back to the fact that if large currents are flowing you don't need high terminal voltages, a Marine pro for instance will draw around 50A when discharged to 50%SOC and connected by around 6 metres of 6B&S cable to a standard alternator out putting around 14.3V. The batteries initial terminal voltage will be around 12.8V when first connected, after around an hour the current will have dropped to around 18A and the terminal voltage will be 13.7V
Total charge put back in to the
battery in 1 hour 40 minutes is around 42.78A (85.5%). A 20A DCDC charger would have replaced 33.33A in the same time. (66.66%)
Your also your assuming the DCDC charger will be putting out more voltage, if your batteries are down it won't, it will be in current limiting mode and the voltage will also be low.
If you had 20mm2 to the camper batteries then the alternator will put the bulk charge back in quicker. Your fridge will be cycling on and off and your lights will most likely not be on when your travelling.
I have two runs of 6B&S cable to the camper, a 100Ah wet aux in the car and two 100Ah AGM's in the camper, if I'm camped for three or four days and run the batteries down to 30% SOC (two fridges running, heating, pumps etc) it takes around a four hour run to recharge all batteries. With a 20A charger I would only bring the campers batteries up to 70%. A 40A charger would be quicker for the camper batteries but adequate cabling would still need to installed and then I would still need another charger for the car aux or a VSR setup.
I fail to see what rear winch has to do with it, your not likely to be silly enough to run the winch via a DCDC charger or direct charge cabling for that matter?
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