Monday, Jan 29, 2018 at 13:08
Hi Rod,
The bottom line is you need to put back in what you take out no matter what system you use. If the car is the only charge source then alternator or DCDC charger must replace this in your drive times. You may not need to replace it in ones days drive, you might be prepared for instance to let the batteries run down over two or three days of short trips knowing that the next trip will be long enough to recharge them fully, or you may just use your solar or other charger to top them up. I have four charge sources in my setup, the alternator, solar and a fuel cell for when the sun don't shine or I don't want to setup up the solar for some reason, and AC charger.
In your case your going to replace around 100Ah daily be so the minimum in a DCDC charger would be a 40A unit for a three hour drive time, if you run the batteries down to 30% your looking at 5 to 6 hours drive time. Of course that's charging off car only, if your supplementing with solar then you need to work out what the solar is contributing and then size the charger appropriately, personally I would size the charger without taking into account the solar to allow for solar charger failure, but depending on how you use your setup you may not need to worry about that.
How are you finding the lead crystal batteries, I have read they don't like high charge currents, I have also read some comments by another that did some testing of various size batteries and indicated charging them form zero% SOC straight off an alternator was not a problem?
Personally I don't believe in putting all your eggs in one basket, when I'm travelling I like enough redundancy that I'm not going to need to purchase equipment or do repairs in the field if something fails as it usually ends up mucking up the trip or cost an arm and a leg.
In my set car aux is charged via a VSR. Van batteries by a DCDC charger which also has an inbuilt MPPT controller. I also have a PWM solar controller in the van that was there before I installed the DCDC, either controller is switch selectable to charge the vans batteries but I usually use the PWM as I find it puts a little more into the batteries on overcast days contrary to the popular belief the MPPT should. The DCDC can be bypassed so that the Vans batteries can be charged directly off the car, or the cars aux charged via the vans chargers, this comes in handy in caravan parks etc as I just leave the car connected to the van and use the van A/C charger to maintain both van and car batteries. Also when camping as most times I can just get away with setting up panels for the van and bypass the DCDC to charge the car as
well without having to set up panels for the car too.
Personally I'm not a fan of Redarc equipment it tends to be expensive for what you get and generally
well behind other brands with allow user many user defined parameters. Their about to bring out a new unit that does everything, DCDC/Solar as
well as controlling all the electrical equipment, lights, water pumps, heating, fridge, water levels display etc all from one display unit. Form one perspective it is the only piece of electrical controller you need to install, but from a redundancy perspective if it breaks down I imagine you'll loose everything. Do the people that come up with these ideas actually use them on a day to day basis I wonder and for remote travel etc. Suppose if you only travel the main roads and never far from someone who can replace the unit then not so bad, but if you do a lot of remote travel/camping etc doesn't seem like a good idea to me. I also wonder if they will be providing a repair service other than warranty for these units or will they be throw away? The other issue is most auto electricians and van manufactures etc never label anything, I would hate to have one of these unit replaced by your typical outback repairer, I certainly wouldn't be expecting all the cables to end up connected to the correct terminals.
Getting back to your question, I would go with the Victron or maybe have a look at the Enerdrive units etc.
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