Another Day, Another Charger

I ticked off one more item on my extensive “to-do” list by wiring up my old Renogy charger that lets me charge the house batteries off the alternator when the engine is running. This was a simple matter of hooking up a bunch of heavy-duty wires to the right places. It turns out my uncle had a spool of 6-gauge wire in the shed, which can handle up to 65 amps of current. My charger only goes up to 50 amps, so this was perfect for the job.

I had a much shorter wiring run than the last van. The vehicle battery is under the driver’s seat, so it only took a few feet of wire to connect that to the charger, and then to the house batteries. After everything was connected I started the engine to try it out, and it worked perfectly.

I got a new message in the Renogy app: “Current limit.” This isn’t a problem, but an indication that the charger is limiting itself to its 50 amp maximum even though more power than that is available. I never saw this message in my previous van! Either the E250’s alternator was less powerful than the Transit’s, and/or I lost a great deal of power through the long wires that used to operate the wheelchair lift. Even at idle, I was getting 685 watts of charging at 50 amps, and will get that anytime the engine is running. It was definitely worth moving this over from the old van! Because I already owned it, it was essentially “free” for the new van.

Here’s something else that blows my mind. I’m going to have 600 watts of solar panels on the roof. I’ll never get the full 600 watts out of them, but 300-400 is definitely possible. That means that when I’m driving down the road, the combination of solar and alternator charging could put more than a kilowatt into my house batteries! That’s crazy, but makes me feel better about adding some higher-draw accessories, like a decent-sized power inverter that will let me run a small microwave oven.

While looking up my SOK batteries’ maximum allowable current output (100 amps) to make sure a microwave is possible, I also noticed that the maximum allowable current input is 50 amps per battery connected in parallel. My charging test was fine, but that was the limit of what the single battery in the new van could handle. After installing solar, I’d actually need both batteries in there just to soak up the current from both chargers. The 600 watts of solar divided by 12 volts equals 50 amps. Add that to the 50 amps from the DC-DC charger, and 100 amps of charging spread across two batteries would push both to their limit, but not beyond. And like I said, I’ll never actually get the full 600 watts out of my solar panels, which builds in a safety buffer to stay below the batteries’ limit.

Since I was thinking about all this anyway, I moved my second battery from the old van to the new one, as well as the cables to connect both batteries together, just to get it done. Now I’m ready for solar, which I think is my next major project now that the correct roof rack mounting hardware has arrived. I took a quick Home Depot run on the motorcycle to pick up the nuts and washers I’m going to need to finish that job.

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