Copper Harbor, MI 2018
Ah, my mistake, I thought you had a 120V coil.
Yes, battery voltage will change the coils heat ouput. Efficiency will stay the same, but it will take a bit longer at lower voltages.
V=I*R V/R=I
12/R=25 R=0.48ohm
13.8V/0.48ohm=29A
12.4V/0.48ohm=26A
29/26=1.12 So a 12% increase in heat output at 13.8V.
After getting that water heater working I got to go on a test run with it to Copper Harbor, MI. Luckily for us it was super cold lol, gave me a chance to test out the water heater and it worked great! Midwestdrifter you were right about the numbers, I noticed that it seemed to heat up in a much shorter time with the van engine running at 13.8v compared to sitting on the dewalt charger I bought, putting the voltage at 12.8v or less. The Dewalt charger didn't output at 30amps right away, seemed to let the battery drain down a bit before it upped the amperage. Which is what I would expect from a automatic float style charger. Either way it worked out great, the water heater would run with the van plugged in or with the engine on. I tried to avoid running it without a charge on the battery for an extended period.
Here are some pictures from the trip. You can see the
outdoor shower tent that I used, which worked perfect and prevented us from doing the swimsuit showers we did last year.
Another place we set up the shower (worked better on pavement than dirt/mud):
The ladder worked as a shower rack also:
In case you were wondering, yes that is a jetski trailer... I had to figure out a way to get 5 bicycles, 5 people, two dogs, and gear 9 hours north and what I came up with was taking my jetskis off my trailer and attached the bikes to that trailer in a makeshift manor and using the trailer cargo box to help out with gear. Turns out it worked out great and we just left the trailer at camp when we didn't need the bikes.
Worked great getting to the trails too: