Couple of questions about DC-Dc charging
I've been thinking about adding a DC-DC charger now that I've added 400 amp hours of AGM batteries. There are lots of useful posts but I haven't run into a couple of things I'm curious about. One ...
Forum Discussion
noteven wrote:Most of the Renogy dc to dc charger cable recommendations result in a 25-50% alternator load penalty. For instance, based on their recommendations, their 40a dc to dc charger at full output would result in a 50-60a load on the alternator. In effect, you end up "wasting" 10-20a of alternator output.
My Renogy DCDC which I haven’t installed yet says input amps are 1.3 x output amps so 60 amp draw for a 40 amp output charger.
The charger is an isolator as well so you don’t need a solenoid or another isolator between the starting battery and the house batteries . . .
The cable run from our truck battery to our 40a dc to dc charger mounted in our truck camper was approx. 23 ft. Renogy recommends 4 gauge for this particular run. We used 2 gauge instead. With a 40a output from the dc to dc charger, our alternator only incurs a 43.5a load (8-9% load penalty). Alternator output voltage was 14.1v at the time we took this current reading.
We chose to mount/use a battery isolator next to the Renogy dc to dc charger in our truck camper vs. running a 20-25 ft. sensing wire from the dc to dc charger in our TC to the truck's engine bay. Another added benefit of mounting the battery isolator in the TC (vs. the truck) is zero parasitic current when the TC is disconnected/off-loaded from the truck.
