DC to DC charger

pianotuna wrote:
Camper Jeff & Kelli,

Is there a cooling fan in the Victron dc to DC unit?

The charging total from the numbers posted suggest about 56 amp-hours went into the 400 amp-hour battery bank.

Were you driving or was this just idling the engine?

Does anyone know the efficiency numbers for the Victron dc to DC charger? (appears to be 87%)

The unit puts out 25 amps at normal input voltage, according to the pdf. That seems a bit strange to me. Perhaps I'm reading the wrong pdf? The "sales" pages says 30 amps continuous to 40 amps, at nominal out put voltage.

From that 87% it appears the alternator had to produce about 65 amp-hours.

The Victron apparently boost charges for 2 hours on the Li settings.

I know my unit does 19.6 amps. It is the 20 amp renogy unit.

I'm glad to hear yours is doing what you need!

I'm out in the TC again today idling the engine. Today I shut off all DC loads except 1 LED dinette table light. Inverter and all else is off excepting for dc electronic controls in fridge and water heater. Idling away, my input voltage is 13.6 and the output charge voltage is 13.7. The unit is hot again. It took half an hour to get to the too hot to touch point. Just guessing, 150 to 160 degrees. The unit has a large heat sink on it. Not smelling electronics. If I were to drive the truck and bring up the speed of the alternator and the output voltage, it may raise the charge voltage lowering the current and possibly the temperature. I have not felt the alternator to see what it's temp is/feels like. I'll run out and do a feel temp test on the alternator, and bring the engine up to 2K RPM for a couple minutes to see if that changes voltage readings to the DC DC input and outputs, hang on...
OK, the alternator is warm on the front just after the big radiator cooling fan, and hot a couple inches back to the rear of the alternator. The truck voltage goes from 13.6 at idle to 13.8 when revved to 2K RPM and current goes up just a little varying from 13.2 to 13.8 according to the BMS. The Victron dc dc charger only reports input and output voltage. I need to look at each battery's BMS for its report which differs and includes current. So, Engine RPM makes a small difference on my setup, I don't know if it's enough to change the time to charge or heat profile. I will have to take a drive to do that. My alternator is 160 amps so it should be able to handle the truck load and the dc to dc. It took an hour at idle to bring both batteries up to 90 and 91 percent charge. My latest weather forecast shows clouds and snow the next 6 days so I'll have to do some driving in the TC to keep the system charged. About an hour a day but tomorrow, I think I'll do some extra running around and bring the batteries back up to about 100%, then watch it slowly go down from there, with all the DC stuff that isn't necessary shut off to make things last longer.
About 5 weeks till I get the new Victron 3000 and get shore power again. Even though I installed 675 watts of solar on the roof, it just isn't enough for winter up here in the Seattle area.