DC-DC charger as an alternative to generator?

[burleyman]

Looks great. I've also seen that my camper's inverter (charger) outputs 13.3vdc most of the time. Not enough.

I'm curious, can you tell if your engine grunts or changes rpm when beginning charging? Mine doesn't, but some have in my past experience.

Waiting around for Lifepo4 prices to fall and to also include bluetooth monitoring is definitely a plus.

More redneckedness years ago. Permanent inverter behind front grill, permanent extension cord to rear. 12v power supply adjusted to 14.4v installed in box on camper tongue. Charging while driving. Inverter turned on and off with continuous duty relay via a toggle switch.

Thanks for the posts and pictures.

 

[Martinjmpr]

Looks great. I've also seen that my camper's inverter (charger) outputs 13.3vdc most of the time. Not enough.

I'm curious, can you tell if your engine grunts or changes rpm when beginning charging? Mine doesn't, but some have in my past experience.

I didn't notice any change in idle speed on the truck while the inverter was running. It's a 230A alternator and the inverter is only pulling about 33A so I can't imagine it would have much effect. Obviously I'm not running a lot of other stuff at the same time I'm charging the battery.

 

[Peter_n_Margaret]

about 33A so I can't imagine it would have much effect.

Assuming 100% efficiency, 33A x 14.2V = 487W divided by 746W per hp = 0.63hp.
Cheers,
Peter
OKA196 motorhome

 

[Martinjmpr]

More redneckedness years ago. Permanent inverter behind front grill, permanent extension cord to rear. 12v power supply adjusted to 14.4v installed in box on camper tongue. Charging while driving. Inverter turned on and off with continuous duty relay via a toggle switch.

As we used to say in the Army, "If it's stupid but it works, it isn't stupid."

My only concern about what you posted above is having the inverter permanently mounted behind the grill. Did you do anything to waterproof or protect it? I would be worried about rain, dirt, etc, getting into the electronic parts of the inverter.

 

[Martinjmpr]

Assuming 100% efficiency, 33A x 14.2V = 487W divided by 746W per hp = 0.63hp.
Cheers,
Peter
OKA196 motorhome

Also you have to remember that using the inverter to charge the camper battery is something that only happens when we are stopped. I don't use this setup when we are moving down the road.

In theory I suppose I could use a setup something like this while moving (as Burleyman did above.) As long as all the sensitive electronic parts could be protected from the extremes of weather I think it would work but in my case, at least, it's simply not necessary.

This coming Summer will be our first "full" summer with the trailer and our first Summer with the LiFePo batteries (I didn't install them until November of last year.) Now that I have a way to monitor the power draw (via the Bluetooth app for the batteries) I'll have a better idea of how much power our 12v fridge actually draws (the 12v fridge is the main power draw in the trailer, everything else is negligible.) Our previous trailer had a 3 way (120v/12v/propane) absorption fridge so getting used to this new-to-us large compressor fridge will have a bit of a learning curve. The fridge itself also needs some adjustment as it is over-cooling by quite a bit and freezing our food (and of course drawing an excess amount of power while it does.)

As with anything else in life, learning how to make everything work is a constant process.

 

[rruff]

Now that I have a way to monitor the power draw (via the Bluetooth app for the batteries) I'll have a better idea of how much power our 12v fridge actually draws (the 12v fridge is the main power draw in the trailer, everything else is negligible.)

I bought a cheap battery with BT last fall, but it doesn't seem very accurate regarding power. A calibrated shunt and meter are needed I think. The one I bought was ~$35. You need to measure energy used over time, not just what it consumes when it kicks on. For room temp conditions a portable fridge typically consumes ~350 Whr/day but some are a little better than others.