DC to DC House Battery Charging?

[cv4wheeler]

I am glad this long series of posts is still of some use to people, that is one of the great things about the internet.

I never felt the need to replace or modify the existing truck alternator. It puts plenty of power out to the batteries without overheating. A second unit would be nice ,as it would provide redundancy, but is not needed for camper battery charging.

As far as I can tell there was no way to provide the needed 14.8 volts to the batteries without electronics between the alternator and batteries. Per my mechanic, jacking the voltage out of the alternator to 15+ volts (even with huge wires) was going to risk the truck electronics. Now, if I had a second alternator JUST serving the camper batteries, then it would be possible to go this route. The Sterling unit was a splurge, but so far I am very happy with it.

Yes, my old Honda EX650. It has served me well over the years, but I still need to get a bigger unit for stays at altitude. Seems like it is just about time to make that purchase, now that spring is in full glory here in California and I have stopped the water infiltration into my garage. Need to replace the fridge too, gotta get on it!

[terry735001]

you did not say what type of truck you had the camper on and all so know post is old

on most 2000 year and up GM truck the alternator is told what to do by a pick up wire in the dash or on top of the motor and then the trucks ECM send a PWM single to alternator

most GM alternator are a 3 wire alternator that is in a 4 pin plug

this is off the top of my head here
1 wire is hot at all time RED to Rccm E739
1 wire is hot when key is on PNK
1 wire is PWM single alternator GRA to PCM E23

what happens is the key when hot wire is Yed off alot on top of the motor and pulls down on side lines and is spiced off so much you get about 15 feet or more of wire before the alt see it

BY moving side pick up wire more to real voltage OR on system you want it could help

if you moved the pick up wire all the way back to your lager battery bank it would read right back there but you could see 15 volts or higher up front

it may cost alot less money to move the trucks 12v batter back with all the others and run new 0.2 or high wire back up to the starter

[cv4wheeler]

For posterity, my truck is a 2000 GMC Sierra 2500, the "light duty" version of the 2500.

[harryn]

Usually alternators don't put out much power until the engine rpm hits around 1000 rpm. That is why some vehicles have a "fast or variable idle" option. I know on sprinter vans this is not that expensive if ordered with the van, but quite an expensive add-on option.

No idea if this is possible on your truck.

I am a big fan of alternator charging, but it does require:
- fast idle
- battery - battery charger
- ideally at least a 200 amp alternator

This also enables making the "house" battery a different voltage if you prefer. For instance, if you ever want to use 3 - 4 KW inverters, then 24 or 48 volt are quite handy. That is why I tend to use 48 volt LiFe house battery packs, as 4 + KW inverters are common for the projects I work on.

To work correctly. Even at fast idle, you won't get 200 amps, more like 50%, and some will go into operating the vehicle. As an alternator ages, it's output declines, so it might be that you can restore some of the output just by replacing the existing alternator.