SpinnerUp

I've got a 2017 Savana with the factory variable voltage charging system running on an 105 amp alternator. Can I just swap in a higher capacity GM alternator or does the ECM/BCM need to be programmed for it? Local dealer says you can swap in a larger but can't go smaller. Anyone have any real world experience with this? I want to connect a house battery charger that can peak at 50 amps to the house battery and am wary of the 105 amp alternator being able to supply that much current. The current required by the house battery would drop pretty quickly but I'd like to have a little more overhead on the supply side, probably go to a 150 amp alternator.

Thanks

oilcanhenry

105 Amps is the standard output for most factory GM alternators. You can go all the way up to 160 Amps, so 150 Amps should not pose any issues that I am aware of.

mountainmanjoe

What kind of devices are you going to use?

GeneveConversionVan

If the charger can peak up to 50amps, doesnt mean It will. depends on the load, and source. But I agree, I would add abigger alternator, just to be safe, and It wont hurt.

mountainmanjoe

Why is there charger?

SpinnerUp

I'll be connecting to a Redarc ,or similar, BCDC1240 DC to DC charger rated at 40 amps, but can draw 50 on surge. It will charge a 220Ah house battery. Camper van conversion. I'll end up with 300 watts of solar panels as well. I get off grid for recreation.

SpinnerUp

And I forgot the main question, from personal experience, is adding a larger capacity alternator a simple plug and play with these variable voltage charging systems? Thanks for the input.

mountainmanjoe

I don't understand what the charger is for. Why not hook the battery up to the main 12v system?

SpinnerUp

Mainly for fuel mileage considerations, the ecm/bcm manages alternator output based on various system inputs like temperature, start battery voltage, headlights/hvac fan running, wipers on/off and vehicle speed. These inputs will vary output voltage from 11v to 15.5v. My house batteries are in the van so I don’t want any off-gassing of course, so I’m using 2 6 volt 220 Ah batteries in series. To get a full charge to prevent/minimize sulphation they need a 3 phase charge cycle. 14.7v bulk charge, 14.7v absorption charge and then a drop to 13.7v float. The van charging system can’t provide it obviously with the output voltage changing all the time. The DC-DC chargers take whatever voltage the system is providing and change it to provide the charge profile required by whatever chemistry batteries you’re using, regular flooded, gel, agm or lithium. The manufacturer of these batteries recommended approximately 44amps for the initial bulk charge part of the cycle, thus the 40amp charger. I added a couple of attachments with additional details on the GM VVA system. The AGM's are spendy, $600 for these 2 batteries. I don't want to trash them quickly with improper charging. The Redarc chargers are pretty nice in that they also take solar as input and give priority to the juice coming from them over the alternator reducing load on the engine.

mountainmanjoe

Yes the RVC system varies the voltage to balance loads but the other goal is precisely to provide charging phases (among other things). It was designed to not cook the battery.

If your charger doesn't get enough power to provide 40A, then it'll just charge a bit slower that's all. I would just try it with the alternator you have and see if it's sufficient or not. For 440Ah I think it will be. (Around 1400W right?) 40A is like running headlights and AC at the same time.

Anyway, I wonder if the charger will play nicely with the van's system. DC-DC converters adjust the input current to regulate voltage, meanwhile the RVC sytem will be adjusting output voltage in order to regulate the current. So I wonder how the two will interact, and if it introduces any instability/oscillation ...

Why did you go with AGM batteries?