question

craftercamperconversions avatar image
craftercamperconversions asked

What’s the best way to join 48vdc & 12vdc Systems

I’m considering installing a 48vdc system (48v 100A second alternator, Wakespeed WS500 Ext Regulator, 48v 200A LFP battery bank, & 48v Multiplus 230ac inverter/charger) to power the living space in my VW Crafter Camper Van. Of course, I also have the original 12vdc factory installed system (12v 180A alternator, 12v 95A starter battery).

I would like both alternators to charge both the 12v and 48v battery systems. So, when I’m driving, and the 12v starter battery is full, the charge then goes to the 48v battery, and when the 48v battery is full, the charge goes to the 12v battery, or all charging stops. I’m simply wanting to extract every amp. I intend to use both 12v & 48v systems to power loads.

I’d appreciate your design suggestions. How do I design this system? At some point I need a crossover between the two systems.

Is it best to leave the alternators charging their respective batteries and introduce a bi-directional converter between the batteries? Is it best to use chargers between the batteries instead? Are converter/chargers available?

Any help would be appreciated, thank you.

48v battery
2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Thomas H. Clancy avatar image Thomas H. Clancy commented ·
As your 48v system has over 4x the capacity of the 12v system, i wouldn't think about transferring power "up". Best install a dcdc charger with an output of ~20a to keep the 12v system happy.
0 Likes 0 ·
Alistair Warburton avatar image Alistair Warburton commented ·

I agree with the previous comment but if you wanted to go from 12 to 48, as a backup or redundant system you may want to look at Orion-Tr DC-DC converters / chargers.
I don't think there is a 12 to 48 converter or charger and you would need a charger not just a converter. Going 12 to 24 and then 24 to 48 may be an option but without a small battery in the middle it could be unstable. Honestly it doesn't sound all that practical.

If it were me I would get a small inverter, an isolated one, to give me 230/120 VAC, whatever your system is, from the 12V and then use that to charge the 48 via the Multiplus.

The AC input current limit can be used to ensure you don't overload the 12V system.

Note that this would be an unsupported configuration and I am not an expert...

0 Likes 0 ·
1 Answer
Kevin Windrem avatar image
Kevin Windrem answered ·

Consider a bidirectional DC-DC charger. The Safety "Scotty" is such a device and includes smart alternator control:

https://www.safiery.com/3kw-12-48v-canbus-integrated-buck-boost-power-char

Since it is bidirectional, you can power your 12 volt loads (lights, etc) from the 48 volt battery, charge the 12 volt battery from solar/Multi or charge the 48 volt house battery from the stock alternator (in addition to your new 48 volt alternator) if desired.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Related Resources

Additional resources still need to be added for this topic