question

sebcbien avatar image

Charging 48V batteries from alternator

Hello,

It's been some time now that I'm trying to find a solution for my next van installation.

I first came with this diagram with 2 victron 12V LifePo4 (24v): https://community.victronenergy.com/questions/65042/wiring-diagram-for-a-van-install-with-multiplus-ii.html

Now I would like to use the Pylontech 48 V batteries and a Multiplus II 48V/3000 for efficiency, price, form factor, ...

I searched for a 48V buck/boost around 50/100Amps and found nothing affordable and easily available. I do not want to install a second 48V alternator... At least not at first, I have a strong 250A 12V alternator.

The basic schematic would be as follow:

- A "small" inverter under the hood would allow to feed the Multiplus at the rear of the van without needing big wires (and losses).

- The inverter would be activated with a D+ signal to avoid discharging the start battery

- The installation would be very simple

- I could easily "tune" the amps drawn from the inverter with the AC input current limiter of the Multiplus

Is it possible ? do you see any problems with this kind of setup ?

Thanks !

Seb


Basic diagram without solar, Cerbo GX etc etc etc.

1608853352113.png

https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom1608852776094.png

MPPT - Solar Charge ControllerMultiplus-IIPylontechdc dc converters48v battery
1608852776094.png (3.0 MiB)
1608853352113.png (161.7 KiB)
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3 Answers
danhig avatar image
danhig answered ·

I wanted to go this exact route for the exact reasons you mentioned as well. Then after months of online research and conversations with people that sell and install these systems for a living i elected to go the 12V route because of the following.

#1 Keep it simple (fewer parts to break on the road)

#2 Off the shelf parts availability

#3 No conversion losses 12-> 48 and then 48 to 12->

#4 For my RV most items are 12 volt except microwave and AC which are not used often so i was designing the 48V for the exception not the rule

#5 LifePO4 battery configuration / upgrades are simple as being in parallel

#6 Dual 2/0 or single 4/0 Welding cable not difficult to crimp and easy to route even in large gauge sizes


Good luck with whatever option you choose.

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bathnm avatar image
bathnm answered ·

A lot of losses and conversions going on.

Take a look at https://www.safiery.com/

They have 48v Alternators and some bi-directional DC/DC devices that are rather cool. All CANBus controlled and can take 3Kw at 12v and convert it up to 48v, to do just what you want.

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pierrot avatar image
pierrot answered ·

Hello,
Did you have a look at the 12V->48V @70A (BB124870) Sterling Power Battery to Battery Charger ?
https://www.sterling-power-usa.com/SterlingPower12volt-to-48volt-batterytobatterycharger.aspx

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Thank you very much !

I already know this brand but I wrongly thought that it was for the American market only but I just just double checked and found they are also imported in EU !

p.s. I'm still interested by someone responding to the possibility to feed the Multiplus with an inverter (this is convenient to reduce cable loss with high amps on DC when the batteries are far from the alternator in the back of the truck)