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Charging from 48V DC

Posted: Tue Sep 11, 2018 11:43 pm
by dracekvo
anybody knows, is it possible charging electric car directly from 48V DC power source?

I have on home sollar pannels with 48V 500Ah lifepo battery (usable 20 kWh energy). If I want charging car, I need use 5kW inverter from 48VDC to 230VAC and original car charger. This solution is working, but not efficient. There is losses energy on conver DC to AC and back to DC.

Nobody know about possibility charging car with charger like chademo, but with integrated DC DC convereter and input 48 volts?

Re: Charging from 48V DC

Posted: Wed Sep 12, 2018 11:04 am
by Don
Most DC to DC converters also go from DC to AC and then back to DC again - I would be surprised if that's much more efficient than your current inverter


Re: Charging from 48V DC

Posted: Wed Sep 12, 2018 11:43 am
by jray3
Indeed Don, and DC-DC converters can be as low as 60% efficient, though I think ours should be in the 90-95% range. They are a major culprit in killing EV conversion battery packs, and their standby losses can EVen kill the 12V battery if you only disconnect the HV side when the car is stored.

I've charged both MR BEAN and a LEAF off of 48V via the Outback Power inverter on my tiny solar garage trailer, but that was just with our stock 8 amp EVSE. Next to try it at 120V 16 amps using my SPX (now Bosch) Power Express dual-voltage EVSE. :mrgreen:

Re: Charging from 48V DC

Posted: Thu Sep 13, 2018 12:40 am
by JoeS
dracekvo, similarly to you, I also have a 48v battery --> 4kW inverter to produce 240vac --> J1772 EVSE --> onboard charger --> i-MiEV battery pack. Haven't measured the 48v power draw to compare to CaniOn charging current&voltage readings, but I'm sure it's not very efficient. In my case, I already have it, it works and is paid for, and I have no need for efficiency, as I have plenty of 'free' existing solar to recharge the 48v pack and I'm not in a hurry. The key point for me is that I have the ability to recharge my i-MiEV when the grid goes down.

Searching to improve efficiency, any other solution will take time and money. The only consumer CHAdeMO charger I'm aware of is SETEC, and it runs off an ac input.

Simply adding more solar panels to recharge the 48v pack a little faster may be the most cost-effective solution for the dc-ac-dc charging system inefficiency.

Re: Charging from 48V DC

Posted: Thu Sep 13, 2018 6:16 am
by coulomb
I wonder if you can connect 48 VDC directly to the L1 and L2 inputs of a J1772 connector. Yes, it's supposed to see AC, but there is a PFC (Power Factor Correction) stage that is capable of boosting say 48 V to the ~400 VDC needed for charging the battery. You can't have it running at full power; even 3000 W would be about 3000/48 = 62.5 A. But with J1772 you get to tell the charrger what current to draw; if you say 6  A and it happens to be 110 V input, then that means 660 W. So for 48 VDC, it should mean 6 A × 48 V = 288 W, which might not be enough to run the blowers and pumps. But say 16 A (remember that there are ~20 A fuses in there, and they are only AC rated, so you don't want to blow them) would be around 768 W. About the same as a 120 V charge at 6 A. This would be as efficient as the charrger itself, with no losses converting the 48 VDC to 240 VAC first. It's possibly about as efficient as you can get.

The custom EVSE would have to have a DC rated relay or contactor inside it; most EVSEs would only have AC rated relays or contactors.

I don't know if it's worth attempting to actually build such a thing; this is more of a thought experiment.