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DC charging at home?

LoudMusic

Member
Jul 21, 2020
698
766
Arkansas
I've done a little searching and not found much. Are there any options for DC charging at home? Home battery systems are beginning to become more common, and home solar definitely is. It would be great if we didn't have the losses of going from DC (PV) to AC (inverter) then back to DC (onboard charger) to get the electrons into our cars. A simple DC to DC converter, even if it's low kW output, could be pretty handy. I've been thinking about a relatively large home battery and solar installation for a future home. Having to add in $15,000 of inverters just so the car can change it back to DC seems silly.
 

RTPEV

Active Member
Mar 21, 2016
1,110
1,301
Durham, NC
This isn't what you are looking for, but it is kind of what you asked for: Wallbox Quasar | The first bidirectional charger for your home

It does make sense that there should be a way, in the Tesla ecosystem, to go directly from Powerwall to vehicle without having to go through an inverter...but given the expected price of the Wallbox Quasar, I doubt it would be as cheap as you are hoping, and certainly not cheap enough to ever give you an ROI over the relatively small losses that you'd get in the inverter/rectifier.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
7,035
8,652
Boise, ID
Are there any options for DC charging at home?
Basically no, unless you want to spend several thousand dollars.
It would be great if we didn't have the losses of going from DC (PV) to AC (inverter) then back to DC (onboard charger)
There are some losses, but they are not too bad really. These kinds of conversion electronics are pretty good, and the point is that at least half of all this is already there in your house to have to convert for the 120V and 240V AC split phase that your house needs to use.
A simple DC to DC converter, even if it's low kW output, could be pretty handy.
But simple output DC wires are not possible for the car to use, because DC charging an electric car is VERY complex with monitoring and managing its control protocol that reads the battery temperature and state of charge, etc.. It must be one of the three main types of DC charging protocols:
1. Supercharger
2. CHAdeMO (can buy adapter from Tesla)
3. CCS (There is an experimental 3rd party adapter for this)

Since you can't build or buy your own Tesla (TM) Supercharger, you are left with probably a CHAdeMO. There ARE some possibilities to buy your own CHAdeMO station, but remember that few thousand dollars I mentioned earlier?
That's about $4,000 and is one of the cheaper ones. You connect an AC input to it, and it outputs a CHAdeMO plug for DC charging. Oh, and you need to buy the $400 adapter from Tesla.

There's just no reasonable way to do this that's not a big waste of money.
 

srs5694

Active Member
Jan 15, 2019
1,276
1,586
Woonsocket, RI
Since you can't build or buy your own Tesla (TM) Supercharger, you are left with probably a CHAdeMO. There ARE some possibilities to buy your own CHAdeMO station, but remember that few thousand dollars I mentioned earlier?
That's about $4,000 and is one of the cheaper ones. You connect an AC input to it, and it outputs a CHAdeMO plug for DC charging. Oh, and you need to buy the $400 adapter from Tesla.

There's just no reasonable way to do this that's not a big waste of money.
What's more, there's really no advantage to this over simply using a regular EVSE, like the one that comes with every Tesla. The point of the original question is to do away with the DC->AC->DC conversion, and because this DC "fast" (20A x 400v = 8kW) charger requires an AC input, all it's doing is shifting the AC->DC part of the equation into an external box, vs. using the car's built-in charger.

In principle, a DC charger that took DC input might be a bit simpler, and perhaps therefore also cheaper, but I'm not an electrical engineer and so I can't be certain of that. I don't know if any such products exist, and I agree that the DC->AC->DC losses for the stated use case aren't likely to be enough to justify the likely cost of a DC charger that takes DC inputs.

As a side note, I'm not sure where @LoudMusic is getting the $15,000 figure for inverters. When I had a ~6kW solar system installed at my house, the total cost was about $22,000. The contractor didn't break that down into panels vs. inverters vs. labor vs. whatever, but I find it hard to believe that the bulk of that cost was the micro-inverters my system uses. Of course, if it's a huge system, $15,000 for inverters might make sense; and perhaps batteries would complicate things and add to the inverter costs. (My system has no batteries.)
 

smitty825

Member
Sep 5, 2019
23
97
San Diego
Basically no, unless you want to spend several thousand dollars.

There are some losses, but they are not too bad really. These kinds of conversion electronics are pretty good, and the point is that at least half of all this is already there in your house to have to convert for the 120V and 240V AC split phase that your house needs to use.

But simple output DC wires are not possible for the car to use, because DC charging an electric car is VERY complex with monitoring and managing its control protocol that reads the battery temperature and state of charge, etc.. It must be one of the three main types of DC charging protocols:
1. Supercharger
2. CHAdeMO (can buy adapter from Tesla)
3. CCS (There is an experimental 3rd party adapter for this)

Since you can't build or buy your own Tesla (TM) Supercharger, you are left with probably a CHAdeMO. There ARE some possibilities to buy your own CHAdeMO station, but remember that few thousand dollars I mentioned earlier?
That's about $4,000 and is one of the cheaper ones. You connect an AC input to it, and it outputs a CHAdeMO plug for DC charging. Oh, and you need to buy the $400 adapter from Tesla.

There's just no reasonable way to do this that's not a big waste of money.
Yea...there is no benefit to using that L3 adapter with a non-SR/SR+ Tesla. Basically, it plugs into a NEMA 14-50 outlet, and then provides the power to the car. With the exception of the SR-class model 3s, all Teslas can take in 40amps and charge at the full speed.

However, if we like lighting money on fire, you can always buy something like this: Delta Wallbox 25kW DCFC 25kW - Dual Port It has both a CCS and Chademo plug, and can charge at up to 25kw (which is more than double what any current Tesla can charge at on an AC circuit). Granted, you'd need to dedicate over 120amps to support full speed charging on this...plus your $400 Chademo adapter :)
 
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nwdiver

Well-Known Member
Feb 17, 2013
8,466
11,668
United States
I've done a little searching and not found much. Are there any options for DC charging at home? Home battery systems are beginning to become more common, and home solar definitely is. It would be great if we didn't have the losses of going from DC (PV) to AC (inverter) then back to DC (onboard charger) to get the electrons into our cars. A simple DC to DC converter, even if it's low kW output, could be pretty handy. I've been thinking about a relatively large home battery and solar installation for a future home. Having to add in $15,000 of inverters just so the car can change it back to DC seems silly.

The losses aren't that bad. Most DC-DC converters aren't going to be any more efficient going from one DC voltage to another DC voltage than simply DC-AC-DC. If you just want a low power charger it makes A LOT more sense to use extra inverter capacity to charge your car than invest in a DC charger. It's just far more cost effective to use 240vac as a 'common currency' for everything.

Teslas solar design methodology really highlights this. Powerwalls are AC coupled... if there was that much of a benefit to DC charging they would be DC coupled.
 
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