EV charging station to 30/50A shore power?

[silvermachine]

[SIZE="4"]Someone mentioned a rather interesting idea to me recently.

They proposed that I charge my house batteries from those free EV charging stations you sometimes see at superstores. I of course responded that this was definitely not a feasible option. Free electricity. Too good to be true, right?

But lately I’ve been thinking that there must be a way. If I have 30/50A shore power I should be able to buy some type of converter to get the voltage/amperage the same?

Of course I want to get a feel for what others, perhaps with more electrical knowledge than me, think of this harebrained idea.

I read that most EVs take in around 32A? Surely there must be some type of converter for a 30A shore power hookup.

Been looking at these type of things:
https://store.clippercreek.com/level...t-32-hardwired


Worst thing that could happen is we theoretically fry our electrical systems. Best thing that could happen is free electricity. Throw your idea into the mix! After all, the question that needs to be asked is why NOT?

Give me your worst.

[TheArgobus]

I believe that most of the chargers also utilize some serial/CAN communication to verify the car is legit, but that might just be Tesla Superchargers.

[DoxieLuvr2015]

Hey that is a really good idea..you could have a shore power connection and next to it a EV connector that way you could just plug in..

[silvermachine]

https://www.jpson.com/product/j1772-...ing_p1034.html

Okay.. surely it can’t be this easy. This inlet is for 120V and runs 30A. The only question is what goes between the EV inlet and the house batteries to make sure everything is sound. Just a standard converter to change the voltage to 12VDC?

My house battery bank consists of 4 Trojan T-105 6V hooked up in series and parallel.

Anybody have a clear idea on how to make this work?

I worry about frying my electrical stuff. And right now I’m excited about the idea but it seems a bit fuzzy. So any and all input is much appreciated!

[Jsneeb]

Electrical Engineer here,

Here is what it would take to make this work...
Argo up above is correct. Every big manufacture EV uses a communication string between the car and the charger to verify the car is legit and that conditions are safe to charge it.
The prongs do not have direct power on them all the time, or else they would be a big hazard to just have energized handheld cable used by the everyday citizen.

So you would need to get an EV ( I would suggest a nissan leaf ) and take out the entire electrical infrastructure of the car intact, charging port, cables, ECU, sensors everything. Now you can "spoof" the charger into thinking it's plugged into a nissan leaf. Presumably you are uninterested in the battery because your bus already has a battery. This leads to the next greatest problem. I'm unsure what power the charger provides, but the only place you will be able to tap into it without faulting out the charger would be at what existed of the battery terminals. Here the voltage is 400+V. So I hope you have some sort of NFPE 70 training or similar electrician level experience or your next DIY project will be woodworking, building a coffin.
You're going to need to step down the voltage from 400+ V DC to 12V. The Nissan leaf you butchered should actually have such a DC-DC converter onboard to charge it's 12V lead acid battery, but this charger was never rated for the power you would need to push out of it make charging your bus at EV stations any sort of worthwhile, think 20+ hour charging time.
To get a sub 2 hour charge you will need to build your own high amperage 400V to 12V DC-Dc converter. No off the shelf item exists that I could find in my 5 min of googling or searching Mouser. The closest I found was this.
https://www.mouser.com/Power/DC-DC-C...yx5k7vZ1yxt7ff
Which could provide an impressive 50 Amps. At 50 Amps you will take about 4 hours to charge, not great.

The cost of this device is 217$

If I were doing this I would build my own, but in this case for 550$ I would just suggest you buy two of them.

That's what it would take. I would expect such a system to be illegal to use at best, require constant troubleshooting, and you would for sure be held liable for any damage resulting to the charger or fires caused by something going wrong.


Not a bad idea, and I'm not here to diss your idea, but I think the execution isn't worth it.

[Jsneeb]

On second thought, and with some more digging.

The J1772 connector standard for EV charging actually uses a fairly simple analog circuit to communicate between the car and charger.
Only Tesla uses a more complicated serial communication for their chargers.

With that in mind, take a look at the circuit and the table that shows the various resistance configurations to "Spoof" the charger into giving you power.
https://en.wikipedia.org/wiki/SAE_J1772

If you could build that circuit then you could get 120V AC out of the charger and avoid the whole DC-DC fiasco I outlined in my other post. Getting 120V out of the charger, at 16A would be ideal for charging your bus because there are plenty of commercially available AC-DC 100A chargers.

[DoxieLuvr2015]

Originally Posted by Jsneeb

On second thought, and with some more digging.

The J1772 connector standard for EV charging actually uses a fairly simple analog circuit to communicate between the car and charger.
Only Tesla uses a more complicated serial communication for their chargers.

With that in mind, take a look at the circuit and the table that shows the various resistance configurations to "Spoof" the charger into giving you power.
https://en.wikipedia.org/wiki/SAE_J1772

If you could build that circuit then you could get 120V AC out of the charger and avoid the whole DC-DC fiasco I outlined in my other post. Getting 120V out of the charger, at 16A would be ideal for charging your bus because there are plenty of commercially available AC-DC 100A chargers.

This is why I really enjoy this place!

[sepudo]

Originally Posted by Jsneeb

On second thought, and with some more digging.

The J1772 connector standard for EV charging actually uses a fairly simple analog circuit to communicate between the car and charger.
Only Tesla uses a more complicated serial communication for their chargers.

I also had thought about this and while tesla does use more sophisticated chargers the "other" guys don't. Plus there are some chargers going up around my area that not alot of people know about. I'm totally on board on searching how to build a adapter to take advantage of 120v AC to DC.
thanks for giving the green light

[steveningham]

In many states, there is a healthy fine for blocking an EV charging space. Oregon is a little less than $300 I believe. And there is also a possibility of a tow, or impoundment of your bus. EV drivers needing a charge view the blocking of a charging station about the same way most people would view cars parked in a gas station and the owner no where in site. Imagine how you would feel if you were about to run out of gas with only one or two gas stations in town. And a lot of people left their cars parked in a way that you couldn't reach the pump.