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DIY Home EVSE
- Thread starter vfx
- Start date
W.Petefish
Active Member
The Pololu AVR programmer works great with the board. I'll have some pictures up after I get the board to see that L2 is available. (or perhaps force the issue in programming.)
My Open EVSE has been working for some time now, so I made a document about how I build it: http://zooi.widodh.nl/ev/tech/charging/building_open_evse_eu.pdf
Lot's of pictures in there showing the infra I put up the connect it all. Some might seem overdone, but it works.
Regarding the CFGI, we use 30mA ones in the Netherlands, those don't get tripped by the EVSE doing the ground check.
Lot's of pictures in there showing the infra I put up the connect it all. Some might seem overdone, but it works.
Regarding the CFGI, we use 30mA ones in the Netherlands, those don't get tripped by the EVSE doing the ground check.
mitch672
Active Member
I'm trying to get "Cinergi" over to my house south of Boston, he has the dual chargers, and I have a 75A OpenEVSE waiting to test with his car. I'm curious myself, as I finalized tonight
Then we share that curiosityI'm trying to get "Cinergi" over to my house south of Boston, he has the dual chargers, and I have a 75A OpenEVSE waiting to test with his car. I'm curious myself, as I finalized tonight
Please keep us and the project updated!
TonyWilliams
Active Member
I'm trying to get "Cinergi" over to my house south of Boston, he has the dual chargers, and I have a 75A OpenEVSE waiting to test with his car. I'm curious myself, as I finalized tonight
I'll have to start lining up a twin charger near me to test my 75amp OpenEVSE on.
Model S is compatible with OpenEVSE. Verified on a 30a unit in Ca and 75a in MA coincidedly both tested on the same day.Then we share that curiosity
Please keep us and the project updated!
i have a Model S pending delivery. I am keenly interested in this. I would like to drive cross country and use a EVSE with two NEMA 14-50 plugs at RV parks to increase my charge rate. Will this device help me do that? My Model S will have twin chargers.
Edward,
Twin chargers is a bit of a mis-nomer. Yes there are two but they're wired in together to handle greater charge current, when you're over 40A. The NEMA 14-50 can handle 50A maximum but the Tesla charges at 40A to stay within the capacity of the circuit. Camp ground outlets are notorious for becoming weak and weathered and can often trip at currents far below 50A.
The Open EVSE will allow you to push the limits to 48A but I'd not recommend it - better to get a 40A charge overnight than find the breaker tripped just after you fell asleep!
Twin chargers is a bit of a mis-nomer. Yes there are two but they're wired in together to handle greater charge current, when you're over 40A. The NEMA 14-50 can handle 50A maximum but the Tesla charges at 40A to stay within the capacity of the circuit. Camp ground outlets are notorious for becoming weak and weathered and can often trip at currents far below 50A.
The Open EVSE will allow you to push the limits to 48A but I'd not recommend it - better to get a 40A charge overnight than find the breaker tripped just after you fell asleep!
mitch672
Active Member
I'm the person with the 75A OpenEVSE, tested on Cinergi's (Ben Goodwin) Signature Model S with Twin chargers, and now used on my own P85 Model S with Twin chargers. It does indeed work well, and I even managed to get a spare J-1772 adapter from Tesla for $95, so I could just leave it on on my J-1772 75A OpenEVSE in the garage (it's sort of my own HPWC for a little over 1/2 the cost)
To answer your question, yes, it has been done, however, there are many many issues with it. The (2) 14-50s have to be "phase aligned", meaning the legs can only be "added together" when they match (0 volts between them).
This can be handled by some logic and relays, if you are at a site using single phase distribution.
However, if the RV Park is using 3 phase distribution, now the legs are 120 degrees out of phase from each other, if 1 pedestal is wired with legs 1 & 2, and the second pedestal is wired with legs 2& 3, it would be impossible to combine them with simple high powered relays, there would always be a 208V potential on at least 1 leg, and you need both legs to be combined to get the required 208-250V at 80A.
Someone has built a portable 75A EVSE, there was a thread about it, and they even had pictures of the unit, with the switching relays etc, but as far as I know, they never published detailed schematics so others could copy the design. And, as I've just described, it won't work in a multiphase distribution system, only single phase, and then only if served from the same transformer.
If you don't understand what I'm talking about, then this is not something you should attempt. Just being honest here.
Just a quick note on circuit ampacities.
NEC derates maximum circuit ampacity by 20% for continuous loads of 3+ hours.
If you plan on charging for less than 3 hours, you can often pull the full rated amps of the circuit without issue.
For short periods of time one can often pull slightly more than the circuits rated ampacity without issue, but always make sure you watch the voltage drop!
NEC derates maximum circuit ampacity by 20% for continuous loads of 3+ hours.
If you plan on charging for less than 3 hours, you can often pull the full rated amps of the circuit without issue.
For short periods of time one can often pull slightly more than the circuits rated ampacity without issue, but always make sure you watch the voltage drop!
TonyWilliams
Active Member
All wise counsel. In addition, I would recommend fail safes to prevent back feeding power from one 50 amp circuit to the other, and auto disconnect for some threshold of power. The simple answer might be either a 40 amp breaker on each leg, or two 50 amp "fast blow" breakers.
mitch672
Active Member
Brian, I have several "cold weather issues" currently:
19 degrees F in the Boston area now, my regen was limited to 30KW, it's now 45KW, that also affects the max charging rate.
I typically charge every time I can, not normally at %50 SOC
Typically I am seeing 30-33 miles/hour, but, I also have a low voltage issue currently, at the 75A load my voltage sags from 238 to 220-222 or so, the utility will be looking into it soon.
In warmer weather, with less voltage sag, i'm sure it would get close to the 62 mile/hour charge rate
This is incorrect. EV charging loads are ALWAYS continuous loads, regardless of time. You may never draw more than 80% of the circuit capacity with an EV charging load (NEC article 625). Advising anyone to try and draw more than rated ampacity is a pretty unsafe piece of advice, let's not do that here, please.
Furthermore, the UMC doesn't let you draw more than 40A from a NEMA 14-50, nor more than 12A from a NEMA 5-15. As @FlasherZ notes, pulling more is a code violation and asking for trouble. (It would be nice, though, if we could get a NEMA 5-20 adapter for the UMC so we could pull 16A when 20A are available.)
Robert, If you don't have, one, I recommend the OVMS and a tweak to the UMC pig-tail:
wht-green open: 12,15A
Diode (cathode to wht): 16A
Diode (cathode to grn): 24A
wht-green closed: 40A
The OVMS allows you to set the charge current in 1A units to tease out every last ounce of power. I was able to briefly (1min) pull 40A from a 120v 5-20 without any signs of heating but, it was a controlled environment with, probably over-spec wiring and new outlets.
wht-green open: 12,15A
Diode (cathode to wht): 16A
Diode (cathode to grn): 24A
wht-green closed: 40A
The OVMS allows you to set the charge current in 1A units to tease out every last ounce of power. I was able to briefly (1min) pull 40A from a 120v 5-20 without any signs of heating but, it was a controlled environment with, probably over-spec wiring and new outlets.
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