Portable OpenEVSE at 40A

[ehelmholtz]

Having been driving EVs for a little while now, I find a portable EVSE quite useful so I took the Tesla Model S UMC and replaced the end with a J1772 plug. This was first described on the mynissanleaf.com forum and later done by others on this forum. The converted UMC was a slick setup but I found it not to be as versatile as I needed because the current is set by the various plug adapters that Tesla makes. For example, Tesla's NEMA 6-50 sets current to 40A but I sometimes use a circuit that can only handle 32A and there's no way to do this. The most germane example for me is that there's not a Tesla adapter to charge at 240V 16A; this is particularly needed if you're using a quick240V device that takes two 120V 20A outlets to make one 240V.

Because of these limitations in the converted Tesla Model S UMC to J1772, I sold the one I converted and put my own portable EVSE together, working at 120/240V with variable current up to 40A based on OpenEVSE. It's housed in a 6x6x3.5" box. The relevant components include the OpenEVSE board and a 40A DPST relay [I've since made another using a so called 80A relay]. I've set it up to allow for current changes in steps of 2A starting at 6A. At first, I was a bit hesitant to run it at the 40A that the relay is rated but I realized that Tesla's UMC used a 30A rated relay at 40A; to be sure, at 40A it gets a bit warm and so normally I just limit it to 38A and it works beautifully. Incidentally, the cost is also a fraction of converting the Tesla UMC yourself. Here's a quick photo:

---------- Update --------------
A forum member sent me a private message, asking questions about how to build one of these and I realized that he wasn't aware of the significant developments with the OpenEVSE and the resources available. Here are general links:

1. Project Home: https://code.google.com/p/open-evse/ -for schematics and instruction.
2. OpenEVSE store: http://openevse-store.myshopify.com/

The history of OpenEVSE shows that it stems from mynissanleaf.com forum posts by Chris Howell:

1. the project was born in February 2011 with this post: http://www.mynissanleaf.com/viewtopic.php?f=26&t=2736
2. the current forum thread is: http://www.mynissanleaf.com/viewtopic.php?f=26&t=6546
----------------------------------

Here's a link to the second iteration with some improvements [I decided to try an 80A relay - the same one that juicebox uses]: http://myrav4ev.com/forum/viewtopic.php?f=9&t=1013&start=53

 

[4EVEREV]

Out of curiosity, which exact relay did you use. Link?

 

[TonyWilliams]

Is that the Leviton / ITT 30 amp plug and cable assembly?

 

[ehelmholtz]

I used the Magnecraft W199X-7 DPST-NO, 12VDC coil, 40A. It's now part of Schneider Electric. There are a couple of other options including one by Dayton that I bought but have yet to try. You can get it for $20-$50. Here's an example from Newark. http://www.newark.com/magnecraft/w199x-7/power-relay-dpst-no-12vdc-40a/dp/56F642

Tony, I am using the Leviton/ITT 75 amp plug and cable assembly which as you know has been discontinued. I've also tried it with the Leviton/ITT 30 amp plug and cable assembly and it worked well without any noticeable warming at 38-40A; I thought about putting it back instead of the 75A since it's much more manageable. I am very tempted to get your J1772 40A cable with the 8 conductors since the diameter is only ~0.55 in as I recall.

 

[TonyWilliams]

I used the Magnecraft W199X-7 DPST-NO, 12VDC coil, 40A. It's now part of Schneider Electric. There are a couple of other options including one by Dayton that I bought but have yet to try. You can get it for $20-$50. Here's an example from Newark. http://www.newark.com/magnecraft/w199x-7/power-relay-dpst-no-12vdc-40a/dp/56F642

Tony, I am using the Leviton/ITT 75 amp plug and cable assembly which as you know has been discontinued. I've also tried it with the Leviton/ITT 30 amp plug and cable assembly and it worked well without any noticeable warming at 38-40A; I thought about putting it back instead of the 75A since it's much more manageable. I am very tempted to get your J1772 40A cable with the 8 conductors since the diameter is only ~0.55 in as I recall.

Yes, I ran the Leviton 30/32 amp cable at 40 amps without a heating problem.

I have a couple of the Leviton 75 amp cables, and I think they are going to stay with my 75-80 units due to weight.

Yes, I spec'd the 8 conductor custom cable at 0.55". That keeps it light and flexible, but obviously not as robust as those big, fat Leviton cables. Maybe I'll drive the Rav4 over a piece of our cable a few dozen times, then cut it open and see how many wire strands were broken.

 

[JasonA]

How's that 40a relay been holding up? I'm currently running the SquareD 70a unit out of a ClipperCreek and even pushing 40a for awhile it starts to get "abit" warm :shock: .. but it's also a 200+volt relay also.

And I've had no issues with my Leviton/ITT 30 plug running full boar at 40a either!

I'm thinking about building a portable unit for the Rav now.

 

[ehelmholtz]

Thanks Tony and Jason for added information about the Leviton ITT 30A cable operation at 40A; maybe, I'll put it back until I order Tony's cable since the 75A cable is heavy. The relay has been fine for the last 3 months running at 38A. I did run it at 40A for a week but the relay heated up enough that I opened box cover to vent. It's probably best to vent the box running it at higher currents. The magnecraft relay has silver alloy contacts but the details of which silver alloy isn't available; I have a Dayton relay with silver cadmium oxide as contacts but I haven't tested it yet. If you want to try it, I can bring it at the next meetup.

 

[pchilds]

This is the relay I used in my 40 amp OpenEVSE. I was able to drive it with the on board power supply, with a few added components. Ask and I will send the schematic. At 40 amps the relay was 125 degs F, after 1 hour, with the cover on.

http://www.ebay.com/itm/NEW-abb-con...t=BI_Control_Systems_PLCs&hash=item5ae335b256

 

[4EVEREV]

A metal enclosure would do better with the heat, plastic is not very conductive.

 

[ehelmholtz]

This is the relay I used in my 40 amp OpenEVSE. I was able to drive it with the on board power supply, with a few added components. Ask and I will send the schematic. At 40 amps the relay was 125 degs F, after 1 hour, with the cover on.

http://www.ebay.com/itm/NEW-abb-con...t=BI_Control_Systems_PLCs&hash=item5ae335b256

Why don't you post the schematic here - in case someone wants to try in the future?

4EVEREV, a metal box is a good thought; I like this case because it has a clear hinged lid that allows you to open the case up easily if venting is needed but you can read the display with the box closed.

 

[4EVEREV]

This is the relay I used in my 40 amp OpenEVSE. I was able to drive it with the on board power supply, with a few added components. Ask and I will send the schematic. At 40 amps the relay was 125 degs F, after 1 hour, with the cover on.

http://www.ebay.com/itm/NEW-abb-con...t=BI_Control_Systems_PLCs&hash=item5ae335b256

Why don't you post the schematic here - in case someone wants to try in the future?

4EVEREV, a metal box is a good thought; I like this case because it has a clear hinged lid that allows you to open the case up easily if venting is needed but you can read the display with the box closed.

But venting is moot if you don't need it. In fact, an aluminum case with good thermal bonding will do very well. Also remember some large relays and contactors generate quite a bit of heat unloaded because of the coil load and design.

 

[ehelmholtz]

A forum member sent me a private message, asking questions about how to build one of these and I realized that he wasn't aware of the significant developments with the OpenEVSE and the resources available. Here are general links:

1. Project Home: https://code.google.com/p/open-evse/ -for schematics and instruction.
2. OpenEVSE store: http://openevse-store.myshopify.com/

The history of OpenEVSE shows that it stems from mynissanleaf.com forum posts by Chris Howell:

1. the project was born in February 2011 with this post: http://www.mynissanleaf.com/viewtopic.php?f=26&t=2736
2. the current forum thread is: http://www.mynissanleaf.com/viewtopic.php?f=26&t=6546

 

[ehelmholtz]

Today was a good example of opportunity charging with an adjustable amperage portable EVSE. I parked the Rav4 in a garage with an available 120V outlet. I've used this outlet in the past to charge the Volt but for some reason, the Rav4 would stop charging after a few minutes. I decided to dial down the amperage from 14A to 8A and it worked without problem (I also tried 12A and 10A but the same thing happened).

 

[TonyWilliams]

Today was a good example of opportunity charging with an adjustable amperage portable EVSE. I parked the Rav4 in a garage with an available 120V outlet. I've used this outlet in the past to charge the Volt but for some reason, the Rav4 would stop charging after a few minutes. I decided to dial down the amperage from 14A to 8A and it worked without problem (I also tried 12A and 10A but the same thing happened).

During BC2BC-2013, between San Luis Obispo and Salinas, going north, I was coming up short in the Rav4 EV. I found some available 120 volt sockets at 1am, and used my 2013 Nissan / Panasonic EVSE that has been modified with 6-25 amp programming at 1 amp increments to plug in. The first one popped the breaker at 12 amps. After several tries, lowering the charge rate at 2 amps at a time, it finally worked at 6 amps. I stayed there several hours to add a few miles to get me to the next charge station.

 

[ehelmholtz]

During BC2BC-2013, between San Luis Obispo and Salinas, going north, I was coming up short in the Rav4 EV. I found some available 120 volt sockets at 1am, and used my 2013 Nissan / Panasonic EVSE that has been modified with 6-25 amp programming at 1 amp increments to plug in. The first one popped the breaker at 12 amps. After several tries, lowering the charge rate at 2 amps at a time, it finally worked at 6 amps. I stayed there several hours to add a few miles to get me to the next charge station.

I remember following both of your BC2BC journeys with much interest! Oddly, what happened to me today doesn't appear to be popping a breaker cos the power to the EVSE was still good but the car just quit charging!

 

[fooljoe]

Voltage drop maybe?

 

[ehelmholtz]

Voltage drop maybe?

That's a good thought - I think you're right.

 

[fooljoe]

I had a similar thing happen when I was trying to charge up (in my Leaf) at 16 amps using a 120 to 240 adapter at my friend's old condo. Charging stopped then started again several different times over the course of an hour's charge. We never repeated the experiment to measure the voltage drop, but I figured that had to be the problem.

 

[GlennD]

Fooljoe, I just finished an enhanced version of the charger I sold you. It has MOV transient protection, Voltage and current metering, a 12V 80A relay, and a GE 40A range cord with a molded 14-50 plug. If you know anyone looking I will sell it for $375. It requires a J1772 cable. It can take up to #6 wire.

 

[ehelmholtz]

Fooljoe, I just finished an enhanced version of the charger I sold you. It has MOV transient protection, Voltage and current metering, a 12V 80A relay, and a GE 40A range cord with a molded 14-50 plug. If you know anyone looking I will sell it for $375. It requires a J1772 cable. It can take up to #6 wire.

Hi, Glenn!
Welcome to the Rav4 forum. Please feel free post a photo of your build here especially if it's portable. Is it a 120V/240V one? Also, I just advertised this openEVSE build on the i3 facebook page for you.