OpenEVSE - Open Source Charging Station

[w6vms]

Thanks, though the coil current on that part is quite a bit higher than the 30 A relay that a lot of folks are using.

What is the max current the open evse can handle?

OpenEVSE itself fully implements the J-1772 Protocol, so 80A.

I was asking about coil current, though.

 

[w6vms]

For the 12V coil current..... you need to investigate the power supply ratings...

The Plus board's on-board power supply is a MicroPower AC/DC converter MPM-04D-1205E.

See datasheet. http://www.micropowerdirect.com/PDF Files/Datasheets/ACDC/MPM/MPM-04E-Datasheet.pdf

For +12VDC, datasheet shows 250mA max output (3W), but only 120mA max for +5V output (0.6W).

I haven't measured it, but Chris Howell told me "The DC\DC uses 0.2w idle and about 0.4w in the charging state".

The Magnacraft W199X-7... The coil is 70 ohms, so it uses about 2.0 watts continuous. This relay should be fine with the OpenEVSE Plus board.

I concur. Thank you.

 

[eHelmholtz]

For 30 amp build, you might want to consider the Magnecraft W199X-7, open contact, but release time 30ms and rated at 40 amps.
http://octopart.com/w199x-7-magnecraft-25415
http://datasheet.octopart.com/W199X-7-Magnecraft-datasheet-11409.pdf
If the car's on-board charger delays pulling current until after contacts close, then you might be ok long term with that 30 amp rated relay.

I wonder if these relays can be used to make a portable 40A EVSE since they're rated for 40A.

On an unrelated question, the LCD display on an Open EVSE can be set to a particular current and when it's connected to the car, it reads charging at L2 at whatever current. The display must mean max current and not what the car can actually pull - right?

 

[w6vms]

For 30 amp build, you might want to consider the Magnecraft W199X-7, open contact, but release time 30ms and rated at 40 amps.
http://octopart.com/w199x-7-magnecraft-25415
http://datasheet.octopart.com/W199X-7-Magnecraft-datasheet-11409.pdf
If the car's on-board charger delays pulling current until after contacts close, then you might be ok long term with that 30 amp rated relay.

I wonder if these relays can be used to make a portable 40A EVSE since they're rated for 40A

Then we are back to the question I brought up, about using the relays at their rated contact current instead of no more than 80%.

 

[GlennD]

Good practice is to leave a reserve but in this case unless the relay opens in an error condition it never opens or closes under current. The car's contactor closes after the EVSE relay closes and it opens before it tells the EVSE to stop. The only time it switches under load is if it sees a GFCI fault. Most of the time a 30A relay will work fine at 30A.

That said, I used a 50A contactor for my 30A EVSE. I believe in never running a part at its max.

The true exception is the Chinese relay ratings. I used a beefy looking 45A relay at 16A. It ran really hot!. At 45A it would make a good room heater. The problem seems to be in the armature wires. The coil never heats up but under load look out!

 

[borland]

Another source of heat is the terminals. For high current builds, using blade terminals is probably not a good idea.

I've found blade terminals for 8 AWG wire, but not any with current ratings. Better to use ring terminals and screw studs.

I'm extensively using ring terminals with the appropriate stud size and wire gage for my 32A build. Ring terminals for AWG 6-8 gage wire and #8 stud are much easier to source from digikey.com. With Digikey.com, you can source parts by specifications like wire gage and stud size to find part numbers.

 

[eHelmholtz]

You have nothing wrong. When OpenEVSE does it's "ground" check, it's sending a small current through the ground, and that trips many (ok, most) GFCI outlets. You would need to disable ground check, and auto L1/L2 detection to avoid the GFI from tripping (this can be done through various menus if you have the LCD display/menu button, if not, they are compile time options or set them through the serial FTDI interface)

Can you override the GFCI by holding the reset button down when you plug in and during the checks?

As an update, 91040, I tried holding down the reset button as you suggest but unfortunately with the reset button depressed the circuit isn't live and so the moment I let go, it trips. Turning off ground check, and auto L1/L2 detection like Mitch recommended worked fine.

 

[GlennD]

The blade terminals that I have used were rated for 25A max. I would not be comfortable running them at over 20A. Always leave a reserve.

91040, you can mod the plus for GFCI use. The simplest way is to open the grounds per Mwalch's mod and then go into the menu to disable the checks.

My way is to do the disable but add a small relay to fake the check. This allows use without access to the menu. If still checks for a shorted driver transistor but not stuck contacts. The relay grounds one of the outputs faking an L1 check.

 

[w6vms]

I saw several references to the 30A Leviton cable for under $140, but the best price I'm seeing now on the link present on several posts on this thread is just under $180.

Is there a coupon needed to get the cheaper price?

They just bumped the price from $134 to $173...

But with free shipping and code "LUVLEVTN" (20% OFF) you can get it back down to $138 before tax

Looks like that code isn't valid anymore. Darn.

 

[GlennD]

I opened my main OpenEVSE today to upgrade the firmware to the 2.0 beta. While I was in the box, I changed the display from an Adafruit shield to an OpenEVSE display to make it all OpenEVSE.

Chris gave me a couple of boards with the surface mount parts installed. This is why it shows no connector. Since my RTC is external it worked out better.



Here it is showing charge with the simulator.

 

[borland]

I was scanning eBay for some spa relays, and came across several 80 amp relays. You can find them with eBay search "Power Relay 80A". Just got this one in the mail from China. I paid $18 with shipping.

It's not the one I ordered from the listing, with a screw mount; what was shipped has a latch for mounting on a rail. It has a couple screw holes, so could be screwed down, but is not designed mounted that way.

Looks perfect for up to 75A builds using the Open EVSE Plus board. The relay has 12 volt coil, closed contact, #8 stud size, uses 2.0 watts, and has a release time less than 26 ms.

Here's a photo of the 80A relay next to the 40A Magnecraft W199X-7.

I measured the coil resistance at 72 ohms, compared to the Magnecraft at 68 ohms (also 2.0 watts).

I've still not completed my build, but you can see the 80A relay fits great inside the Bud enclosure I'm using with still some room to spare.

 

[GlennD]

The interconnect wires look beefy enough for the power. Try it and see how much heat is generated. My experience with a 45A relay at 16A was not good.

 

[borland]

That's what I thought Glenn. The contacts look pretty big too.

Most relays have contact resistance of about 0.20 ohms (other than silver alloys). If you consider contact resistance rating of this relay, and the power lost across the contacts ( I squared * R), with a 75 amp load the power dissipated would be over 560 watts. So that rating must be pretty conservative for what ever silver alloy it uses, otherwise it makes you wonder how they can rate it at 80 amps.

 

[sorphin]

I saw several references to the 30A Leviton cable for under $140, but the best price I'm seeing now on the link present on several posts on this thread is just under $180.

Is there a coupon needed to get the cheaper price?

They just bumped the price from $134 to $173...

But with free shipping and code "LUVLEVTN" (20% OFF) you can get it back down to $138 before tax

Looks like that code isn't valid anymore. Darn.

It worked for me.

 

[chris1howell]

This weekend I was able to add Wifi for about $60 to my EVSE... Here is how I did it.

http://code.google.com/p/open-evse/wiki/OpenEVSE_WiFi

 

[borland]

WiFi... Cool!

I purchased another eBay 80A relay from China. Similar to the one of my earlier post, same overall size but with a clear cover. Same 12V coil. Appears to be from the same factory too.

Only significant difference is the coil resistance which measures 52 ohms. So, it's coil draws about 2.8 watts of power.

That current draw is slightly too much for the Plus board's 4 watt power supply from MicroPowerDirect.com. Micro Power sells another model that's rated at 8 watts, and has the same footprint as the 4 watt version, but the pinout arrangements is slightly different.

With the extra 12V power capability, one could use that for cooling the enclosure with a 12V fan like is used on most PCs.

Here's the datasheet for the 8W unit...

and for comparison, the 4 watt unit..

Maybe Chris could offer the 8 watt unit as option with future PCB board revision.

 

[nworbekim]

Will the integrated power supply work with the 2watt version of the power relay?

Are any of these relays UL rated?

 

[mitch672]

Borland, the problem I see on your 80A relays is the terminations. It's going to be difficult to terminate #3 THHN to those screw terminals, even the #6 from the 75A J-1772 will be difficult.

The contactor I used has a hex wrench style lug designed up to 1/0 wire. The other issue is having enough space to bend and route #3 and #6 wire in a smaller enclosure, difficult to bend/route

Check the pictures on my build: http://code.google.com/p/open-evse/wiki/75AOpenEVSE" onclick="window.open(this.href);return false;

 

[TonyWilliams]

I posted a bunch of pics of two separate 70/75 amp J1772 plugs that I took apart. The one on the left is a "No-Name" from http://www.TucsonEV.com" onclick="window.open(this.href);return false; for $155, and the one on the right is an ITT J1772 plug:

http://www.mynissanleaf.com/viewtopic.php?p=292087#p292087" onclick="window.open(this.href);return false;

 

[borland]

Borland, the problem I see on your 80A relays is the terminations. It's going to be difficult to terminate #3 THHN to those screw terminals, even the #6 from the 75A J-1772 will be difficult.

Good points. For any build over 60 amps, I think you'd need plenty of cooling air flow in order to use those 80A relays.

Sourcing appropriate sized terminal rings is not easy. I found Digi-Key.com the best source, where you can use their search filters to locate parts from the catalog..

Here's a link to the "Product Index >Connectors, Interconnects > Terminals - Ring Connectors"...

http://www.digikey.com/product-search/en/connectors-interconnects/terminals-ring-connectors/1442844

For 60A build using cord/plug set with 8 AWG wire, or 75A build cord/plug set with 6 AWG wire.....

Searching with filters for Stud/Tab Size: "#8 Stud" and Wire Gauge: "6 AWG" or "8 AWG" finds suitable parts.