OpenEVSE Advanced Kit (Long, Boring & YMMV)

Discussion in 'Clarity' started by K8QM, Apr 11, 2018.

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  1. K8QM

    K8QM Active Member

    The OpenEVSE ( ) Level 2 charger was mentioned in a couple of threads so I thought I would share my experiences from this week.

    I received and built my OpenEVSE Advanced kit Monday evening (about 3 hours due to a wiring error as it should have been less), wall mounted it Tuesday evening (about 20 minutes) and set up the WiFi today (about 20 minutes). So far I've been through 3 charging cycles with zero problems and 2 1/2 hours instead of 12-14 is a bit of a game changer when you want to use the car in the evening after depleting the batteries during the day.

    I've been somewhat agonizing about what to say about the kit aspect and I think the best advice is:
    1. If you have some kit building/electrical skills and want to save some money then it's a good choice, although you might end up scratching your head at the instructions in a couple of places.
    2. If you don't have some kit building/electrical skills then choose to build the kit for the learning experience not for saving money. You will probably be dazed and confused at times but if you take advantage of the OpenEVSE tech support and forums you should be successful. Note that I learned as a kid that if you get stuck, get a friend to take a look even if they don't know anything about electronics - they might notice a wiring error that you overlook since you're "sure" you followed the directions exactly.

    The unit is fully featured and allows a variety of set up options. All the details can be found here:

    Note that the pre-built unit is $599 US, the complete kit (with WiFi is $489) but you can get a 10% discount coupon from a current customer - if you are going to buy, it would probably be worth mentioning it on the forum as that's how I ended up with a coupon code. With a NEMA 14-50 cable, mine was $464.85 USD including shipping.

    There are several of on here with these chargers, so ask any questions and I'm sure you will get an answer.

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  3. Hobbesgsr

    Hobbesgsr Active Member

  4. hngo

    hngo New Member

  5. Kendalf

    Kendalf Active Member

    I also built the OpenEVSE Advanced kit. I've had mine going since late January. K8QM, I'm very curious what your temperature readings are since the kit was installed? Can you share a screenshot of the temp sensor readings from your monitoring chart (if you have that connected already)? And a rough idea of the ambient room temperature that the EVSE is installed in?

    I've been battling with what I feel are high temperature readings since I got the kit. I've written a long post about my struggles in the OpenEVSE forum here, and I've been working with Chris Howell from OpenEVSE on the issue since the start. Comparisons with what other users are reporting for temps seem to suggest that I'm getting higher readings than usual, but most others have slightly older versions of the OpenEVSE. You may be the first that has the same kit that I got.
  6. K8QM

    K8QM Active Member

    Since I just brought the WiFi up yesterday I haven't done much set up except for the built-in OpenEVSE page. Didn't drive much today so the starting charge was 70%. Max current was set to 30Amps. The unit is wall mounted in a detached garage with an ambient temperature of about 20C. I've been in electronics for a long time so I took the readings the old fashioned way - paper and pencil!
    Time(minutes) Temp1 (Degrees C) Current (Amps)
    00 23.0 29
    10 30.5 29
    20 36.2 29
    30 40.5 29
    40 43.2 23
    45 41.2 5
    47 41.2 0
    Time 47:22 4.73kWh

    Hope that helps - I'll get some of the graphing over the weekend.

    Kendalf likes this.
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  8. Kendalf

    Kendalf Active Member

    Thanks! That does help, and it does provide another set of data to show that my temperatures are abnormal. My main concern are the excessively high temperatures when the EVSE is sitting idle. I'm getting sensor readings of close to 20°C above ambient when the car is not plugged in (eg. I would have idle temps ranging from 42-50°C when ambient temperatures peaked at 25-30°C during that time period. In contrast, your starting temperature was barely above ambient, which is what I would expect from an idle system.

    For example, here's about two weeks worth of temp data from a month ago, when my garage temperatures never hit more than 25C.
    OpenEVSE Temp Range.png
    I'll be very curious to see your temperature charts when you get the chance to connect your OpenEVSE to the EmonCMS site!
  9. K8QM

    K8QM Active Member

    There's a weeks worth along with the outside temperature for the same perios
  10. Kendalf

    Kendalf Active Member

    Thank you, geo! This is excellent. And it clearly shows my OpenEVSE has a problem with high idle temperatures. Your idle temp readings are no higher than 5C above ambient temperatures, whereas mine are nearly 20C above ambient (eg. my sensor is currently showing 45C while idle, even though the garage temperature is only 27C. Only thing is, I can't think of anything else to change or fix to try to resolve this temperature issue. :/
  11. K8QM

    K8QM Active Member

    Can you get your hands on an infrared thermometer? I would give it a shot and see if I could find a specific part that was really warm. If you give that a shot let me know and I could probably take some comparison measurements if you find something suspicious.

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  13. Kendalf

    Kendalf Active Member

    I don't have an infrared thermometer but I did get a digital thermometer probe previously to verify if the temp sensor in the EVSE was accurate. Unfortunately, the temperatures are real, and it is the MinMax AC/DC power module that seems to be the primary culprit. The two pictures below show the temperature with the probe taped to the surface of the power module. The image on the left shows the temperature at night while charging at 10Amps (ambient 21.5 °C, temp1 sensor reading=47.7°C). The image on the right shows the high temperature of 46.2°C while idle (ambient temp = 25.4 °C). The probe shows that the surface temp of the power module is even higher than the reading given by the Temp1 sensor in the OpenEVSE, as that sensor is attached to the LCD screen module and is not in direct contact with the power module. Delta is about 5-7°C.
    Auto Generated Inline Image 3.png

    Be any chance do you have any images of your wiring? Here's a few images of mine:
    IMAG0537-rs.jpg IMAG0465-rs.jpg IMAG0466-rs.jpg

    A bit difficult to see, but it sure doesn't seem that my wiring is off.
  14. AlanSqB

    AlanSqB Active Member

    It looks good from what I can see. You could expect some higher temps on charging because you're using the 12v relay and it probably uses more current to stay closed than the 240 only setup does. However that doesn't explain the higher idle temps.

    You might want to let Chris know over on the support forum on his website ( I'm not sure what the expected temps for that transformer are, but it seems high.If it's out of spec, he's usually really good about replacing any faulty parts. Nevermind, I see on re-read of your posts above that you're already working with Chris.
    Last edited: Apr 21, 2018
  15. AlanSqB

    AlanSqB Active Member

    BTW, I build my DIY V2 OpenEVSE Plus back in 2014. My controller board came as a flat circuit board with the Minmax transformer and the atmega "brain" IC. I sourced all the other components from Digi-Key and soldered them all together. It's been working like a champ since then which is a testament to the really well done design of the control module.

    When I first built it, I used the original 30A "Ice Cube" relay setup. A year later after some issues with the relays (mainly my crimping), I switched over to a 240V packard relay, which required keeping one of the ICE Cubes for switching. Not very elegant, but much safer. Finally, when the Struthers/Dunn relays that are currently in the advanced unit became available, I purchased and installed. It's a perfect upgrade for someone with the original 12v relay board.

    Later on I added a Huzzah module with the original WiFi firmware. Just today I uploaded the latest firmware to the controller and the Huzzah. It's like having a whole new EVSE. The graphical webpage is really neat and beats typing RAPI codes in by hand for each setting change.

    The only other upgrade I've considered is the 40A cable/handles that they sell. My current cable/handle combo is only 30A, but it's a pretty high quality cord/plug (Dostar I think) so I hadn't bothered yet.

    Anyway, lost point of this long story is that you can buy it, hang it and forget it or you can fuss with it and make it a hobby. Either way, I think it's fun to know how the mystery box on the wall works.
    Kendalf likes this.
  16. gmansuperg

    gmansuperg New Member

    Based upon weeks of agonizing research into all of the Level 2 options, I've finally decided to go with the Open EVSE advanced kit. Being a EE with previous open source hardware experience, it would be nice to support a OSHW initiative and end up with a customizable charger to boot.

    I saw a mention at the top of this thread of a 10% discount code from an existing OpenEVSE customer but couldn't find anything on the OpenEVSE website about it.

    Are there any OpenEVSE customers here that want to share a discount code with a fellow Clarity owner? I'm already setup with a NEMA 14-50 outlet, 40A breaker but they are just sitting there lonely and unused right now :)
  17. AlanSqB

    AlanSqB Active Member

    PM sent
  18. K8QM

    K8QM Active Member

    Since this thread is alive again I'll mention that I cut my maximum current to 24 Amps which still give a fast charge time and has kept my chargers internal temperature below 50C. With summer coming up I thought it was worth sacrificing an hour of charge time for cooler electronics.

    Last edited: May 6, 2018
  19. AlanSqB

    AlanSqB Active Member

    That seems like a good idea. I typically keep mine at 24 because I don’t have any TOU or incentive to charge faster. I recently upgraded the Huzzah module to the latest firmware so now I have the nice interactive web-page where you can change all the settings. Really enjoying that.

    My unit is a DIY build using the old 2.0 DIY kit and it’s almost 4 years old. Still working strong, all my soldering is holding :). Here is the path of evolution my OpenEVSE has taken over the years...

    Aug 2014 -Original build with DIY 2.0 unit and 30A “ice cube” relays. Includes DIY RGB LCD with RTC.

    Sometime in 2015 -Replaced relays with 240V contactor using one of the ice cubes to provide the 240 for the contactor

    Sometime in 2016 -Added a temperature module

    Sometime in 2016 or 2017 - Added a Huzzah WiFi module

    2017 - Replaced the contactor with a DC “Struthers and Dunn” relay to restore advanced functionality

    My next mod is to add a UBEC (universal battery eliminator circuit) to power the Huzzah. The WiFi kit from OpenEVSE comes with this, but I just bought a Huzzah and loaded the firmware myself. Currently my Huzzah is getting powered over the serial interface, but that takes too much power and flubs up the RGB. After that, I have considered swapping out my 30A J1772 cable for one of the 40A ones, but it’s really not going to do anything for the Clarity.
    Kendalf likes this.
  20. Kendalf

    Kendalf Active Member

    For my daily overnight night I usually use the lowest 10A setting, in hopes of greatest efficiency and lowest resistive heating losses. The crazy thing is that my EVSE hits higher temperatures during the day sitting idle than when I charge at night (eg yesterday when it got to 50C during the day but only went up to 47.5C while charging -- lower ambient temps overnight, of course). I've come to just accept this as a problem with my particular OpenEVSE as I can't think of any other steps to try to resolve these high idle temps.

    Any of you experience a bug where pushing the button to go from sleep to ready mode causes the last charge session kWh to be added to the overall total kWh? Here's a video I made to illustrate what I'm talking about:
  21. gmansuperg

    gmansuperg New Member

    That's a pretty strange temp graph. What was the ambient temperature that day? Unit mounted inside on an exterior wall I assume?

    Thanks to the kindness of forum members K8QM and AlanSqB I'm on my way to Level 2 charging as soon as my Open EVSE kit arrives (and i have time to put it together). I've gotta say this forum is a great resource for fellow phev owners who will undoubtedly have a few questions after taking the leap.

    Looking forward to sharing my Open EVSE experiences here. If I get a few extra minutes, I'll take a peek at the schematics and software (assuming the source code is there) to see if I can shed any light on the temperature and cumulative kwh strangeness.

  22. Kendalf

    Kendalf Active Member

    @gmansuperg Yes, it's definitely a strange temperature graph. If you read some of the earlier posts in this thread, I describe some of my troubleshooting attempts on this issue. Unlike most other OpenEVSE temp readings that I've seen, in which idle temps are not much higher than ambient, my idle temps are about 15-20 degrees C above ambient.

    My OpenEVSE is mounted inside my garage on an East side wall. So the outside wall gets some sun during the morning, but from around 11-12pm it's in shade. While the wall that the EVSE is mounted on feels warm, it is barely warmer than ambient temp (and I confirmed that today with a contact thermometer on the wall right beside the EVSE. The casing of the EVSE itself feels much hotter in comparison.

    In the case of the temp graph I attached today, the outdoor temperature reached a high of 92 F (33C) but inside the garage was no more than 85 F (29.5C) at about 5pm when the temp of the OpenEVSE peaked at 50C. Clearly the power module is active and resistive heating is taking place, to the same degree as it would if the EVSE is actually charging a car. But I can't for the life of me figure out why. Chris Howell (the main OpenEVSE guy) has given up trying to figure out the cause and basically just declared the behavior "normal" and within the temp rating of the module, but clearly something is not normal, as an idle electrical device should not have a temperature that is 20C higher than ambient.

    Any additional ideas that you may have would be greatly appreciated!
  23. K8QM

    K8QM Active Member

    @AlanSqB - you're definitely willing to be on the (b)leading edge of these things! Did the original kit come with a chassis/case? Packaging is my bugaboo with electronics as I hate building enclosures. Probably because my first job was with an ultra high end stereo manufacturer and the slightest blemish meant a part had to be scrapped or reworked.

    @gmansuperg - The build was pretty easy but here's a couple of things that caught me:
    Step 3 When mounting the ground bar use the screws that came with the kit not the ones that came with the ground bar.
    Step 5 It's easy to miss that last ground wire.
    I would definitely have a schematic handy if you can find one - some of the photos in the build guide are pretty ambiguous.

    I think you'll be quite satisfied once you're charging with it.

    ClarityDoc, lordsutch and MarkClarity like this.

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