High Power Module temperatures even when not charging

[Ken Yeh]

I put together an OpenEVSE Advanced 40A Kit about a month and a half ago. It's been working fine for charging my EV, but unfortunately I've been seeing persistent high temperature issues from the start. We're talking about a Temp sensor reading of 60+ °C when the device was sitting idle (not charging).

I opened a ticket on the OpenEVSE Support site, and Chris helped with some troubleshooting steps, and we swapped out both the MinMax AC/DC Power module and the LCD module. I at first thought that this had resolved the temp issue, as idle and charging temperatures were significantly lower after the swaps. Here's the chart showing the Temp1 sensor readings, with the high spike at the start showing the temps prior to the LCD swap, and then three days of temp rise and fall during the day and then a charge session overnight. My overnight charges are set at 10Amp current (EVSE indicates ~8.5 Amp actual current passing).



I did think that the idle temps of 35+ °C were still a little high, considering that ambient temps within the garage were no higher than about 28°C. We had a bit of a cold snap over the next week or so and temps remained reasonable.

I then had one day where I had to do a faster daytime charge at 24Amps. I then noticed that the daily temperature range indicated by Temp1 sensor was now about 10°C higher than it had been for the week before. In the image below you can see the temps ranging from a low of 30°C to 45°C, whereas the week before the temp1 sensor would indicate a max of 35°C even while charging overnight. This was odd, because ambient temperatures the week of Feb 26 were actually lower than the temperatures the week before.



I wanted to eliminate the possibility of a faulty temp sensor so I ordered a couple of external temperature probes. I taped a probe to the top surface of the power module and verified that the high temperature readings are very real, and the actual surface temperature of the power module is even higher than the reading indicated by the temp1 sensor in the LCD module.



The peak temperature on one afternoon when not charging was 46.2 °C (ambient temp = 25.4 °C) while at night the temp of the power module went up to at least 54.6 °C (ambient 21.5 °C, temp1 reading=47.7°C) while charging at 10Amps. With the power module hitting these high temperatures in relatively mild ambient temperatures and at the lowest current, it will definitely be throttling as temperatures increase into the Spring and Summer.

Additional troubleshooting steps I've taken since then is do disconnect the wifi module and disconnect and reconnect each of the wires going into the power module as well as the grounding bar. This was to try to eliminate the possibility of a poor connection creating high resistance. I also tried switching to using the DC_Relay_2 connection. But none of this has stopped the temperature issue of the power module; it would of course cool down to ambient when power was removed but as soon as power was restored the module would heat up again, rising over 15C above ambient within 20 minutes.

Here's hoping that this community can help me troubleshoot and resolve this perplexing problem!

[chris1howell .]

I am not sure there is a problem here at all. Temperatures non-running fluctuate with the seasons 45C while not running is not unusual. Here is the graph from my station this fall.

Temperatures while running are influenced by three major factors, two are fixed and the third is variable based on current. While charging the power required to hold the relay closed is the largest factor, this is the same regardless of the charge current. The second is ground monitoring which sends power to ground through 47k resistors, this accounts for 1.2 watts of waste heat, again this is the same regardless of current. The third is resistance through the AC high current path, as current increases so does heat.

You will see some difference running above 10A but it is not going to be a huge factor.

I have some temperature data charging at 0A vs higher currents. I will see if I can find it.

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[chris1howell .]

I found the data...

This is the rise at 0A it represents the relay coil and test circuit and accounts for about 7C rise.

Here is the temperature rise at 16A over a 5 hour charge session, started at 29.5 and peaked at 40.5.

Here is the graph for 24A. Starting 28C Max 44C for a rise of 16C.

[Ken Yeh]

Thanks for that chart, Chris. But do you recall what the ambient temperatures were during that time period? I don't know what your location is. I would imagine that the temperatures in late Aug/early Sept. were considerably higher than it is for me right now. It looks like you were getting mainly less than 41C idle temps during the day with a couple peaks close to 45C, whereas I'm seeing several 42-45C idle temps even though ambient temp in the garage peaked at 25C during that time period.

Do you have some of your temperature readings from the past couple weeks that you could share?

In your discussion with Craig about temperatures from several years back you described consistently getting temperatures while charging that were about 20-22C above ambient, whereas that's the kind of temperature delta I'm seeing while the EVSE is idle.

The charts you provided showing that higher charging current does not have a significant impact on temperatures is reassuring, and in fact it appears to me that my temperatures while charging are pretty normal and not too high. I looked back at the last couple weeks of data I have and noticed that on average my temperatures while charging are right about at 20C above ambient, fully consistent with what you and Craig described. But what bothers me is that my idle temperatures are close to 15-20C above ambient.

[chris1howell .]

The temperature Delta is 20-22C over the Ambient (starting) enclosure temperature. Not the ambient Outside temperature.

There are a lot of factors. Low temperature, High Temperature, rate of change, timing of charge... Etc.

[James Klafehn]

Anyone interested in Tesla battery modules? I know this isn't really a B/S/T group but I have been one of the open users since the beginning so that makes it all ok. HAHA

I wont bother you with the details if you are not interested. But if you are, let me know.

[Ken Yeh]

I've pretty much given up on having this temperature issue resolved, and I strongly believe that there is a design or component flaw in the system, as I've been hearing others who recently purchased the OpenEVSE kit reporting issues with high temperatures. Chris showed a chart of his temperatures where he hit an idle peak of 45C one time. Well, this entire past month, my OpenEVSE has never dropped below 44C when idle. Instead, it's consistently hitting peak idle temps of 53-55C. You can't even tell without looking at the time when I'm actually charging versus when the temperature is high while sitting idle during the day.

I am not able to charge at higher currents during the day because I hit throttling. This hasn't been as big of an impact on me personally because I do most of my charging in the middle of the night, and at the lowest 10A current. But this continuous exposure to high temperatures can't be doing the electronics any good in terms of longevity. While I really like the vision for OpenEVSE, I've been disappointed by this temperature issue, and as a result, I've not been recommending it to the EV forums and groups that I belong to.

EDITED 8/18 to post correct picture of past month temperatures

On Friday, August 10, 2018 at 9:03:11 PM UTC-7, Bradley wrote:

We're also having high temp issues.  I measured the AC to DC converter at 165F (74C) under full load (LCD + WiFi + solenoid on).  That's simply too hot.  Maybe something is drawing more current then spec'd on paper?  I wouldn't be surprised if the coil of the solenoid has a loose variance. 

[chris1howell]

OpenEVSE has implemented a feature no other manufacture has. Any other station on the market will charge and charge regardless ot the internal temperature. You can do the same thing with OpenEVSE if you wish by disabling temperature throttling in the button menu or WiFi. We do not recommend this. We believe throttling during the hottest days at high current is a good thing to protect your station, not bad thing. If you can charge at a slower rate or night it is even better for your vehicle and your station.

There is nothing we can do about outside air temperature, the station is consuming power and will always be warmer than outside temperature. There in nothing we can do about solar radiation, the heat radiated by the sun for a given area is the same. Again the station will be warmer if the sun is shinning on the station.

The only  thing we can control is the amount of power the station consumes at idle (which is what determines heat over ambient). Check the Energy Star page for charging stations. The 240v 80A Wattzilla Uno has been tested by Energy Star (it is based on a OpenEVSE v4 controller with color LCD and OpenEVSE Firmware) uses 1.62w at idle the least of any other L2 station on the market. The only station that did better was a 120v 12A unit. The v5 OpenEVSE kits use even less, we have reduced current on both the 5v power supply and the +- 12v power supply.

OpenEVSE offers a 1 year warranty on kits and 3 years on prebuilt stations. We will provide prepaid return shipping and a full refund for who is not happy with their station.

On Tue, Aug 14, 2018, 8:38 PM Ken Yeh <ken...@gmail.com> wrote:

I've pretty much given up on having this temperature issue resolved, and I strongly believe that there is a design or component flaw in the system, as I've been hearing others who recently purchased the OpenEVSE kit reporting issues with high temperatures. Chris showed a chart of his temperatures where he hit an idle peak of 45C one time. Well, this entire past month, my OpenEVSE has never dropped below 44C when idle. Instead, it's consistently hitting peak idle temps of 53-55C. You can't even tell without looking at the time when I'm actually charging versus when the temperature is high while sitting idle during the day.

I am not able to charge at higher currents during the day because I hit throttling. This hasn't been as big of an impact on me personally because I do most of my charging in the middle of the night, and at the lowest 10A current. But this continuous exposure to high temperatures can't be doing the electronics any good in terms of longevity. While I really like the vision for OpenEVSE, I've been disappointed by this temperature issue, and as a result, I've not been recommending it to the EV forums and groups that I belong to.

On Friday, August 10, 2018 at 9:03:11 PM UTC-7, Bradley wrote:

We're also having high temp issues.  I measured the AC to DC converter at 165F (74C) under full load (LCD + WiFi + solenoid on).  That's simply too hot.  Maybe something is drawing more current then spec'd on paper?  I wouldn't be surprised if the coil of the solenoid has a loose variance. 



On Thursday, March 15, 2018 at 11:19:19 PM UTC-4, Ken Yeh wrote:

Thanks for that chart, Chris. But do you recall what the ambient temperatures were during that time period? I don't know what your location is. I would imagine that the temperatures in late Aug/early Sept. were considerably higher than it is for me right now. It looks like you were getting mainly less than 41C idle temps during the day with a couple peaks close to 45C, whereas I'm seeing several 42-45C idle temps even though ambient temp in the garage peaked at 25C during that time period.

Do you have some of your temperature readings from the past couple weeks that you could share?

In your discussion with Craig about temperatures from several years back you described consistently getting temperatures while charging that were about 20-22C above ambient, whereas that's the kind of temperature delta I'm seeing while the EVSE is idle.

The charts you provided showing that higher charging current does not have a significant impact on temperatures is reassuring, and in fact it appears to me that my temperatures while charging are pretty normal and not too high. I looked back at the last couple weeks of data I have and noticed that on average my temperatures while charging are right about at 20C above ambient, fully consistent with what you and Craig described. But what bothers me is that my idle temperatures are close to 15-20C above ambient.

On Thursday, March 15, 2018 at 6:10:22 PM UTC-7, Chris wrote:

I am not sure there is a problem here at all. Temperatures non-running fluctuate with the seasons 45C while not running is not unusual. Here is the graph from my station this fall.

Temperatures while running are influenced by three major factors, two are fixed and the third is variable based on current. While charging the power required to hold the relay closed is the largest factor, this is the same regardless of the charge current. The second is ground monitoring which sends power to ground through 47k resistors, this accounts for 1.2 watts of waste heat, again this is the same regardless of current. The third is resistance through the AC high current path, as current increases so does heat.

You will see some difference running above 10A but it is not going to be a huge factor.

I have some temperature data charging at 0A vs higher currents. I will see if I can find it.

[Ken Yeh]

Chris, I think it is excellent that OpenEVSE has the temperature monitoring and throttling under extreme conditions. But the issue here is that even in less extreme conditions, throttling is occuring. The cause for concern is the fact that the OpenEVSE is getting to such high temperatures that throttling is necessary even when the air temperature is not unreasonably hot, in addition to the high idle temperatures even when not charging.

You described a test you did several years back, stating:

"Here is last night... It was very hot yesterday (105F) and garage did not cool too much.

Charged at 40A and reached 60C.

The current temp in my idle charging station is 41C or about 105F. Looks like a pretty very consistent 20C rise."

You describe tests you did when your garage temperatures were close to 100F where your EVSE stayed under 60C even after several hours of charging at 30+ Amps.

In contrast, here's my brief 40 minute charge session this afternoon in my garage, with air temperature at 32C (90F). The EVSE has been idle all day, yet started at a temperature of 52C. Pilot current was set at 32A.

Here's the zoomed in charts showing Power and Temperature.

As you can see, the station hit 65C after 27 minutes, causing it to throttle down to half the current. I disconnected after another 10 minutes.

Something must be different between my kit and the one you tested with several years ago for there to be such difference in results. Your garage temperature was about 15F higher, and your current was 8A higher, yet your peak temperature was 60C and no throttling. Yet for me, I've hit throttling at 32A in the past even when my garage temperature was only 85F. It seems unreasonable to not be able to charge at full capacity even under relatively mild environmental conditions.

My OpenEVSE is mounted inside my garage, with no sun exposure. The wall that it is mounted on is at the East side of my home, with no afternoon sun exposure to heat it up. You state the the only thing that can be controlled is the amount of power the station consumes at idle, but clearly that is something that is not being controlled properly to cause these extreme idle temperatures. If my station was only using a couple Watts at idle, it should not be able to raise the temperature to 20C above ambient, and this constant exposure will inevitably have long-term consequences for the electronics, though probably not until after the 1 year warranty is past. But because of this temperature issue I don't have confidence that the OpenEVSE will last for the life span that I would expect from something at this price point, so I do want to take you up on the offer for a refund for my station. What would be the steps I need to take for this?

[James Klafehn]

I noticed for the first time that mine throttled power last week. I dont know if it has happened before, this was just the first time I've noticed it. I was charging at 40 amps for a few hours. It was around 90 degrees in upstate NY.

Of course it would no longer be weatherproof, but has anyone added cooling fans?

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[chris1howell]

Cooling fans are not reccomend. The enclosure is sealed for a very good reason. If a component does get very hot and something ignites a fan would provide lots of fresh oxygen allowing a fire to spread and grow. In a sealed enclosure oxygen is consumed instantly and temperature monitoring will safely shut down.

[chris1howell]

Ken,

The station I tested was a stock v4 advanced kit (was called deluxe) with color LCD and WiFi. I am currently running a stock v5 kit with color LCD and WiFi.

For your station the best path forward would be to try to identify what is causing the excess heat at idle. The best way to identify would be to unplug and let the station cool overnight. Then open the enclosure and power the station with no vehicle attached for 30 minutes or so. Then unplug and see if any of the components are hot. Check the main controller, LCD, WiFi and the WiFi UBEC power supply.

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[chris1howell]

If it is helpful data from my station is public anyone is welcome to browse it is located in zipcode 93536 for historical daily temperatures. 

http://data.openevse.com/emoncms/chris1howell&id=3

[Ken Yeh]

Hi Chris,

As I reported in the first post in this thread, I did perform those steps to identify the source of the heat, and verified that it was coming from the main controller/power module. This was confirmed with a temperature sensor with the probe directly in contact with the top of the main controller. I disconnected power to the station and waited until the main controller cooled down to ambient air temperatures, but within 20 minutes after plugging the station back in, the module temperature had jumped 15 degrees above ambient.

The kit I purchased was the v4 Advanced.

[chris1howell]

Ken, 

We will open support ticket and send you a prepaid label to return your station for a full refund.

OpenEVSE Support

On Fri, Aug 17, 2018, 9:08 PM chris1howell <chris1h...@gmail.com> wrote:

Ken, 

Didn't we already replace your controller? The AC/DC power module is doing a lot of work. It is normal for power supplies to be warm and they get hotter with the more load. We can send a third module but it is extremely unlikely you got two faulty modules. We would think it is more likely that another device is drawing a higher than normal amount of current generating its own heat and causing high current and heat from the power supply.

OpenEVSE Support

[Topher Eliot]

How does one know if the unit is throttling?

[chris1howell]

Throttoling is a feature we added to OpenEVSE as an added level of safety and to extend the life of the equipment. We choose a fairly conservative temperature of 65C to reduce the charge current by 25%. At 68C the current is dropped to 50% and at 72C charging is shutdown. In most cases the first step is enough to reduce internal temperatures.

You know throttoling is occuring if you the charge current is reduced, screen turns red and the temperature is displayed on the screen. 

This feature can be disabled if you wish for your station to charge at full power regardless of temperature, however we feel it is a important feature. It is also possible to change the temperature thresholds in the source code, 65C is fairly consertitive.

On Aug 18, 2018 7:12 AM, "Topher Eliot" <eliot....@gmail.com> wrote:

How does one know if the unit is throttling?

[Ken Yeh]

Thank you, Chris. Greatly appreciate the gesture, and I respect that OpenEVSE stands behind their product. I will be shipping it back next week, and perhaps you will be able to investigate why mine in particular seemed to have this temperature issue.

[chris1howell]

We are very interested to see if there is a component in your station that is operating ourside of normal parameters. We are planning to tear down your station and inspect each and every electronic component.

We are also working on a blog to explain all the heat sources both environmental and components within the station both at idle and while running. We have lots of data and have done significant testing for a customer in India where they will be pushing the temperatures way beyond the 65C we have chosen to throttle. We will also explain the maximum temperatures of the power supplies, cable insulation and ICs and show how much margin we have left.

A few spoilers most components are rated to at least 90C - 105C...

An station with the sun on 2 faces top and front is at this very minute at a external temperature 139.2F outside air temperature is 92F... And it is not even plugged in...

The same model station in the garage at the same time and external temperature with a garage temp of 89 has an external temperature of 91.2...This one IS plugged in and used last night.

[Ryan Press]

On Fri, Aug 24, 2018 at 12:49 AM Bradley <bottlew...@gmail.com> wrote:

NO other EVSE gets hot like your EVSE.  Ford just recalled their EVSEs due to overheating.  Tesla has done a recall due to melting.

Sorry, I couldn't help but LOL at this irony!  

I'm an engineer designing power electronics for a living.  Power electronics get hot.  Power supplies get hot.  A waterproof enclosure with no air vents is going to get hot.  As in everything else in engineering, things are a trade-off and temperature is just one of those things.

I haven't seen anyone have an argument against the OpenEVSE's temperatures other than they don't like the temperature readings.  The issue seems like it's not really temperature, but the psychological effect of having it measured and available for monitoring.  Perhaps it should not report the actual temperature?   Car manufacturers have been doing this for decades; the temperature gauge in your car does not report actual temperature.  There is a large measurement window of "normal" and this is indicated by the gauge point straight at the center of the range.  They found long ago that people can't really handle the truth.

As as aside, I was trying to find the temperature rating of the Packard C240C contactor but it wasn't readily apparent.  Anyone have a datasheet?

Ryan

[Lee Howard]

On 08/24/2018 05:44 AM, Ryan Press wrote:

Power electronics get hot.  Power supplies get hot.  A waterproof enclosure with no air vents is going to get hot.

Not necessarily does the enclosure need to get hot just because the electronics get hot.

A properly-sized enclosure made of the right materials will dissipate the heat adequately so that it will not get "hot".  I have two EVSEs inside of a single 13"x7"x17" fiberglass enclosure mounted on a wall inside my garage which is on full-time and never turned off, and it never gets but one or two degrees above ambient temperature.

All enclosures have a given "heat dissipation" characteristic determined by their surface area and construction materials.  It's worth considering that characteristic when choosing an enclosure to use for housing electronics.

(I'm not saying that the OpenEVSE enclosures are not adequately sized or constructed; I'm merely responding to the statement that water-tight enclosures with electronics in them must get hot.)

Thanks,

Lee.

[Ken Yeh]

On Friday, August 24, 2018 at 5:44:27 AM UTC-7, Ryan Press wrote:

I haven't seen anyone have an argument against the OpenEVSE's temperatures other than they don't like the temperature readings.  The issue seems like it's not really temperature, but the psychological effect of having it measured and available for monitoring.  Perhaps it should not report the actual temperature?   Car manufacturers have been doing this for decades; the temperature gauge in your car does not report actual temperature.  There is a large measurement window of "normal" and this is indicated by the gauge point straight at the center of the range.  They found long ago that people can't really handle the truth.

If one station exhibits significantly higher temperatures than others under similar, or even less harsh operating environments, such that it affects the ability of the station to perform its normal function, I wouldn't call that "psychological effect." I have seen plenty of temperature charts for other OpenEVSE stations and I recognize what is in the "normal" window, but my readings were quite a ways outside of "normal". It wasn't the raw temperature values that caused me to raise a case for my station, but the significant difference between the temperatures I saw on mine vs what I saw from others. The vast majority of OpenEVSE stations out there are probably running cool and fine, but I believe the data that I've posted in this thread shows that mine was not "normal".

[chris1howell]

We have seen both "psychological effects" and actual issues. Safety has been our number one priority, we implemented temperature monitoring to detect hardware issued and improper assembly. For a while, a big issue was improperly terminated cables (input and EV). This was the driver for the temperature monitoring feature and moving to factory crimped cables. We know a station while at idle will run about 3C over the External Ambient temperature (not in the sun) and while charging will run about 20C over the starting enclosure temperature. 

When we see a station that is running way over the outside ambient air temperature at idle or the temperature rise while charging is 30+C over the internal starting temperature, we replace components. We have seen static damaged controller chip on the LCD run very hot in a couple of instances. The temperature sensor is on the display right next to this chip so the issue is pretty easy to spot. We have also seen bad temperature sensors that are way out of calibration indicating very high readings at room temperature. Any of the electronics can have an issue (WiFi, Wifi Power supply, controller, Display).

We have also seen poor choices for placement. One customer placed his station in an area that appears to receive direct sunlight all day. He reported a hot button and surface temperature 138.5 on a day that was almost 90F and sent a photo with a laser temperature reading. In order to determine if this temperature was outside of normal we placed a station outside at the same angle as the photo and took temperature readings with a Fluke laser temperature meter. The station was NOT PLUGGED IN and the temperature was 144.0 at 10am with an outside air temperature of 90F. He is insisting the hot surface temperature is from the electronics and not the sun.... There is nothing we can replace to reduce to reduce surface temperature in the sun. Any other EVSE (or object) will have similar surface temperatures given the same exposure (dark colored stations will be worse). He has been offered a full refund.

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[Chris]

On Fri, Aug 24, 2018 at 12:49 AM Bradley wrote:

NO other EVSE gets hot like your EVSE.  Ford just recalled their EVSEs due to overheating.  Tesla has done a recall due to melting.

On Friday, August 24, 2018 at 5:44:27 AM UTC-7, Ryan Press wrote:

Sorry, I couldn't help but LOL at this irony!  

True... It is also worth noting the Ford recall is due to actual fires and property damage...

We are discussing the station reducing charge power at 65C.... Adding a few additional minutes to a charge session.

 

[Ryan Press]

On Fri, Aug 24, 2018 at 10:36 AM Lee Howard <fax...@howardsilvan.com> wrote:

On 08/24/2018 05:44 AM, Ryan Press wrote:

Power electronics get hot.  Power supplies get hot.  A waterproof enclosure with no air vents is going to get hot.

Not necessarily does the enclosure need to get hot just because the electronics get hot.

For the same internal wattage dissipation, I could think of only one way to substantially reduce the enclosure temperature: Increase the surface area.  (Your 13x7x17 box is a good example of this!)  There are other options too but I don't think they would be significant. (Increase emissivity, reduce thermal resistance of enclosure material, etc.)

The other option is to decrease internal dissipation.  That could be accomplished with larger wires, higher spec relays, more efficient power supplies, etc.  All those cost money/size and are part of the trade-offs in designing the product.

Ryan

 

[chris1howell]

All good suggestions Ryan...

The OpenEVSE v4 controller (in the Wattzilla UNO) was already tested by EnergyStar and found to have the lowest idle current draw of any L2 EVSE tested. We have made several improvements for the new v5 controller.

The v5 incorporates several improvements over the v4.

Improvements for idle draw.

- The +- 12v supply current was reduced from 240mw to 57mw, reducing 183mw on the 12v primary supply.

- An additional 435mw was removed from the 12v primary supply. 

Improvement for draw while charging.

- The Dual Ground Monitoring (GMI) ICs (MID400) were replaced with a single dual channel 2731, the resistors changed from 2 x 47K to 2 x 330K. Resulting in a total current draw for GMI down to 40mw from 306mw on the v4.

The advanced kit includes a relay rated at 50A continuous so we already have a bit of headroom there.

For the future we are working on moving the relay coil drivers over to PWM pins. We believe we can reduce the relay hold consumption (70 ohm coil at 12V) from 2.05w to less than 400mw. We will close the relay at full power then activate PWM to reduce hold current.

--

[Ryan Press]

65C does seem like an awfully low temperature to start throttling.  But as they say, "When in doubt, make it stout."  What's the real limiting factor?  90C nylon wire insulation?

The products I design are generally spec'd for an outside ambient of 50C.  On the products with only natural convection it's not uncommon to see 85C ambient (air temperature) inside the enclosure even with large perforations in the sheet metal all over.

Ryan

[chris1howell]

The insulation is rated to 105C, enclosure even higher 251F.

The limiting factor is the AC/DC module with a normal operating range from -25C to 60C and it's own thermal protection shutdown of 142C. 

[chris1howell]

I am still gathering tons of data and working on the blog. I have setup 2 Advanced Stations and shared the data (see link below).

Station 1 has a v5 controller Color LCD, WiFi and an additional Color LED display with temperature sensor. The external display/sensor is to measure the ambient air temperature in the garage. The total power consumption at idle for this station (with 2nd display) is 1.30w. This is 0.3 watts less than any station EnergyStar has measured to date. The data show the station internal temperature at idle runs about 3°C over the ambient air temperature. The internal temperature changes slowly compared to the garage temperature so there is some lead/lag in the temperatures.

Station 2 has a v5 controller LCD, WiFi, the stock configuration.

Here is the data for both stations.

http://data.openevse.com/emoncms/dashboard/view&id=1305

Over the next few days the charge rate will be adjusted to show the difference in temperature rise. It should be no surprise that charging at 9600 watts produces a lot more heat than charging at 1440watts.  We are also isolating each source of heat while charging to show the overall impact each has on the total heat profile. 

[gnuarm.del...@gmail.com]

On Friday, August 24, 2018 at 6:18:28 PM UTC-4, Chris wrote:

All good suggestions Ryan...

...

 

For the future we are working on moving the relay coil drivers over to PWM pins. We believe we can reduce the relay hold consumption (70 ohm coil at 12V) from 2.05w to less than 400mw. We will close the relay at full power then activate PWM to reduce hold current.

Just a comment.  After reading a fair bit in these forums I have no doubt your company does a great job of designing and manufacturing these units.  I would just make a comment that if you use PWM to adjust the relay coil current that it would be good to use a modulation frequency above the range of human hearing.  It is surprising what can make sounds in equipment and relay coils can make rather good transducers.  I remember as a teenager I could hear the sounds produced by TV sets through the 15 kHz flyback transformers, like a mosquito buzzing all day. 

I can also see the flashing of LED brake lights when I turn my head.  Very annoying.  They need to raise the frequency of those. 

  Rick C.

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