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EVSE and Ventilation

OK first yes, I did a search and found a few posts overall not much info out there.


That said I wanted to post some results.


I have the advanced kit hardware installed in my Tesla wall connector and have 2 other advanced series kits.


The Tesla is set for 48amps and the other 2 are set for 44 amps.


Also note all temps will be in F since here in the US we are still stuck on it, and I am used to it.


Monitoring all 3 chargers with MQTT and displayed on a dashboard.


When idle the Tesla wall charger unit display temp is always about 3 degrees over room temp where the other 2 units are always 5 degrees over room. I have figured that the Tesla enclosure has about 50% more cubic inches of space allowing for slightly better temps.


When charging at 48 amps the Tesla rises average of 45 degrees over room temp where when the other 2 units rise average 50 degrees over room temp. Again, more space seems to allow for lower temps.


I found an old post that recommended against venting to keep oxygen out in case of fire. But where this sounds logical, I am not sure I agree. First off been in the industry for many years and keeping things cool is always the best policy. Any high-power unit I have ever seen has cooling or at the very least vents. Now yes, this enclosure can be mounted outside and sure it needs to be weather resistant, but I am mounting in a garage and never plan to mount outside. True most every other EVSE are in a weather tight enclosure but compare the size. Many of the other EVSE are rated for lower outputs 40- or 32-amps max and are in enclosures 3 or 4 even 5 times the size. Now there is no need for this size except for the cooling it provides from the extra space.


So, I have taken one of my advanced units and done some mods and testing. First, I drilled some small vent holes along the bottom and side of the cover. This small amount of vent drops the average temp rise by 7 degrees. I did not want any holes in the top, so I designed a hood vent and 3D printed. I drilled a ¾ inch hole in the top and installed the hood vent. This is important as it is at the top and this is where hot air is going to pool so it needs a way out. This dropped the average temp rise another 8 degrees for a total temp drop of 15 degrees.


IMO this is significant. For example, imagine a power management product designed to run in environments up to 120 degrees with an MTBF of, say, 20,000 hours. Operating at 140 will effectively cut its life in half. Alternately, if the environment were cooled to 105, the MTBF could be extended to 40,000. Heat is what kills so there is no reason to operate a EVSE at a high temp if it is not needed and can be cooled.


Yes of course lower charging limits will allow for less heat but if you buy say a 40-amp charger generally you expect to use it at 40 amps. I can drive my car at 40 MPH many components will probably last longer so why does not everyone do this? I can drive my Tesla at 55 MPH it will go farther on a charge, but no one does this why? OK you get my point, I hope.


Other factors that affect the heat in the EVSE and a big one is wire size. I did some testing with both an 8AWG cord and a 6AWG cord at 40 amps. The display temp was always 10 degrees more with the 8AWG cable in use. So same car, same room temp, same charge rate, same charger, just diff cord. So, it’s very imp that you use the correct size cable for both the input and the output to the EV. Also please make sure if you are doing your own crimps use the correct size crimp and wire with the correct crimp tool. This is probably the single weakest link when it comes to high current and high heat.


Now I still think the overall box is small, so I found a small, tiny fan 40mm 40mm 10mm. I have designed a hood for the fan, and have it run only when the unit is charging. Original plan was to use a 12v fan tapped off the 12v for the relay. Issue is the relay draws the voltage down to about 4v so not going to happen. Next idea was to use the other pins for the AC relay, but we got 240v on those. There are no small 240v fans out there, so I improvised. Decided to use a 5v USB fan plugged into a tiny iPhone like charger. This seems to be the only way to get things adapted and working. The 240v AC goes into the USB adaptor USB fan plugs in and we have 7 cfm of air.


Now I was not having any overheat issues and it’s been hot here some days 90-100 degrees here. I just know that lower temp will give me longer life and a safer unit. I don’t see why I would want to operate the units at 50 degrees over ambient when I can lower that by 45 degrees operating at 5 degrees over ambient.


I have this setup now in all my units and internal displayed temp is steady at 5 degrees F over ambient temp. This also lowers the cable temps so now nothing even feels warm in anyway. Basically, it all feels the same as the room and IMO this is safer and will last much longer. I did do a lot of temp measurements with the IR and probes too much to post but bottom line is ventilation equals lower operating temps.


Before someone points it out yes there are bricks with no air space in them like the ones the Tesla comes with, and they do run hot to the touch. Many posts out their people asking is this supposed to be so hot. Plenty of pics of burnt up bricks and cables and plugs too. So, if you like your electrical devices hot to each his own. IMO cooler is always better. Remember this is Open EVSE open so I can do what I want you can do what you want the beauty of open.





Thank you for this feedback. 

you have a picture ? 

OpenEVSE is sold in kit form, we can not guarentee all users will build their stations properly. Most users do not have the technical abillity to setup monitoring. Our reccomendations are directed to the community as a whole. But as an open project stations can be customized as a user technical abilities and wishes.

Our design is intended to be as safe as possible for a wide range of EV owners, we do all the critical steps in the factory such as crimping. We have seen several cases where builders of kits do not properly torque the high current ring terminals. In all cases OpenEVSE did its job and stopped charging with nothing more than a half inch of melted insulation.

The OpenEVSE kit was designed to address each of the three sides of the "Fire Triangle" Oxygen, Heat and Fuel. A fully sealed enclosure has a very limited source of oxygen, If a fire did start it would be estinguished almost immediatly. Heat is addressed by the temperature sensor on the display. Current is reduced at 65C and the station is shutdown at 72C which is 30+C less than the rating of the majority of the components. Fuel is addressed by using UL certified components with flamibility ratings. The cables and wiring in all the high voltage and high current paths are all rated to 105C and the relay insulation is Class F 155C.

Adding a fan may help reduce temperatures a little at the expence of protections from oxygen. If a fire were to start, the fan would ensure there is plenty of oxygen to allow the fire to grow and spread. The moving air will also cause the sensor (located on the back of the display) to falsly read lower as fresh air is introduced, circulated and mixed. We agree cooler is better, however in a scenario where the ring terminals are not properly torqued, the heat could ingnite the issulation and start a fire before the sensor can shutdown the station. Even if the station did shut down and the heat generated is reduced the fire could continue and spread.

Our reccomendation remains to keep the enclosure sealed, the small reduction in temperatures which are already significantly below ratings will not signifficanltly extend the life of the components.

Above are valid points I am not here to argue one or the other as noted to each his own opinion.

Here are a few pics let me know if you need more details. Note I wanted the hood to keep dust from entering when not in use. If you need the 3D shroud file let me know.

As a note I did do hours of temp testing on all components. For example the J1772 cable at 1 foot from the EVSE unit is 5 degrees F lower with the fan. Again this is the cables outer shell measured at 1 foot from the enclosure. This would indicate that the fan lowering the internal temp of the enclosure actually lowers the conductive heat transfer to components like the cables.

True all components are rated for the higher temps and the cable is designed to operate very hot to the touch.

Again I am a tinker many things I own are modified to my liking.

You should make your own decisions and if you are not comfortable with modifications you should leave things as the original manufacturer designed them.

Again I think this is imp to note the single most important connections are the lugs on the relay. Make sure you are using the correct size wire if in doubt go up in size. If you are doing your own crimps use the correct lug with the correct tool to make the final crimp. Make sure things are tights lose connections get hot.

Kits are fun to build and fun to play with always follow safety guidelines.

Again if you are not confident in making changes/modifications it's best leave it as the manufacture designed it.

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