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Low Amperage Charging - is it possible?

 Hi All, please be kind this is my first post.

I am a proud owner of a Mitsubishi PHEV and have just come home from a trip around Europe with a caravan. Most times in the UK I can use the camping site power supply to charge the car (10A over 5 hrs) Problems arise in Europe when the campsite power trips at 6A, sometimes 4A. Often I am unable to use the electric kettle.

I would therefore like to know if an EVSE has ever been created to only use a low current, say 4A. I would be happy to use it in the above circumstances by charging overnight for 8 hrs or more.

Thanks Clive.  I'll load the Raspberry Pi Os with 32 bits assuming its available at startup time.  I have an old windows PC I put windows 8.1 32 bit on and it runs legacy software and the 64 bit system does not.  I need to fire up that Rp Os now that its all sitting on my desk....Gene


The OpenEnergyMonitor EmonPi combined with OpenEVSE would be all you need. 

Here is a guide for solar diversion integrating OpenEVSE and OpenEnergyMonitor.

Hi Gene, your project sounds very ambitious. If successful, you would be a trailblazer in the Pi community. I'm sure that your project would attract heaps of forum support. I've used Pi's for years at home, mainly for audio visual applications. Recently I've added a Pi 4 to the collection and used Pi Os as the base software. There are a few flavours of Linux available, most notably Ubuntu, that can now be used on the Pi 4. I would suggest that you stick to the 32bit as the 64bit is still new and probably not needed on the Pi 4. If you don't want a desktop then there are other headless OS's that would work. I've used PiCore for years and found it very stable and trouble free. Try this site for a review

Hope this helps.

Im trying to have my Tesla charging amps be variable depending on the amount of power available from the solar inverter.  I have the output of the inverter feeding into the grid (my home 120 volts) and to the Tesla 120 VAC charger.  The power coming out of the inverter changes the power going to the grid automatically depending on the suns output.  What I want to do is hold that power constant at 200 watts going to the grid and ramp up and down the EV charge rate as the inverter output changes.  So there are two loads on the inverter, one is the EV and the other is the home.  If I manually set the car to some level the power to the home wall outlet varies.  I want to vary the EV charge rate so the power to the home stays constant.  I have ordered the energy monitor described as split single phase energy meter EmonCMS.  I have the small 20 amp to 25 mA clip on CTs.  I will clip them on to the current going to the grid and to the Tesla charger, acutually the openevse charger.  I will need to have a small program that reads this data and converts the CT readings to a raise lower settings on the openevse J1772 charging port.  I.e. Im going to have to do some math to hold the power constant to the grid.  If the sun power drops too low the open evse is set to the lowest amps and can draw its power from the grid.  If the sun power goes too high, i.e. over 1700 watts, 1500 to the car and 200 to the home, then the power to the home is increased above 200 watts.  I have seen this solar inverter go to 2000 watts output once and if that had happened a peak power of 500 watts would go to the grid which is ok.  Its rare.  I thought I would do this control using a raspberry pi just like these fellows did in their tesla charging circuit posted at  They had to use a computer to do the extra math and control.   thanks....Gene

Gene, we are puzzled by your question. OpenEVSE does not use or depend on a Raspberry Pi in any way, nor is OpenEVSE an expert on Raspberri Pi (we do know what they are and have played with a couple over the years). Your question contains no info, so our answer still stands. It depends on what you needs are. 

This thread is about low amperage charging and your original question is about tracking solar. Are you trying to do something like the Open Energy Monitor EmonPi?

I was wondering if openevse is best set up using raspberry pi OS?  The default OS?  Im going to assume this is the case and start there.  The reply isn't useful because it contains no info on which op systems would be useful to use openevse.

There are many options for operating systems on Raspberry Pi, the best OS will depend on your needs. 

Should I load the Raspbian operating system on my new raspberry pi computer?

@ Gene Preston

OpenEVSE Advanced support this out of the box. All you need to do is send your solar output from your system in watts to a MQTT server then have OpenEVSE subscribe. Turn on ECO mode and OpenEVSE will follow the solar output.

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Is it possible to build a system that charges a Tesla Model 3 using 120 volts L1 charging that is variable from 6 to 16 amps?  What I want to do is to have the Tesla charge rate track the suns output.  My panels can put out 1800 watts see however when clouds come over I would like to have the solar inverter supply less power to the Tesla when less sunlight is available.  This allows the use of a smaller 24 volt battery on the MPP LV2424 inverter since the load would throttle with the solar power.  Right now in the winter time I can get on average about 120 miles range per week off this system from sunlight.  I would like to make it more automatic using the J1772 in these articles.  Is this possible?  my web page is 

Although this should work you may find that the inrush current to the stepdown transformer will trip the breaker. As long as you can reclose the breaker (it might take a couple of attempts before it latches) you'll be fine.

Don't give up disappointed if it trips out right away.

Thanks for the interest Andy. This solution sounds as if it will work, I shall try it on my next foray into Europe.

Whoops, miscalculation by me above, and I can't see how to edit my own append! Running a charger at 115V AC and 6A (the minimum the spec allows) would be drawing 690 Watts, and if powered from a 230->115V transformer, this would mean 700W at the 230V side (assuming 98.5% efficiency for nice round figures!). That's 3.04A at the 230V side, which might be doable for a campsite maybe?

The CCS simple protocol (AC charging) specifies the the EVSE can signal the car of charging currents from 6 to 80 amps.  So you can't send a number below 6 to the car. 

Afaik, the J1772 std allows 120V operation. e.g. as in USA. So there's nothing I can see in principle to stop someone using a 230->115V step-down transformer, and running  a 6A EVSE off that. Power draw would then be about 3 kW. Presumably if all EVs obey the standard, they shouldn't mind only being offered 115V or thereabouts?

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