How to Trickle Charge Your Tesla from DIY, Off-Grid Micro-Solar (+12 miles/day)

[erictstahl]

This is just a proof of concept that I did while stuck in quarantine. It shows how you can build your own micro solar system for trickle charging your Tesla (or anything else). I will add more panels / batteries over time. By the end of the day it added 12 miles of range to to the car / day (4,380 miles/year). It's the middle of January, so I'm curious to see what that gets to in the summer months. I will post an update in a few months.

The trickiest part of was properly grounding the inverter so the Tesla charger would accept it. Watch this video to see how to bond the 120v AV output to the inverter chassis https://youtu.be/ehK0uYNtaIY

Solar: 8 x 100 watt Renogy
Charge Controller: Victron 30 amp, 100 volt
Battery: SOK 206 amp hour
Inverter: Victron Phoenix 1200 watt
Car: 2001 Tesla Model 3 Long Range

Will, thanks for all of the great videos. Even though this is a teeny-tiny system, I had fun making it... and it actually works!?!

 

[orangezero]

Good to see. Thanks for sharing.

 

[merlin714]

Nice video! I'm looking to build a similar micro setup. One question, Victron says at 12v the 100/30 controller is spec'd for 400 watts of panels. Under ideal sun conditions is there any concern about frying the controller with your 800w? I'm looking to get 600-800 watts of solar up and am considering controller options. Thanks.

 

[erictstahl]

Nice video! I'm looking to build a similar micro setup. One question, Victron says at 12v the 100/30 controller is spec'd for 400 watts of panels. Under ideal sun conditions is there any concern about frying the controller with your 800w? I'm looking to get 600-800 watts of solar up and am considering controller options. Thanks.

Thanks. The charge controller is spec'd at 30 amps and 100 volts, so as long as you stay under that, you are fine. I have two arrays of 4 panels each. Each array is wired in series, then the two arrays are wired in parallel. According to this calculator, it's only going to peak at 74.4 volts and 11 amps, which is well within the range of the charge controller. I might add another array of 4 more panels soon https://mowgli-adventures.com/wiring-solar-panels-in-series-vs-parallel/

 

[circus]

wired in series, then the two arrays are wired in parallel. According to this calculator, it's only going to peak at 74.4 volts and 11 amps, which is well within the range of the charge controller.

Sorry Merlin is right, the thirty amp rating is at 12v going to the battery.

 

[erictstahl]

Thanks for flagging this. I've been researching all night and you are right! I'm new to all of this. So you are correct that I'm over paneled with this controller. I think it will be ok on the input, but the output is limited to 30 amps x 12 volts = 360 watts into the battery... which wasn't my intention with 800 watts of panels. My battery can take 50 amps of charge, so I can upgrade the charge controller, to 50 amps, but that would only get me to a max input of 600 watts. To get to 800 watts, I'd need to get a second battery and upgrade my controller to one that can put out 66.66 amps. Thanks for helping me get my head around this!

 

[erictstahl]

Or I suppose I could get a second battery, wire it for 24v and charge it at 30 amps to get to 720 watts... but then I'd need to replace my 12v inverter. Expensive lessons!!!

 

[erictstahl]

Or I can get a second 30 amp charge controller and wire it to the second array. Then each array/controller can put out 360 watts into the battery for a total of 720 watts. This is probably the easiest/cheapest option.

 

[Ampster]

I know this is an experiment and thanks for the information. As one tries to scale up this concept the following is offered:

There is too much overhead charging at 120 volts so I charge at 240 volts. I match my Amperage to the output of my solar panels and can get 40 to 50 miles per day depending on my other house loads. I have a 7kW system grid tied. I usually adjust the charging current to 10 to 20 Amps which is 2.4 to 4.8 kWs. A kWh gets me 3 to 5 miles of range depending on the vehicle. I have an All In One inverter and it is easier to manage.

 

[merlin714]

Or I can get a second 30 amp charge controller and wire it to the second array. Then each array/controller can put out 360 watts into the battery for a total of 720 watts. This is probably the easiest/cheapest option.

I thought your controller should handle 30 amps on the input as well and wasn't understanding why it was only rated for 400 watts on the spec sheet. It took Circus' message for the light bulb to go on for me. I agree the second controller is probably the best option, that way you also have redundancy. If there's any concern about exceeding the 50 amp battery charging limit, I believe you can set each controller to a max of 25 amps in the settings. Not sure if that's necessary. Thanks for giving me some good ideas!

 

[efficientPV]

I'd be feeding PV directly into my inverter and skip the battery and CC.

 

[Ampster]

I'd be feeding PV directly into my inverter and skip the battery and CC.

If I understand the architecture correctly, that is what an All In One inverter does . Internally it decides how much of that power gets distributed to loads such as charging and sub panel load. Then any extra gets sent to the grid if set up with a Grid Tie configuration.

 

[curiouscarbon]

great work!!

 

[erictstahl]

@merlin714 i added a second charge controller today. I capped each at 25 amps. I’ll see how it goes tomorrow. In hindsight I wish I built a 24v system, but it’s just the learning curve.

 

[ohmboy]

This is just a proof of concept that I did while stuck in quarantine. It shows how you can build your own micro solar system for trickle charging your Tesla (or anything else). I will add more panels / batteries over time. By the end of the day it added 12 miles of range to to the car / day (4,380 miles/year). It's the middle of January, so I'm curious to see what that gets to in the summer months. I will post an update in a few months.

The trickiest part of was properly grounding the inverter so the Tesla charger would accept it. Watch this video to see how to bond the 120v AV output to the inverter chassis https://youtu.be/ehK0uYNtaIY

Solar: 8 x 100 watt Renogy
Charge Controller: Victron 30 amp, 100 volt
Battery: SOK 206 amp hour
Inverter: Victron Phoenix 1200 watt
Car: 2001 Tesla Model 3 Long Range

Will, thanks for all of the great videos. Even though this is a teeny-tiny system, I had fun making it... and it actually works!?!

This is the set up that I plan on doing for a project!!! Thanks for the information!