Level 1Charging a Tesla Model 3 off grid

[chrisski]

I did level 1 charging with my Tesla model 3 with my solar setup, and these are the results:

4.33 miles / hour charged
322 wh/mile from the ac inverter
367 wh/mile from the Batteries to cover AC losses
AC draw from inverter while charging 1400 watts +/-2watts.
AC Draw from inverter before charging 0 watts

Drove 28.2 miles
AC 9.1 kWh used (This accounts for wattage from the inverter only, not DC to AC conversion loses)
DC 10.289 kWh used to cover AC to dc conversion losses. Turns out my inverter is 87% efficient
6.5 hours to charge

Idle Draw of Tesla when it plugged in for charging and sentry mode on=200 watts. This added up over the 10 hours the car was unplugged at 100% before i went to work and when I left after that time, it was 97%

The numbers above were measured using a Victron Shunt for the DC readings, and the AC readings were by the Samlex 3000 watt 24 volt inverter.
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The tesla app on the car and the phone gave me some numbers that don’t quite match up to above. The tesla app showed 204 wH per mile and an 8 kWh charging session.

So, after a little reading on the Tesla boards, the batteries are supposedly heated when the car is charged, and the guess is its 500 watts of power. It seems that tesla is not counting the energy to run the battery heater in the aps display of 204 Wh/mile. If the heater is 500 watts, about 900 watts goes into charging, so the proportion is close enough. The numbers I got off the Tesla boards for actual watt hours per mile was 320 WH/mile, so close to what I had, but again not matching the Tesla display.

The other thing the Tesla software may no count is the idle draw. So, the watt hours per hour is a little misleading. If I drove 10 miles and only looked at the Tesla app charge stats, I would think the charge session would cost $.56 if I charged it off the grid at $.17 per kWh. The actual cost would be $.84.

The Tesla app was also a little inaccurate on kWh used. I used 9.1 kWh for my 28.2 mile drive, when the app displayed 8 kWh. I trust my shunt more than the tesla app.

After all this, I saved 9.1 kWh of grid power on the 28.2 mile drive, or $1.55. I can almost get a small pack of M&Ms that I like with the money I saved, but not the coke or chips to go with it.

 

[Supervstech]

What’s the setup? How much solar is connected to it? How big a bank?
Does it have 240V output? With enough inverter size, 240V moves it faster.

 

[chrisski]

What’s the setup? How much solar is connected to it? How big a bank?
Does it have 240V output? With enough inverter size, 240V moves it faster.

The set up is:

120 volt Samlex 3000 watt 24 volt PST inverter
13.3 kWh Lithium 24 volt battery bank
2.65 kw of solar panels.

The 2.65 kw of solar panels struggles to keep up with the 1500-1600 watt demands on the system this time of year with the low sun angle.

With the 240 volts comes level 2 charging, and that is supposed to be more efficient. This heater is supposed to stay at 500 watts even though 5X as much power goes in so that extra power goes straight to miles.

With me and this equipment in my RV, Level 2 charging at 240 volts is not realistic. With 24 volts, I’m pretty much maxed out at the wattage I could deliver. If I did level 2, I would want a 48 volt upgrade and a lot more than the 2.55 kWh of power I have now.

 

[Supervstech]

The set up is:

120 volt Samlex 3000 watt 24 volt PST inverter
13.3 kWh Lithium 24 volt battery bank
2.65 kw of solar panels.

The 2.65 kw of solar panels struggles to keep up with the 1500-1600 watt demands on the system this time of year with the low sun angle.

With the 240 volts comes level 2 charging, and that is supposed to be more efficient. This heater is supposed to stay at 500 watts even though 5X as much power goes in so that extra power goes straight to miles.

With me and this equipment in my RV, Level 2 charging at 240 volts is not realistic. With 24 volts, I’m pretty much maxed out at the wattage I could deliver. If I did level 2, I would want a 48 volt upgrade and a lot more than the 2.55 kWh of power I have now.

Not necessarily.
If you only need 10kWh of charging, 240V sends it quicker, and gives more sun hours to recoup the loss.
I would want to use a 6 to 8Kw inverter for the load.
But even with the current 24V inverter load you have, at 240V, you'd get the full 3kw output of it, for around $400 with a European 240V model...

 

[400bird]

The tesla app on the car and the phone gave me some numbers that don’t quite match up to above. The tesla app showed 204 wH per mile and an 8 kWh charging session.

It's pretty standard to count watts/mile as watts that come out of the battery vs watts from the wall.

I think those are two different calculations.
One is driving efficiency and the other is charging efficiency.

So, after a little reading on the Tesla boards, the batteries are supposedly heated when the car is charged, and the guess is its 500 watts of power.

It's not just a heater. A summer charging session would do something similar and it wouldn't be heating the batteries then.
There's overhead to run electronics, power the charger, close contactors, and the efficiency of the charger. Most converters are less efficient at the lower end of the output range.

The quicker you charge, the less time these overhead loads have to slow down charging speed.

 

[chrisski]

It's pretty standard to count watts/mile as watts that come out of the battery vs watts from the wall.

Even though may be standard, only counting the actual watts out of the battery from the wall is misleading.

At least to me, but I’m the type of person who wants to know how much something will cost, and not just the sticker price, but aftermarket also. Kind of a pet peeve.

I want to know how much my electric bill will go up for an x mile commute 5 days a week prior to getting the car. I also want to know how big of a system I need to build to charge this off solar and not find I actually needed something 50% - 80% bigger.

 

[MichaelK]

Chrisski, are your panels actually all mounted on the RV? How are they positioned in relation to the sun?

At my own homestead, I have my two systems, the 48V cabin, and the 24V workshop. My solar arrays though are all at about the same 115-120VDC, so what I've done is made one of my workshop arrays with an either/or breaker so if I chose to, I can divert extra power from the workshop to the cabin. This works for me in the early morning, and the late afternoon, when the cabin's primary arrays can't quite cut it.

I wonder if you might be able to implement the same idea, maybe an array that is normally going to your main system, but can shunted off to the EV instead? Could you place an extra ground mount next to the RV, and dock the RV into it? What are all the voltages you work with?

 

[chrisski]

Chrisski, are your panels actually all mounted on the RV? How are they positioned in relation to the sun?

At my own homestead, I have my two systems, the 48V cabin, and the 24V workshop. My solar arrays though are all at about the same 115-120VDC, so what I've done is made one of my workshop arrays with an either/or breaker so if I chose to, I can divert extra power from the workshop to the cabin. This works for me in the early morning, and the late afternoon, when the cabin's primary arrays can't quite cut it.

I wonder if you might be able to implement the same idea, maybe an array that is normally going to your main system, but can shunted off to the EV instead? Could you place an extra ground mount next to the RV, and dock the RV into it? What are all the voltages you work with?

I’m pretty happy with my setup. This is a travel RV, so with 2550 watts of panels and a 13 kWh battery bank, there’s not a lot I want to change.

Intent was to give someone who wants to level 1 charge some realistic data to design their system.

I have 1650 watts of panels are flat mounted on the roof. In the shortest days of the year with antenna, vents, and AC, not much production from the roof. Perhaps peaking at 700 watts. None of the obstructions I will move.

I have 900 watts of ground panels I orient to the sun, moving them three times a day. I may increase the ground panels by 300 - 600 watts.

I set the ground panels up and tear it down daily. It’s a strong wind thing at night.

 

[cx415]

I have a newbie question about a similar setup. I have the Tesla mobile charger (for my used Model 3). I have a MPP LV2424 off-grid. I must not have it setup correctly (no ground, no neutral-ground bond) because my M3 does not want to charge from my LV2424 inverter. It throws an charger error. The LV2424 does have a grid/Utility plug, which supplies the ground. When I plug the mobile charger to the same grid outlet, it works fine, but not thru the inverter. Mobile charger is set to draw only 5amps. My setup can power a lot more than that, and have no problem running other 120v appliances (dehumidifiers, heaters, shop vacs, etc.)

Thanks for any ideas? (this more for my curiosity, as charging my M3 isn't a serious application for my off-grid setup)

 

[yabert]

Thanks for any ideas? (this more for my curiosity, as charging my M3 isn't a serious application for my off-grid setup)

Your EVSE need a proper ground.
But when you connect ground to neutral the EVSE will don't see anything strange and will allow the current to flow from inverter (120Vac) to EV charger.
At least, it's my experiment with EVSE and inverter.

 

[Ampster]

Thanks for any ideas? (this more for my curiosity, as charging my M3 isn't a serious application for my off-grid setup)

I am currently charging a Model 3 with a 16 Amp Clipper Creek EVSE through my SolArk 12k while disconnected from the grid. This was more of a test about AC coupling my micros. I may decide to try my Mobile Connector at 24 Amps as a test later sometime. Some EVSEs are more sensitive than others.

 

[chrisski]

There have been issues with EVs not charging on inverters I've seen on this forums. This is one I got from "Tesla won't charge on Inverter."

There's other threads on this.

 

[curiouscarbon]

There have been issues with EVs not charging on inverters I've seen on this forums. This is one I got from "Tesla won't charge on Inverter."

There's other threads on this.

With a goal zero inverter, there was no ground connection, and the tesla wouldn't charge.



using a splitter and one of these N-G bond plugs, the car would accept a charge from the inverter

 

[cx415]

With a goal zero inverter, there was no ground connection, and the tesla wouldn't charge.

View attachment 151636

using a splitter and one of these N-G bond plugs, the car would accept a charge from the inverter

Took me a while to get to this, but the N-G bond plug is a winner! Thank you very much! Works great now!