August 2022 was actually not the first month we have been charging the Tesla Model Y from the trailer, but the first month we have full data captured.
We have actually been charging for 3 months now. July was pretty low since we went on a 3 weeks trip using Super Chargers for most of the month.
Staying in the middle of nowhere using Super Chargers often requiring to drive many extra miles. Because of that is the cost saved from the energy charged to the car from the solar panels not even close to the needed super charging. When we stayed in Florissant was the closest super charger 35 miles from our location.
317 kWh added or around 1270 miles of driving with our average 249 Wh/Mile. We could have charged a lot more but we did not drive enough. Comparing this to the Jeep we used to own that got 13 miles to the gallon is almost 100 gallon of gasoline saved for a cost of over $400 with the current pricing.
The reason for a lot of the charging being done in other places is that Tesla cannot use a GPS location as home address. This is making the statistics look strange, but also make navigation to "Home" not working, Tesla please add this for boondockers.
We have dual inverter/chargers working in parallel and able to provide 10 kW that can charge the Tesla with 40 Ampere at 240 Volt. The Solar Setup on the trailer is only 7 kW so charging with 40 Ampere is good for a quick top up before a long drive, but really take half the energy from the batteries. We normally charge with 20 Ampere that pretty much match the solar production during the day.
A full charge takes a long time, but we rarely drive the car down to low state of charge and only need to top up on the energy used. So most days are the Tesla sitting at 80% state of charge ready to go 250 miles if needed.
August 31st was a day where we charged a lot to the car 17 kWh, both using 40 ampere and 20 ampere. Most of the day was the air condition (small windows unit) also running in the trailer. the total consumption was 23 kWh and because the batteries started at a pretty low state of charge was 36 kWh created from the sun.
We created a total of 500 kWh in trailer for the month of August. A lot went to the car, but the building and welding of the trailer required a lot of power too. Even when not being used is the idle load overnight pretty high at 150 watt. This drain the battery 2 kWh (10%) overnight and need to be refilled next day. But again since all the parts are paid is energy free.
One issue by pushing a lot of power through a system like this is the efficiency. The inverter/chargers are 95% efficient, but when pushing 10000 watt is 5% loss still 500 watt. That like a small electric space heater. Because of that is the air condition set to maintain 72 Fahrenheit in the trailer to avoid overheating the electronics. So we really need to add the energy used by the air condition as losses too. In the future is a ventilation system being added and a mini split air condition that is probably going to use 1/2 of the energy for the same cooling.