Looking for critique on my 24 volt solar system

[Sully7912]

I have 4 lithium weize batteries in series to make 2 24 volt batteries. I live in Michigan so I have them in an old fishing cooler that I insulated and placed one rv heater. Rover solar controllers 40 amp. Transfer switch. I current am hooked to the house and run a full size refrigerator and full size freezer 24/7. Have a load center in the shed and load center in the house. I have a 1500 watt ground array made up of Renogy and Hqst 100 watt solar panels. Looking for suggestions to improve or upgrade my system. Tried to follow Will Prowse 24 volt system to charge a Tesla . Don’t know whether to get more solar panels or more batteries. Although you can always need more of them. I also thought about getting an all in one 48 volt system but I have built this from a 12 volt system and like to use what I already own.

 

[chrisski]

Really would like to see equipment specs, pics and diagrams prior to making recommendations. Also, goals like provide 5 kWh of power daily with a peak output of 2 kW.

More panels and batteries to level 2 charge a Tesla. IME your system may provide enough power to level 1 charge a tesla at 8 amps in the sun without any other loads. Also IME, Level 1 charging even at the full 12 amps is very slow and if plugged in overnight will charge my 35 mile commute in about 8 hours. I did that for 10 months and upgraded to a level 2 charger.

This is a write up I did for a one day charging of my Tesla while camping:

Level 1Charging a Tesla Model 3 off grid

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...

diysolarforum.com

 

[Rednecktek]

As I understand it, L2 charging requires 240v which is difficult to do with 24v systems as so few inverters can either parallel up or provide the 240v split phase the car is looking for. There are some inverters from Aims and the like that can do it, be prepared to drop $1000 minimum for that.

Another thing to consider is that your car has a zillion-kwh battery and when the sun goes down it's going to want to pull that from your batteries on top of everything else drawing from them. Figuring out how to tell the car to stop is another challenge.

 

[krby]

As I understand it, L2 charging requires 240v which is difficult to do with 24v systems as so few inverters can either parallel up or provide the 240v split phase the car is looking for. There are some inverters from Aims and the like that can do it, be prepared to drop $1000 minimum for that.

Yep, Level 2 charging is 240VAC (single phase) or 208VAC (three phase) and a min of 6A. But at that 6A min, you're at ~1.4kW, which you could also get from L1 charging on 120VAC.

Finding a 24V inverter that will do ~220V/60Hz for the US may be tough, if you find one, post here!

Another thing to consider is that your car has a zillion-kwh battery and when the sun goes down it's going to want to pull that from your batteries on top of everything else drawing from them. Figuring out how to tell the car to stop is another challenge.

Many modern EVs have configurable charging. Things like "only charge between these hours" or "never charge between these hours" or "charge up to 50% as soon as you plug in, then do whatever you have to do to get to 90% by 6AM". I assume a Tesla has some of those bells and/or whistles.

 

[chrisski]

As I understand it, L2 charging requires 240v which is difficult to do with 24v systems as so few inverters can either parallel up or provide the 240v split phase the car is looking for. There are some inverters from Aims and the like that can do it, be prepared to drop $1000 minimum for that.

Another thing to consider is that your car has a zillion-kwh battery and when the sun goes down it's going to want to pull that from your batteries on top of everything else drawing from them. Figuring out how to tell the car to stop is another challenge.

For planning, my Tesla uses 367 real watt hours per mile from the battery. This includes the power to run the battery heater and ac to dc conversion losses going in the battery.

Tesla said it was 204 watts hours per mile, so a huge discrepancy.

Level 2 charging is expensive. The Victron Multiplus can be paralleled.

Not sure what the OP wants, but it’s something he could upgrade to.

Yep, Level 2 charging is 240VAC (single phase) or 208VAC (three phase) and a min of 6A. But at that 6A min, you're at ~1.4kW, which you could also get from L1 charging on 120VAC.

Finding a 24V inverter that will do ~220V/60Hz for the US may be tough, if you find one, post here!




Many modern EVs have configurable charging. Things like "only charge between these hours" or "never charge between these hours" or "charge up to 50% as soon as you plug in, then do whatever you have to do to get to 90% by 6AM". I assume a Tesla has some of those bells and/or whistles.

The Tesla does do that, but can only set one time parameter and can’t make exceptions, even for weekends.

Leaves a bit to be desired for multiple rate plans.

 

[krby]

The Tesla does do that, but can only set one time parameter and can’t make exceptions, even for weekends.

Ya, each mfg seems to have their own idea of configurability. I was surprised my VW eGolf had the following:
- Set immediate charge level (go to X% as soon as you plug in)
- Set recurring schedule for "be charged to X% (typically 90% or 100%, but could be something X) by 6AM M-F. I could have three of these to cover things like weekend and weekday.

It was NOT intuitive to most people, but eventually figured out how to get what I wanted out of it.


Now...back to helping the OP.