Help sizing a system to charge an EV

[John117]

Hello, I need help planning out this system. I am thinking of buying an EV in the coming months, my round trip to commute to my job is 40 miles. I am a solar enthusiast and would like to be able to charge this mileage with a homemade solar system. I am on a budget and don't want to hire anyone to do this and I know I cant afford a full-blown system to fully charge the tesla.

Searching on Google I can see that the model Y has a 60 kWh battery and a range of 244 mi. Is my math correct?

244 /60 = 4.06 so this means I get 4 miles every 1kwh right? That means I need to charge at least 10kwh to get my 40 miles right?

If so, these 2 batteries suffice?
2X 51.2V 100AH LiFePO4 Battery $1,099.99 5.1KWh

Having said that, how many solar panels do I need given that I live in Georgia, and they can get at least 4 hours of sun on average.
And what will be a good ALL IN ONE inverter capable to hold this system and connect to the grid to charge the batteries when the sun is not enough? I would like to use a level 2 charger and those are 220v, so this all in one must be capable of delivering 220v I guess.


****UPDATE*****


I made this drawing in paint to hear your opinions




Anyways, is this crazy? or doable?
Please let me know and thank you in advance!

 

[sunshine_eggo]

10kWh of storage battery will certainly help you optimize your PV.

10kWh/day with 4h/day of sun:

10kWh/4h = 2.5kW of PV - round up to 3-ish for good measure.

Many AiO can handle this, it depends at what rate you want to charge... 1kW for 10 hr; 2kW for 5h, 5kW for 2h?

 

[400bird]

Hello, I need help planning out this system. I am thinking of buying an EV in the coming months, my round trip to commute to my job is 40 miles. I am a solar enthusiast and would like to be able to charge this mileage with a homemade solar system. I am on a budget and don't want to hire anyone to do this and I know I cant afford a full-blown system to fully charge the tesla.

Searching on Google I can see that the model Y has a 60 kWh battery and a range of 244 mi. Is my math correct?

244 /60 = 4.06 so this means I get 4 miles every 1kwh right? That means I need to charge at least 10kwh to get my 40 miles right?

The easier way to get there is to use watts per mile. Google and a reddit post says that is about 280-350 watts per mile. It's going to be worse when it's cold or if you have a lead foot.

Let's say worst case 350 watts per mile x 40 miles is more like 14 kWh. But then you also need to include MPPT/charger (90%), inverter(90%), battery (99%), and EV charger inefficiency (unknown to me, likely around 85% because there's a lot of overhead to run the car). Plus inverter idle draw (depending on the inverter, this could be 2.4kWh per day)

The above numbers are just rough guesses.

If so, these 2 batteries suffice?
2X 51.2V 100AH LiFePO4 Battery $1,099.99 5.1KWh

Having said that, how many solar panels do I need given that I live in Georgia, and they can get at least 4 hours of sun on average.

Punch your location into NREL PV watts and play around. I'd recommend concentrating on the lowest production periods. There will be plenty of extra in the spring/summer, but if you need to drive daily, then every cloudy January day is important.

And what will be a good ALL IN ONE inverter capable to hold this system and connect to the grid to charge the batteries when the sun is not enough? I would like to use a level 2 charger and those are 220v, so this all in one must be capable of delivering 220v I guess.

Anyways, is this crazy? or doable?
Please let me know and thank you in advance!

Not crazy, but I'd just go simple and install a full system for everything. Shifting energy from daytime production to night time EV charging can be difficult.

What's the plan for extremely low production weeks? Do you have an alternative way to charge?

 

[zanydroid]

so this means I get 4 miles every 1kwh right? That means I need to charge at least 10kwh to get my 40 miles right?

Those Tesla numbers might be overly optimistic even for summer. Better to ask on a brand forum for the EV

What is the local inspection regime like? If they are picky you need to use more expensive equipment. Sometimes the Man sees solar panels and sends some G-men to you to see wuzzup

 

[John117]

The easier way to get there is to use watts per mile. Google and a reddit post says that is about 280-350 watts per mile. It's going to be worse when it's cold or if you have a lead foot.

Let's say worst case 350 watts per mile x 40 miles is more like 14 kWh. But then you also need to include MPPT/charger (90%), inverter(90%), battery (99%), and EV charger inefficiency (unknown to me, likely around 85% because there's a lot of overhead to run the car). Plus inverter idle draw (depending on the inverter, this could be 2.4kWh per day)

The above numbers are just rough guesses.

Punch your location into NREL PV watts and play around. I'd recommend concentrating on the lowest production periods. There will be plenty of extra in the spring/summer, but if you need to drive daily, then every cloudy January day is important.

Not crazy, but I'd just go simple and install a full system for everything. Shifting energy from daytime production to night time EV charging can be difficult.

What's the plan for extremely low production weeks? Do you have an alternative way to charge?

Thank you for your time on this!! So, I was watching videos about all in one systems and I notice they all have an option to connect to the grid. If I am not mistaken, you can set them up so they use the grid to charge the batteries if the sun wasn't enough that day. I just want something that gives me some range and is scalable, like maybe start with 20 miles charge and grow keep adding panels and battery.

 

[John117]

Those Tesla numbers might be overly optimistic even for summer. Better to ask on a brand forum for the EV

What is the local inspection regime like? If they are picky you need to use more expensive equipment. Sometimes the Man sees solar panels and sends some G-men to you to see wuzzup

I wasn't thinking on ANY of that. I will dive into it. Thanks!!

 

[zanydroid]

Thank you for your time on this!! So, I was watching videos about all in one systems and I notice they all have an option to connect to the grid. If I am not mistaken, you can set them up so they use the grid to charge the batteries if the sun wasn't enough that day. I just want something that gives me some range and is scalable, like maybe start with 20 miles charge and grow keep adding panels and battery.

For EV charging it doesn’t really make sense to charge the AIO battery from grid, unless grid is cheap at a time that you can’t plug in the car. Usually grid is cheap overnight and most people have their cars at home at night.

 

[zanydroid]

Hello, I need help planning out this system. I am thinking of buying an EV in the coming months, my round trip to commute to my job is 40 miles. I am a solar enthusiast and would like to be able to charge this mileage with a homemade solar system. I am on a budget and don't want to hire anyone to do this and I know I cant afford a full-blown system to fully charge the tesla.

Searching on Google I can see that the model Y has a 60 kWh battery and a range of 244 mi. Is my math correct?

244 /60 = 4.06 so this means I get 4 miles every 1kwh right? That means I need to charge at least 10kwh to get my 40 miles right?

If so, these 2 batteries suffice?
2X 51.2V 100AH LiFePO4 Battery $1,099.99 5.1KWh

Having said that, how many solar panels do I need given that I live in Georgia, and they can get at least 4 hours of sun on average.
And what will be a good ALL IN ONE inverter capable to hold this system and connect to the grid to charge the batteries when the sun is not enough? I would like to use a level 2 charger and those are 220v, so this all in one must be capable of delivering 220v I guess.


****UPDATE*****


I made this drawing in paint to hear your opinions

View attachment 211673


Anyways, is this crazy? or doable?
Please let me know and thank you in advance!

Don’t do 4 batteries in series unless you want to get into manually managing balance or adding a balancer across those batteries.

I do appreciate the desire to have smaller to handle batteries.

For EV charging 48V is definitely more scalable than 24V system voltage.

 

[olivinelife]

my round trip to commute to my job is 40 miles...would like to be able to charge this mileage with a homemade solar system

Is your job a standard M-F 9-5 job where you will be away from home during most of the day's solar production? This plan isn't particularly making sense to me. Yes you can store that energy in a battery and charge when you get home but you lose some efficiency. From what I can tell Georgia Power offers an EV rate plan that charges $0.018/kWh from 11pm-7am (+ other fees). You can't compete with that value even with DIY solar.

If this is the case, it would make more sense to have a standard solar+battery setup with hybrid inverter to self-consume your production over the course of the day+evening. It doesn't look like Georgia Power offers a compelling NEM plan.

 

[chrisski]

244 /60 = 4.06 so this means I get 4 miles every 1kwh right? That means I need to charge at least 10kwh to get my 40 miles right?

That is math, and looks like it is a little more than 4 miles per kWh, you may need to pull twice that to charge it. That does not take into account AC/heater, idle draw when parked, or inverter efficiency losses.

IME, Tesla plays with the numbers a little. In their app, they only put the kWh from the battery to drive the car and none of the other factors.

This is my experience of level 1 charging a Tesla model 3

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

There is a draw on the Tesla just to have it on, especially with the security cameras which I and others measured at could 500 watts per hour.

Also, running the air conditioning or heater could burn another kWh.

Now you actually need up to 16 kWh into the car batteries, but the inverter has conversion losses of 85%, so 18 kWh could be needed.

 

[John117]

Is your job a standard M-F 9-5 job where you will be away from home during most of the day's solar production? This plan isn't particularly making sense to me. Yes you can store that energy in a battery and charge when you get home but you lose some efficiency. From what I can tell Georgia Power offers an EV rate plan that charges $0.018/kWh from 11pm-7am (+ other fees). You can't compete with that value even with DIY solar.

If this is the case, it would make more sense to have a standard solar+battery setup with hybrid inverter to self-consume your production over the course of the day+evening. It doesn't look like Georgia Power offers a compelling NEM plan.

Thank you! This is another valuable insight for me. Yes I be away from home from 7am to 6 pm, never thought about those Georgia Power rates, definitely worth checking out.