New to Solar

[starkiller239]

I am planning to build a 7-8kW off-grid solar battery for purposes of charging my plug-in hybrid car. What I'm seeking is how square feet in solar panels would I need to charge the battery. How many square feet would I need to charge it in 1 day, how many square feet would I need to charge it in 2 days, etc, etc up to 5 days.

If anyone can provide a link to some literature, I would greatly appreciate it.

Thank you

 

[BentleyJ]

This link is from forum member sunshine_eggo. Lots of resources in the footer of their posts.

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

 

[MichaelK]

A couple of important questions, starting with units. You mention 7-8kW. That's not the unit usually describing a battery bank. You would normally describe it in terms of kilowatt hours, or kWh. Did you actually mean 7-8kWh? Solar arrays typically could be described by their instantaneous output, which could be measuring in kW. So did you mean a solar array with an output of 7-8kW?

A battery with a capacity of only 7-8kWh would be quite small, and in no way could fully charge an EV battery, which might have at least a 40-50kWh battery. How much you have to charge it is directly proportional to how far you drive it, so to answer the question for a fully depleted battery, you need to charge it with at least 40kWh of power. Are you talking about charging your EV at night solely from the battery, or do you mean during the day, while the sun is shining?

I personally have a 4500W rotating array, and my personal best for production was 25kWh last year while pumping irrigation water, With about 7000W of panels, I'm likely to make the required 40kWh from 8am till 4pm if I could rotate the arrays East to West during the day. Without tracking though, 8kW of panels is not likely to make you 40kWh over the course of the day.

There are three tiers of EV charging...
Level 1: 12A at 120V
Level 2: 20-50A at 240V
Level 3: 480V DC.

That's the US standards. What are the EV standards in the UK? I'll assume you'll be charging with 230VAC?

I'm in California, where my single most important load is irrigation water. On cloudy days, max production of irrigation water is not needed. For you however, you'll need to charge your EV rain or shine. What is the plan going to be for rainy days, which I know are a lot of in the UK, when you just have to drive somewhere?

I hope that gives you a few things to think about before moving forward with this idea.

 

[starkiller239]

A couple of important questions, starting with units. You mention 7-8kW. That's not the unit usually describing a battery bank. You would normally describe it in terms of kilowatt hours, or kWh. Did you actually mean 7-8kWh? Solar arrays typically could be described by their instantaneous output, which could be measuring in kW. So did you mean a solar array with an output of 7-8kW?

A battery with a capacity of only 7-8kWh would be quite small, and in no way could fully charge an EV battery, which might have at least a 40-50kWh battery. How much you have to charge it is directly proportional to how far you drive it, so to answer the question for a fully depleted battery, you need to charge it with at least 40kWh of power. Are you talking about charging your EV at night solely from the battery, or do you mean during the day, while the sun is shining?

I personally have a 4500W rotating array, and my personal best for production was 25kWh last year while pumping irrigation water, With about 7000W of panels, I'm likely to make the required 40kWh from 8am till 4pm if I could rotate the arrays East to West during the day. Without tracking though, 8kW of panels is not likely to make you 40kWh over the course of the day.

There are three tiers of EV charging...
Level 1: 12A at 120V
Level 2: 20-50A at 240V
Level 3: 480V DC.

That's the US standards. What are the EV standards in the UK? I'll assume you'll be charging with 230VAC?

I'm in California, where my single most important load is irrigation water. On cloudy days, max production of irrigation water is not needed. For you however, you'll need to charge your EV rain or shine. What is the plan going to be for rainy days, which I know are a lot of in the UK, when you just have to drive somewhere?

I hope that gives you a few things to think about before moving forward with this idea.

Sorry, 8kWh system
Plug-in hybrid cars do not have large batteries unlike EV's, for instance, my car is only 7ishkWh
Currently using a level 1 charger, takes about 5 hours to fully charge the car and this doesn't bother me
Southern new england is in the united states

 

[starkiller239]

This link is from forum member sunshine_eggo. Lots of resources in the footer of their posts.

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

Thank you for that link. Using their calculator, I was able to get a rough estimate of how much space I would need to generate the 70kWh per month I would use.

 

[Redflyer]

One of my main goals with solar was to charge my EV car. I ran a 240v circuit directly off the solar sub. I then purchased a Lectron NEM 14-50 level 2 charger. I bought it because it didn't cost as much and got good reviews. After the fact, I really like that I can select the amperage output. The highest is 32 (that's the max the car can accept), then 16, 13, 10....as far as I can remember. Allows me to tailor the charge rate to the solar setup.

My system is 7.6kw system and I have more than enough power to do everything I wanted, and more.

 

[MichaelK]

Sorry, 8kWh system
Plug-in hybrid cars do not have large batteries unlike EV's, for instance, my car is only 7ishkWh
Currently using a level 1 charger, takes about 5 hours to fully charge the car and this doesn't bother me
Southern new england is in the united states

Sorry, somehow I didn't catch the "New" in England? Poor reading comprehension skills?

If you really need only 7-8kWh per day, a system the size of my 24V workshop will suffice. Three 8V Rolls Surrette batteries, Midnight200 charge controller, Conext 4024 Sine-Wave inverter, and 2000W of panels, eight 250W 30V residential panels, wired 4S2P.

One rotating mounts, that can be tracked East to West, this should make you ~12kWh of power per day. Here are a couple of my mount pics. They are not motorized. I rotate them East to West by hand.

If you wanted to go whole-home, powering both the house and the plug-in, I'd suggest simply doubling all the numbers, a 48V battery bank, same controller, maybe the 6848 XW-Pro, and 4000-5000W of panels. Say maybe 8kWh to the car, and 16kWh to the house.