February 29, 2024


I bought one 18 months ago About 1/2 the price of the Chevrolet Bolt. The Bolt is great, with the exception that I can’t charge it at my wife’s house, which is off the grid and is over an hour away.By the way, I would like to say that the key to a happy marriage is owning a detached house, I found that I real When my wife is not around when I come home, I am grateful for her. Familiarity often breeds contempt when we’ve been together. I’ve been working on upgrading her old system and when we met it only had a 1000W panel and about 1kWh of battery capacity. That’s far from enough to even consider charging an electric car. This article describes how I created an off-grid system with 4kW panels and 16kWh batteries to charge electric vehicles and why I did it this way.

Here you can see a recycled Volt battery pack with a 3000W inverter on top and two solar charge controllers mounted on the wooden sides

The current solar system was installed about 15 years ago and is a 24V DC based system. My wife had already had 3 sets of lead acid batteries (two of which actually nearly exploded) and we decided to switch to lithium. I want to separate the old system that runs the house from a new system that both runs the house and acts as a dedicated system for EV charging. We plan to keep adding panels and hope to install a hot water heat pump in the next few years, but the new panels will work with the new system.

The new system is based on an electric tractor I built using recycled Chevrolet Volt battery packs (how-to article here). The battery pack has a capacity of 16kWh and a usable charge of about 14kWh. It is connected to a 3000W inverter and a solar charge controller is also connected to the tractor. When I need to use the tractor or mow, I just disconnect the solar panel and AC extension cord and do what I have to, then come back and plug it back in. We also use the tractor as a portable power station to run our electric log splitters, electric chainsaws and electric rototillers. The eTractor is stored outside because I run the battery without a BMS and if it suddenly catches fire I don’t want it to take the house with me. I placed a large plastic box over the battery, inverter and charge controller to keep it out of the rain and snow. This bin helps keep electronics warm in the winter so they don’t accumulate moisture inside. This setup is the worst, but actually worked pretty well and got us through last winter pretty well.

This shows you what a 4Kw panel looks like, I think that’s the minimum you’ll need to charge an EV off grid

Trying to charge an electric car without a battery large enough to absorb the ebb and flow of the sun behind the clouds is a colossal mistake. I wouldn’t consider trying to run an EV charger with anything with a battery capacity of less than 5kWh. I also prefer a 48v system as the much lower amperage means you can use thinner copper wire between the inverter and the battery. The only battery pack I currently recommend is Signature Solar’s EG4 server rack battery. Last year I tried to buy LifePO4 batteries from China and it was the worst mistake of my life.You get a high-quality server rack system The price here is about $297/kWh That’s almost as cheap as buying directly from China.

All-in-one systems with a bunch of built in inverters and solar charge controllers are great, many of which can also be set to a 240v setting (about 5x faster for level 2 charging).Will Prose’s DIY Solar Channel It’s a place to see where new stuff is being tested and released all the time. I really like the setup he recommends, but they are more expensive and have a 50-80w continuous vampire drain that I would rather not use on our system. If you want a larger system, you may need to add 2 additional panels to compensate for the ongoing draw of the higher wattage inverter. That being said, the all-in-one system is far better than any I’ve ever designed, and far less likely to catch fire. (if this sort of thing matters to you)

I built the new system with a Renogy Rover 60 Amp charge controller I paid $297 on eBay and $300 on Amazon for a 48v inverter here (Compared to other cheap Chinese inverters I killed, this one is very reliable). It’s hooked up to 2.6Kw panels that I bought locally new on Craigslist for around 40 cents per watt. Adding in the 10 cents per watt for the roof mount, the total cost of the entire system is about $3900 ($1500 volt battery + $300 MPPT charge controller + $300 inverter + $400 copper wire + $40 DC breaker + $40 MC4 crimpers and connectors + $280 roof rails + $1040 panels).

I tried a Cheap $40 PWM 30 Amp Charge Controller Got it from Amazon that I connected to other 1.5kW panels we have. It’s surprisingly good for the price, but its efficiency is only around 80% compared to over 95% for MPPT controllers. At first I was very excited about the PWM controller, but it really doesn’t do well on cloudy days, while the MPPT controller works surprisingly well. I also bought two other PWM charge controllers with programmable charge limits and tried to work, but both failed. The BSC3048 is the only one I can currently recommend.

This awesome programmable PWM 48v charge controller costs much less than any MPPT capable controller, but is also about 20% less efficient

The crazy part is when you start comparing how many miles you need to drive to get your money back versus just buying gas. If gas is $5/gallon and your car gets 30 miles per gallon (which is the speed of most Bolt-sized economical dumpsters), the system will fully pay for itself after 24,000 miles. ($4000/5 gal x 30 mpg = 24,000 miles) There have been many times in my life where I’ve driven over 24,000 miles in a year, so the payoff for off-grid solar is the vehicle that exists if you’re willing to absorb it The purchase price is higher. The biggest downside is that with such a system, the charging rate of the Bolt’s battery is rather slow. I can charge it at 12 amps (4 mph range) but I feel like it’s stressing the inverter so I’m only charging at 8 amps (3 mph range). Since most of the time the car is idling and doing nothing, this isn’t really a problem. I don’t charge overnight, only when the sun is shining, because I don’t really want to add more rides to the Volt battery on the tractor.

With a little ingenuity, some coolie work, and enough luck, you can set up an off-grid system to charge your EV and start gASS like I did. It’s fun, rewarding, and ultimately makes a lot of financial sense for those who like the long game and are tired of being ripped off by Big Oil.

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