Converting Your Old Allis-Chalmers "G" Cultivating Tractor to an Electric Vehicle:
Notes on Solar Panel Charging
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Charging Your Electric Tractor with Solar Panels

Overview
We added solar panels to charge the tractor. This is a decision you really need to think about before you do it because it is expensive. Ideologically it feels nice to have a tractor running completely free of fossil fuels. In addition, it is a long drive for us from our back growing fields up to the barn and power, so being able to leave the electric tractors out the back field to be fully recharged by the sun actually saves us 30 minutes a day per tractor, which... over the course of a season is tremendous.

We are much more likely now to just throw in one bed of carrots when we used to bundle things to save driving time. Perhaps more importantly, we are more likely to tractor-cultivate at the right time -we used to bundle cultivations like we bundled seedings... and then if it rained we missed our chance entirely.

So these are some good points, but... the "bottom line" problem in that we calculate that we spent under $12 last year charging BOTH our electric tractors for the entire season. $12 in electricity is not a lot. From THAT perspective, it makes the solar panels a pretty silly addition.

Of course as Farmers, we've learned to look very creatively at our bottom line problems. When you look at the cost of solar panels AND the conversion, the electric "G" is still far cheaper than a new cultivating tractor. It also just "feels" SO COOL to not have to plug the tractors in. We also have a converter (which we haven't used yet) that allows us to power the whole house (and our walk-in cooler) off the tractor batteries, which were charged off the sun, so... that's literally cool . And from a marketing perspective, saying we run the farm on electric tractors is good, but getting to say we run it on SOLAR electric tractors... well, that just takes the farm right over the top!

Finally, in trying to justify the solar panels to my much more practical wife, I must return to the labor saving factor. We value our personal farm-labor time at $20/hour. In the years we are planting in the back fields, we will save over $800/year in our own labor-hours! And maybe MORE if you consider that sometimes we try to do things by hand that should and could have been done by the electric G's if they were closer-to-hand. Doesn't that sound nice? Kate doesn't completely buy this argument, because she points out that we've never actually MADE $20/hour working on the farm, but... it's the best I can come up with for now and anyway she DID let me buy the solar panels.

Cost and Components
We budgeted $1300 for this and we ended up spending at least $2200 (I stopped counting at that point), but it seems the prices on these components are changing rapidly. Even the components themselves are changing so rapidly that you may not be able to order what we ordered. That is why my description is so general. You just need to find components that do the job listed here, rather than wasting your time trying to find the exact components we used.

A GREAT website to get an idea of prices is www.mrsolar.com. We didn't use them, but they have terrific free technical support (which I did use) and their prices look really good now that I've done more research. We hired a local solar expert here in New Paltz, Dawn Hein, to order the parts and worked with her to set them up on pallets so they can be easily moved to the "active field."

There are plenty of different ways to go about doing this... more and less complicated. You or whoever advises you may suggest a different way. Obviously I like the way we did it, but it is NOT the only way this could be approached.

Our system consists of 4 panels, hooked together to create 48 volts of output. You can order ANY panels you want as long as you end up with a total of 48 (nominal) volts of output because we are working with a 48 volt battery system to run the tractors.

We didn't NEED to buy 4 panels... we could have bought two panels and it just would have taken longer to charge the tractors. Do whatever you can afford. You can also add more later. But of course, don't forget that you must end up with 48 volts coming out the back end of your charge-controller.

[Not to be overly complicated, but what I just wrote isn't actually true. You could get one 12 volt panel, and hook the charging wires of your four 12 volt batteries in parallel to a 12 volt charge controller coming off that 12 volt panel. There are benefits and problems associated with this approach too... but if I go into them, I will never finish this section of the manual. So you need to decide what you want to spend, and then do a lot of research or find an expert to help you, or better yet, do what I did and convince your wife that if you just double the budget it will make your life a heck of a lot easier.

Okay, let's talk about the 48 volt charge controller we bought. It was under $100. Great Bargain! All it does is to decide how much power will ACTUALLY go into the batteries. a nominal 48 volt solar panel system may actually put out a LOT more than 48 volts (or a lot less)... So... you need a controller to temper and adjust it. Also, the batteries may be charged at different voltages at different times. This device takes care of all that, and they keep coming up with better and better versions of these devices.

We also purchased a fused D/C "on-off" switch. It was ridiculously expensive for what it does. We could have bought an A/C version for 1/4 the cost at Home Depot, but it would have sparked and melted if we had tried it out on a sunny day. You don't need to know why I know that. Anyway, this expensive one is rated to handle many times the amperage that we are putting out, but... we are safe and the tractor is safe and nothing is catching on fire... and metal isn't melting... and so we bought it.

You can purchase frames to hold the solar panels, or you can make them yourself. We made a simple triangle out of angle-aluminum and bolted it to two pallets. You can see it in the picture. What you make or what you buy will depend entirely on what panels (and how many) you end up purchasing.

Why Not Bolt the Panels to the top of the Tractor?
This seemed like such a good idea. It would shield us from the sun, and we talked to the panel experts and they said that the panels should be able to hold up to the jolting and bouncing of the tractor. They are so expensive, that it sort of scared me though.

But that's not why we didn't end up bolting them to the top of the tractor.

They are also pretty heavy, and we like our tractor to be light to minimize compaction. But... that's not why we didn't bolt the panels to the tractor either.

We didn't bolt the panels to the top of the tractor because we wanted both sets of panels to charge our two tractors. We are often using one or the other tractor. So... we could leave one tractor charging while we used the other. Also, we wanted the solar panels to "condition" the batteries during the winter -and we didn't want to leave the tractors themselves outside, just the panels.

Okay, finally, the biggest reason we didn't bolt the panels to the top of the tractor is because I like to drive fast, and they are heavy enough, that the framework required to safely keep them from falling on one's head is not a joke. I either had to committ to slowing down OR do a lot of really complicated engineering and building that I just didn't want to take on. Plus, we have a pallet lifter for the back of our tractor, so it was a no-brainer to just use that to move the panels to where-ever they will be most useful for the next few weeks, and then we can go ripping through the fields safely unencumbered. Judge me if you want, but that's the whole truth.