I'm responding to this email and some of the ones that followed. I first converted my MTD tractor. Here I thought the motor was bad, but it turns out it was the hydrostatic tranny. It took 200 amps to barely move on level ground! Converting it was a waste of time.
A buddy gave me an old John Deere 112. Wow, what a difference! It does better than the gas MTD ever did. It moves on level ground with around 40 Amps at a pretty good clip, and mows at a pretty good pace at around 80 Amps. The old MTD gasser would stall in high grass. My electric John Deere cuts tall grass at 2x the speed of the old MTD gasser's top speed without slowing down! It'll start up a steep slope from a standstill, blades running, in 4th gear with no problem. I used a sepex motor on 48V. I use Optima Deep Cycle batteries. 6 or 8 Volters would be too much weight IMHO. The Optimas were years old. I estimate I have around 100 cycles on them. 3 of the 4 are going strong, one is a little weak. It generally takes 2 or 3 charges to mow my 1/2 acre. I'm not sure that lithiums would make sense. Sure, maybe I could get 2000 cycles with lithium... but for weekly mowing 1/2 the year that would be 20 to 40 years of mowing (depending on the Ahr rating). Is the calendar life that long on lithium? Scrounging used lead in this case probably makes more sense. It's not like it is a disaster if you run out of charge 50 feet from home, or have to charge fairly often. I take off the cables once in a while and charge the batteries in parallel to balance them. With just 4 batteries this isn't too painful. Alternatively sometimes I'll charge them one at a time with an RC smart charger. Sure, that takes 4 days, but since I mow just once a week that's fine. I do "quick" 2 hour charges between mows with a 17 A golf cart charger. I have thought of doing a version of Lee's battery balancer, where I would use the SLI battery to round robin hook up in parallel to each battery. This would prop up that low battery as I mowed and give me better mowing time. ----- Original Message ----- From: Michael K Johnson Sent: 12/30/13 03:23 PM To: Electric Vehicle Discussion List Subject: [EVDL] Michael's 48V lawn tractor/mower conversion: update While I haven't yet created an evalbum page (stuck on a few answers, like what to name the project...) I thought I'd send an update on my progress. TL;DR: This MTD platform was definitely not designed with electric conversions in mind. Not only do I recommend against it for conversions; with my newfound experience of the level of quality of the product, I don't recommend it, period. Mid-December I finally did my last lawn mowing session and started tearing down the old ICE donor. Discovered that the smoke that I had attributed to an engine problem was from gas leaking on the back of the muffler, which explains a few other things, too. Also motivational for converting to electric. I use the word "old" with respect to the donor advisedly, despite the fact that it's less than 10 years old. Taking it apart, it has become very clear that this tractor was not designed for long life. Lots of otherwise undamaged paint bubbling over rust, the "lifetime" (of the product) drive belt shr edding, and everything about the design making it clear that it wasn't intended to be easily repaired, let alone converted. I had once hoped that I could fit three group 24 batteries under the existing hood and one under the seat. Taking it apart made it clear that was a fantasy, which made it easier to give up on the fantasy that group 24s would have enough capacity, and made me quit worrying about my choice to move to group 27s for more capacity; I have to make this thing look really weird anyway to fit any batteries on it without being top-heavy. I'll end up with two group 27s end-to-end sticking over the front wheels, a heavy-duty bumper protecting them, and two group 27s starting under the seat and forward to the console, so that I'll have to be slightly more athletic getting on the tractor, but at least won't be top-heavy. I've just finished making, test-fitting, and priming the mounting plate to which the motor will be mounted and which will in turn be mounted to the frame using the original motor mount holes. I had hoped to drill holes in the frame to mount the motor directly, but the motor shaft hold in the frame was so large that two of the requisite holes would have gone through empty space. I used 16GA sheet steel for the mounting plate. I started with a 12"x24" piece, and rather than cut it off, I bent it up to be the front of my motor box which I'll be using for forced-air cooling for the motor. The rest of the box will be plexiglass to showcase the motor, both for fun, and because I'm tired of bending sheetmetal without a brake. (I have a mostly woodworking shop, so I'm low in metalworking tools.) You'd laugh if you saw the ersatz brake I made from pieces of angle iron, a woodworking bench, clamps, and 2x4s. It functioned, but was quite a pain. Generally, my impression is that MTD generally are very "busy" designs that aren't easy to work a conversion full of large rectangular prisms (batteries) into, even if the quality otherwis e made it worthwhile. I hadn't intended to buy a low-quality tractor when I purchased it in the first place. I was trying to not "cheap out", buying only one grade lower than the top of their line. I didn't have the experience to know that I was barking up the wrong tree in the search for quality... In order to hope to be ready to start mowing as soon as spring has sprung, I'm starting by doing the least work I need to: mechanical, then the electrical power system. I'll leave adding fancy power control systems for after the basic conversion works. One step at a time. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20131230/59e1ee59/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) -------------- next part -------------- An HTML attachment was scrubbed... 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