I don't know if this has been shown here already, but a former classmate and her husband have this company, and it is a very interesting site to look at. They also have a FaceBook page: http://www.aclectrictractors.com/
If we cannot afford to take care of Veterans, then we should stop making them. David C. Wilker Jr. USAF (RET) On Mon, Jul 28, 2014 at 7:59 PM, Michael K Johnson via EV <ev@lists.evdl.org > wrote: > I got lots of useful help here on my lawn tractor conversion project — > http://www.evalbum.com/4841 — so I thought I'd post some lessons > learned, both positive and negative. None of this is intended as > advice for anyone else, for obvious reasons. I'm not doing everything > as safely as I might! This is just the "brain dump" I wish someone > else had written for me to read when I was getting started. > > Biting the bullet and buying real batteries (Deka Intimidator 9A31) > was a good idea. Mowing my half-acre lot that's not much more than > half lawn sometimes brings me close to 50% DoD, occasionally perhaps > very slightly below. It took a bit of convincing myself to spend $1K > on batteries—almost twice what I spent on the Motenergy ME1004 motor. > Part of what got in the way of accepting that reality early on was a > silly idea that I could fit everything under the existing hood and it > would look the same, just be quieter. Things got a lot easier when I > decided to ditch the "hood" and embrace as part of the conversion the > fact that this was going to look way different when I was done. If I > were starting over today, I'd seriously consider getting together with > friends on breaking a scavenged Volt battery and doing a 2p15s or > 3p15s arrangement (I don't recall the capacity of the volt cells). > Scavenged Volt batteries seem to be going for around $2K so if enough > people wanted to get together on it, this would have been an > opportunity to get more capacity for less money. I hope that by the > time my current batteries are going downhill, lithium cells are a dime > a dozen. > > Installing muffin fans pulling cooling air through a reticulated foam > filter (like they use for aquariums) to provide positive pressure > cleaned air in a plenum around the motor was a good idea. The motor > stays clean. I don't know if it matters for cooling, since I'm running > the motor well under rated load. But cleaned air can't hurt brush > life. I count that as worth the 1.2A continuous draw. Using plexiglass > to make that plenum was a great idea. Using 1/8" plexiglas for the > sides and 1/4" only for the top where the muffin fans were mounted was > a false economy; if I were doing it again I would make the whole > plenum out of the more expensive, but more robust and easier to work > 1/4" plexiglass. Given the frame I had to build to support the 1/8" > plexiglass, I think that it would have taken me less than half the > time if I'd done it all in 1/4" plexiglass. However, using a sectional > picture frame (the kind where you purchase two packages to make one > frame, one package for each dimension) as the holder for the > reticulated foam worked quite well. I'd do the same thing again even > if I weren't so incredibly lucky as to find the frame packages on sale > for 95% off... I used a combination of glue and brass screws to hold > the plexiglass together; if I were doing it again I'd just use the > brass screws. They look pretty cool in the plexiglass box if I do say > so myself. > > Talking myself into doubling my 4awg welding cable for the equivalent > cross sectional area of 1awg was almost certainly overkill. Joe > Lorenzi has 8awg in his JD with the same motor, and he told me that it > gets a little warm and thicker than 8awg would be useful, but I really > don't think I need 1awg equivalent. Even immediately after mowing > through thick grass with no breaks for nearly half an hour (down to > 50%DoD) my cables are cold. If I were doing it over, I would just use > the 4awg cable. Would be easier and use lighter, easier-to-manage > lugs, and routing would be less of a challenge than it was. > > I bought both 400A and 200A fuses, not sure whether it would blow the > 200A fuse. I needn't have worried. I do see over 100A continuous, but > the 200A fuse hasn't blown. The batteries just can't push that much > current through that motor... > > Hooking up my power switch so that the charging cable is connected in > one direction, and the contactor in the other, means that I can't > accidentally try to charge it and run it at the same time, and makes > it less likely that I'll drive away and leave the charger connected. > Buying SB50 anderson connectors for charging at 48V 6A max was silly; > the charger came with C15 (just like in the back of your computer) > which works fine. So I have some unused SB50 anderson connectors... > > I was originally going to connect both sides of the motor through an > SB350 anderson connector for a disconnect. Instead, I put a single > pole PP disconnect (using exactly the same internals as the SB350) > inline next to the fuse as my emergency disconnect / safety > maintenance disconnect. Requires only half the effort to pull it open > in an emergency, and the loop of wire that doubles as the emergency > disconnect handle is also convenient for my clamp ammeter! So I also > have some unused SB350 anderson connectors... > > I wanted to avoid a 12V house battery and run everything off of 48V > due to my initial expectation to install one of my batteries under the > seat, before I settled on the 9A31 batteries that couldn't possibly > fit. After deciding on batteries, I didn't go back and reconsider my > design. Because of that, it was hard to source the muffin fans (found > surplus fan FRU for rack-mounted hardware), and the contactor solenoid > draws more power than it otherwise would. And now I need 12V house > power anyway if only because the amphour meter I purchased requires > isolated 12V power, so I intend to put the original starting battery > back in the empty hole under the seat and use it for house power, and > regret that it's not running my fans and contactor since they are 48V > units. It also got in the way of taking Lee Hart's excellent advice > for using two contactors to reduce the power draw. And it also kept me > from hooking up the safety interlocks — which it turns out would be > more of a pain than I expected for other reasons, so even when I add > the house battery I'm not sure I'll get the safety interlocks > connected. I do keep that in mind when using it, though. I did spend > my early childhood (as soon as I could physically reach the pedals) > driving around a couple of simplicity tractors with no interlocks... > > The MTD transmatic belt-and-pully variable transmission isn't as bad > as I thought (it's not hydrostatic and by most reports it's more > efficient than a hydrostatic), but it's really imperative to get the > MTD belts and not belts advertised as "OEM replacement". The non-MTD > belts were both unsafe (the tractor wouldn't come to a complete stop) > and were so sticky that they cost me something like 20A. Also, using > them damaged the transmission a bit and made it harder to shift, > though that's gotten better since I replaced them with the MTD belts. > > I was surprised to find that the bearings in the mower deck were free > and turned easily; I had expected to have to refurbish them but did > not have to do so in the end. I did replace the mower blades. > > Having two of the batteries cantilevered over the front tires requires > excessive tire pressure and makes steering a lot of work. There is way > more weight forward than in the ICE configuration. I expect to replace > the steering pinion every few years; the first one lasted about 7 > years but this is much heavier service. Having the other two batteries > between the console and the seat such that I have to straddle them > while I drive works, but it doesn't put enough weight at the back, so > I sometimes have to shift my weight to the back of the tractor to keep > the rear tires from spinning. The advice to instead mount them > cantilevered off the back of the tractor was good; I didn't do it > because it would get in the way of bagging. I normally mulch, but I > bag when I mow leaves in the fall. So I don't think I personally would > change that, but for anyone else considering this, if you don't need > to bag, I'd strongly suggest considering mounting rear batteries > behind the seat for better traction and balance. Better still would be > lighter batteries, like the broken Volt battery idea, or other lithium > ion, that can source the current and won't be hurt by much deeper > discharge. Would have taken a different charger, of course. > > Mounting a wood bumper in front of the front batteries to protect them > was a good idea. Especially when I had the non-MTD belts installed > that didn't come to a complete stop. That protected those expensive > AGM batteries! > > I definitely expect to have to sharpen the blades often; they will > draw more current if they are dull. If I remove the batteries, I can > easily and safely tip the tractor on its side to sharpen the blades. > I'd like to be very clear that this isn't advice or a recommendation. > But in doing that I know for sure that the motor can't start while I'm > trying to sharpen the blades! ☺ > > I did use a DPDT on-off-on switch to connect positive pole to either > the contactor or the charger, and I routed through both poles in > series so that each half sees 24V for less arcing in the switch for > longer life. I have not yet built a snubber, though on an oscilloscope > I measured a 1ms -100V pulse from the contactor solenoid. Basically, > that means that I got a 1ms -100V pulse with a 10MOhm 15pF RC snubber. > ☺ I finally got an assortment of rectifier diodes and high voltage > polypropylene capacitors so I can cook up a RCD snubber to put on the > contactor solenoid thanks to Lee's excellent page on the > characteristics of various types of snubbers. No need to snub the > permanent magnet DC motor; I couldn't measure any back-EMF from it and > I have a vague sense that's typical due to the permittivity of > permanent magnets. > > I'm considering making a simple PWM motor controller for the fans > since I think they are probably way overkill and I could reduce the > 1.2A draw. But first I need the snubber to keep the power cleaner. One > I have that, I have a HV buck converter to supply the control circuit, > and it just takes a 555 timer, resistor, potentiometer, a few > capacitors, a few diodes, and a MOSFET to reduce the power draw from > the fans. But there's really no need. That would be just for fun. > > I have not built the battery balancers. The batteries are all within > .02V of each other so far. The one balancer I built was a pain to > build. I can't figure out how Lee manages to solder the diodes to the > lugs without overheating the diodes. I had already ordered the parts > from mouser before I saw that Lee was selling them, at which point I > thought I'd just build them, and then I discovered what a pain that is > and gave up after building one that I don't really trust because the > zeners got so hot while I was soldering them into the lugs, despite my > best efforts. So if my batteries start getting out of balance, I think > I'll just cut my losses and buy a set from Lee who knows what he's > doing. I'll just add the zeners etc. to my kit of random electronics > parts and someday find a use for them. > > Oh, and it seems like everyone I talk to about my project exclaims > about how cool it is that I can mow my lawn silently. Maybe they are > remembering how a Leaf or Prius or (if they are lucky) a Tesla can > sneak up on them. My motor running alone on the bench was > uncomfortably loud and I wore ear plugs for comfort when I was > breaking in the brushes while it was on the bench in the workshop. > Before the conversion, the ICE was louder than the mower deck but the > mower deck made the tractor much louder when it was engaged. Now, the > mower deck is much louder than the motor. I still wear ear plugs while > I mow the lawn. > > But still, with all the mistakes and downsides and things I'd do > differently next time, I still get the EV grin while using it, which > is impressive since I really really hate to mow the lawn. Making me > happy while I mow the lawn is a definite accomplishment. > _______________________________________________ > 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... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140729/9eddf2d6/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)
