| Owner | Sean Bingham | ||||
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| Location | Tracy, California United States map | ||||
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| Vehicle | 1992 Sears Craftsman II 42 Conversion of a 12.5 HP IC, Sears Craftsman 42" Riding Mower with 6 speed transaxle. | ||||
| Motor | Mars ME0708 Permanent Magnet DC Mars ME-0708 Permanent Magnet Pancake Brushed motor. Etek-R equivalent. 48V, 8 hp continous - 15 hp peak. Weight: 30 lbs. | ||||
| Drivetrain | Stock 6 speed, belt driven transaxle | ||||
| Controller | Not required Motor typically runs between 2000 and 2500 RPM, which is equivalent to the ICE that was removed. No need to throttle down. Can use the transaxle to manage the speed. | ||||
| Batteries | 4 Super Start 24DCMJ 12V Deep Cycle 140ah, 12.00 Volt, Lead-Acid, Flooded Picked up some deep cycle batteries at Kragen/O'Reilly. Will monitor their true amp/hours. | ||||
| System Voltage | 48 Volts | ||||
| Charger | Solar Renogy Installed two Renogy RNG-100D panels for 200w of solar on the shed. Used the 12v/24V charge controller from the Renogy kit. This charges 4 12V Lead-Acid deep cycle batteries in series. Using a 500w Black and Decker inverter to plug in the mower charger and to charge my other battery powered tools. | ||||
| Heater | Noon day Sun. | ||||
| DC/DC Converter | None required Not using the key start, so no need for to power a contactor. Using 2 manual contactors (kill switches) to a open and close the circuit. Albright ED250. | ||||
| Instrumentation | Fuel Gauge (voltage) for now. | ||||
| Top Speed | 5 MPH ( 8 KPH) Speed is regulated by the transaxle for the 1992 Craftsman mower. The manual lists the speeds at: 1st gear = 1.1mph, 2nd gear = 1.4mph, 3rd gear = 2.0mph, 4th gear = 3.0mph, 5th gear = 4.2mph, 6th gear = 5.0mph, Reverse = 1.5mph | ||||
| Acceleration | Starts off easily in any gear and with blades engaged. | ||||
| Range | 1st mow on 1/2 acre, mostly grass lot was barely completed on the initial charge (battery pack was not fully charged). Speeds ranged from 2.0 to 4.2 mph. Grass was tall - lots of rain. Will retest after full charge and then some equalizing charges of the individual batteries. | ||||
| Watt Hours/Mile | Need to put in an ammeter. Have a voltmeter hooked up to look at general state of charge, but need a way to look at current output to optimize my operations. | ||||
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| Seating Capacity | 1 adult | ||||
| Curb Weight | 0 Not sure how much weight was taken out, but added in about 250 lbs. of Motor, Battery and metal. | ||||
| Tires | Standard Turf Saver tires | ||||
| Conversion Time | Took about 3 months, mostly doing cardboard prototypes and waiting for parts. Actual conversion work time was 3 weekends. | ||||
| Conversion Cost | Will put it actuals later, but about $1200 including shipping costs. The adapter plate, pulley adapter and angle iron battery frame added about $300 to the cost in labor/materials. | ||||
| Additional Features | Battery Charger that I'm hooking into the Solar charge station is a "Save A Battery" 2365-48 48V Battery charger/maintainer. I replaced the previous Interacter 48V 5amp charger as it failed after 18 months. The solar charge station consists of 2 100w solar panels charging 4 12v Lead Acid deep cycle batteries, hooked up in series for 12v output. I have a 500W inverter and a power strip to hook in other battery chargers as well as the mower. I have the strip hooked into a timer so that I'm charging the batteries when the sun is out. Had been running a small Sunforce solar panel kit on the shed to charge up the mower and other battery powered devices. In Sept 2014, I replaced this with a Renogy 200w starter kit consisting of 2 100w, 12v panels, plus z-bracket, and a 30A PWM controller. The installation was quick and this does a much better job of keeping all the batteries charged. So after 4 full years, the mower is still running strong. With better battery management, I'm getting better battery performance from the new set of batteries, which are now 2 years old. | ||||
| 25-Oct-2014 - I've upgraded the solar charging station recently, which will reduce the occasional need to plug into the wall to top up the batteries. With better battery management, ie not draining down the batteries too much, I now have 2 years on this set of batteries. I get great mowing performance by splitting the mowing over two days. The motor is just a work horse. Looking at saving up to convert this to Lithium in order to save some weight. That could cost $1200, so I'm in no hurry. 18-Jun-2013 - Little late on the update. I fried two of the four batteries. Discharging too deep and recharging while hot did them in. In September 2012, I changed the batteries to AGM style batteries and have modified my mowing to doing the front one day and the back yard the next day. This keeps the batteries from cycling too deep and I get really good performance throughout the entire mow. Solar charging on the weak system I have is great for keeping a charging station for my other battery powered yard tools, but isn't quite good enough for the mower except in summer. I need to add a panel or two to bump up the wattage. 07-Jun-2011 - Correction on the Solar Charger. It's actually taking about 4 days to complete the charge. The charger unit wants to stop charging too early. I need to get these batteries up beyond 13V. Doesn't look like this base unit has any adjustments I can make, so I'll probably look around for a different charge controller. In any event, with a little tending, I'm still solar charged. 02-Jun-2011 - Update - Now Solar Charged! Was happy to find a relatively inexpensive solar panel kit on Amazon for a Sunforce 12V 60 watt panel set, charge controller and 200w inverter. I've been able to move the mower off the patio power outlet and into the back shed where I installed the solar kit. I have been swapping the wiring from 48V serial to 12V parallel on the batteries so that I can use the solar panel charger directly. Seem to get a full charge in about a day. I might buy a couple of deep cycle batteries and put those on the solar charger, then just hook up the 48v battery charger to the inverter. The 200w Inverter works fine with the 48V charger. The Kit was $270, which is the lowest I've found. I didn't see a good way to cobble together pieces for less cash. With the warmer weather, I'm back to doing a full mow on a single charge with capacity to spare. Having the mower in the shed will help when the weather gets cold again. Oh yes, I did replace the 10 year old tires with new ones that now stay inflated. I keep the pressure up to about 20psi. 22-Mar-2011 Update - Have used this as my primary mower for a full season. Late Spring through Early Autumn, there has been no problem doing a complete mow on a single charge. During winter, where we are in California, the lawns do not go dormant and still need to be mowed every 2 to 3 weeks depending upon the average temps and rainfall. When overnight temps are in the 30s and daytime temps are low 50s, the batteries cannot handle the full mow. I had to break out the Gas Powered lawn tractor 2 times this year. I'll need it a third time this week. So a couple of things to work out. 1) Method to warm up the batteries and their internals to an acceptable operating temperature so that I can do the cold mowing. 2) Dealing with early spring tall and wet grass. Same as we encountered after the initial build. The motor really draws down the batteries when the cutting is very heavy. Haven't installed the ammeter to measure the drain, so will make that my 2011 update project. No new additions since the final build. Overall, very happy with the quality of the speed, cutting and endurance for most of the year. Will be replacing the tires so that they'll stay inflated each week without me breaking out the fatboy tire pump. Will be installing the Ammeter to get a better reading of amp per hour requirements. I'm thinking of converting to LiFePO4 batteries to reduce the weigth and to improve the performance until reaching the state of discharge. The Lead Batteries can sag pretty much at the end of mowing long grass, which affects the RPMs for the mower blades. Lithium is a much better curve. Will need more accurate Amp/Hour specs for the wet and cold mows to plan capacity. Converting the batteries will also mean a new charger. The upgrade will likely cost about $800 unless I can find some good deals. 05-Apr-2010 Update - 4th Mow on the conversion was very good, with plenty of power left. The first 3 mows just barely had enough power left in the packs to complete. A day after each full charge, the pack would register 52.6 to 52.9 volts. At the end of my second mow, the pack showed 45.5 volts. Whereas at the end of my 4th mow, the pack showed 48.9 volts. Without the Ammeter, I can only guess at the reason. 1) Mowed entirely in 4th gear. The cut speed was good, the grass was long. Total cut time was about 5 minutes less. 2) Bagged instead of mulched this week. No real difference in motor load on the high patches though. 3) I left the pack on the charger longer. Left it on for 20 hours instead of 12. The charger shows complete after about 8 to 10 hours. I'll have to see if it continues a trickle charge. In any event, if the performance is sustainable over the next 5 mows, I'll stop worrying about selecting another battery. ===================================================== Original Post - Received good inspiration off evalbum when viewing Carl Ervin's Green Machine, also a 1992 Craftsman, David Eshbach's TEE (The Electric Eshbach), and Wayne Riske's "'Ol Sparky". Needed a Motor adapter plate to bolt the electric motor to the chassis. The Chassis had a 6" hole where the ICE was mounted, but the outer mounting holes for the Mars 0708 were 5 7/8" apart. They had no metal to grab onto. Needed a Pulley adapter to deal with the difference in diameter and length of the motor shaft. The ICE had a 3 1/8" long shaft that was 1" in diameter. The Mars 0708 has a 7/8" diameter shaft that is 1 1/2". Wanted all 4 batteries on the chassis, so fabricated a battery rack from 1" angle iron. Needed to modify the hood since the upper batteries would hit the hood at the stock angle. A bit of 'fitment' was required. Used some schedule 40 PVC to make new mounts and stops for the hood. Still need to add some screening to keep the motor compartment clean. Also needs some serious lubrication and other cleanup. The donor mower had been sitting outside, unused for about 2 years. | |||||
1992 Sears Craftmans II EV Conversion
“Gray ZEVphyr”
Last Updated 10-25-2014
Copyright © 1997-2024 by Mike Chancey