The Electric Tractor is Alive!

 

It's Alive! - This is the video of the first run.

The pulley's finally arrived and were installed (with a bit of fluffing around to get everything aligned), but all seems to work fine. The video above was our first run. Sounds a bit noisier than it is now - I found the main drive belt was binding on the pulleys, so needed more adjusting and a bit of silicone spray to help the belt from sticking on the motor's pulley. But, all good now.

Time for more test runs...

After a bunch of tweaking (controller settings, adding an idler gear to the longer PTO belt, replacing a bad battery, etc), I've now completed a 10min mowing test run with the tractor and rotary slasher - results were:

1. PTO motor start and PTO shaft to 700RPM (2.6:1 so motor running at 1820RPM), raise mower & lock* = 0.17Ah
2. PTO motor stop, Drive motor start and travel to paddock (approx 250m - High 3rd gear = 8km/h at avg 60A draw) = 1.90Ah
3. Start PTO motor, lower mower, start mower (PTO shaft to 1000RPM - using RPM sensor on PTO shaft pulley) then mow weeds (docks) in the paddock for 4mins = 5.33Ahr (PTO avg 30A and Drive avg 50A in high 2nd gear - A estimated using eyeball on gauges 😀)
4. Stop mower, raise & lock*, stop PTO motor and then drive back to the shed and park = 2.10Ahr
5. Total = 9.50Ahr and approx 10mins of running all up. (150Ahr Lead Acid batteries were probably getting near the max usable depth of discharge after that run).

*NB. The David Brown 880 has a lever to lock the hydraulic arms in the up position, which is nice as it saves having to run the PTO motor to run the hydraulics while traveling to & from the paddock.

Overall a successful run. However, from the way the tractor traveled over the paddock's ups and downs, I feel the drive motor is a bit under-powered. Time to investigate further...

Further testing and it seems that the QS-180 motor & ND72850 controller doesn't seem to have much low rpm torque, which makes the tractor quite sluggish when pulling away from a standstill in higher gears and when driving over undulations in the paddock. It's ok once you get moving along a bit, so I need to use the gears to get her moving (but I think it would struggle pulling out a small tree stump 😂 ). I've played around with the controller programming settings, but none of the setting changes seem to make much difference (and there isn't a decent manual or information anywhere that explains what all the controller's settings do).

So, investigating further, even though the QS-Motor's sales guy said the ND72850 controller and QS-180 motor would work ok at 48V, I do think it's more suited for 72V plus (brochures say it's rated for 72V to 96V). Time to get a couple of extra batteries and try 72V I think...

Extra test batteries installed for 72V

 

Ok, so I scrounged up a couple more batteries and hooked up the QS-180 main drive motor and controller to 72V (increased from 48V) and that has made a definite improvement. Tractor is quite lively now and from the couple of short tests I've made the motor doesn't seem to be straining as much as it was at low RPM and it's definitely got more high-RPM speed in top gear too!

72V is definitely the go for the main drive motor, so it looks like I'll need to buy a 72V VEC500 controller for the PTO motor now though...

No, it turns out the 48V VEC500 controller and motor (Golden Motor 10kW) I have for the PTO can run at 72V. Just needed to reprogram the controller for 72V. So, the whole project is now running at 72V and everything is working well - yay!

72V Test Set-up

72V Test Set-up (note the idler pulley too)

I now need to find some time (and clear weather) to do some some decent test runs, including mowing grass, towing a laden trailer, etc, so that I can better measure the power requirements for sizing the final battery configuration (and type). Catch my next post to see the results.