Hello,

I'm new to this forum and am working on a project to use an 82V Greenworks electric mower deck in a large RC and autonomous robot lawn mower. The mower is larger than standard robotic mowers, as it's designed to cover bigger areas.

To power both the drive train (which I bought separately using 4 electric wheelchair motors, 24V) and mower deck, I’m using powerful 24V batteries, and a step-up converter to reach the required 82V for the mower deck. Here are the converter specifications:

• Output power: 1800W
• Input voltage range: 10V-60V
• Output voltage range: 12V-90V
• Input current: 40A
• Output current: 22A
• Conversion efficiency:
  • 48V to 60V @ 8A: 98.1%
  • 48V to 72V @ 8A: 98.1%
  • 48V to 84V @ 8A: 97.6%
• Charge regulation: 10% to 50% (72V output)
• Temperature coefficient: 50% load
• Ripple and Noise: 20MHz bandwidth (48V-72V @ 4A): 100mVp-p
• Switching frequency: VIN = 48V, VO = 72V, 4A: 110kHz
• No-load current: VIN = 48V, VO = 72V: 18mA
• Input reverse protection: Yes
• Storage humidity: 95%
• Operating temperature: -20 to 65 °C
• Storage temperature: -40 to 125 °C
• Operating temperature rise: 48V to 60V @ 5A: 45 °C
• Overheating protection: 60°C
• Wiring method: Solderless terminal block for input and output
• Cooling method: Strong air cooling

I always wear safety goggles while working with it.

First question: Is this setup safe or advisable?

Currently, it works as expected initially, but the mower motor stops after 2-3 seconds, accompanied by a two-beep signal. I suspect this may be due to the yellow wire, which I think either:

• Requires a specific signal
• Functions as a temperature sensor

For testing, I manually connect the yellow wire to the red/positive terminal upon connecting the battery, then disconnect it. Sometimes this method works, and the motor runs normally, but more often, it doesn’t.

Unfortunately, I don’t have a circuit diagram, and the control electronics are encased in resin, likely for waterproofing, so I can’t examine them directly.

Second question: Any idea what is going on here and to solve this yellow wire issue to get motor always running?

Thank you!

 

If you can find the manual or datasheet for the mower or its motor controller, it will likely describe the function of the yellow wire.

 

sorry but I really tried everywhere - nothing in whole internet or at manufacturer page

 

A few years back I 3d printed an adapter to run my 60V Greenworks mower on 3 Ryobi 18V batts connected in series.

It worked for about 3 seconds then the light blinked and it beeped.

After alot of research I found the battery sends a signal to the motor controller board. I captured the signal and replicated it using an Arduino.
I reconnected everything and guess what, it ran for 3 seconds then stopped and the light blinked and it beeped.

I found that the battery and the motor controller board both talk to each other. So, in the end I had to buy a Greenworks battery, and I used the 3 Ryobi batts to extend the run time.

I don't know if there's a way to make it work. This was my experience though. It's frustrating because we all know inside those batteries is just a bunch of 18650s, and the motor is just a basic brushless motor and controller.

Your best bet it probably to find a aftermarket motor controller.

 

Oh, I also considered replicating the signal with an Arduino if necessary. However, I don't have the original battery, and since it’s quite expensive (around 300 EUR with the charger, which I don’t really need), I haven’t been able to test that route. It’s interesting that you encountered the same issue with such a similar setup, so I appreciate hearing about your experience. Thanks for the feedback!