I use Makita 18V (5s) batteries to power any brand tool, ebikes and anything else needing DC power. I've replaced a heavy old gas motor on a high end front throw reel lawnmower with early Currie brushed motor (free) and it's a perfect close cut machine for bermuda. I have tons of experience building and repairing ebikes and etandems, their motors and controllers.
I have a need for a sturdy rotary mower to control weeds at a rental with a large lot. Harbor Freight has a decent looking 80V (20s) Atlas brand machine; cheap. I'd planned to power it with 4x18V Makita's in series (20s) since I have many. A simple 2 wire 81V connection, 4 Makita's in series starts the mower fine, but cuts off after a few second burst. The troubleshoot page says the motor will cut off if overheated so I assume both battery and motor are protected.
Makita 18V tools connect to only 2 pins on the battery (+18V, ground). The Atlas battery is dual voltage (40/80V) and has 7 pins slots. The 2 outside are 80V/ground and connect to the controller, the next 2 toward center are 40V/ground and not connected, the next 2 slots have no pins. The center pin is connected to the controller and I assume monitors battery temp via a thermistor.
I don't have a Atlas 80/40v battery so I can't open to verify the center pin's function. Makita's battery thermistors are ~24k ohms at 70F. Another brand I have is ~11K ohms at 70F. I substituted a 50K ohm variable resistor and tested about 25 different resistance settings. The results were always the same; start then off.
Any suggestions to make this mower work with a non proprietary battery? Or other test to try? I could buy an Atlas battery to return after looking inside, but that doesn't seem exactly fair. I could probably also run the motor using a ebike controller but an expensive Makita mower is probably a better choice.
BTW, the Atlas Brushless 80V brushless motor is wired just like most ebike motors. 3 phase wires and 5 wires to the 3 hall sensors. The controller is fairly standard with 3 throttle input wires and 2 other wires I assume to the start switch. It has bays for two 80V 4ah batteries which are automatically switched via 2 relays. Both batteries are never used together and the manual notes there is a brief delay during the switch.
