My original e-bike thread was started with a SK Electronics buck converter in mind, connected to a Bafang BBS02 motor and a 60v 4Ah Greenworks Pro ‘lawnmower’ battery. However, that step-down or ‘buck’ converter didn’t pass muster and I’ve replaced it with one which appears to be a better design – the DROK 75v 12A adjustable buck converter.
Adjustment on the DROK is done with buttons on the circuit board and it can be a little challenging to follow directions at first. Amperage on the DROK can be adjusted to a maximum of 12 amps and a capacity of 99.9 amp-hours. Not sure exactly how to set ‘capacity’ yet. DROK specs say output power goes up to 720 watts, close to the BBS02 wattage of 750w. DROK voltage input is 10v-75v and output range is adjustable from 0v-60 volts. I haven’t planned to see if 80v battery input voltages will burn up this DROK regulator, and don’t plan to do this in the future.
Note that Greenworks state that their batteries are Panasonic type. Available in 2.5Ah, 4.0Ah and lately 5.0Ah. They are making 40v and 80v batteries, along with other competitors, such as Kobalt. The 60v batteries can be fully charged to 64v, and that an over-voltage will immediately shutdown the Bafang controller. It didn’t fry the controller in my case, likely thanks to the excellent protective hardware and software designed into the Bafang.
In my experience, and this may conflict with what Luna Cycle says about the maximum voltages possible on the Bafang BBS02, you can run a slightly-discharged Greenworks 60v battery (with 61.5v, possibly 62v) but of course you will be much safer running the stock 48v Bafang BBS02 motor on lower values.
When I first installed the DROK converter, the Bafang motor shuddered and jerked a lot in every PAS mode, which is indicative of low current flow. After adjusting current output settings again, and installing a second 60v battery in parallel, that problem seems to have disappeared.
My initial tests with DROK appear to show the maximum bike speed remains the same, whether I set output voltages to 48v, 52v, or 60v. I have set amperage output to 10-12 amps. In every case, my top speed is limited to 20kph. OTOH I have ran the bike with same 60v battery but without a step-down converter and maxed out at 35kph. I’m willing to stick with the DROK and compromise on top speed, because I don’t have to worry about over-voltages going into the Bafang motor with freshly-charged 60v batteries.
The days of running my 60v lawnmower for 5 minutes to discharge its battery prior to using it on the e-bike, this is one less chore to deal with. A decent buck converter is money well spent IMHO.
More test results and photos will be posted here.
Exitor Magna mountain bike, dual suspension, 24in tires
Bafang BBS02 motor 48V / 750W
46T Bafang chainwheel / 20T Shimano SF-1200 single freewheel
KMC Z140 1/2” x 1/8” single-speed chain
dual 60v 4.0Ah Greenworks (Panasonic) batteries
DROK DC-DC Adjustable Buck Step Down Converter
set to 50V/12A output - top road speed w/DROK- 29kph
"Will mow for ebike ride"