Bafang BBS02, DROK and 60 volts

Get all your technical information about electric bikes here.
Post Reply
User avatar
ngant17   10 mW

10 mW
Posts: 26
Joined: Jan 06 2018 8:28pm
Location: Chuluota, Florida
Contact:

Bafang BBS02, DROK and 60 volts

Post by ngant17 » Feb 11 2018 12:19am

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"

Hummina Shadeeba   1 MW

1 MW
Posts: 1603
Joined: Apr 25 2014 10:26pm

Re: Bafang BBS02, DROK and 60 volts

Post by Hummina Shadeeba » Feb 11 2018 12:54am

why use the step-down drok instead of get a power supply at the voltage you want?

User avatar
ngant17   10 mW

10 mW
Posts: 26
Joined: Jan 06 2018 8:28pm
Location: Chuluota, Florida
Contact:

Re: Bafang BBS02, DROK and 60 volts

Post by ngant17 » Feb 12 2018 4:37am

There are several reasons I have gone this route. Economical, first and foremost.

1) Why spend $400 for a Panasonic 48v 11.5 Ah battery to run the Bafang BBS02? (almost double that price if you want 60v). I already have a 60v battery (w/ Panasonic cells) and it is not being used except when I'm mowing lawns with my Greenworks mower. In fact, I just bought another (reconditioned) 60v 4Ah Greenworks battery on ebay for $95, and it is good as new.

Yes, I could have saved money by building up thirteen to fifteen Panasonic 18650 batteries in order to get +48v, but factor in the shop time to do the job and you're probably at +$300 for parts and labor to power an e-bike.

But again my existing 60v Greenwork batteries are money-makers by themselves in my lawn mowing business. Time spent working in a shop to make batteries is unpaid labor, and my time based on cash flow is happening when I'm walking the turf, outside in the sun pushing a mower for a hour or two. Really it's 6 one way, or half-dozen another. It''s cost-effective to keep my existing 60v batteries to serve a dual purpose. Others will go a different way which is cost-effective for themselves.

Of course, in my case the additional $30 investment in a decent buck controller (aka voltage regulator) is mandatory as the controller will shut itself down if voltage is over 61.5 or 62v . Fully charged 60v 4Ah Greenworks batteries will have +64v. I don't think Bafang will build a 60v version of the BBS02 in the near future.

The downside of using the drok step down is that my top speed appears to be reduced to about 20kph max on PAS. This is a compromise. OTOH I don't particularly care to fly down a street at 35kph on direct feeds with the 60v battery and no regulator in circuit. Probably will shorten life on Bafang in the long run.

BTW I had a flat tire yesterday, and it was no problem riding on a flat for a mile with the electric motor pulling the load until I could get the tire fixed. Try doing that with pedal-only, not fun!
Last edited by ngant17 on Feb 12 2018 5:01am, edited 1 time in total.
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"

User avatar
ngant17   10 mW

10 mW
Posts: 26
Joined: Jan 06 2018 8:28pm
Location: Chuluota, Florida
Contact:

Re: Bafang BBS02, DROK and 60 volts

Post by ngant17 » Feb 12 2018 4:56am

Here's a few things I'm learning about amperage with the DROK. Most people don't completely understand the differences between amp-hours and amperage! Including me.

Amp-hours and amperage are different conditions and have different meanings. My batteries are rated at 4
amp-hours but the electric motor is not always needing an average demand of 4 amps for an entire hour. So I am thinking it will be best for me to set the input power to a small average amount less than 4 amps, such as 1 or 2 amps for output power, since I don't need to go fast on the electric bicycle.

Occasionally I notice a slight jerking and shuddering from DROK supplying output current to motor. My amp output setting was not synch'ed with what the Bafang wanted at that particular moment, but that issue goes away after a few seconds. I probably need to find the right setting for amperage output to feed the Bafang.

After setting the amperage output, I noticed that the drok will return to zero or a nominal amperage close to zero. I think it's because the settings are kept in memory and it waits until the motor is running and under a load to regulate current output based on these settings.

However, I believed it caused me some initial confusion when setting up DROK's amperage memory. Apparently it reverts to a partially volatile state when the motor is not in use so that must be why it reverts back to zero or a nominally small amount until motor is under a load. It needs to have an operating current flow to "remember" the amperage settings and then once the motor is under a load, the amperage and current is controlled as it is designed.

This does not mean the DROK is unable to regulate amperage. It will display a volatile zero state
automatically until the motor (or whatever electrical device) is under a load and current is flowing. After that the DROK regulates the amperage based on its settings in memory.

Also if input power is lower than the output power that you want, the drok's current settings will not work properly.

Dual 60v 4Ah batteries should allow up to 8 amp-hours for the Bafang to use if needed.

If I got any of these above explanations wrong, please inform me of the confusion.
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"

Post Reply