Last year I built the 250W Bafang front hub, (Alien Ocean kit from a previous bike build) into a Dahon Espresso folding bike.
I found that the hub at the front and battery at the back of the bike produced a reasonable balance. But on loose surfaces and steep hill climbs, the front wheel often seemed to lose traction and felt skittish. On rough surfaces (including potholed roads) the extra weight of the front hub made an uncomfortable ride, and seemed to jar up through the forks.
So earlier this year I decided a rebuild with a rear hub was the ticket. There has been much talk about the Bafang BPM hub on this and other ebike forums. So I decided to order a 36V 350w code 12 hub with hall sensors from BMS Battery in China.
After many weeks of waiting, the hub, controller, and a few other bits and bobs arrived, all ready for the wheel build. I had previously ordered a rim from a UK supplier, in readiness for the build. But I hadn’t checked the rim, and I was disappointed when I came to lace the wheel. It was a 32h rim not the 36h I'd ordered! This then lead to another frustrating delay waiting for the replacement rim to arrive. Yet another delay when the spokes I got from BMS Battery were not suitable for my rim. I had to get some more, custom cut, and supplied from the USA. It would have been easier and cheaper to have bought the wheel laced in China!
Eventually I built the wheel and fitted a Sunrace 7 Speed Freewheel - 13/28T, and all looks good; it fits in the rear drop out perfectly, and runs round and true.
The Espresso frame has no disk brake mounts. So I am using rear V brakes, not the originals as they were catching on the SKS mudguard. I have some Deore M530s spare, so they are fitted and working OK. I had intended to refit the original Espresso forks, but they also have no disk brake mounts. I wanted some stopping power for all the downhill runs in my neighbourhood. So I kept the Gusset Cr-Mo; which I used when I fitted the 8Fun front hub last year. These do have a disk mount, so I’ve fitted an Avid BB7 185mm disk on the front, connected up with Goodridge cable. The front wheel is a temporary solution until I have the time, and energy to fit a better one.
The controller is a 12 FET 36-48v universal type from BMS Battery. And the battery is a homemade 36v (36-41v) 12s A123 pack. I am not using a BMS, as the controller has a 31V LVC. The battery can be varied in size from a small 2.3Ah 12s1p weighing ~940g for light weight short trips; through to 13.8Ah 12s6p @ 5.5Kg for the longer more strenuous journeys. I made the packs up in 2 X 6s cells this allows me to balance charge them with a standard charger. I have a couple of iCharger 106B-plus 250W chargers, and two 13.8v 20A power supplies. Alternatively the batteries can be charged with a standard LiFePO4 charger with 43.8v cv 5A output (12 X 3.65v). A123 cells appear to keep their balance well, and therefore do not require balance charging so frequently. One of the drawbacks of this battery arrangement is the number of external cables and connectors I’ve had to make up. But the versatility of the battery is what I wanted, so I am happy with this arrangement.
Just on a quick test ride the BPM hub has plenty of torque, and the peak power I am seeing on the watt meter, is around 1100W!
The bike feels better on the road with the rear hub, less jarring on the handlebars. But with the battery at the back as well as the hub the bike does have an unbalanced feel when lifted. I will look at other places to mount the batteries if I can. After many vague ideas, there are not too many locations on this folding bike to fit batteries. I am thinking of making some bags to fit over the frame somewhere up front. Not sure whether to fit the matching SKS Chromoplastic mudguard, or as the front wheel is QR removable, a clip on MTB mudguard. The modified and converted bike with hub, rack, controller, and cables etc, but excluding the battery, weighs 20Kg.
The build has taken quite a long time, partly due to delays in shipping, and unfortunately, my health problems (ME), which have hampered the speed of the project. At the moment I’m not up to long rides, but I do hope that I can continue with some more extensive tests soon.
I do have, yet another part finished project on the go! Based on my very much modified Claud Butler MTB, (basically just the frame is left from the original bike) to which I am fitting a MAC geared rear hub motor from Paul Cell-man.
It seems very similar to the Bafang BPM motor; slightly larger in diameter. When I bench tested them both, I think it may be quieter and have less drag, I will have to wait and see when I finish the MAC build.
I will get back to the MAC build later and post some more details, and try a comparison with the BPM.
Anyhow here are some pictures of the rebuilt Espresso.
Right side view
Left side view
Controller and switch box
BPM and sprockets
Chris
I found that the hub at the front and battery at the back of the bike produced a reasonable balance. But on loose surfaces and steep hill climbs, the front wheel often seemed to lose traction and felt skittish. On rough surfaces (including potholed roads) the extra weight of the front hub made an uncomfortable ride, and seemed to jar up through the forks.
So earlier this year I decided a rebuild with a rear hub was the ticket. There has been much talk about the Bafang BPM hub on this and other ebike forums. So I decided to order a 36V 350w code 12 hub with hall sensors from BMS Battery in China.
After many weeks of waiting, the hub, controller, and a few other bits and bobs arrived, all ready for the wheel build. I had previously ordered a rim from a UK supplier, in readiness for the build. But I hadn’t checked the rim, and I was disappointed when I came to lace the wheel. It was a 32h rim not the 36h I'd ordered! This then lead to another frustrating delay waiting for the replacement rim to arrive. Yet another delay when the spokes I got from BMS Battery were not suitable for my rim. I had to get some more, custom cut, and supplied from the USA. It would have been easier and cheaper to have bought the wheel laced in China!
Eventually I built the wheel and fitted a Sunrace 7 Speed Freewheel - 13/28T, and all looks good; it fits in the rear drop out perfectly, and runs round and true.
The Espresso frame has no disk brake mounts. So I am using rear V brakes, not the originals as they were catching on the SKS mudguard. I have some Deore M530s spare, so they are fitted and working OK. I had intended to refit the original Espresso forks, but they also have no disk brake mounts. I wanted some stopping power for all the downhill runs in my neighbourhood. So I kept the Gusset Cr-Mo; which I used when I fitted the 8Fun front hub last year. These do have a disk mount, so I’ve fitted an Avid BB7 185mm disk on the front, connected up with Goodridge cable. The front wheel is a temporary solution until I have the time, and energy to fit a better one.
The controller is a 12 FET 36-48v universal type from BMS Battery. And the battery is a homemade 36v (36-41v) 12s A123 pack. I am not using a BMS, as the controller has a 31V LVC. The battery can be varied in size from a small 2.3Ah 12s1p weighing ~940g for light weight short trips; through to 13.8Ah 12s6p @ 5.5Kg for the longer more strenuous journeys. I made the packs up in 2 X 6s cells this allows me to balance charge them with a standard charger. I have a couple of iCharger 106B-plus 250W chargers, and two 13.8v 20A power supplies. Alternatively the batteries can be charged with a standard LiFePO4 charger with 43.8v cv 5A output (12 X 3.65v). A123 cells appear to keep their balance well, and therefore do not require balance charging so frequently. One of the drawbacks of this battery arrangement is the number of external cables and connectors I’ve had to make up. But the versatility of the battery is what I wanted, so I am happy with this arrangement.
Just on a quick test ride the BPM hub has plenty of torque, and the peak power I am seeing on the watt meter, is around 1100W!
The bike feels better on the road with the rear hub, less jarring on the handlebars. But with the battery at the back as well as the hub the bike does have an unbalanced feel when lifted. I will look at other places to mount the batteries if I can. After many vague ideas, there are not too many locations on this folding bike to fit batteries. I am thinking of making some bags to fit over the frame somewhere up front. Not sure whether to fit the matching SKS Chromoplastic mudguard, or as the front wheel is QR removable, a clip on MTB mudguard. The modified and converted bike with hub, rack, controller, and cables etc, but excluding the battery, weighs 20Kg.
The build has taken quite a long time, partly due to delays in shipping, and unfortunately, my health problems (ME), which have hampered the speed of the project. At the moment I’m not up to long rides, but I do hope that I can continue with some more extensive tests soon.
I do have, yet another part finished project on the go! Based on my very much modified Claud Butler MTB, (basically just the frame is left from the original bike) to which I am fitting a MAC geared rear hub motor from Paul Cell-man.
It seems very similar to the Bafang BPM motor; slightly larger in diameter. When I bench tested them both, I think it may be quieter and have less drag, I will have to wait and see when I finish the MAC build.
I will get back to the MAC build later and post some more details, and try a comparison with the BPM.
Anyhow here are some pictures of the rebuilt Espresso.
Right side view
Left side view
Controller and switch box
BPM and sprockets
Chris
