Converting a Bakfiets cargo bike

General Discussion about electric bicycles.
john61ct   100 GW

100 GW
Posts: 5000
Joined: Dec 18 2018 2:06pm

Re: Converting a Bakfiets cargo bike

Post by john61ct » Aug 16 2019 5:03pm

Yes I see no hard and fast rule, but in this use case, your answer means no,

a 48V nominal, (51-58V) packs will be ideal, no need to go higher.

I have no problem with thick AWG wires as needed, used to dealing with up to an inch thick on boats.

The battery design will be driven by optimizing the drivetrain and of course range requirements, not the other way around.

It's great to eliminate one of the many variables.

If **lower** voltages are better for the motor / conditions, I assume that's the controller's job, I plan to oversize capabilities so normal operations leave plenty of headroom, lower stress on all components.

Going to small diameter wheels is not an option,
they need to be large for dirt/gravel, desert and forestry tracks, likely fat if I need to forego suspension,

and that context will thus require spending more on higher power and very strong / robust and reliable motors - suggestions welcome.

Speed not being important, will look for slower windings, get familiar with the simulator, rpm etc.

Obviously temp sensing will be critical given climbing and descending big hills.

Thanks for your help.


MalcolmG   1 mW

1 mW
Posts: 11
Joined: May 09 2018 5:52am
Location: Auckland, NZ

Re: Converting a Bakfiets cargo bike

Post by MalcolmG » Aug 22 2019 5:07am

dilkes wrote:
Aug 15 2019 9:37pm
Here's a possible kit option.
https://www.ebikekit.com/collections/et ... no-battery
No personal experience with it, but has good reviews.

Here's another (long) thread about a gentleman who has done probably way more than you would want to do with your Bakfiets.
https://electricbike.com/forum/forum/ki ... its-flames
Thanks for the link, unfortunately that kit is for a trike and mine is a 2 wheeler; also I'm hoping to put the motor into the front wheel rather than the rear. I did read some of that thread you linked, far more ambitious than what I'm up to! Good on him though, looks like fun.

MalcolmG   1 mW

1 mW
Posts: 11
Joined: May 09 2018 5:52am
Location: Auckland, NZ

Re: Converting a Bakfiets cargo bike

Post by MalcolmG » Aug 22 2019 5:30am

qwerkus wrote:
Aug 16 2019 10:38am
MalcolmG wrote:
Aug 15 2019 3:54pm
That's a bit part of why I was hoping to avoid a DD (plus the better torque vs weight from a geared motor). It would be nice to have less noise and regen braking though.
This is a big misunderstanding. Justin showed years ago that even under basic ride conditions (short trips, lots of stops and gos) the the amount of regen power you get during brakes is greater than the power loss due to stator drag. You can calibrate the controller so that PAS level 1 is just strong enough to overcome drag (around 1-2% of motor power) and just leave it continuously on.
That's a good point, I definitely like the idea of regen so I've broadened my search to include DD motors.
I drive around 2 kids too here and I can't but stress the importance of an additional brake. That's a super advantage of DD hubs. If the usual 6kg hubs are too heavy for you, I suggest the lighter shengyi dwg09c http://www.syimotor.com/productDe_5.html
Only 5kg and plenty of power.
Otherwise I suggest a mac (4.3Kg), Greenpedel M58 (https://www.greenpedel.com/Product/M58R.html#pro_detail) or a shengyi x2 (3.2Kg). All geared though. The mac is surely the best of the lot but also super expensive. And you can have regen: ask for a locked clutch when ordering the mac, and you have both a geared hub and regen.
I wouldn't go with 36V. Lower tension means bigger wires.
Unfortunately the shengyi motor appears to be rear drive only, and all of the front hub motors they have are smaller geared ones. Given my requirements are relatively low speeds but high loads I suspect a geared motor is probably going to be the best option still, but I think it's probably going to be worth looking at locking the clutch and making sure I get a controller capable of regen.

I've spent quite a bit of time going through different motor options with the simulator; I'll keep playing and report back when I think I'm closer to making a choice.

Thanks for all the feedback everyone

Bikegirl   1 W

1 W
Posts: 52
Joined: Apr 02 2019 5:30am

Re: Converting a Bakfiets cargo bike

Post by Bikegirl » Jan 23 2020 8:05am

Hi Malcolm, have you made any progress?

I'm keen to see how you go with a dd hub as we have a 350w geared hub motor on our bakfiet, front wheel.

Good performance although our area is fairly flat. Small amount of motor noise but nothing outrageous. Throttle only control, keeps the chain guarding original. Hub drive, of any kind is great as you can add as much leg power as you desire depending on the day.

Added a cycle analyst 2.4 recently to get more battery info.

My advice, always get a bigger (parallel) battery than what you think you need, it's great not having to worry about range. We have a 36v 21ah tiger shark and have done 40+kms and not gone flat.

As said elsewhere, Em3ev and grin are top quality suppliers, and I have shopped at both as well as solarbike in Perth Australia where this particular setup came from.

positiv   10 µW

10 µW
Posts: 6
Joined: Nov 29 2019 7:04am
Contact:

Re: Converting a Bakfiets cargo bike

Post by positiv » Jan 23 2020 10:12am

what is the weight of such bike ?

MalcolmG   1 mW

1 mW
Posts: 11
Joined: May 09 2018 5:52am
Location: Auckland, NZ

Re: Converting a Bakfiets cargo bike

Post by MalcolmG » Jan 23 2020 8:38pm

I'll post a bit more detail of what I've done later, but I'm nearly finished with the conversion. I got a 500W 48V Bafang geared hub motor; unfortunately all my trials have been pretty brief as the 2nd hand battery I purchased isn't behaving very well at the moment.

Bikegirl   1 W

1 W
Posts: 52
Joined: Apr 02 2019 5:30am

Re: Converting a Bakfiets cargo bike

Post by Bikegirl » Jan 25 2020 10:43pm

Positiv, bike would be about 30kgs I reckon, give or take the amount of crap in it. We have been testing on some decent hills this weekend and I have been surprised it hasn't cut out. That said we use the pedals going up hill to help with torque and carry momentum into it.

Malcomg, I'm keen to see how you go as I'm looking at setting up another cargo bike for a friend and trying to weigh out differences with motors again.

Sent from my SM-G950F using Tapatalk


MalcolmG   1 mW

1 mW
Posts: 11
Joined: May 09 2018 5:52am
Location: Auckland, NZ

Re: Converting a Bakfiets cargo bike

Post by MalcolmG » Mar 10 2020 3:34am

Bikegirl wrote:
Jan 25 2020 10:43pm
Malcomg, I'm keen to see how you go as I'm looking at setting up another cargo bike for a friend and trying to weigh out differences with motors again.
Well I've been using it quite a bit now and pretty happy with everything. I don't have many photos but I'll attach the few I have got. Main thoughts so far:
- The 500W motor has more than enough power. The controller has 5 settings and I mostly use it on 1 or 2 unless I don't feel like doing any work and then I'll bump it up to 3 or 4. 5 feels silly fast for riding with my kids in the front.
- Having a hub motor with a throttle is really useful when it comes to getting going from awkward parking spots and in any tight situations like pulling out of a driveway or getting through a gap in traffic
- The battery is 48V & 10Ah. I get about 35km of use out of it which I'm not that satisfied with. When I first got the battery the BMS seemed to be struggling with keeping the cells balanced which meant that some of the cells were not charging as high as they should, and consequently they get depleted before the others and cause the BMS to shut down. I've replaced the BMS and it seems to be a lot better but I need to open it up again and have a look at the cell voltages. I have a few other options for batteries but not a lot of time to mess around with it at the moment
- The motor controller is OK but I might look at getting a Cycle Analyst sometime as it would be nice to be able to make a few adjustments to how it responds to the throttle and cadence inputs.
- The motor is fairly quiet, and it's nice that it freewheels when turned off; there are a few places I regularly ride where I'm mixing with pedestrians and it's nice to just turn the motor off completely and ride without extra drag from spinning a motor over.

Anyway some photos attached. Since taking these I've added another panel to enclose the battery and controller which has tidied it up a lot
Attachments
battery.jpg
battery.jpg (465.69 KiB) Viewed 240 times
motor.jpg
motor.jpg (364.92 KiB) Viewed 240 times
battery2.jpg
battery2.jpg (326.69 KiB) Viewed 240 times

User avatar
dogman dan   100 GW

100 GW
Posts: 35582
Joined: May 17 2008 12:53pm
Location: Las Cruces New Mexico USA

Re: Converting a Bakfiets cargo bike

Post by dogman dan » Mar 10 2020 6:13am

Nice neat install. I like the way the battery tucks under the seat.

To force your battery to balance, try charging full, let sit 30 min for the bms to discharge any high cells, then recharge full again. If the charger won't restart, ride a very short ride, then charge. This will force the bms to continue charging any low cells further than one charge can.

Persistent out of balance is usually just the cells, one group being low capacity causing an early stop to charging all the time.

Bikegirl   1 W

1 W
Posts: 52
Joined: Apr 02 2019 5:30am

Re: Converting a Bakfiets cargo bike

Post by Bikegirl » Apr 18 2020 3:54pm

Thanks MalcomG

Very nice install. There are a few steps to go before we install the electric motor and I will use this post for reference.

The bike's gear selector was very sticky and the handlebars are very narrow but we dropped it off for our mates and I will send them the link. They are keen for a project whilst there is not much else to do in these corona times.

Post Reply