Converting a Bakfiets cargo bike

[john61ct]

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]

Here's a possible kit option.
https://www.ebikekit.com/collections/etrikekit-no-battery/products/e-trikekit-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/kits/cyclone-mid-drives/62641-bakfiets-earns-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]

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]

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]

what is the weight of such bike ?

 

[MalcolmG]

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]

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]

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

 

[dogman dan]

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]

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.

 

[nooneenooner]

Sorry this is a bit off topic, but can someone tell me whether I can convert my 8 year old bakfiets to electric without having any alternative brake attachment points? I'm new to ebikes and don't understand a lot of this discussion yet, but currently I'm thinking I'm screwed because I can't upgrade my brakes (rollerbrakes). The rear wheel has an internal gear hub, so seems like I can't replace it with an electric hub. A mid drive seems out because the frame is weird (and the chain guards are nice). I was really hoping to replace the front wheel with an electric hub, but my front fork doesn't have attachment holes for disc brakes or for rim brakes. Any chance there's a special disc brake kit that clamps onto old forks without attachment holes? From reading this post, sounds like direct drive hubs have electric braking. Would electric braking be enough to replace a mechanical brake? If so, presumably I would lose the front brake if I ran the batteries down or a cable came loose, which is a little worrisome...

 

[amberwolf]

Any chance there's a special disc brake kit that clamps onto old forks without attachment holes?

There are; shown in a few threads about adding such things. How well they work depends.... I've used clamp-on rim brakes that worked well enough for a 400lb cargobike&rider (not counting cargo).

But first, a question since you don't show your bike or give any info about it's model/brand/etc: Is your front fork nonstandard, with steering connections that can't be made to the fork without that specific one? If not, then you can just change the fork to one that has a mount for ohter brake types.

From reading this post, sounds like direct drive hubs have electric braking. Would electric braking be enough to replace a mechanical brake?

Generally, no, but it depends on how much you depend on the front brake vs the rear, whether you need it to work down to a stop, etc., and which motor and controller you use, and whether you are willing to never charge your battery to full so that your brake will work even at a full charge (or use a controller that doesn't regen back into the battery but instead does it some other way).

Also, most controllers only do on/off braking, so if you have hard enough braking to be useful in emergencies, it would be too strong for typical usage.

Some have proportional regen (sometimes called variable regen), so you can use an analog control to have as fine a control over the braking as you would with a mechanical--but only some setups will be able to provide the same amount of braking you could get with mechs.



FWIW, there area number of types of non-hub motor drives, that do not fit in the BB area, that depending on your bike might work for you. Most of them will be more DIY than plug-n-play, and probably require manufacturing brackets and moutning clamps specific to your frame.

 

[Balmorhea]

I think it’s worth considering having an electric brake on the front wheel and a mechanical brake on the rear. Electric braking is inherently anti-lock, while most of the bike’s weight will always rest on the rear wheel.

 

[MikeSSS]

We bought a Bafang G311 and Grin 25A controller for my wife's 24" wheel Townie. The Grin 25A controller is programmed for a direct drive motor, it is programmed for regen. It has significant throttle beginning dead band, used for adjusting regen braking, followed by sending too much power to the motor when you get past the regen dead band. A CA V3 can fix this, but the controller for regen should never have been sold with a geared hub motor, it's not programmed for a gear hub and the sudden onset of too much power makes it dangerous to the rider. Other than that, the G311 is perfectly adequate for a 50 kg woman on a light bike. The Grin kit was very neat and tidy, the G311 is the normal wind. Both the G310 and G311 can throw magnets if the bike goes too fast.

My rear hub MAC 12T and matching controller, and CA V3 all came from EM3ev. Initial throttle is too sensitive but it can give you a slow walking speed if you're careful. My wife's G311 and Grin controller cannot give controllable slow speed. On 52v the MAC provides more power than I care to use. 120kg all up weight isn't even close to a problem for the MAC. A MAC is much larger than a G311, heavier too.

Noise from the G311 and the MAC 12T is minimal, it's less than that from my sensorless DD, at certain combinations of throttle and speed.

Climbing is sort of a catch-22, geared hubs climb well but don't have a good heat rejection path, so they overheat quicker than a DD hub. Direct drive hubs don't climb as well but can climb longer without overheating.

One way to think about turn numbers is: low turns climb on the Amps, high turn motors climb on the volts. Two RC crawlers, one with low turns and one with high turns: the low turn car needs to climb over something, you add more and more amps until the vehicle suddenly takes an often uncontrollable leap forward, with the high turn car, you just add minimal amps and the vehicle climbs over the object with little or no drama.

 

[MalcolmG]

I think it’s worth considering having an electric brake on the front wheel and a mechanical brake on the rear. Electric braking is inherently anti-lock, while most of the bike’s weight will always rest on the rear wheel.

I'm not sure I'd agree with this. Electric braking may be inherently anti-lock but that is because it's just not generally as good. With a front-loader cargo bike you'll often have more weight on the front wheel, especially when braking due to longitudinal weight transfer.

With a decent disk brake on the front now I'm much happier with the braking performance than when we had roller brakes front and rear, I would strongly suggest trying to find a replacement fork that has mounting tabs for disk brakes or consider having some welded to your existing forks if they're steel.

 

[Balmorhea]

My experience with rear weight biased bikes is that it's possible to skid the front wheel (instead of tipping up), and the weight transfer while braking isn't as pronounced as it is on a bike of normal wheelbase.

Just as hub motors work better in smaller wheels, disc brakes work "better" (less sensitively/controllably) on smaller wheels. If you're going to the trouble of adding brake mounts, cantilever studs aren't a bad idea, because V-brakes work about the same regardless of wheel size.

 

[pajtaz]

Malcolm, hello from Netherlands.

I am researching if I can convert my new old (just purchased used) bakfiets for reasonable price. I will only do it if cost is low and I can use a front motor. My bakfiets is just like yours: only one front wheel, same box for kids to sit in, same size front wheel, roller brake on the front and rear. Mine is 2012 Bakfiets Cargobike Short.

Can you please tell me which specific motor, controller, and battery you got? How did you get the motor, did you buy the motor alone or did you buy it with the wheel? If you bought the motor one, how did you get it installed into the wheel?

For others, is front roller brake adequate if I keep the speeds at max 25 km/h? Bike would be 150 kg with kids, rider, and bike itself plus battery and motor. Or do I need to look to install disc brake on the front? Installing disc brake is not possible on current fork so if I have to buy a new fork with disc brake mounts, it might be game over for the conversion (too much money and work).

Thanks ahead for the help.

 

[MalcolmG]

Malcolm, hello from Netherlands.

I am researching if I can convert my new old (just purchased used) bakfiets for reasonable price. I will only do it if cost is low and I can use a front motor. My bakfiets is just like yours: only one front wheel, same box for kids to sit in, same size front wheel, roller brake on the front and rear. Mine is 2012 Bakfiets Cargobike Short.

Can you please tell me which specific motor, controller, and battery you got? How did you get the motor, did you buy the motor alone or did you buy it with the wheel? If you bought the motor one, how did you get it installed into the wheel?

For others, is front roller brake adequate if I keep the speeds at max 25 km/h? Bike would be 150 kg with kids, rider, and bike itself plus battery and motor. Or do I need to look to install disc brake on the front? Installing disc brake is not possible on current fork so if I have to buy a new fork with disc brake mounts, it might be game over for the conversion (too much money and work).

Thanks ahead for the help.

Hi Pajtaz

I bought this kit: https://www.aliexpress.com/item/32841242481.html (500W, 48V option) and combined it with a 48V 10Ah LiFePO4 battery that I found second-hand locally. The motor was already built into a wheel, the wheel is OK but a bit narrower than the original bakfiets one. I also bought one of these torque-arm kits https://www.aliexpress.com/item/32841242481.html

If you install a motor on the front wheel, you will lose the roller brake anyway. Surely if you're in the Netherlands you should be able to find second-hand forks with disk brake mounts?

 

[pajtaz]

Thanks for the link. I can't figure out if the shipment is tax free to EU, this is a big cost to consider. Also finding a battery for a good price within EU is not easy. But this kit is actually not bad if it comes in a wheel and has everything except the battery.

Do you know specifically which motor is it? It seems to say it is Bafang SWX02 but it is not clear. And the one you got, 48V 500W, you are not worried about the motor overheating? Meaning, it seems to have enough torque at low RPM for the large weight it needs to pull?

As for finding a second-hand fork with disc brake mounts for bakfiets, this should be possible but the bakfiets last a long time and they are rarely cannibalized. I did a quick search but couldn't find anything quickly. I need to do a detailed search. This sucks because then I need to buy a disc brake and install it, in addition to the fork. Maybe it is possible to find somebody selling parts and I get lucky and find the fork and disc brake.

 

[MalcolmG]

I'm not sure on the exact model of the motor, it may be stamped on it but I'll need to have a good look.

I'm not worried about it overheating, I don't tend to use a lot of assistance, the controller has a scale of 1-5 and I usually have it on 1 or 2. Probably the worst case would be going up a long and steep hill while heavily loaded, but I haven't had any problems yet.

I used a second-hand disk brake caliper for a mountain bike and just made a new (longer) brake hose, so it didn't cost me too much. I was lucky that the fork already had disk mounts on it, I suppose you could also check whether bakfiets.nl will sell you a fork with a disk mount?

 

[pajtaz]

I'm sure bakfiets.nl will sell the fork with a disk mount but it will be way overpriced. I might get lucky finding it on a large online bike parts shop or locally on second hand goods website.

If you got LCD3 screen, I have the same one, I know all about the settings and PAS levels. Do you know what is the power usage at levels 1 and 2? On my other bike I have mine set up to show me the real time Watts that are being used by the motor. For my 48V 500W rear hub motor and a similar controller as yours I have it set up to use 100W for level 1 and 175W for level 2.

My point is that I would go for 250W motor if that would save money but if it does not make a difference then I would just go for 500W.

 

[LewTwo]

Have you considered something like this ?

https://nl.aliexpress.com/item/1899546461.html

 

[Chalo]

Have you considered something like this ?

https://nl.aliexpress.com/item/1899546461.html

Ewwww don't do that. It isn't strong enough, it won't stay aligned, and it's skankier than (the rhetorical) your mom.

 

[LewTwo]

Ewwww don't do that. It isn't strong enough, it won't stay aligned, and it's skankier than (the rhetorical) your mom.

Mom is very stable. She has been resting comfortably in her grave for over 40 years.

If I understand how the caliper is arranged on the front fork, then the adapter should always be in rotational tension when it is applied.

 

[Chalo]

If I understand how the caliper is arranged on the front fork, then the adapter should always be in rotational tension when it is applied.

Braking force at the pads isn't aligned with the caliper mounting tabs, so there's a twisting component these bodged-on mounts are ill-equipped to control. I've never seen one in person that wasn't rubbing on the rotor all the time.