Upgrading controller and battery advice

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Jun 20, 2020
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, Hi everyone!

I am a happy owner of a small Bafang/8Fun motor used on my cargobike. I am currently looking into upgrading my battery(36v) and controller(13amp) and thus, in need of advice. Unfortunately, I have no information about what bafang model I have. It is however really small, and seldom get hot.
I am looking to get a little bit more juice to climb and a better performance overall. Right now, I find that I don't get "enough" power when the battery falls below about 60% under load. Of course, this battery has a couple of years on it as well. Of course, I want my next battery to last a year or two longer than the one I own right now.

1. Can I upgrade my battery/controller to either a higher voltage (48v) and/or higher amperage without damaging the motor? If only one of these can be fulfilled to protect my motor, which one would be my best bet?

2. Suppliers of batteries/controllers. I would prefer to buy a battery that can be placed as part of the rear rack and bundled with the controller, just as the one I have today. For example this one
https://bmsbattery.com/ebike-battery/952-18033-48v10ah116ah14ah-case-02-battery-pack.html#/510-inner_controller-with/512-cells_capacity-25ah_high_c_rate_10ah/532-rack-with
The controller that comes with this battery is rated for 18A, and that together with 48v is even more power than I need.
They are unfortunately out of stock. Any hints to other suppliers are welcome!

3. Of course, I prefer not to re-wire everything, and thus prefer HiGo connections as these are the ones I have today.

Thanks!
 

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Can I upgrade my battery/controller to either a higher voltage (48v) and/or higher amperage without damaging the motor? If only one of these can be fulfilled to protect my motor, which one would be my best bet?
Yes you can. I can't ID exactly which Bafang your motor is by that engine code, but I suspect it's rated 350 Watts. The Watts rating is just a guide and generally, that value can be safely doubled, even more for brief periods. Max Volts is more a matter of what the controller can handle. The capacitors in even the budget controllers are rated 54V, and most are 63V rated. I have run 54Volts and 20 Amp controllers on a mini geared motor (Q100H) smaller than your Bafang. This doesn't mean you would want to go looking for steep hills to conquer, but 48V on a 18 Amp controller will give a useful boost in hill climbing power and a gain of 2 to 3 mph in top speed.
For example this one
https://bmsbattery.com/ebike-battery/95 ... -rack-with
The controller that comes with this battery is rated for 18A, and that together with 48v is even more power than I need.
They are unfortunately out of stock. Any hints to other suppliers are welcome!
You can never have more power than you need, especially on a cargo bike:)
There is no vendor like BMS Battery that offers the range of products at their price level.
I quickly looked at some of the bigger vendors I have used, but no one offers the rack/batt./controller combo you are looking for. There might be a store somewhere that might have one in stock, but I think it would at a higher cost.
Anyhow, if you want to look around, here they are;
https://www.greenbikekit.com/e-bike-lithium-battery/li-ion-lifepo4/48v.html
https://www.pswpower.com/collections/battery-bms-charger
http://www.topbikekit.com/dolphin-03-48v104ah-liion-18650-rack-battery-pack-with-charger-p-478.html
Topbikekit offers rack/batt. combos, but no intergrated controller.
Random thoughts;
1)Contact BMS Batt. and see if they can give you a time when their rack/batt/controller might be avail. Maybe a 50% chance what they tell you(if they can tell you anything)will be accurate.
2) fit a batt to your existing rack and add external controller.
An item of note; The BSM Batt combo requires a speed sensor feed (For the sine wave display to work right), but your Bafang system uses Higo connector and that tells me it's a newer system and would have the speed sensor
 
Thank you for your reply motomech!
Since I'm in Europe, the motor(the bike came with the motor) was sold to me with rated 250w. Your answer is right about what I was thinking. For the motor, wouldn't it even be best with 48v and lower amperage rather than 36v and higher amperage? I mean, high amperage might give a lot of heat. All this assuming that a power upgrade is nnessecary.
Yes, my motor does have internal speed sensor and HiGo connectors. I figured this one out when I had to replace my LCD 'cause some looney stole mine. When setting it up, I came across the "number of magnets" to determine speed. "Hell if I know" and started guessing for a couple of hours(!!), until I finally tried setting it to zero. Apparently zero=internal on my LCD/controller setup 😆

Thank you for the supplier links!!
 
If you buy a battery/controller that uses the KT controller family and select an LCD3, one can set the current levels anywhere between 50-100% of the rated value. Some of their other displays also have this feature, but I don't kown them. If they use the same 9 pin motor connector, it's almost plug and play. Depends on your brakes, throttle, etc.

As for putting a 48V battery directly on your existing system, depends on what the designers did. Some will run. Some have overvoltage circuits. Capacitor families include 50V and 63V ratings. I've never seen 54V. I wouldn't recommend running the 50V designs on 48V. It's easy enough to remove the rear plate and see if you can spot a capacitor.

shunt.JPG
 
Hi docw009!

Thank you for the input. I am almost surprised that you recommend the KT controllers because of that , since I assumed (faulty?) That every LCD/controller have this function. If not, that should become industry standard.

Since I intend to replace both battery and controller this will not be an issue. If I end up buying a 36v volt battery, I want more than my current 13A, and if I buy a 48v battery I want a new controller anyway.
 
Petterflensburg said:
If not, that should become industry standard.
Unfortunately, the longer you are into this, the more you will discover the only industry standard is not having one. ;)
 
The main issue with hitting your current motor with more power is going to be its load. If you try to haul more than 200 pounds total weight of bike, rider, cargo, battery, up too steep of hills, your motor may fry. It lacks the size of magnets, and the amount of copper in the winding to handle a lot of watts. I would not go a lot more amps into it, or volts. What I mean is not a 48v 30 amps controller. 48v 15 amps, maybe, but not if you are a larger person.

Lots of variables here, including weather. But your best bet for a cargo bike, and steep hills will be an upgrade of everything, including the motor, with the best approach being a mid drive.

However,, one way to stiffen up your power some at 36v, is simple. Next time get a much bigger battery. Then as it gets to 60%, its gone twice as far. The big battery will sag less under load, so you get a perkier ride the first half as well. This is a win win. Pretty clear the motor is already handling the current controller, and your weight, up the hills you ride. A bigger capacity 36v battery won't change that, it will only change how much voltage drop you have along the way. And a huge battery will be able to go the distance you ride with less discharge rate, and less % discharge. This makes it last longer, usually.
 
Thank you for your reply dogman dan!

I totally agree with you, and I am not looking into go all crazy with power. I have been using my cargobike with the current setup for four years was thinking about adding just a little bit extra.
Personally I don't really get why someone would want that much power on bike, 'cause it won't be bike any longer- but that's just me.
 
It depends on the usage.

I worked up to much higher than typical power levels over a long time trying to find the safest practical ride.

For instance, on my SB Cruiser cargo trike, I have to be able to accelerate at normal (quick) rates up to the 20mph max so that regular street traffic doesn't get all pissed off and try to run me over when I'm stuck up at the front of the line at a traffic light...while hauling a few hundred pounds of groceries, dog food, or dogs, or other cargo (for a total weight of around half a ton, sometimes). That's about 4 seconds to 20MPH, Iv'e found, so that most drivers tolerate me being "in their way" that long till I can get across an intersection and over to the bike lane (if there is one)...and that takes about 4-5kw of power with that kind of load, at least with DD hubmotors (eventually I'll have the right stuff to use something thru a shiftable-gears drivetrain that won't break under these loads). Similarly, climbing a slope (like the underpasses on the canal paths) even unloaded takes that kind of power.

My old CrazyBike2 took a little less power, but not by much; all it's really big loads, or things like the dogs, had to go in a trailer, which took more power to pull (extra weight, rolling resistance, etc).

(riding on sidewalks around here is much more dangerous than riding in the street with traffic, unless you only go at a walking pace and stop at every driveway, etc, and are able to ride off and onto the curbs easily whenever pedestrians, other cyclists, piles of junk, trash, or whatever, or cars, are using the sidewalk).
 
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