Slow first build

[Slowrider]

First of I would like to say thank you to all contributing to making this a great forum.
I have learned a great deal by just reading old topics and this inspired me to my first build.

So I ordered the following from BMS Battery
Q100 24V250W-350W Front E-Bike Kit with LED Meter
24V10Ah LiFePO4 EBike Battery Pack
A Pair of EBike Torque Arm

The package was sent on a friday from Hong Kong and I recived it the following monday here in Norway so I was very impressed with shipping!
Assembled the kit on a quite light hybrid bike and everything is working ok, but it seems very slow and max speed is only about 25 km/h.
I also think it has poor accerelation and very sensetive to any head wind. The kit has 3 different settings slow, medium and high but I can not feel any different performance from slow to high.
I way 70kg and I was expecting a bit more speed than this from a 350w kit, but maybe this is normal speed.
I have checked wiring and can not find any faults, is there some way to check how much power the motor is actually producing ?

Any help and input would be greatly appreciated.

 

[Drunkskunk]

Welcome to the forum. You picked out about the tiniest, lightest weight, lowest power motor there is. Its a good little motor, but with emphisis on the "little".

There are some ways you can upgrade it. First, make sure the speed limiter isn't engaged. On many controllers, Its a loop of white wire that plugs into it's self. Unplugging it lets it run unrestricted. Since you said your speed switch did nothing, I would check that first.
If it's not speed restricted, you can get more performance by Using a 36 volt battery along with a 36 volt controller should get you about 50% more torque and more speed.

 

[ian.mich]

ya for 350W and 24V that sounds about spot on. Not sure about the 3-speed though, either the controller is misprogrammed so all settings are 100% or somethings broke.

 

[dogman dan]

I agree, a 24v kit cannot be expected to do much faster than that. At 36v, the same motor could perform better, but tiny motors just flat out die when you hit a real headwind. Stuff like 30 kph headwinds or more will make them just slog. To do 20 mph into wind takes 800w or more.

This is why I just don't like the smallest stuff. Just when you need the assist the most, on a steep hill or into the wind, it's got you wishing for more. My favorite rides have lots of watts for when you need it, but still go fairly slow and easy on the watts in normal conditions. 48v 20 amps controller, and a slower winding motor.

 

[d8veh]

The 350w rating means that you can run it at higher power than you are at the moment. You have approx 24v x 15 amps = 360w max. I run the same motor with 12s lipos and 18 amps, so 48v x 18amps = 864w max. Now you can see what you're missing.

The first thing you should do is add some solder to the shunt in the controller to increase the current. If you stick with 24v, you can go to about half the length of the shunt - maybe even a bit further. This will give the motor a lot more torque, but speed will still be no higher than about 28kph.

If you decide that you need more speed, you have to increase the voltage. A 36v battery will increase the speed to 40kph, but it'll still slow down on slight hills and into the wind. A 24v controller can manage a 36v battery, but, as the controllers are quite cheap, if you order a new battery from BMSBattery, you might as well get a 36v controller at the same time (KU65). You should then solder about a third of the shunt for 18 amps. Don't use the 24v controller with more than a third of the shunt soldered at 36v.

To solder your shunt, you only need to remove the end-plate from the controller. Here's one with 30% soldered:

 

[dogman dan]

Soldering the shunt will help some. Quicker off the line, better in a headwind. But top speed won't be affected a lot unless you go to 36v or more.

The big cost of the upgrade is, of course, the battery. Solder the shunt anyway, and ride it awhile unless you can find somebody to buy your stuff now. Either way, you made a costly mistake buying such a small kit if you wanted to really have good performance.

 

[Slowrider]

Thank you dogman, d8veh, ian.mich and drunkskunk I really appreciate your help.

What I wanted when I bought the kit was a light bike with a light assist. The torq from the motor now is ok, as I have solder the shunt, what I am still missing is the top end speed. I like to peddal along with the motor but as it is now I outpace the motor.
I think that step 2 is to go for 36V. I only have a 4km commute to work so I am considering a battery pack from Hobby King, Ideally a light battery pack that can go in a saddle bag from the seat.
Can you please suggest a nice battery pack and charger for me ?

 

[d8veh]

Hobbyking supply mainly lipos. Are you familiar with the charging and management of lipos? If not you need to do a bit of research first. Any pair of 5S 5000mAH packs will do.
You need a permanently installed voltmeter;
Any 5S (or more) intelligent lipo charger;
A 12v power supply;
Cables and connectors;
Maybe a couple of lipo 5s alarms.