Questions from newcomer ebike diy

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Jul 28, 2012
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63
Hello, here is a couple of easy questions for the veterans:

Im planning to convert my bike to an ebike and am considering ordering the stuff from BMS Battery since they seem to be cheapest option (?).
Im thinking of a Bafang kit on either 36V-350W or 48V-500W or the Q100 36V250W-350W. What speed will those give me? I have no need to travel faster than 40 kmh. Which of those kits would you recommend?

I see that the Bafang kits states "Brake type: disc brake". Does this mean that I can not use Rim/V-brakes with these kits? I don't have disc brakes on my bike.

I've read about "overriding" the engine with higher Watt than it is made for. As I understand, the voltage can be raised by using a higher voltage battery? but how do I raise the current?
How would you recommend me overriding the kit: Q100 36V250W-350W to get a little more power, say 450W.

Thanks.. more questions to come probably!

//Rikard from Sweden
 
You need to run at least 48V on these mini's to get any kind of speed or hill climbing ability.
Top speeds vary w/ winds, different bikes, rider's weight, etc.
Ton's of info here, so start reading.
I think the slightly lager MXUS geared motor sold by emissionsfree.com is the best mini by far and olny costs slight more. It's also known as the Minimight or the Ampedbikes geared motor.
It can be somewhat more difficult to mount, depending on the bike, forks, gears, etc., so I would only recommend the Cute for special, hard to mount cases.
 
Also keep in mind that BMSBattery may not send you what you actually ordered, although you may not be able to tell from the outside. Or they may be delayed for weeks, or months, or worse. Might want to do a forum search on them and see what people say.

Cheapest option does not equal best option, or even most cost-effective option, and sometimes may well end up a much more expensive option by the time you get it all done. ;)
 
Thanks for the info. Well, i looked at the emissions-free website but they dont have alu cased batteries - Im not very handy when it comes to dyi skills, so i rather go for complete kits. From BMS battery its possible to get battery with alu case and specially made luggage rack.

So what about the rim, in kits where its stated that its for disc brakes - its still possible to use with V-brakes right?

Ive looked around on the site for basic info about "overclocking" the engine, but i cant find any real basic info for us newcomers. Any tips for searchwords?

//Rikard
 
Cell_man makes battery packs out of A123 cells, much higher quality and more powerful, but more expensive.
If you go with a Q100 on a BMS Battery @ 48V and weigh more than 150 lb.s, you should get the '201" slow speed motor and settle for it's relatively low top speed[approx. 21 mph].
Sorry, I have no idea what you are referring to by "overclocking".
Yes, you can use V-brakes on a disc brake motor.
 
Overclocking = overvolting, running at higher than designed rpm, etc. Clock originally was the tachometer on gas stuff i think.

Cellman is currently out of 26650 A123 cells. Hopefully he can secure a new suppy soon. If you get his muxus kit from him, at least you know what you will get for sure. Others have been happy enough with bms battery.

Rule of thumb for lower c rate batteries would be 1 ah per 1 amps of controller, or at least .75 ah per amp. Other considerations apply, like 48v 20 amps is just too dang big to carry well.

Pingbattery 15 ah lifepo4 batteries are a good choice for most ebike motor kits. No box. So what, a metal or plastic box is very cheap. You wanna good box, or a good battery? Box is a super easy problem to solve.Axxiom pannier rack and supports.jpg
 
amberwolf said:
Also keep in mind that BMSBattery may not send you what you actually ordered, although you may not be able to tell from the outside. Or they may be delayed for weeks, or months, or worse. Might want to do a forum search on them and see what people say.

Cheapest option does not equal best option, or even most cost-effective option, and sometimes may well end up a much more expensive option by the time you get it all done. ;)
The delivery times from BMSBattery have improved a lot and are now quite reasonable. It's true that you sometimes don't get what you expect, but the differences are very minor, and I've never heard of anybody being particularly unhappy about what they got. I think there were some suspect batteries a while ago, but I haven't heard of anything recently. IMHO BMSBattery are still the best value supplier for Europeans, because the stuff is cheap and you often don't have to pay import duty.

Manneokoko says that his DIY skills are not so good. That's worrying because you need to be able to solder and change connectors etc with BMSbattery stuff, and the same applies to most DIY kits. You can get plug-and-play kits like the EZee kits, but they tend to be a lot more expensive, or other kits with under-powered batteries that are fine as long as you don't want to go over 15mph.

IMHO the 250W Bafang motors are stronger than the Q100 (except the small SWXU), but not as smooth and quiet.

To get more power out of the Q100, you only have to increase the amps from the controller. As standard, with a 36v battery and 15 amp controller, you get 600w max. The 350w stated is how much it's happy to run at all day. The Q100 is still reliable with 18.5 amps, which is about 750w. You can get more power by over-volting, but power = torque x rpm. The extra power from over-volting comes from allowing the same torque to run at higher rpm, but if you don't have the torque to reach the higher speed available by over-volting, then you don't see the theoretical increase in power. Instead you get less, because you make more heat running in a less efficient range of operation and can end up with a burnt motor. That's why it's important to match the correct motor, controller and battery to your desired speed. It would be different if you could use a gearbox to always run the motor at the higher rpm available. You can overvolt a motor and then use smaller wheels to let it rev to the higher speed to get the extra power available, The Q100 is not a high torque motor. To me, the optimum for a 201rpm version is 48v actual from a 44v battery and 18.5 amps - as long as you don't use max power too often.

To get the controller up to 18.5 amps, you remove the controller end-plate opposite end to the wires and the shunt is right there waiting for you to add solder to about half of it to get the desired increase. It's best to use a watt-meter to see the before and after so you don't overdo it. Here's a photo showing solder on about 1/3 of it:
KU63solderedshunt.jpg
 
Thanks allot for the explanations. My DYI skills aren't that bad. I can do some soldering and changing connectors, but I am not so knowledgeable about electronics - so its a great help to find this forum.

You say that overvolting is only beneficial when riding with high rpms. Since I will not be riding at maximum speed very often, maybe its not a good idea to overvolt?
To increase power, would it be sufficient to just the increase the amps from the controller or do I need increase Voltage also? What top speed would it give me if I only increase the amps to 18,5 and still use a 36V battery?
In raising the amp, would it be possible to just use a higher Watt controller instead of soldering? 12Mosfets 500W?

d8veh said:
To me, the optimum for a 201rpm version is 48v actual from a 44v battery and 18.5 amps
There are no 44V batteries available at BMS, do you think this 48V would be OK?
 
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