Buying bike motors etc on sale from china

Joined
Apr 16, 2017
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291
Location
Winnipeg, Manitoba
November 11 is the biggest sale day in China, they call it singles day as in 11:11. I use Aliexpress when I purchase items on that day. A brief explanation follows. Aliexpress is kind of a chinese ebay, thousands of small business's sell their goods on the platform, there are of course other such as DH Gate, Alibaba etc. My experience is e bike motor purchases so I will describe the process. Last Nov I bought 2 48V Tongsheng 500 watt motors along with 2 17.5 watt hour rack mounted batteries. The vendor i chose offered free shipping and each cost me $900 Canadian. Buying just that battery from a Canadian vendor would be around $700 and the motor would be in the $500 range.
If you purchase an item Aliexpress holds on to your money till it's delivered. The vendor always sets a delivery date, usually giving themselves something like a couple months. Once you receive your order Aliexpress releases the money to the vendor. If it doesn't arrive or is really late you can opt for a reshipment or a refund. Again I'll use a motor as an example, when you see a vendor that might have what you want click on the company name, its on the left side near the top. That will tell you how long the business has been active. Personally I don't use ones that are only say 2 or 3 years in business, much preferring a business thats been around for a longer period of say 7 or more years. I check items and put them on a "wish" list now and on the 11th if still interested move to purchase. I have saved myself quite a bit of money by this method. Buying a battery from an established company also reduces the odds of getting counterfeit cells, you want Samsung, LG etc cells you can count on
 
Joined
Oct 19, 2012
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1,080
Location
Wakefield, UK
I've used Ali Express many times, most recently for a pair of Avid Speed Dial brake levers. They came in just 1 week which is a little unusual as it normally takes about 3 weeks and were 2/3 the price on ebay. I'd never buy a Chinese battery though. There's far too many Chinese sellers advertising anything from 5000mah to 15000mah 18650 units. Given the best South Korean units don't make 4000mah the Chinese claims are outright lies. Indeed I saw some tested at just 500mah making them utterly useless. Doubtless there are some good Chinese batteries but it seems too much a lottery for me. There are places such a Fogstar in the UK who have a reputation of ensuring the batteries you are buying are genuine.
 
Joined
Jan 16, 2011
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328
Location
Vilvoorde / Flanders / Belgium
I have one of the "cheaper" 13S 5P batteries. For a 250W Bafang midmotor these would be great. But for my 750W variant, they are not good enough. I have 3 options now. Cheapest is to buy the same battery and link them up parallel. Less cheap, is to buy one "branded and assured" high end pack with a simular capacity. Easiest, expensive option is to buy 2 14S 6P packs from leading brands. (52V 24Ah)

Extreme work intensive, and not cheap, is the route Emiel is following, is to assemble your own pack from scratch.
 
Joined
Oct 19, 2012
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1,080
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Wakefield, UK
There's still some eig cells on ebay which simply bolt together for a 20ah battery. Only the BMS would need soldering and given you'd be soldering to the busbar there'll be little heat hitting the cells so a spot welder would not be needed. They're designed for electric cars so have a massive potential discharge rate.
 
Joined
Sep 16, 2018
Messages
490
Location
Netherlands
I hot my tsdz2 250w motor from aliexpres. Shipping was fast, because it came from Germany.
For my new build will I get a bafang 350w 36v with the 750c Bluetooth display.

I also got my battery for the bike from Aliexpres. But you must lookout with that. Most of those batteries are rated a lot higher than they really are. As you really want cheap batteries that are good, than building them yourself is the way to go. My 17,5 ah from aliexpres was over 300 euro, where I can build a 19,25ah for about 200 euro and the second one will be cheaper.
Don't order cells from aliexpres. The real ones aren't cheaper than buying them in the EU or somewhere else in the world.

Shopping can be very long ad the moment. Some things take 3 months, where others arive in 2 weeks or even less.
 

Radical Brad

Garage Hacker!
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Joined
Mar 13, 1999
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5,984
Location
Kakabeka Falls, Ontario, Canada
And in my neighbourhood, Lynac has some great LifePo packs.
I have used these in several robotics projects.
More expensive than Lithium, but no worry of carrying around a bomb.

 
Joined
Sep 16, 2018
Messages
490
Location
Netherlands
I am not worried that much about lithium. I work for years with them and never got any problems with them. For e-bikes, they aren't having it that hard.

Lifepo is nice, but you need more cells and they are a lot more expensive.

I get my cells near me. I can pick them up, so they don't have to be send to me. Saves me some money and it's easy to get more if needed.
 
Joined
Jan 16, 2011
Messages
328
Location
Vilvoorde / Flanders / Belgium
LiFePo is a lot safer tough. On the other hand, with some knowledge and a decent BMS, I don't see a problem.

In 15 years of LiPo ue in Robot Wars/Battlebots, the team were I'm the mechanic in, had only 1 accidental LiPo fire. And that was because a non regular pit crew member mixed 3 and 4S packs.
The 4S pack started overcharging the 3S pack. POOF. Lots of smoke, some flame, the machine got dumped in the steel container and put outside untill burned out. Damage , wire loom, 1 ESC and the poor 3S pack.
I have to admit, the 3S pack was exact the same packaging and size as the 4S pack, just a few mm flatter.
 
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