Are any good those cheap 10$ BMS from eBay?

[bikegeek]

Hi,

I've build my first battery pack (10S4P) a few weeks ago and I realized I've made some "mistakes". Now I want to rebuild it and also make another battery pack. In my first pack I've used this BMS: http://www.ebay.com/itm/PCB-BMS-for-36v-Li-ion-Battery-Pack-with-Equilibrium-Temperature-Switch-DIY-/172025098672?hash=item280d7eb1b0:g:yR4AAOSwPhdU1z9M

I was looking for BMS on eBay and Aliexpress and I don't see the difference between those that are 10$ and those that are 30$.

Exemple 10$: http://www.aliexpress.com/item/Brand-New-High-Quality-Battery-Protection-BMS-PCB-Board-For-10-Packs-36V-Li-ion-Cell/32373531909.html?spm=2114.01020208.3.1.GWSWRj&ws_ab_test=searchweb201556_3,searchweb201644_4_79_78_77_82_80_62_81,searchweb201560_2

Exemple 30$: http://www.aliexpress.com/item/10S-15A-BMS-for-36V-li-ion-battery/1195130789.html?spm=2114.01020208.3.28.GWSWRj&ws_ab_test=searchweb201556_3,searchweb201644_4_79_78_77_82_80_62_81,searchweb201560_2

What makes good a BMS? What do I have to look for? Why not use those that cost 10$?

I've look on the forum for question but I couldn't find it.

 

[ntr]

I'm curious for opinions too. I have the 10 dollar BMS for my 10S3P pack. The $30 is reduced to $20 at the moment. I see the 2 more expensive ones have bigger heatsinks, buts thats all I can tell. The 10$ one is suitable for 30A too, and it is small in size (thats an important thing for me).
I saw this one used in this tutorial, so i thought it would be OK.

 

[Ykick]

BMS cost seems related to parts count and component quality. $10 version might work fine if you’re not pressing the maximum ratings but they also might not? Then how much did you save if you gotta buy a replacement?

You do know this type stuff is never covered under warranty, right?

 

[spinningmagnets]

It's my understanding that a faulty BMS is the most common cause of a fried battery, so...no.

 

[Syonyk]

It's my understanding that a faulty BMS is the most common cause of a fried battery, so...no.

I've seen a whole lot more stone dead batteries (sub-0.5v/cell) than I have batteries that were badly out of balance (even if only protected at full pack voltage level).

You get what you pay for an awful lot of the time, and I wouldn't trust a $10 BMS with a pack worth more than about $5.

 

[bikegeek]

Ok, I agree with you, a better one is the choice but how do you know a BMS is a good one? Just by the price?

The only place where I've seen "high quality" BMS is here: http://www.aliexpress.com/store/group/BMS-System/1807188_501681388.html

Do you have other recommendations?

 

[tomjasz]

Blather removed

 

[Mammalian04]

13s gets all the love.

Any suggestions and/or experience on a 20s BMS?

 

[tomjasz]

It's my understanding that a faulty BMS is the most common cause of a fried battery, so...no.

What constitutes quality? How do we judge? Can a visual of the solder job reveal anything? We really need a Ron investigation and report. That would be fantastic. I really hope you take this story on. It needs a trusted source like electricbike to reveal some facts.