hi, for 1 year i builded my own electric longboard with a 10s3p lithium ion (lg He4) in this time my bms has broken 3 times.
as bms i used
this one
i pulled and charged through bms they never lasted 3 monthes …
as tutorial for my battery i used ;
why my bms always breaks ? all balance wires are 100 % correct i checked several times. maybe it´s because of it does only support 40 amps discharge ?
what bms would you suggest ? iam german so pls excuse my english.
greets
Stop throwing your money away on cheap bms’s from eBay and buy a quality BMS from either battery supports or Bestech. I’ve been using Bestech since July 2016 with no problem.
You could bypass the bms for discharging and only use it for charging. Since you used quality cells, drifting shouldn’t be a problem. If you pull 50 amp through a 40 amp BMS the breakdown is programmed!
what bms is used in space cell ?
How can I bypass the bms for discharging? Do you have a wiring circuit?
BMS B- to BATTERY MINUS BMS C- to CHARGE PORT MINUS BATTERY PLUS to CHARGE PORT PLUS
Discharging is connected to the battery directly. You need additional plugs or soldered cables on battery plus and minus. In my case i soldered short cables with bullet connectors to my anti-spark input ports. I plugged it just for this picture so you can see how it looks.
@rich
Thank you very much 
Is it possible to bypass this bms for discharging as it uses the same port for charging and discharging? BMS: https://hobbyking.com/de_de/6s-li-ion-10a-pcm.html
And another question I’ve got: Is it possible to use a XT90 to split my positive wire into two ?
Thanks for your help !!
You are welcome @mkd! Of course you can bypass this BMS as well. Do you use Lipo or Li-ion? Which Setup do you use in general? Which charger? Which way you connect discharge ( on/off switch, key loop, XT90 Antispark)?
Hehe, some questions but otherwise it’s hard to help…
Thats good news.
I use two of these Lipo in Series (5800mAh / 6S): https://hobbyking.com/en_us/turnigy-5800mah-3s-25c-lipo-pack.html
The charger I want to use (24V / 6,25A / 150W): https://www.amazon.de/gp/product/B01MFFDI1Z/ref=ox_sc_act_title_1?smid=A2Z54WBF904K0X&psc=1
I want to use a XT90 Antispark to connect discharge.
The picture shows how everything is supposed to be wired (I wanted the system to be modular):
Hopefully I could answer all your questions.
Do the parts fit together and is the wiring circuit correct?
Thanks for your help
Do you plan a huuuuuge enclosure? Too much connectors here… 
I don’t like XT90 connectors at all, they are too big and you don’t need them, also you can’t bend the cables the way you like (the same problem with XT60).
I prefer single bullet connectors so you can route the cables any direction. I like 4mm bullet connectors (90A), the same as in XT90 but nice and compact, or 5,5mm bullets (140A but big).
But one picture speaks more than 1000 words…
Ok, first of all, your wire diagram shows discharging through the BMS, THIS IS NOT BYPASSED and you would damage your tiny BMS immediately, or at least it would shut off everytime when you pull the throttle!! You need to connect discharge minus to battery minus, now it’s only connected to C- /P- on BMS.
Like this:
You can plug plus of Lipo 1 directly to minus of Lipo 2, this is what i do, it’s 5,5mm bullet male/female. If you put BMS and charging port in the battery section you can save cables and space. 5,5mm bullet connectors for charging cables is way too much, i use 3,5mm (still too much). And 18AWG wire for charging and BMS connections is enough.
I think you’ll use to much cables, keep it short.
DON’T USE THIS POWER SUPPLY!!! YOU NEED 25,2V LI-ION CHARGER, this is something different.
Also you need a fuse for safety. I don’t trust Loop keys and you should buy an anti spark switch. Esk8.de sell them for 29,90 free shipping, including fuse. It’s so nice to have a switch!!!
It is dangerous to play around with Lipos and BMS, just one wrong cable and you could get in troubles 
It’s probably overheating. Need a heat sink on those MOSFETs (big ICs). That’s why they left nice big holes for you!
Yours will probably fail like OP’s - those MOSFETs need to be able to dissipate heat when under load!
What do you mean? A bypassed BMS should not get warm when discharging because there is no load.
Ah, I missed the part when you said you were bypassing. Hopefully you are using another mechanism for over-discharge/over-current protection? Otherwise that’s really dangerous.
Throw a fuse on there and you’re all set. For me personally, I’m not using anything besides cell fusing. I’ll risk it
I use Lipos so i’m good with my fuse and vesc settings only 
That’s your prerogative, but for the record and anyone else considering this architecture, it’s very dangerous and likely to catch fire.
Fuses are not substitute for BMSs. Remember, fuses are designed into circuits to protect chassis wiring from overheating and starting fires, and not from the various failure modes that LiPo’s can experience including a failing or buggy VESC. There’s a reason you’ll never see this architecture in any shipping product.
I would say 95% of the people using Lipos without BMS… just a balance charger for charging. In my case i bypass my cheap BMS just because of easy charging. You are right that everybody should use BMS on any build… but in real world i think it’s more dangerous when people make wrong balance cable connections and short their Lipos instead of just take the risk.
Is there a product with Lipos and not Li-ion out there?
Technically starry (and i think the new evolve) uses lipo pouches, but starry is also one that has blown up even with a bms
Ok, interesting…
