Bafang kit problem

[ade]

hi all I'm wondering if anyone has experienced the problem I'm having with my Bafang bbs02 kit ,i fitted this kit a few weeks ago and have been using it along with my Ping 36v 15ah lifepo4 batteries with no problems at all as these batteries are coming towards the end of there service life (4 years old)i decided to have a new bigger battery built which was a 17.5Ah Ncm pack when using it with the kit after about 4 miles with mid assist level the power level noticeably drops and the battery fully discharges after 6 miles, after sending the battery back twice the battery builder thinks the problem is with the kit as the cut off voltage is set at 31v on their controller as they are set up to use lifepo4 batteries therefore prematurely cutting the battery off .having carried out numerous tests all point to the battery fully discharging and not being cut off by the controller even using with a lower power kit with voltage cut off @ 27.5 v . i have never come across this and have always used bagang kits with different battery chemistries with no such problems has anyone experienced similar? any information appreciated

 

[trex]

The BBS02 36V 25A 500W should be paired with a 36V battery fitted with high discharge rate BMS to support the full 25A continuously.
It expects to see 42V when the battery is fully charged and 31V when the battery is totally flat.
Most cheap battery packs can only do 15A-20A. If your battery does not have a high discharge BMS (28A-30A), it will suffer cutouts when the current exceeds its setting and also sags a lot when your motor makes strong demand. The result: your battery can be half full and still cuts out when you pull hard on hills. Check first the voltage of your battery when fully charged and contact the battery vendor for information about the maximum continuous current.

 

[Nealh]

Your problem is you may using the wrong battery the BBB02 needs a 48v or 12/13s battery , the LVC for BBS02 is about 39.6 - 4.1V not 31v. Crossed with Trex's reply forgot about 36v BBS02 you need to confirm which BBS02 you have.

 

[ade]

the battery pack is 36v ,the full charge voltage is 38,2 v and in my opinion this is wrong in full discharge state voltage is 32.4v peaks amps drawn during test was 19-20amps the battery pack consists of Ncm pouch packs which are normally used in the electric car industry

 

[Geebee]

The charge voltage does seem to be very low?
According to Battery university Lithium Nickel Manganese Cobalt Oxide:
Charge (C-rate) 0.7–1C, charges to 4.20V, some go to 4.30V; 3h charge typical. Charge current above 1C shortens battery life.
Discharge (C-rate) 1C; 2C possible on some cells; 2.50V cut-off

Can you hook a meter up so you can read it whilst riding and see if the battery reaches LVC under load, if not confirm the LVC with your older pack?

http://batteryuniversity.com/learn/article/types_of_lithium_ion