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arber333 · 03-10-2013, 06:52 AM

Hi,

I am currently experimenting with Nevilles BMS, the low balancing version. I have two issues now. I have 40 cells and 130VDC system.
System works very well and shows all parameters untill i press the pedal and drive. At that time master shows over 300V and over 60 cells!!!
I have three banks of cells and like 3m of 7wire shielded cable between them. I didnt put the shielding mesh to ground, should i? Would this be the problem here? Clearly EMI is causing comms go wild. BUT comms do not drop out!

Another capital problem is when i try to balance cells in bulk. Display normally shows "balancing 40" and then after a minute or so comms drop out! I mean i get "no comms" sign. I use 3R3 5W wirewound resistors with ceramic core. Should shunt cca 1A from 3V.
After i disengage balancing switch the comms return after a minute or so! Weird no? Maybe master optocoupler is giving trouble...hm?

Link to my build: mazdamx3ev.wordpress.com/tag/bms/
This site is in Slovenian, i intend to translate in the near future... as the time will allow.

Does anybody have any experience with this or suggestion what could cause this? I consider second problem more critical, as it means i cant even reliably balance my cells.

edit: When i connected one cell to master it was balancing ok for cca 1hour, hm... i have to try individual banks and determine where the error is.

A

03-10-2013, 06:52 AM	#101 (permalink)
arber333 EcoModding Lurker Join Date: Jul 2011 Location: Slovenia Posts: 70 Thanks: 0 Thanked 20 Times in 13 Posts	BMS Help Hi, I am currently experimenting with Nevilles BMS, the low balancing version. I have two issues now. I have 40 cells and 130VDC system. System works very well and shows all parameters untill i press the pedal and drive. At that time master shows over 300V and over 60 cells!!! I have three banks of cells and like 3m of 7wire shielded cable between them. I didnt put the shielding mesh to ground, should i? Would this be the problem here? Clearly EMI is causing comms go wild. BUT comms do not drop out! Another capital problem is when i try to balance cells in bulk. Display normally shows "balancing 40" and then after a minute or so comms drop out! I mean i get "no comms" sign. I use 3R3 5W wirewound resistors with ceramic core. Should shunt cca 1A from 3V. After i disengage balancing switch the comms return after a minute or so! Weird no? Maybe master optocoupler is giving trouble...hm? Link to my build: mazdamx3ev.wordpress.com/tag/bms/ This site is in Slovenian, i intend to translate in the near future... as the time will allow. Does anybody have any experience with this or suggestion what could cause this? I consider second problem more critical, as it means i cant even reliably balance my cells. edit: When i connected one cell to master it was balancing ok for cca 1hour, hm... i have to try individual banks and determine where the error is. A Last edited by arber333; 03-10-2013 at 08:22 AM..