Forum

Does 14s bms have low voltage protection?  

  RSS

52v Evan
(@52v-evan)
New Member
Joined:11 months  ago
Posts: 1
05/01/2019 2:33 am  

Wondering if the 14s bms sold on vruzend has low voltage protection cutoff during discharge or if it only does balancing for charging. 


ReplyQuote
Micah (Vruzend Rep)
(@admin)
Street cred = 5 Ah Admin
Joined:3 years  ago
Posts: 484
13/01/2019 11:28 am  

Yes, it has low voltage cutoff.


ReplyQuote
jbracey
(@jbracey)
New Member
Joined:9 months  ago
Posts: 1
05/02/2019 7:55 pm  

Tacking on to this question, I have a 14s 4p pack with the correct BMS (from here).  Batteries are Samsung INR18650-30Q (15A 3000mAh)

Currently, fully charged on the pack is showing about 57.7, which seems a bit lower than charts I have seen with voltage vs % remaining.

The BMS is cutting out (low voltage, I assume) around 46v, which, according to the same chart, is ~30% left.

Anyone have thoughts on whether this is an accurate cutout for this package, whether my BMS is off, or i have some cells that are degraded and causing the whole thing to cut out early?

Appreciate any feedback.  The bike has been a blast, FYI.

John


ReplyQuote
Micah (Vruzend Rep)
(@admin)
Street cred = 5 Ah Admin
Joined:3 years  ago
Posts: 484
19/02/2019 9:46 am  

Hey John, sounds like two different things here that might be connected. For the full charge stopping at 57.7V, that's likely a balance issue where not all cells are balanced. It's cutting off charging when the first cells reach full, but the lower cells don't have as high of voltage, and thus the total pack voltage isn't 100% (58.8V for a 14s battery). It could solve itself if you leave it on the charger for a while, but a good method to check would be to measure the voltage of each parallel group if you can still access them. One or more much lower voltage groups might need manual balancing (charge them up with a single cell charger) to get them closer to 4.2 and help the BMS with an easier job.

The cutoff on discharge is likely from voltage sag. What is your discharge current, and are you using a V1.5 or V2 kit? The V1.5 is more prone to voltage sag as the kit is rated for lower current due to its higher resistance than the V2. However, if there is a balance issue then the lowest cell group could be causing a premature cutoff when it dips to the low voltage cutoff before the other cell groups.


ReplyQuote
bkhouri1
(@bkhouri1)
Street cred = 10 mAh
Joined:2 years  ago
Posts: 4
01/11/2019 2:09 pm  

Hi Micah,

When you say, "the lowest cell group could be causing a premature cutoff when it dips to the low voltage cutoff before the other cell groups," what is that LVC number exactly for Vruzend's 14s BMS 

I'm troubleshooting an issue with my 52V pack cutting out at ~48V. Pack has 1.5V kit, is a 14s5p using samsung 25R5, pushing 20amp continuous (which seemed somewhat okay for a 5p, 4amps continuous per cell...). Also, the voltage sag you mention is worse for the 1.5v kit. When my pack cut out, there was a group that got down to 3.1V but under heavy load with voltage sag could this group have dipped low enough to trigger the LVC?

 

Thanks for your words Michah,

Brian 


ReplyQuote
  
Working

Please Login or Register