mancuz28
100 mW
Hi All, First time battery surgeon here. Purchased this 36v "30ah" pack used. Previous owner says it used to work fine, but has been sitting for 4+ months. Battery appears to come from "BTRPower" on ebay / amazon.
Upon initial inspection, voltage reads ~14V
However, once I put it on the charger, voltage jumps to ~41V...then charger shuts off. Pack now reads ~40V. I decide to give it a try on my bike...bike powers up fine, give it some throttle and it starts moving for a few seconds...then dies. Pack is now back to reading ~14V. So I decide it's time to suit up for my first surgery.
To my surprise...I find 10s 1p pouch cells, not the expected 18650s. I disconnect the BMS input wires (1 red, 1 black, and 8 white), and find the pack now reads 37.5 volts on the charge port (still 14V on the discharge port).
With my negative probe on the battery negative terminal, and positive probe at the lower most BMS pin (empty slot beneath the black wire) I get:
[EDIT: Updated with corrected measurements]
0 (no wire here)
...then moving up one pin at at time:
4.19 (the black wire...4.19 difference from previous)
7.0 (2.81)
11.19 (4.19)
15.38 (4.19)
15.38 (no sense wire here)
15.38 (no sense wire here)
19.5 (4.12)
23.7 (4.1)
27.8 (4.2)
32 (4.2)
36.2 (4.2)
40.4 (4.2)
40.4 (no sense wire here)
So obviously the 2.81v cell needs help. This would be the second pouch from the bottom right?
So now I am at the end of my knowledge. What would your next steps be?
Does anyone know anything about these pouch cells? Should I look for a replacement for the 2.8v cell? Any idea where to get them?
Or should I try charging the low cell up to ~4v and letting the BMS balance from there? I have not ever charged cells like this before...do I need to disconnect them from the rest of the pack? Or can I just charge directly on the pouch tabs (wherever they are...I haven't found them yet)
PS after reconnecting the BMS sense wires to the BMS, it took a charge for awhile, then the charger turned off again (as expected, as most of the cells were at ~4.2v already.
Upon initial inspection, voltage reads ~14V
However, once I put it on the charger, voltage jumps to ~41V...then charger shuts off. Pack now reads ~40V. I decide to give it a try on my bike...bike powers up fine, give it some throttle and it starts moving for a few seconds...then dies. Pack is now back to reading ~14V. So I decide it's time to suit up for my first surgery.
To my surprise...I find 10s 1p pouch cells, not the expected 18650s. I disconnect the BMS input wires (1 red, 1 black, and 8 white), and find the pack now reads 37.5 volts on the charge port (still 14V on the discharge port).
With my negative probe on the battery negative terminal, and positive probe at the lower most BMS pin (empty slot beneath the black wire) I get:
[EDIT: Updated with corrected measurements]
0 (no wire here)
...then moving up one pin at at time:
4.19 (the black wire...4.19 difference from previous)
7.0 (2.81)
11.19 (4.19)
15.38 (4.19)
15.38 (no sense wire here)
15.38 (no sense wire here)
19.5 (4.12)
23.7 (4.1)
27.8 (4.2)
32 (4.2)
36.2 (4.2)
40.4 (4.2)
40.4 (no sense wire here)
So obviously the 2.81v cell needs help. This would be the second pouch from the bottom right?
So now I am at the end of my knowledge. What would your next steps be?
Does anyone know anything about these pouch cells? Should I look for a replacement for the 2.8v cell? Any idea where to get them?
Or should I try charging the low cell up to ~4v and letting the BMS balance from there? I have not ever charged cells like this before...do I need to disconnect them from the rest of the pack? Or can I just charge directly on the pouch tabs (wherever they are...I haven't found them yet)
PS after reconnecting the BMS sense wires to the BMS, it took a charge for awhile, then the charger turned off again (as expected, as most of the cells were at ~4.2v already.