Salty Ping Battery - Help Please?

[theRealFury]

Thanks, I have one (hopefully) more question for you guys. After posting last time, I checked the cell voltages individually both by measuring from B- to each sense wire and subtracting each consecutive cell, and then by measuring from one sense wire to the next to test the cell voltages. All the cells were exactly identical. I then ran the bike while it was up in the stand for about 2.5 AH (the battery is 15AH) and now I checked the cells again (the morning after the 2.5AH drain) and the cells are still identical, they are all 3.334 V. This seems weird since they used to be so unbalanced, and all I did after soldering on the new BMS was to solder on a new wire to the B- pad as an extension of ground to help me measure the cells when it's all wrapped up, and I put it on the charger for about 2 minutes until it started doing the odd on/off thing from my last post. Are the cells really all exactly balanced, or am I measuring it wrong?

I would say your measuring it wrong but im not following 100% how you were measuring them. The chance of every cell being balanced to 1000th of a volt even on a brand new and fully balanced battery is practically impossible. i would check your readings again. My guess is that somehow you were always reading the voltage from 1 particular cell. Personally i would have balanced the cells up (either by using a 5v phone charger on the 3 lower ones or by bleeding the higher cells to reduce voltage) before i hooked up the BMS. then you could have just topped the carge off as per normal to test the BMS is working properly.

 

[mlt34]

Hey everyone,

I just wanted to post my update now that I have the bike back together. The charger going on and off near the end of the cycle seems to stop after a couple minutes, and otherwise everything seems fine. Here are the cell voltages, and this is how I measured them. I have a black wire soldered to the B- battery negative terminal on the BMS board, and for the first cell I measured from that wire to the first sense wire port, as seen here:View attachment 1

For all the other cells I measured between the two sense wires, as seen here:

Here are the voltages:

1: 3.410
2: 3.391
3 :3.442
4: 3.411
5: 3.576
6: 3.595
7: 3.566
8: 3.597
9: 3.595
10: 3.434
11: 3.449
12: 3.572
13: 3.435
14: 3.416
15: 3.614
16: 3.585

So things look pretty good in terms of balancing, right? All I did was run the bike on the stand at about a 2.5 Amp discharge for a couple hours, then charged it up and did the same thing twice. The battery appears to have balanced itself pretty well, as far as I can see. What do you guys think? The original battery cell voltages are earlier in this thread, for comparison. Thanks for all your help guys, and I look forward to seeing what you all think.

 

[999zip999]

It,s O.K. for your ping charger to turn on and off with all the leds lit or not. This is part of the balance process just don,t overdischarge or run it at to high at the controller 22amps, what motor and controller do you have ? 48v x 22amps =1000watts or more your ping is rated for 1000 watts or so. Watch it.

 

[theRealFury]

Here are the voltages:

1: 3.410
2: 3.391
3 :3.442
4: 3.411
5: 3.576
6: 3.595
7: 3.566
8: 3.597
9: 3.595
10: 3.434
11: 3.449
12: 3.572
13: 3.435
14: 3.416
15: 3.614
16: 3.585

So things look pretty good in terms of balancing, right?

Well im no expirt in balancing of batteries but if it were my battery i would be worried about the cell voltages. you have 0.223v difference between your lowest and your highest cell so thats almost a quater of a volt difference, if i have worked it out thats a difference of approximately your lowest cell having 40% less charge in it than your highest one (think of it more like that cell will be dead when the highest ones have still got 40% capacity left.). to be well balanced all the cells should be within ~0.1v of eachother as far as i'm aware.