Ping signalab BMS 16s to 15s - how?

J

joelh

10 µW
Joined
Sep 13, 2017
Messages
6
Hi guys, this is my first post and I would very much appriciate some guidance

I have a ping 2.5 48v10ah battery since two years back and one cell-group (two 5ah cells/tabs) has gone bad only measuring 0.6 v . I have openened the battery and managed to remove the two cells with the help of dnmuns instructions in earlier posts. But now I would like to use it as a 15s pack instead of 16s. But I have no clue on how to hack the signalab BMS to work as a 15s. As I understand it it needs to be hacked. I still want the lvc to function for the 15 remaing cellgroups. I know its possible to lower the voltage of the charger so that shouldnt be a problem but what about the BMS?

Here is a picture of the signalab bms. Which row should I focus on and what to solder/desolder?
https://photos.app.goo.gl/5tBgg9ChX4qvLgDF2
 
This topic is about modding the BMS, but you'll have to ask Swbluto if he can repost the images as they seem to be damaged or missing.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=8342

You may be able to use it without modding the BMS, but you'll have to shift the sense wires "down" toward the negative side, so that there's no "gap" between the cells.

Meaning, if the bad group was the 14th group up from the main battery negative, you'd need to unsolder the balance wire that was on the 15th group, and then solder the one from the now-missing 14th group to the 15th. Then do the same for the 16th (using the one formerly on the 15th for it). Then the 16th wire just gets taped off and not connected.
 
Nobody ever posted the pictures and instructions that explained the 16s->15s mod well enough for me to do it on my early Ping BMS.

Posting pictures of your board may help. Good luck.
 
Thanks! I will start by just changing the order of the signal wires and se if that works. Im also considering only using the bms for charging and use cheap lipo alarms/buzzers when riding. The alarms can be set to 2,7 v and if I hook it up to he weakest cell group it should be enough
 
A 16s BMS would have 17 wires going to it. The main + and - wires might be one of the 17. Starting at B-, I count the cells up toward the positive side, so if you have 15s, number 15 will the the positive most cell.

To reduce the cell count, tie together the wires for the top two cells and run that to cell 15. You can probably make this work all the way down to 4s.
 
Thanks all for the great assistance! I contacted Ping and he responded quickly and gave me instructions on how to diagnose the problem. His suggestion was to replace the bad cellgroup since this is probably the easiest way and will get me the most power but since I dont need all the voltage im trying the 15s solution instead.
 
I have to agree with Ping. You may need a new charger if you drop one cell group off. Plus the V2.5 BMS gets its power from just four cell groups and if one of those cell groups is the bad one you will have to figure out how to rewire that part of the BMS also.

I think Ping quit manufacturing the V2.5 batteries in mid 2014 so no matter what you do the battery is already over 3 years old.

Good luck with your project however you do it.
 
If you go to 15s, then you would need a new charger or need to adjust the one you have to a lower voltage.
 
It seems another cellgroup might be under-performing so I have tried a 14s setup. Connecting chanel 14, 15 and 16 from the BMS to the 14th cell on the battery. It seems to charge alraight but the LVC on the BMS seems to cut out the main voltage output from the battery most probably becauase chanel 15 and 16 is reading 0 v. Any ideas how to fix that?

I managed to lover the voltage of the charger from 59 to 54v but that seems like the lover limit. I gues the desired voltage from the charger should be 51-52 volt for a 14s lifepo4 pack? any ideas how to go ahead?

For future reference its the trim pot in the red circle that change output voltage:
https://photos.app.goo.gl/rD7MftXdmOadFUbk1

The charger is a kp4802wl
 
joelh said:
Connecting chanel 14, 15 and 16 from the BMS to the 14th cell on the battery.
Click to expand...
Why connect them together? If they're unused, leave them unconnected.

If that doesn't fix it you'd need to disconnect the outputs of their LVC comparators from the BMS FET gate control. There are some at least partial schematics of the Ping BMSes around ES, but it will probably take some poking around to find them.

Ping himself posted a way to do this at some point, so I'd check his posts first.
 
amberwolf said:
joelh said:
Connecting chanel 14, 15 and 16 from the BMS to the 14th cell on the battery.
Click to expand...
Why connect them together? If they're unused, leave them unconnected.
Click to expand...

You could try that, but when I tried that in the past, the open wires would pick up noise when the motor was running and false trip. In the typical BMS, you need at least 1.5v or so to trigger the cutoff. If you tie the wires together, they have zero volts and can't activate the trigger. On more advanced designs, the BMS will detect wiring faults and trip. On these, there is usually a jumper at the chip to set the cell count.

I think it should work with the unused channels tied together. Measure all the cell voltages and make sure there aren't more bad ones.
 
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