Eboard drastically discharging on it's own

[mfkubak]

Hello,

I've been riding my new board for a decent chunk of the summer and still getting a few rides in during the fall. However, as of late, I have noticed that my board dies at a much sooner voltage than it used too.

Quick Specs:
6S - 5000mAh (6 separately wired batteries, not in packs)
60A BMS
260kV motor
FVT ESC - set to a 3.2V cutoff voltage

For more info, check this link of my board build:
https://endless-sphere.com/forums/viewtopic.php?f=35&t=81540

About a month and a half ago, my board would regularly die at 20.9V. A few weeks ago, it died at 21.9V. A few days ago, I recharged it and when I check the volt meter on my board, the batteries had discharged from 23.9V to 23.5V, then down to 23.0V, then to 22.2V, then 21.9V, and is now remaining at 20.7V... all within a day of no use.
I have no idea what is causing this.
Could I have overcharged my batteries, causing them to discharge on their own?
The BMS supposedly has overcharge protection:
http://bestechpower.com/222v6spcmbmspcbforli-ionli-polymerbatterypack/PCM-D149V1.html

The charger that I use has a red light for when it's charging and it turns green whenever it's been fully charged. I've only seen the light turn green once after charging, and it was about a week or 2 ago. I've always been afraid to let it keep charging as I was afraid of overcharging. I would stop it at 23.9V or 24.0V. It turned green at 24.7V.

I checked all the connections and it all appears to be fine.

If anyone can give me an idea as to what might be going on, I'd really really appreciate it.

Thank you so much,
Mateusz

 

[mfkubak]

Bump
Any thoughts?

 

[Ianhill]

There's got to be a fault with the BMS I would have thought can you fully charge it then disconnect the BMS and just leave the cells stand so you can check that the battery's are OK then work backwards process of elimination ?

 

[mfkubak]

That's a really good idea. Once I get home tonight, I'll give that a shot.
If it is the BMS, then it'll be a simple swap to fix it. However, I hope to find out what caused the BMS to malfunction in the first place.

I'll update the thread once I give your test a shot.
Thank you!

 

[mfkubak]

Update:

After disconnecting the balance lead connector to the BMS, the board stopped discharging on its own.

However, after riding for about 15 minutes, the batteries died at 23.5V, instead of the usual 20.9V.

Does this mean my batteries are messed up?

 

[MagiicHat]

Do you have a maintenance/cycling function on your charger? Can help a lot.

 

[s28400]

Do you have an anti spark between the batteries and the motor controllers?

 

[mfkubak]

Do you have a maintenance/cycling function on your charger? Can help a lot.

Not that I know of. I checked the website specs (barely existed), and saw nothing on a cycling function.
But I will look into buying a new charger with such function if that turns out to be the problem.

Do you have an anti spark between the batteries and the motor controllers?

I do. I use anti-spark connectors along with torqueboards anti-spark switch circuit.

 

[Hummina Shadeeba]

thats a lot of energy to disappear. does something get warm or hot during the time it's discharging? the bms?

 

[s28400]

Disconnect the torqueboards anti-spark switch and see if it still discharges. I am currently having issues with my anti-spark switch where it gets stuck on.

 

[mfkubak]

thats a lot of energy to disappear. does something get warm or hot during the time it's discharging? the bms?

The only part of the board that get hot is the ESC which is directly under the heatsink. Both the batteries and the BMS do not heat up. But I don't see how the ESC could be causing discharging malfunctions.

Disconnect the torqueboards anti-spark switch and see if it still discharges. I am currently having issues with my anti-spark switch where it gets stuck on.

Your anti spark switch gets stuck on? What do you mean?

 

[mfkubak]

Also, I thought this would be important to mention...

I haven't been able to discover the root of the problem as I haven't had a chance to rewire the batteries directly to the anti spark switch to bypass the BMS.
However, I charged it up last week. It stopped charging after 24.5V, discharged fairly quickly down to 23.5Visit, then died.
After I got home I left it alone. A few days later, it discharged on its own, down to 21V and going
...
I'm stumped at this point. I'll continue to try and figure out what the problem is, but from what's been happening, I feel as though it has to be malfunctioning batteries.

 

[Hummina Shadeeba]

can you use a multimeter and check for current in different parts? find where the current is going.

 

[s28400]

Your anti spark switch gets stuck on? What do you mean?

The actual circuit won't turn off regardless what position the mechanical switch is at. It is a fairly common issue with this cheap style anti-spark switch. Try measuring the output from your anti-spark switch when it is supposed to be turned off.