Care and charging of LiPo batteries in heated gloves

[Zambam]

I bought these heated gloves on Amazon and been happy with them so far. On low, which keep my hands comfortably warm, they run for a little over 5 hours before shutting itself off. How long should I run these before I charge the batteries? When I do charge the batteries, should I let the charger run till the red LED on the charger turn green indicating a full charge, or should I stop charging at 80% to prolong battery life? I can take voltage measurements to determine state of charge of the batteries.

I have one data point so far:
Full charge = 8.4 V
Run for 4 hours on low = 7.14 V or 3.57 V per cell

I will run them till they shut off and take another voltage measurement to see if LVC is set to a safe level (which I believe is 3.2 V for LiPo ?).

 

[Zambam]

With a full charge, I ran one glove on high till it shut off at 2 hrs 43 min. Measured the voltage and it was 0 V! Battery was not warm to the touch when it was running or when it stopped. I am guessing the "smarts" in the battery has cut off the output and that's why I measured 0 V. If the battery really was discharged down to 0 V, I would have had a fire no?

I'm going to wait till tomorrow, take another measurement. If still 0 V, put it on the charger and see what happens.

 

[Zambam]

Woke up this morning anxious to see if if I ruined the battery or not. Took another measurement, still 0 V. Plugged it into the charger, went to make coffee, 4 min later measured 7.0 V. Whew didn't kill the battery! So there's some smarts in the system.

Is this article on LiPo batteries credible? How to Prolong Your Lithium Polymer Batteries | Battery Monday

 

[circuitsmith]

Thankfully, virtually all commercial lithium-ion batteries have protection circuitry, so output was cut to 0V.
Might have cut off at 3.2V per cell under load, but then rises to 3.5V when load removed.
The linked article is pretty good. Here's another:

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

 

[eMark]

With a full charge, I ran one glove on high till it shut off at 2 hrs 43 min. Measured the voltage and it was 0 V! Battery was not warm to the touch when it was running or when it stopped. I am guessing the "smarts" in the battery has cut off the output and that's why I measured 0 V. If the battery really was discharged down to 0 V, I would have had a fire no?

Maybe not a fire, but a warm battery depending on the rate of discharge.

More likely scenario is that the BMS shutdown occurred around 6.2V (3.10V). Then figure actual bounceback resting voltage at say around 6.3V NOT 0V. The BMS disconnect resulted in a 0V reading; however the actual bounceback resting voltage was say closer to 6.35V . For example it's possible the BMS won't indicate actual battery voltage until at least say 6.4V (after shutoff).

Woke up this morning anxious to see if if I ruined the battery or not. Took another measurement, still 0 V. Plugged it into the charger, went to make coffee, 4 min later measured 7.0 V. Whew didn't kill the battery! So there's some smarts in the system.

After JUST 4 min on charger measured 7.0 V. That's an increase from say 6.5V to 7.0V; which might be possible with a 2-3amp charge rate after only 4 minutes. Anyway it's impossible for the actual resting battery voltage to be charged from 0V to 7.0V in JUST 4 minutes. If the actual resting battery voltage was 0V you would get a fake floating charge voltage reading. One that's not sustainable as the floating voltage will quickly recede after removing the charge. Also, when trying to regenerate such a low battery voltage you'd use a trickle charge e.g. 0.3V to see if the battery will even take and hold a charge after 1-2 hrs.

Suggest charging your gloves' battery somewhere between 85% to 90%. Then discharging to 6.70V for prolonging cycle life ... instead of draining battery to BMS cutoff voltage.

 

[Zambam]

Thanks for the replies. I'll be changing my charging method by incorporating a timer to shut the charger off at between 80 to 90%. Will also do this on my ebike battery. Running the batteries till they no longer run was just a test to get an idea of when to stop using the heat on the gloves and put it on the charger.