SMC Lipo cells won't balance out?

[DoNoHarm]

When you drain a pack to 0 volts, no matter how slow you do it, it will always go high resistance. Just because of instability. Here’s a video demonstrating this (it’s not a fully drained lipo just understand the principle)

 

[Wheels007]

What charger do you have?

I use HTRC T240 DUO AC 150W DC 240W 10A Touch Screen Dual Channel Battery Balance Charger Discharger. Thankfully over the lifetime of my batteries, none have puffed or lost their shape.

 

[jkflow]

It's an ok charger but don't think you can adjust the end voltage.
I'd just take them off when it starts doing the balance thing. Give it 10 min after it reaches full charge just for good measurement and you should be fine.

I take my Lipo's to a battery place, fully discharged and wires crossed.
Throwing them into the trash is dangerous. The lithium will react rather violently with water, if that happens in the trash truck, it could start a fire.
Any decent place that sells batteries should take them but then again, haven't been doing it in ~5+ years.

 

[arrmadillo]

On one of our beer night weekend runs, a friend had a 2S pack he wanted to get rid of, so I found a nail in the parking lot and pierced it on the ground. Guess what happened... nothing, no smoke, fire, nothing. Left it there all night until we left and threw it in a trash can. For now on I will just shoot them with a .22, pyromaniac in the house!

 

[Wheels007]

It's an ok charger but don't think you can adjust the end voltage.
I'd just take them off when it starts doing the balance thing. Give it 10 min after it reaches full charge just for good measurement and you should be fine.

I take my Lipo's to a battery place, fully discharged and wires crossed.
Throwing them into the trash is dangerous. The lithium will react rather violently with water, if that happens in the trash truck, it could start a fire.
Any decent place that sells batteries should take them but then again, haven't been doing it in ~5+ years.

It has an adjustable end voltage.

 

[Wheels007]

Adding to my original post since it's somewhat related. Quick IR ohm question. When the battery is depleted and I plug it in, the ohms were 4, 5, 4. After it's charged it said 8, 10, 9. So which readings to I go by for accuracy?

 

[jkflow]

Technically important, this is in milli-ohm, not Ohm, factor of 1000 difference. You can use that value to calculate your true C spec of the pack.
(max current = voltage/(R1+R2+R3) for your 3S 12.6V/(.008+.01+.009)= 466Amps Take it with a grain of salt as this is theoretical and you charger is only giving an equivalent IR. Not added are loss in the wiring and connectors. If this is a 5000mAh pack this would be 466/5 = 93C. This is typically how manufactureres come up with the value and doesn't relate well into reality.

Which value to pick? To determine pack health, makes no difference as long as you are consistent. Resistance does change according to charge level i.e. what you are seeing is normal. Pick the value at the same voltage level all the time.

The values should be less than 20% of each other for a healthy pack i.e. pick the middle value and add/subtract 20% and the pack is still 'good'.
Bigger variations result in unbalanced discharging, packs are dangerously unbalanced whne they differ by 100% but anything above 20% will typically deteriorate fast.

For you, 9 mOhm +/- 1.8mOhm gets you between 7.2 and 10.8 i.e. you are good.
With our chargers, you simply can't be all that accurate though. When it 'measures' 8mOhm is could be anywhere between 7.6 to 8.4. Don't use it as a bible, just as a good sanity check.