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Thread: Uneven Cell Discharge - SMC 3S Lipo

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Old 06-12-2019, 06:05 AM   #21
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Default Re: Uneven Cell Discharge - SMC 3S Lipo

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Originally Posted by Voodoobrew View Post
The cell that is always low probably has a higher internal resistance, that would cause it to lose power faster. If you have or know anyone with a battery internal resistance meter i would say check that, its good information to report back to SMC with.



My charger has this function and works well.

Ive noticed on many SMC packs cell 2 is a bit lower during high drain( not crawling but in the yeti)

I was told this is due to heavy discharge rate and cell 2 usually drops a bit more. But matched resistance will tell you individual cells resistance. Ive never seen this in my crawlers though. I do set my lvc at 3.4v
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Old 06-12-2019, 10:43 AM   #22
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Default Re: Uneven Cell Discharge - SMC 3S Lipo

A cells being mismatched is just them being cheap and not matching them before assembling. Something I expect and tolerate with my $10 packs, not $100 packs...

It's not rocket science, it's chemistry.
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Old 06-12-2019, 02:40 PM   #23
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Default Re: Uneven Cell Discharge - SMC 3S Lipo

I ended up ordering 2 lipo alarms. He's gunna set the alarm to 3.6V and run the battery down to see where cell 1 and 3 end up when cell 2 hits 3.6V.
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Old 06-14-2019, 09:24 AM   #24
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Default Re: Uneven Cell Discharge - SMC 3S Lipo

even lipos have lifespans of ~400 charges I believe.


it's fun to use a pellet gun or .22 on a charged but bad cell pack.

watch the smoke and flames to learn dangers of Lipo fires!
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Old 06-14-2019, 09:55 AM   #25
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Default Re: Uneven Cell Discharge - SMC 3S Lipo

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Originally Posted by CodeEzra_RC View Post
My friend got a response back from SMC and they are willing to refund if he returns it but still sees it as a non-issue do to the small variance in a cells mAh capacity and IR.

Ill agree on the theory but I would assume a .4-.6V ending discharge difference would indicate a substantial difference in Cell 2's IR versus the others.
Send it back and get the refund, buy a different brand lipo.

IR testers are cheap, many chargers now have this feature.

Quote:
Originally Posted by mikemcE View Post
My charger has this function and works well.

Ive noticed on many SMC packs cell 2 is a bit lower during high drain( not crawling but in the yeti)

I was told this is due to heavy discharge rate and cell 2 usually drops a bit more. But matched resistance will tell you individual cells resistance. Ive never seen this in my crawlers though. I do set my lvc at 3.4v
Poorly matched cells and/or meh quality cells.
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Old 06-14-2019, 10:27 AM   #26
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Default Re: Uneven Cell Discharge - SMC 3S Lipo

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Originally Posted by CodeEzra_RC View Post
Good Afternoon Folks,

A friend of mine recently purchased a True Spec Premium 3S battery from SMC for his stock TRX-4.

He is experiencing some oddities with this battery pack. After running a full balance charge and running the truck there is quite a difference in cell voltage.

Once LVC kicks in, he'll let the pack cool, and hook it up to his Hota charger.

Every balance charge and discharge cycle, Cell 2 is always sub 3V.

I told him to reach out to SMC to get their input and they told him this is not a fault battery, pointed out the stock ESC's lipo cutoff, but suggested that he get a lipo alarm, set the cutoff to 3.6V, and see where all 3 cells end up after the next discharge.

I suspect he is going to see Cell 2 at the cutoff value and Cell 1 and 3 much higher in voltage.

Personally to me, this sounds like a bad cell from the factory and I dont see how the ESC would possibly be pulling more power out of Cell 2 but I'm still quite new to the RC/Lipo game and wanted to collect ya'll input on the matter while he awaits the delivery of the lipo alarm.

Thanks!

I would invite your friend to join us here on RCC!
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