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02-07-2011, 08:51 PM
| #1 |
| Quarry Creeper Join Date: Jun 2010 Location: Elk Grove
Posts: 225
|  3s lipo cell balancing concerns
Here's the scoop, I balanced charged my 3s pack before I left home, got to the course and ran for maybe 5-10 tops. The rig started to lag almost like the motor was stalled, put it on flat ground and it just slowwwwwwly rolled a foot or two then stopped, I thought LVC had kicked in. I grabbed another pack and threw the offending pack on the charger, the cells measured 2.80 3.67 2.80  , I got home and slow discharged the pack to to 9v the chargers auto 3s setting, then I balanced charged it back to capacity. The cells now show there normal voltage and are within .01 volt of each other. Any ideas on what occurred?
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02-07-2011, 09:00 PM
| #2 |
| owner, Holmes Hobbies LLC   Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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You over discharged the pack. The cell at 3.67 probably has a few mah more capacity than the other two, so it didn't crash as hard and managed to bounce back a bit after you unplugged it.
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02-07-2011, 09:10 PM
| #3 |
| Quarry Creeper Join Date: Jun 2010 Location: Elk Grove
Posts: 225
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That was my concern, I run a BEC to power my receiver since my MMP has no internal BEC. I will assume that the dig and steering servo consume juice that the MMP LVC can't account for, but shouldn't the LVC shut things down one the preset is reached, regardless of which device has consumed the power? I understand if I was to cycle my dig or steering until the point of being overcharged, but I was driving the rig as usual. What should I have the MMP cutoff at? I haven't ran the pack after balancing it when I got home, since it charged ok, would you say its still good? Thanks for the help.
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02-08-2011, 05:11 AM
| #4 |
| RCC Addict Join Date: Jul 2009 Location: reelsville
Posts: 1,871
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The ESC reads total pack voltage, so it was within reason. My guess is your battery isn't passing enough amps for your setup and two cells are now trash from overdischarge. The BEC has nothing to do with it.
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02-08-2011, 01:09 PM
| #5 |
| Quarry Creeper Join Date: Jun 2010 Location: Elk Grove
Posts: 225
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Would dead cells take a charge then? When I slow charged the pack, all cells came back up as normal. Everything I have read says a dead pack wont charge, I'm prepared for decreased capacity if it does hold its charge, I just want to make sure I don't have a mishap while its in the rig. Can a battery have a catastrophic failure while not being charged, ie: burst into flames while being ran?
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02-08-2011, 02:03 PM
| #6 |
| owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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The low cells may have some capacity damage. Just keep an eye out for heat during charge or discharge. Charging is generally the dangerous part. |
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