Rocker Posted February 6 Share Posted February 6 Have a 6 s 4000 lipo and the charge gets to 99% but one cell is 4.18 and the other cells are between 4.19 and 4.2 The charger does not show fully charged but carry on charging but the charge rate is 0.0.What is going on ? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 6 Share Posted February 6 It sounds like your charger is just taking a long time trying to balance the cells. It won't want to put much charge into the pack and risk overcharging the fully charged ones so it will be discharging them slightly and putting in energy at a very low charge rate in between. All you can do is let it work for an extended time - or perhaps try another charger which may be less conservative... It may be a sign that the cells are getting past their best though. 1 Quote Link to comment Share on other sites More sharing options...
Brian Cooper Posted February 6 Share Posted February 6 When a cell (or two) doesn't reach its cut-off voltage, it is usually an indication of the cell being past its useful life. Leaving the charger running for few hours to balance the cells might bring the "moody" cell back up to the correct voltage but it will only collapse again after the next usage. Changing the old battery pack for a new one will give that "woo-hoo" factor which will highlight how tired the old pack had become. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted February 6 Share Posted February 6 It's probably better not to charge to 4.2v/cell anyway in the interests of longevity. Set your charger to 4.15v/cell. Was the pack balanced before the charge and what's the internal resistance of the cells (if your charger offers the option of measuring it)? If the cells are over 10 milliohms each, then they're probably past their best, but it depends on how hard you're pushing the output current if that's really an issue. You may have opted for a high voltage pack to keep current low for the power you need. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 6 Share Posted February 6 The other possibility is the balance plug into the charger. We are taking measuring 1/100 of a volt so just a slight resistance on one balance pin will seriously upset the chargers balance cycle at the very end of the charge. I have had exactly the same happen a few times with a couple of cells "stuck" at 4.19 and the charger showing zero charge tate. Give the balance plug a little jiggle and surprise, surprise after a few seconds the charger switches off indicating "full charge" with all cells showing 4.20. 😊 1 Quote Link to comment Share on other sites More sharing options...
Philip Lewis 3 Posted February 6 Share Posted February 6 35 minutes ago, Simon Chaddock said: The other possibility is the balance plug into the charger. We are taking measuring 1/100 of a volt so just a slight resistance on one balance pin will seriously upset the chargers balance cycle at the very end of the charge. I have had exactly the same happen a few times with a couple of cells "stuck" at 4.19 and the charger showing zero charge tate. Give the balance plug a little jiggle and surprise, surprise after a few seconds the charger switches off indicating "full charge" with all cells showing 4.20. 😊 Now THAT is a very good point, haooens to me frequently, especially it seems in damp weather conditions. 1 Quote Link to comment Share on other sites More sharing options...
Rocker Posted February 7 Author Share Posted February 7 Thanks everyone .Did check the balance lead jiggle it about and Bingo ,problem solved 👍 2 Quote Link to comment Share on other sites More sharing options...
RedBaron Posted February 7 Share Posted February 7 If you measure the Internal Resistance of each cell with an appropriate measuring device I feel pretty certain that you will find that IR of the difficult cell will be rather higher than the other cells. Trying to balance the charge will not really solve the issue as the chemistry is not really reversible. When a cell starts increasing its resistance out of line with the others it is time to think about a new LiPo. 2 Quote Link to comment Share on other sites More sharing options...
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