Balance charging is incredibly slow!

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Don
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Balance charging is incredibly slow!

I've been charging six 18650s of identical capacity, but varying state of charge for ten hours now! Last time I looked the voltages were within a few millivolts of each other. It might be interesting to see what voltage they all come off the charger at and how well or otherwise they maintain it. Which might give some idea as to condition of the cells.

 

For routine use, I think I will be going back to charging them in parallel, especially for single cell lights where cell balance is irrelevant. It is a lot faster.

 

By setting the charger to maximum rate charge I can charge as many cells as I can fit on top of the cooker at once at 5 amps divided by the number of cells I'm charging. I can fit about 12 between a pair of 30cm steel rulers (I use magnets to stick the cells to the rulers). From stone dead that should get me 12 fully charged cells in about half the time the balancing is taking. Balancing only really matters in multi-cell lights.

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...

Don
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And I still got a variation of 16mV between the highest and lowest voltage. This may well be covered by the accuracy of the meters used or the varying conditions the cells have been exposed to - though they were all bought at the same time and I do try to take care to rotate them.

What was that charger doing for all those hours?

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...

agenthex
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If the cells started at different level, it might take forever to balance them. I thought these things worked by stopping CC charge when the first battery hits 4.2v, and then it does CV until they're all level?

Reading this makes you smarter: http://lesswrong.com/

Don
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I don't actually know what it is doing - should probably stick some datalogging meters across a few of the cells to see if that shed any light on it. Another set of six now running that ought to be pretty evenly charged - I'll be interested to see what happens, and when. It has now been running for just under 2 hours and has stuck in only 390mAh according to the charger.

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...

agenthex
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Wouldn't CC rate depend on what charger you use and the current setting?

 

I've also seen claims that some chargers actually discharge individual cells through the balance leads for faster charging rate overall.

Reading this makes you smarter: http://lesswrong.com/

Don
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Second set of six tried - they took about 5 hours from discharged to storage level which appears to be about 3.7V on this charger. Slightly mor consitent voltages off the charger too: 4.184 to 4.194V.

 

The CV part of the charge is never fast, whether single cell or multi-cell. According to the charger it regards anything less than about 50mA (Would need to stick a meter on it to see) as zero current.

 

I must remember to check voltages before batch balancing them in future.

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...