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LIPO 4S Battery Cell 4 Not Fully Charging


Jackal
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The DNA250C board display only shows "77%" battery and will not fully charge cell #4 (cells 1-3 fully charged with cell 4 about .2 below others). Escribe shows cell 1-3 having the same charge and discharge rate, while cell 4 is off by about .2 volts when fully charged and off by .2-.5 when at zero charge. Not sure why cell 4 is not fully charging and not allowing the display to show or 100% charge all batteries. Enclosed is a screenshot at 3%. At 77% cell 4 shows about 3.98 volts and will not get to 4.2 like cells 1-3. The battery is a Turnigy 1600mAh 4S 20C Lipo Pack (https://hobbyking.com/en_us/turnigy-1600mah-4s-20c-lipo-pack.html)

All help appreciated!
 

dna250c batteries at 3 percent 30 JUL 18.jpg

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Does the battery plug into the device or is it soldered in?  If plugged in an you check the voltage of each cell with a meter when unplugged and fully charged?  Could cell 4 be failing and has the battery started to swell?  Have you ran the device in Power Supply Mode with battery pack plugged in also?  How old is the battery?  

Have you tried the USB Battery Recovery  Charging function?

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retird, thanks for your quick reply!

The DIY mod shown below has the battery and charge balancers connected via  connectors to the DNA250C board. Multimeter test confirm the voltages measured by the board are accurate. Not sure if cell 4 is failing but do not see any noticeable swelling. Have not tried (1) power supply mode with  battery pack plugged in, and the battery was only purchased on June 20. Have not tried (2) USB Battery Recovery  Charging function. Will read about functions (1) and (2) and see if this helps, and post results. At the end of the day, cells 1-3 show 4.2 while cell 4 only shows 3.98 when display shows 77%, so it is not the end of the world. How do functions (1) and (2) help troubleshoot the noted problem?

Cheers!

Jackal

 

dna250c mod.jpg

Edited by Jackal
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I had a 3 cell that just wouldn't balance so I used a juice bottle with wire taped to it's ends and placed in an 18650 charger. The leads from the bottle are plugged into the respective  ports of the JST plug on the pack for the low cell. While it looks "Mickey Mouse" it worked quite well.

While it appears that the "T" connector  here is being used, it just looks that way, it is not used here.

 

charging low cell.jpg

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dwcraig1, thanks for the charging tips! Will try that as last resort, as the mod has barely enough room for the components and dread having to pull the battery just to charge the cell that is only off by 0.2 volts. Did that above charging scheme fix the mischarged cell for you long term?

Cheers!

Jackal

Edited by Jackal
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If you leave it on USB charge when it appears finished it should eventually balance on it's own, it will take awhile though (couple of days maybe.

The problem with mine was juice under the JST connector on the board causing the cell to slowly drain while just sitting. So as it balanced it also un-balanced later again.

If it's working OK I would just let it go at least a few days, as long as you don't have a draining problem as mine it should eventually correct it's self.

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USB recovery charge is for when the cells are below some where around 2.5 volts and the charger will not charge. USB recovery will let charger start slowly under that too low of voltage condition. So I doubt that it's doing a recovery charge, probably just charging/balancing.

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It would only let the mod still work if it had a problem with the built-in charger/balance circuits, example: 1 cell said .1 volts and all others were 4 volts but you knew that the one that said 0.1 was really 4 volts. The mod under this condition would stop working because it sees a battery problem with a cell. Power supply doesn't use the JST plug so it would let it work.

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Thanks again! I cleaned the mod with alcohol in case of any discharging due to flux, etc., and will see what happens. As a side note, the USB recovery charging or load balance charging may be working per below picture, as voltages are starting to slowly converge.

Cheers!

Carlos

dna250c batteries at 27 percent 30 JUL 18.jpg

Edited by Jackal
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9 hours ago, Jackal said:

retird, thanks for your quick reply!

The DIY mod shown below has the battery and charge balancers connected via  connectors to the DNA250C board. Multimeter test confirm the voltages measured by the board are accurate. Not sure if cell 4 is failing but do not see any noticeable swelling. Have not tried (1) power supply mode with  battery pack plugged in, and the battery was only purchased on June 20. Have not tried (2) USB Battery Recovery  Charging function. Will read about functions (1) and (2) and see if this helps, and post results. At the end of the day, cells 1-3 show 4.2 while cell 4 only shows 3.98 when display shows 77%, so it is not the end of the world. How do functions (1) and (2) help troubleshoot the noted problem?

Cheers!

Jackal

 

 

Function 1 was just a question as to whether you used a power supply while the battery was installed....

I thought Function 2 was worth a try and may recover the battery cell 4 , maybe not.... but worth a try I thought...

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retird, thanks for clarifying. The USB recovery charge did not work. Cell 4 is still off by .2 volts. Will try leaving it on USB charging to see if it will eventually charge up or try single cell charging as previously suggested. May also try to reflow solder connections on the board if cell 4 will not charge.

Cheers!

Jackal

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3 minutes ago, dc99 said:

I have the same issue with a 3S pack. Why do they never say 100% charge?

It seems that the lowest cell of the pack determines the percentage charge shown, so if one cell is low, the percentage will be low, and you may have to charge that cell separately to balance the pack . A bad connection on the board could cause a cell to not charge and discharge properly,  and this may be the problem with my mod.


Cheers!

Jackal

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18 minutes ago, Jackal said:

It seems that the lowest cell of the pack determines the percentage charge shown, so if one cell is low, the percentage will be low, and you may have to charge that cell separately to balance the pack . A bad connection on the board could cause a cell to not charge and discharge properly,  and this may be the problem with my mod.


Cheers!

Jackal

I really dont want to take this battery out but if I have to so be it. I left it on charge to see if it would balance itself. Its a brand new battery so it was shipped a little off. Batt 2-3 will get to 4.2 and keep backing to 4.198-4.199 and battery 1 is at 3.946. It did go up to 71% from 70

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Yeah, mine was only getting up to 77% because of the unbalanced cell. Ran battery analyzer now that all cells are fully charged and will monitor cell 4 to see if it is misbehaving. Part of my problem is this was my first mod and the solder joints probably suck. After running the battery analyzer, all cells are now balancing. The weird thing is that the battery curve the analyzer generated sets 0% at 3.9 vdc and 100% at 4.18 vdc.


Cheers!

Jackal

Battery curve 31 JUL 18.jpg

dna250c batteries at 13 percent 31 JUL 18.jpg

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