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Cell levels;6S Lipo


Basil
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Just charging my first 6s Lipo. The cell levels that are acheived are 98%.100%,95%,100%,100%,100%, been on charge for some while and they seem static; @ Winter room temp,19deg appx

Are these levels the norm or should they be all 100%, if there is generally a difference what sort of level would you expect.

bas

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Do other batteries balance out on your charger correctly?  Perhaps the charger isn't calibrated correctly but I'd have thought that the program would only terminate once readings hit 100% on all cells.  Do you have access to a DVM to check the individual cells via the balance lead?

 

If the cells are a long way (5% is a lot) out of balance, it may take a number of hours to equalise them as it's a slow process due to avoiding overcharging the full cells. To be honest, I would be questioning the imbalance with the supplier.  Can your charger tell you the IR of the cells - variation would be a good indication of a poorly matched pack.

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It may be a good idea to cycle the pack a few times. Also get yourself a battery doctor. Mine lives with my batteries and is incredibly useful for checking individual cell voltage at the field or balance and discharge to storage if needed. 

 

https://www.addlestone-models.co.uk/cgi-bin/sh000001.pl?WD=battery doctor&PN=ETRONIX-BATTERY-DOCTOR-ET0500-LI-PO-LI-FE-BATTERY-BALANCER---DISCHARGER---METER-ET0500.html#SID=40

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I agree voltages are far better than %.

 

Be careful of Lipo checkers.

I have one which I have seen under numerous brand names.

I tested one of my slightly defective lipos with the my checker and it came up as a 4S Nixxx battery with very poor voltage.

When placed on my Toolkit charger, it showed one cell defective and 2 cells with semi OK voltages.

Upon lightly squeezing the lipo, the defective cell came back to life on the charger although below 3v.

 

Lipo has since been discharged prior to disposal as I would never trust this lipo in use.

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Basil

Even a battery cell capacity checker is actually measuring cell voltages and 'interpreting' the values into capacity..

A good charger should take time at the end of a balance charge cycling around each individual cell until not only is it at exactly 4.20 V but that it holds that voltage for a short time when off charge. The charger should then stop and the battery is considered to be at 100% of the available capacity. What ever that may be. ?

 

I suspect if you have a checker giving only 95% full that cell will not be at 4.20 V so the balance charge will continue until it is or the charger timer stops the charge.

If you charger does not do this sort of thing I would strongly suggest you get one that does.

Even the cheap 'clone' I MAX four button charger does.     

Edited by Simon Chaddock
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Bear in mind that the voltage of each cell is measured by a different bit of circuitry (voltmeter) in the charger. The balance charging circuit depends on these different "voltmeters" being uniformly calibrated to be able to uniformly balance the cells. If any cell voltage is being under-read compared with others the charger will try to over-charge it or if the time limit is reached that cell will show a lower voltage than the rest.

Best check & compare the cell voltages individually with a DVM.  

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Run the battery down a bit, to say around 4v per cell, and then balance charge it at a low charge rate, say 0.2amps. In balance mode chargers balance the cells by reducing the current on the high cells by 100 to 200 ma, so if you are charging at a high rate the balancing is only a very small percentage of the charging and only catches up when the battery is very nearly full, charging at a low rate allows the low cells to catch up without the high cells getting any charge.

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My charger is a Turnigy Reaaktor T-240. I am aware that the temperature of the battery is important.It had been in my workshop so I did allowe a couple of hours to reach room temp.

After I made the posting I decided to charge and discharge the battery a little. Due to its size and capacity I also theorised that it should be allowed 20/30hours indoors to come to room temp. So did some discharge and got all the cells down to 93%, then charged until the low cell started to drop down below the rest from memory ca 96%.  Did this a cuople of times. Waited the 24+ hrs and did the same again, then charged this time they all got to 100%. I assume due to its shear bulk that it needed time to get to room temp  .So many replies I will need some time to digest them. Many thanks to every one.

I presume the Battery Doctor is a battery capacity checker. I have one , made in China, like many others, so I presume may be of dubious quallity therefore may not be accurate.Was this your Battery Doctor LHF, or does yours offer something more?.

Bas

Edited by Basil
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We all want to know what our packs are doing Bas,

And that we have been sold the best, but at some point store them until you use them.

Not 6 cell in my case, but am certain I tested the life out of one 3 cell pack in the past.

I never quite got 100% and only succeeded in going lower and lower over the season.

The number of cycles I did, I am sure added to its demise.

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There is little tangible benefit in endless cycling for testing purposes - best to use the packs and monitor the key data - IMO it's best practice to monitor the individual cell voltage after each flight and I also routinely check it before each flight. Personally I've never noted, looked at, or considered the percentage charged -for me it's the measured voltage that matters -introducing the display of that information as a percentage is just making a completely unnecessary interpolation of the data, probably assuming a simple linear relationship. Whilst there is undoubtedly going to be variation in the absolute accuracy of the meters and battery checkers in use, you are really looking for changes in the values and any trends which might illuminate deterioration of your packs. The Reaktor chargers display the individual cell voltages during and after charging with a single press of one of the buttons.

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For comparison, nothing replaces using a DVM to check - otherwise you’re subject to the vagaries of mass produced chargers. I spent some time calibrating my ISDT charger (it offers this facility) to ensure that it actually balanced packs correctly and although close, it did need a little adjustment. 
 

Subsequent checks have indicated that the calibration has remained valid. 

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My name is Mark, and I am a LiPo abuser.

 

When I get a new plane/pack, I have a couple of flights to see where I should set my flight timer, then pretty much ignore the packs after that.... I shove them on my chargers until they beep, them fly until my timer says stop, then take them home.  Then repeat.  I only check them if they start to obviously deteriorate or become puffed.

 

I don't lose many packs even abusing them this way. 

 

But, I don't have any packs above 4S, and none of my planes need optimal performance, or push the packs overly hard.  My little edf packs are probably the hardest worked but they have lasted hundreds of cycles - so far.

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Grumpy, I needed a large LIpo but ordered incorrectly, so I am stuck with them.It's good to get a view on their use from another user.  I think my problem was that they were so cold and the normal couple of hours was not enough time to warm up.After all they are so bulky. Thanks

Bas

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On 04/01/2022 at 21:08, Andy Gates said:

 

 

Be careful of Lipo checkers.

I have one which I have seen under numerous brand names.

I tested one of my slightly defective lipos with the my checker and it came up as a 4S Nixxx battery with very poor voltage.

When placed on my Toolkit charger, it showed one cell defective and 2 cells with semi OK voltages.

Upon lightly squeezing the lipo, the defective cell came back to life on the charger although below 3v.

 

That is clearly a broken lipo issue, not a suspect checker issue.

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I use an Excel workbook for keeping most of my modelling data, but it's manually collected, I don't connect meters or chargers to the computer or anything as advanced as that. I just run a worksheet in there to monitor my packs, though the data is incomplete- I didn't record when I put some packs into service - I also haven't kept a tally of how many cycles they have on them- I did start, but when my first large packs failed after half-a-dozen flights I stopped. ?. I j do keep an eye on and a mental note of the cell voltage before and after each flight to detect any anomalies. Every now and then, I'll go through and measure the cell voltages and put that in the workbook, and look for any signs of puffiness or damage etc.

Here's a snapshot of a corner of the spreadsheet -it's much bigger than this, but would be unreadable - I've set the conditional formatting to highlight the state of charge of each cell -ideally you would want the same colour across all the cells, if any one or two cells departs too much it should stand out and warrant taking some action- like that 5s1p pack in Row 23.

lipocellvoltages.thumb.JPG.45b80237aebfb9560c597db53cb727b5.JPG

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