Not sure what settings to use on battery charger/discharger

TheBikeMan

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Mar 23, 2018
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Hi,
I've got a SkyRC D100 V2 charger/discharger. I've set up a 4 cell and 6 cell testing trays wired in series.
So with the 4 Cell we have a maximum charge voltage of 16.8 Volts. The question I have is that each time I put cells in to charge them and then do a discharge test on them, the machine asks me how many amps I want to set if for and it is defaulted to 1.0A. I've left it at that for the charge though I think that 2 or 3 would be okay yea? And when I set it to discharge the batteries the maximum discharge amperage it will let me select is 2. I would think that since these are 3000mh cells that they should be capable of 3.0 drain or if they are 2c then even 6.0. Am I looking at this from the wrong perspective? Can I charge them at 2 or 3 amps and shouldn't I be able to discharge them at 3 or 6A?
 

soundwave

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May 23, 2015
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Charge Current Range - 0.1-10A
- Discharge Current Range - 0.1-5A

- LiPo/LiFe/Lilon/LiHV Battery Cell Count - 1-6S


you will have to go in to the settings as i bet its limited in there ;)
 

soundwave

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DSC_0566.JPG
depends on the cell holder ;)
 

soundwave

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if your just testing the cells just do it at 1a it takes forever but less strain on the cells.

more amps will just do it faster end result will be the same.
 

TheBikeMan

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Mar 23, 2018
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Thanks again Soundwave. My goal here is to test the fittness of the battery cells so that I know they are good enough to build into an E-Bike battery. I'm new to the cell load testing game and I just want to be sure I'm using a process that tells me that these cells are going to handle the load put on them by an ebike. Does the amperage setting when load testing make any difference to this?
 

wheeliepete

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Feb 28, 2016
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Testing cells in series groups is not really that helpful. If you get a lower than expected mAh reading from your discharge test, it will be impossible to tell which cell is low on capacity. It helps if you know the spec. of the cells you are testing to determine if they are suitable to build a battery pack for your bike. What make and model of cells do you have? Cells have differing loading ratings depending on their end use.
 

TheBikeMan

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Mar 23, 2018
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I have a mix of about 100 cells from old bike batteries. The tester that I using does have a plug so you can plug a BMS plug into it and it does measure everything by individual cell but the instructions were not that helpful when it comes to understanding what goals I'm asking it to produce to determine if a cell is good or not
 

wheeliepete

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Ok, so you have the balance lead connected to the cells and the charger to show the voltage of each cell. This will only show voltage and not the capacity of each cell. If you have a mixture of cells, only connect like cells in series. Just fully balance charge the pack, then set it to discharge. It dosn't really matter on the discharge rate, you are looking for bad voltage sag in any of the cells during the process and the overall mAh at the end of discharge. With a healthy 3000mAh cell pack, this should be close to 3000mAh. I would prioritize any branded cells you have.
 

TheBikeMan

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Mar 23, 2018
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Yes, Wheeliepete. that is it. That alone was helpful in that I was not balancing the voltage before I started. It wasn't a problem until today as I've been measuring the voltage before starting and using cells that were very close but this will make that easier. Most of the cells I have are Samsung 22F so they are 2200mAh I also have some unbranded light blue ones which I assume are 2000mAh but can't be sure. The instructions with the Sky RC charge leave a lot to be desired so I'm easing in to it. Thanks everyone for helping. Now I have to see if I can figure out how to see the overall mAh at the end of the discharge cycle.
 

wheeliepete

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The Samsung 22F only has a max. discharge rate of 4400mA, which is fairly poor for even a modest 15 amp system and would only really work if you were to build something like a 7 or 8P pack. If these cells have been used in a 4 or 5P pack they are going to have been worked pretty hard and may not have a great deal of life left in them. I am by no means trying to put you off what you are doing, as I did the same about 4 years ago and it was a very good learning experience, but all I will say is I deff. won't be doing it again.
 

TheBikeMan

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Mar 23, 2018
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Well I was planning on using them for a 36V 10Ah battery. I have a bike sitting here that is like new but no battery. I've built many batteries but this is my first time trying to use recycled cells. They originally came out of 36V 10Ah batteries but even after sitting around for about 6 months they all measured at over 35V which made me think that there may have been a problem with the BMS boards rather than the batteries in the first place. That is why I decided to try to load test them.
 

TheBikeMan

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Mar 23, 2018
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I'm also not sure what to set the cuttoff capacity to on the discharge setting on the Sky RC D100 V2. I'm assuming this would be the number of cells in series * the capacity of the cells?
 

wheeliepete

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They may well be good cells, but that dosn't mean they are going to make a good ebike battery pack. If they are going to make up a 5P10S 11Ah pack, fitted to a legal 250 watt bike, doing a 3 amp discharge test on them will give you an idea on how they will perform in use on the bike.
 

wheeliepete

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I'm also not sure what to set the cuttoff capacity to on the discharge setting on the Sky RC D100 V2. I'm assuming this would be the number of cells in series * the capacity of the cells?
No, when connected in series the capacity is the value of 1 cell. Parallel connections multiply the capacity by the number of cells.
 

wheeliepete

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I don't know your charger, but on the ones I've used, they automatically stop discharging at 3.0v or multiples of. I've only ever increased the discharge capacity for testing large packs to prevent the charger stopping part way through testing. Setting to 2200mA should be OK, but I would keep a good eye on things, esp. as you are unfamiliar with the charger.
 

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