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Old 06-28-2019, 03:53 PM   #1 (permalink)
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Default Shallow discharging results.

I didn't want to do a deep discharge on an unknown battery from the advice given here previously, so I did 2 shallow cycles down to 100V including a pre-charge using a Genesis One. These are the results. Seems pretty good compared to other batteries I've done. Should I do a third cycle like I usually do?

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Old 06-28-2019, 05:39 PM   #2 (permalink)
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Hmmm... discharge time INCREASED. Capacity gains result in a shorter discharge time as more capacity is burned at higher voltage, so you also get more current per minute. Your results are not indicative of substantial improvement.

Assuming you're using Mike's work lamp discharger, I would make a very crude estimate of 1.25A average. That's putting you at about 4.4Ah for the first and 5.1Ah for the second, but that would include capacity below 1V/cell, which is considered unusable.

Assuming you don't have cell or self-discharge issues, nothing stands out as negative.

Probably worth a 3rd. If you can time it, check taps at 144, 132 and 120V.
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Old 06-28-2019, 06:53 PM   #3 (permalink)
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Quote:
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Hmmm... discharge time INCREASED. Capacity gains result in a shorter discharge time as more capacity is burned at higher voltage, so you also get more current per minute. Your results are not indicative of substantial improvement.
If @atikovi is starting from the same higher voltage and ending at the same lower voltage for both rounds, and the load resistance is constant, and the source resistance is negligible compare to the load resistance, then the current at any particular voltage is constant on both cycles, and a longer discharge time can only mean a higher capacity...

V = IR
P = V*V/R

(and @atikovi, it sounds like you could continue doing cycles until you see the improvement between cycles flatten out - assuming there isn't something detrimental going on like a cell repeatedly reversing...)
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Old 06-28-2019, 07:00 PM   #4 (permalink)
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If I remember correctly, longer discharge time is better because it indicates greater capacity. More mAH and WtH charged indicate the pack can hold more power. That's my understanding from Mike's explanations but could be wrong. I do know the the packs I had with half those numbers, I needed to replace.
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Old 06-28-2019, 10:06 PM   #5 (permalink)
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You are missing a few things:

1) Input at 350mA isn't an indicator of capacity. It's how long the charger pushes current. I've pushed 25% more capacity into packs than the cycles you posted, and they yielded what they yielded independent of input (provided input exceeded what came out). The Genesis One has more advanced termination criteria, but I wouldn't regard it as an absolute.

2) Voltage depression (VD). It reduces capacity. Cycling eliminates this by consuming the capacity at the VD levels - below 1V/cell or 120V at the pack level. This is the purpose of grid charging and pack level discharging.

2a) You have X mAh of capacity at > 1.0V/cell and you have Y mAh of capacity at < 1.0V/cell (VD capacity). You improve X capacity by consuming X and Y capacities where X2 = X1 + Y (roughly).

3) Load resistance isn't constant. R is a variable. Light bulb V to I ratio is not linear.

4) Given #1, Y capacity is consumed at lower voltage and thus lower current, e.g., 1000mAh of capacity consumed at > 120V is at higher current and thus takes less time than capacity consumed at < 120V.

As an exaggerated example, using a HA automatic discharger that steps down the current at various levels (like swapping light bulbs), a severely voltage depressed pack may take 12 hours to discharge to 0.8V/cell. Subsequent discharges take 4-6 hours since the bulk of the capacity is extracted at higher voltage/current. All cycles extract similar capacities.

I don't know what the Genesis One logs, but time to 120V would be a very useful measure. If D1 to 120V takes 3 hours and D2 to 120V takes 3.6 hours, that's direct evidence of improvement. When you lump >1.0V capacity and <1.0V capacity as a single discharge time, the evidence for improvement is less conclusive.

As I indicated, nothing jumped out as negative. The data indicate that the pack did not experience a substantial improvement in capacity (about 16%), which is low for a pack with a lot of VD.

Maybe it will help for me to add that the battery may not be in a state where it will benefit from reconditioning, which may be good or bad.
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Last edited by S Keith; 06-28-2019 at 10:09 PM.
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Old 06-28-2019, 10:43 PM   #6 (permalink)
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I don't know what the Genesis One logs, but time to 120V would be a very useful measure. If D1 to 120V takes 3 hours and D2 to 120V takes 3.6 hours, that's direct evidence of improvement.
Well, I do have time to 100V. From 175.6V it took 3.5 hours the first time and from 177.8V the second time it took 4 hours.
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Old 06-28-2019, 11:08 PM   #7 (permalink)
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Your response indicates that you didn't read or didn't understand my post.
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Old 06-28-2019, 11:27 PM   #8 (permalink)
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Read it, maybe didn't understand it correctly. Assumed time to discharge to 100V would be almost as meaningful as to 120V with the other parameters being equal. Anyway, if nothing negative stands out, that's all that counts. Thanks for the analysis.
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Old 06-29-2019, 12:15 AM   #9 (permalink)
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Key takeaway is that the capacity below 120V isn't usable, and the amount extracted between 120 and 100V will vary depending on the amount of VD present.

Given that you're cycling to something around 0.8V/cell, you're probably not capturing a lot of the voltage depressed capacity, but you're minimizing potential for reversals, and 4.4-5.1Ah of capacity above 100V likely indicates a pack in a reasonable state of health.
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Old 06-29-2019, 03:32 PM   #10 (permalink)
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Quote:
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Read it, maybe didn't understand it correctly. Assumed time to discharge to 100V would be almost as meaningful as to 120V with the other parameters being equal. Anyway, if nothing negative stands out, that's all that counts. Thanks for the analysis.
These sound like good assumptions to me.

I think another 2-3 cycles down to 120V won't hurt as 5 cycles is apparently something used for conditioning (first link below).

Also, it would probably be best to allow the battery to rest after discharge until the voltage stabilizes before charging. Probably should wait the same amount of time after charging for a similar internal process to occur. It probably has a beneficial balancing effect. Reducing the charge/discharge current when you get near the end will probably have a similar beneficial effect. And cooling!

http://data.energizer.com/pdfs/nicke...ide_appman.pdf
http://www.scarpaz.com/Attic/Documen..._technical.pdf
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Last edited by *sean*; 06-29-2019 at 03:37 PM.
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