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    Reconditioning Pb, losing track of MgSO4 -- or it worked *too* well???

    I know I'm a year late to the party, but in reply to your first question, for future reference, you might be able to determine which cell was which by testing the specific gravity of the solution using a hydrometer (basically a turkey-baster with a weighted, graduated float inside). Pure...
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    Reviving old NiMH cells using science?

    So quick update, I've had some success with one of the cells I recovered from my old walkera 22e electric helicopter. It had a 9-cell 650mAh battery pack. Each sell is the size of an AA battery. For my testing I chose the worst cell, this one had an internal short so terminal voltage would...
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    Highest capacity cells in each size.

    Re: Maximum capacity of cylindrical cells by form factor. Gotcha, list updated. List updated List updated.
  4. L

    Highest capacity cells in each size.

    Re: Maximum capacity of cylindrical cells by form factor. I'm surprised that D cells are quite a bit more expensive per watt-hour than lithium cells. The Ansmann in my table are €40 for a pair!! Vapex sells reasonably-priced D cells, their LSD variant is 8000mAh (€19 for a pair), and the...
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    Reviving old NiMH cells using science?

    Agreed, a lot of my "bad" cells are ones that have been cooked by dumb chargers that continue pumping 200-400mA of current into them long after they're charged. There's usually some discolouration around the vents near the positive terminal where the electrolyte was vented out. I've attempted...
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    Reviving old NiMH cells using science?

    I came across this scientific paper: https://www.mdpi.com/2313-0105/2/1/3/htm (full text and PDF are free, just click the link). In the last section, it states Does anyone have any information about this? I couldn't retreive the original paper that describes the 33% SOC method, however I...
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    21700 Cells

    There are already electric cars that use different cell technology (such as prismatic cells). Larger cell sizes are a tradeoff, on the one hand the amount of packaging overhead per mAh decreases (it only takes one container for a 100Ah cell instead of 30 cans for 30 cylindrical 3.3Ah cells); on...
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    Highest capacity cells in each size.

    Re: Maximum capacity of cylindrical cells by form factor. Phew. Just added all the data and made a neat table of it. Sources listed above. I think this will make a good "quick reference guide" for pack building. I certainly learnt a lot when compiling the table - such as to skip anything...
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    Highest capacity cells in each size.

    Re: Maximum capacity of cylindrical cells by form factor. I've been using your comparison page up till now. I just stumbled upon your table, and now I understand what you mean. I can just filter and sort to get the data (facepalm). So much less work than going through the comparison! Looks...
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    Highest capacity cells in each size.

    Re: Maximum capacity of cylindrical cells by form factor. Thanks for filling that in, Parametrik. Looks like some very high quality data there. Agreed re quirky voltages for some numbers. I think the 18650 cells I listed in my original post had oxidation- resistant electrolyte to allow them to...
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    Highest capacity cells in each size.

    Re: Maximum capacity of cylindrical cells by form factor. Good point, I've added an indication of discharge current. Moderate use, so currents in the range of 0.5-1.5C. HKJ, I used your comparator before I made this post, was hoping you'd know the approximate capacities off the top of your...
  12. L

    Highest capacity cells in each size.

    I'd like to make a list of the approximate maximum capacity of each form factor of currently available cylindrical cells. This would firstly help to guide new users so they don't fall into the trap of buying Chinese cells with completely fictitious capacity numbers. Secondly it will be useful...
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    Status for 2018

    Happy new year HKJ! And big thanks for the many high-quality reviews you do on your site (you may remember me as the user who asked for the raw data for the eneloop charge tests last February - unfortunately I never succeeded in finding a better dV/dT termination algorithm). I have an idea of...
  14. L

    identify: NiCad or NiMh?

    Can you upload some images from all sides? Perhaps there's the crossed-out rubbish bin with "Cd" under it that reminds you not to throw away cadmium-containing batteries? Anyway, you can "jump start" it by connecting it in parallel with a battery of the same voltage. Eventually it will recover...
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    Looking for raw voltage vs time data for an NiMH charge cycle.

    @hiuintahs Interesting idea. So let me see if I understood your algorithm. I've paraphrased it in steps below: 1. Pulse-charging for 500ms with 10ms off time (98% duty cycle). 2. Store voltage in memory 3. Every 30 seconds, check if current voltage is greater than stored voltage. 4a. If yes...
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    Looking for raw voltage vs time data for an NiMH charge cycle.

    That was the first thing I tried - setting a filter to disregard data when current ready in the row is below a threshhold value. It wasn't sufficient, because the voltage slope (dV/dt) in the preceeding and trailing data points is still many orders of magnitude greater than the dV/dt value...
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    Looking for raw voltage vs time data for an NiMH charge cycle.

    Just wanted to update this thread with the status. Firstly thanks Gauss for the tip, I will read through some of those eventually to see how they implement the algorithms comercially. What I'm trying to do I suppose is to derive a workable algorithm from first principles. To that end, here's the...
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    Looking for raw voltage vs time data for an NiMH charge cycle.

    Thanks for the offer 😁. I will study the curves and send an email with the one or two I want over the coming days. Much appreciated!
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    Looking for raw voltage vs time data for an NiMH charge cycle.

    Re Silverfox - Interesting theory. I have been cycling a set of new AAs in a battery box on my hobby charger at different charge rates and I can't say I really noticed a voltage drop after full charge at 0.1C. I did however notice an increase in temperature (about 7-10*C over ambient) for the...
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    Looking for raw voltage vs time data for an NiMH charge cycle.

    Hi HKJ. I'm honoured to be getting a reply from the author of lygte.info himself, I'm a huge fan of your charger and battery reviews :). What I was planning to to was to work out the differentiation of the voltage-time curve to actually plot the dV/dt in the mathematical sense. This is simply...

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