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You are on the right track. LFP is the hardest to find because the charge discharge curve is so flat. Not so with any of the othersexcept LTO.
Do you have the means to measure AH Discharge Capacity? Example many of the RC Hobby Chargers can charge or discharge any battery type. You can see what goes in, and what goes out. You would start by fully charging and then discharge and measure maximum capacity at 4.2 volts. Then Recharge to 4.1 volts and discharge, and so on until you get to where you want.
Another way is you charge at 4.2 volts but terminate at a higher current than C/33. Example say it is a 10 AH cell instead of terminating at .3 amps, terminate at say 1 amp. Then do a discharge test to see where that lands.
Assuming you cannot do a discharge test, you can use your flashlight and a timer. Fully charge it. then discharge in the flashlight until it goes dim and clock it. Lower the charge voltage a bit, repeat. If it goes 120 minutes on a full charge, you are looking for something like 100 to 110 minutes. If the flashlight is a single cell model, you do not have to worry about over discharge especially on LEd models. The driver will shut off before any thing can happen, You only worry when you have more than 1 in series. It takes another stronger battery to drive the weaker one into reverse polarity.
So you are on the right track and just have to experiment a bit.
If you really want to dive into it, here is a good White Paper on the subject. You can cut to the meat on pages 9 and 10 graphs. But I can tell you from experience on a 3.6 vpc cell you charge until saturated @ 4.1 to 4.15 volts. That will get you 85 to 95% range. Another clue is Nissan Leaf battery max charge voltage is 4.1 on NMC batteries. No commercial EV manufacture allows the customer to fully charge a battery. They would go bankrupt if they did. They only time they allow it is at the end of life to get at that last bit of capacity they have been banking and saving for the end of life. Tesla did it already on older Roadsters and released the last top 20%. EV's operate 20/80 to 10/90 range. The golden rule is to stay away from the knees of the charge discharge curves.
Do you have the means to measure AH Discharge Capacity? Example many of the RC Hobby Chargers can charge or discharge any battery type. You can see what goes in, and what goes out. You would start by fully charging and then discharge and measure maximum capacity at 4.2 volts. Then Recharge to 4.1 volts and discharge, and so on until you get to where you want.
Another way is you charge at 4.2 volts but terminate at a higher current than C/33. Example say it is a 10 AH cell instead of terminating at .3 amps, terminate at say 1 amp. Then do a discharge test to see where that lands.
Assuming you cannot do a discharge test, you can use your flashlight and a timer. Fully charge it. then discharge in the flashlight until it goes dim and clock it. Lower the charge voltage a bit, repeat. If it goes 120 minutes on a full charge, you are looking for something like 100 to 110 minutes. If the flashlight is a single cell model, you do not have to worry about over discharge especially on LEd models. The driver will shut off before any thing can happen, You only worry when you have more than 1 in series. It takes another stronger battery to drive the weaker one into reverse polarity.
So you are on the right track and just have to experiment a bit.
If you really want to dive into it, here is a good White Paper on the subject. You can cut to the meat on pages 9 and 10 graphs. But I can tell you from experience on a 3.6 vpc cell you charge until saturated @ 4.1 to 4.15 volts. That will get you 85 to 95% range. Another clue is Nissan Leaf battery max charge voltage is 4.1 on NMC batteries. No commercial EV manufacture allows the customer to fully charge a battery. They would go bankrupt if they did. They only time they allow it is at the end of life to get at that last bit of capacity they have been banking and saving for the end of life. Tesla did it already on older Roadsters and released the last top 20%. EV's operate 20/80 to 10/90 range. The golden rule is to stay away from the knees of the charge discharge curves.
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