Hobby Charger settings and batt refurb - high delta V

The amount the "full 7200 Mah" indicated on the charger is only an indicator of how much charge is sent, not how much charge makes it into the battery as there's much loss with heat and other factors. You need lab grade testing equipment to accurately measure how much charge each module is getting.

Also there's not much heat when you're only discharging to 6v and back up to full charge. But that's just the first round of conditioning... The second round and third round discharge much further. I usually discharge down to 5v, then 3v, then 1v... And that final round is the most dangerous in terms of generating heat and toxic fumes coming out of vent tube. I use tiniest size water balloons over each vent to catch the fumes, which also is a good indicator of one that's venting. Third round of reconditioning is where the most break up of crystallized poorly conducting material is broken up, but I do it in stages because it gets hot if you recharge all at one.

The more cool you can keep things the better. A thermal camera is a huge help to find hot cells that are going to fail sooner than others. Also the discharger inside the chargers are painfully slow. Consider 12v 50w bulbs to bring the charge level down to the 5v, 3v and 1v first, then use the discharger in the charger at the final voltage desired before recharging.

 

If all your modules are testing in the 6000's, then there's really no need to do anything further.

Now, if you want to experiment, try using the 2 amp charge rate with an 8200 cut off point. This will get you into the heat generation area at the top of the charge. Make sure you have good airflow cooling the modules. Keep in mind you're likely only getting an 80-85% charge efficiency. If you think of it as just units of energy being pushed into a module's chemicals and units of energy available for discharge from the chemicals, a 7200 unit charge at 85% efficiency is 6120 actually stored in the chemicals for discharge. The modules "new" rating is 6500, but when new they test >7000 (using 2 amps charge and 1.5 amp discharge with an 8200 cutoff). I have many dozens of Gen 2 modules that test 6500+ using the exact same methodology.

Also keep in mind that if your charger is programmed to discharge to 6 volts, you are likely at 6.2-6.3 volts at the module terminals. You may want to drop that setting to 5.8 volts. This will depend somewhat on the wire gauge you're using for the cables. Hopefully you're using 16ga or better. Smaller than that may cause additional voltage drop issues.