What would be acceptable resistance for 1.5 yr old cells, Panasonic green 3400 mah protected? around 60-70 recharge cycles at most.
Also i have an ongoing debate with my friend, about charging current. He insist that charging at lets say 0.375ma would results in noticeably higher charge capacity of the cell, compared to 1A.
Is this true? did anyone measured obtained end capacity at different charging current? 0.3, 0.5 vs 1A? thanks.
It is unlikely the capacity is impacted signficantly by the charge rate unless the battery is near end of life, and has high internal resistance. If you have a high internal resistance, the voltage under load will be lower, and as a result, the low voltage cutoff will occur earlier, and the charging voltage will appear artificially high, cutting off charging early. In effect with cells with high internal resistance, you are getting burned at both ends of the candle.
The energy required to reach that charge however could be significantly different. The I^2 x R losses would be about 9 times higher (however because the 1 amp charge is 3 times faster than the .3 amp charge, it would run for only 1/3 as long). So you are going to end up with 3 times as much energy ending up as heat at 1 amp versus 333ma charge rate. This is why your cells are going to get warmer with a 1 amp charge than with a .3 amp charge.
Also keep in mind that the figure quoted is the peak charging rate during the CC phase which is used for only part of the charging cycle. Once you enter the Constant Voltage phase, the current will be determined mostly by the internal resistance of the battery, so by the end of the charge cycle, there is probably very little difference in the charging current.
In the end I’d say the answer depends, at 60-70 charge cycles I doubt it makes much difference, but at 300 cycles it may.
On a lot of (most?) chargers the termination current is a percentage of the initial current, so your friend is partially correct though likely for the wrong reason. On the common Turnigy hobby chargers I think the termination is 10% of whatever you select for the initial, so for a 1 amp setting it'll shut off when current drops to 100mA. 0.5A charge rate terminates later, when current drops all the way down to 50mA, and to be really silly a 5A rate terminates at 500mA, which will be way early and the cell won't be nearly full. So a lower charge rate can end up putting more energy into the cell but only because it drags out the CV part of the cycle longer. A cell with lower internal resistance is 'easier to fill up', to make a bad analogy, so can get closer to full with a higher initial rate/higher termination current.
thanks guys. So to make it clear, lets say i charge BRAND new cell, with some uber high end charger, to make it equal.
First charge, i charge at 0.3A
Second charge i charge at 0.5A
Third charge i charge at 0.5A
This cell would be 2900 mah and lets say an actuall 2850……
How much mah will the #1, #2 and #3 get? (approximately) thanks.
Also one more thing, what is acceptable resistance (measured with the Opus) of 1.5 y old cells? is ~ 120 acceptable?
It really depends on how much the IR has changed from when it was new.
Lets say they are all recharged around 10 times only. They where stored in perfect conditions, and are of equal quality/model/age/batch.
What would be theoretical charge capacity? lets say are cells are completely the same but are charged at difference current @300mA, 500mA and 1000mA? thanks.
It depends on the cells, and on the charger (how it handles the termination point, if it changes with different initial charge currents). It depends on every single variable, really. It's kinda like asking 'how much does the color blue weigh, is it lighter then green?'
I’m talking about hypothetical situation here. I said imagine some uber charger, with perfect charging algorithms and everything other being the same, its just a fun thing 
Not to mention a cell charged at lower currents will show less resistance to the charger. Lithium cells (in a pack) need balancing for a reason, resistance varies from cell to cell no matter how close they are to performance. Too many variables.
I’ll try to answer you, but it’s not easy.
First, an acceptable IR for your unprotected cell is something like 80-120mOhms.Add 20-40mOhms for a protected cell. I don’t own an Opus charger but I assume it reads correct values.
Second, as explained earlier, because of that IR the charge termination current will have an impact on the charge. I assume here that your Opus has a termination current proportional to the charge current set (like the Accucel chargers). So you would get values like this:
First charge, i charge at 0.3A: 2850mAh
Second charge i charge at 0.5A: 2845mAh
Third charge i charge at 1A: 2835mAh
These values are just estimates!!! It’s just to give you an idea. The difference will be very small in my experience, unless you go to really high termination currents. The difference is also directly proportional to the IR of the cell.
The ideal termination current is given by the manufacturers in their datasheet.
Overall I wouldn’t worry too much about that, except for the IR measurement which is a pretty good indicator of the cell health. If you really need that last 1% of capacity, you can charge at 1A, the charger will cut at 100mA and then charge again at 0.3A so that the charger adds a few more mAh until it cuts at 30mA.
I hope I didn’t make any mistakes.
Thanks!