Steamcrave Titan PWM Battery Usage

[CrazyChef v2.0]

So I needed to charge the batteries from the Titan PWM, and this is what the Golisi charger says for the info. Why is there such a difference between batteries? These are 4 Samsung 25Rs hat have been married since I got them.

 

[PoppaVic]

I'm not sure which end of 2S gets drawn more, but they do. This is why I number AND letter my cells and rotate my duals so everyone takes a turn up or down.

You have it even "worse" in that you need to rotate everyone thru all 4 slots in the mod.

 

[cascadian]

Why is there such a difference between batteries? These are 4 Samsung 25Rs hat have been married since I got them.

In a 2S configuration each cell has a differing electrical demand. If you were to model the demand of each individual cell you will find that the internal resistance of each cell plays a role. As the electricity flows from positive to negative you would include the additional point of contact resistance, and the internal resistance of the other cell in the model for the cell closest to the positive circuit connection. So effectively the circuit has a different resistance for each cell. When you measure the resting voltage of the cells after discharge the amount of variation will be solely determined by the quality of the battery tray and the internal resistance of the cells used. The variation you are seeing of 16-23%, depending on which cells were paired, would be greater with cells that posses a higher internal resistance, or less with cells that posses a lower internal resistance. In a regulated device using a 2S battery configuration one would think that a pair of LG HG2 cells would last twice as long as a pair of LG HB6 cells, due to the manufacturers capacity ratings. But due to "battery sag", directly related to internal resistance, and the unequal discharge of the cells in the 2S configuration the difference is usually half that in devices that employ a low voltage cut-off.

As mentioned rotating the cells in a married pair is important or one cell will degrade far faster than the other.

 

[gsmit1]

To chime in here for what it's worth, Mooch says that in a para-series configuration, each pair of cells in parallel will balance each other's voltage, just like in a regular dual parallel mod, but the 2 pairs being in series with one another will not.

In other words, what your charger is telling you. Slots 1 and 3 were a parallel pair and slots 2 and 4 were the other pair with the pairs running in series with one another.

In OTHER other words, it would only take one cell of the pair in slots 2 and 4 to be weak for it to pull the other one down some as they balance each other.

OR, the mod just discharges unevenly

I don't pretend to have more knowledge than you do, but maybe it's been a while since this has been on your radar.