The internal impedance of a battery is a metric which determines the ability of that battery to deliver instantaneous current - the lower the impedance, the better. The 6mOhm of the A123 cells were the first thing that attracted me to them as I knew from past reading & people's experience with batteries that the lower the internal impedance seemed to correlate to a better the sound (this was when people were using 12V SLA Optima batteries for instance).
I have a suspicion that this also determines the noise of these batteries when delivering current - again the lower the internal impedance, the lower the noise.
So, the 13mOhm of the WN08AH battery, on paper, would seem to be worse but some people will suggest that the wiring from the battery to the circuit will be equivalent to>13mOhm so the internal impedance doesn't matter. Yes, correct but that is missing the other possible benefit of the internal impedance - the lower noise of the chemical reaction taking place inside the battery when delivering current.
So, it may be difficult to judge without trying them, which battery is most suitable for this role as power plant for an amp. Is noise below a certain level important? Is transient current delivery important above a certain speed? Questions which are difficult to answer
