Apart from this, I'm skeptical about an algorithm that tries to measure opencircuit voltage in the manner described. The voltage will be artificiallyhigh when the battery has just been removed from charge. However, there maybe some details of the algorithm that the description you quoted left out.
I did leave out some details, as you point out. The basic idea, as I understand it is: When the charger turns off, yes the voltage will be artificially high, as you point out. The voltage does decay. When the batteries are in a state of discharge, the total pack voltage will decay below the controller's turn on setpoint. It then turns on, for some ammount time (pre-programmed) and then turns off and repeats the cycle. If the pack has been discharged fairly well, then the decay time will be extremely short (intantaneous?). This would lead to nearly 100% duty cycle. As the pack approaches full charge, the duty cycle drops as the decay time increases. Eventually, it becomes only a maintenance pulse.
Equalization is normally a constant current charge applied with either no voltage limit or with a rather high voltage limit, for a specified time.I'm not aware of any benefit in fully discharging a battery before applyingan equalizing charge, and in fact such a practice risks cell reversal and the consequent damage.
From what I've read, the best way to accomplish cell equilizatoin is totrickle charge the pack at C/100 or less. My understanding of this is that doing so will only maintain the cells which are fully charged, and bring the charge up on the cells that are not. In an ideal world, I suppose this would be done after every bulk charge.
You are correct about the possibility of cell reversal during a complete pack discharge. If you have a cell in a battery which is significantly lower than the two, this is a real danger no matter how the discharge is approached. However, if each of the batteries' cells are fairly uniform and the batteries are all disconnected from each other, then this likelihood diminishes significantly, wouldn't you say? Especially if each battery is only taken down to about 20% or so?
Either way, perhaps the reason they recommend deep discharge is to allow charging at a high current to address sulfation issues. I will note that this is not explained in the text I quoted, it is just a guess on my part. I agree with you - I don't see any benefit in completely discharging a pack either. The largest benefit that I can see for deeply discharging the batteries is to allow high current charging.
The handbook addresses many, many types of batteries, but I will assure you the information I presented did come out of the flooded lead-acid section, not the NiCd. LOL. Thanks for the discussion!
Nick