Nitty Gritty of "3-Phase" charger operation

[areddon]

We have all seen manufacturers' marketing graphics on "smart" chargers.

Bulk is described or pictured as the constant current phase with full current and linearly rising voltage until the preset absorption voltage is reached. In practice the current begins tailing off almost immediately as voltage rises, depending on condition of battery and the current is anything but constant in an older battery.

Then, reference is made to the absorption phase where voltage is held constant while the current declines, with some suggestion that the current tail is controlled by the device.

Having read what is available from my manufacturer (xantrex) and having looked at currents and voltages in practice, it seems to me that bulk charging may involve simply holding the preset absorption voltage at the charger's output (or at battery terminal with remote sensing). During this phase the battery's "internal" voltage rises. Once the battery gets to the absorption voltage (I would like to know how the charger determines that) it seems like the nothing is changed and the absorption phase is merely the natural current decay, at constant voltage, due to the rising internal resistance of the battery.

Then, the absorption phase shifts to float voltage, probably based on time or some algorithm, but not by assessing the current tail.

This may be all wrong but I would like to know if anyone can clarify the principles of operation. That is, I am not interested in the exact algorithm(s) but the basic operating principles.

Thanks.

[smac999]

Bulk is constant current yes. Full current untill the batery. (Well charger output). Reaches bulk / absorb set voltage. (Normally same thing. Except balmar has created 2 different ones).

Absorb holds the absorb voltage. Generally timmer based. It can’t really do it based on current. Because dc loads cause charger current. And then it wound never go to float if stuff was on.

Float holds the float voltage.

In bulk the current does not drop. If current is droping. It’s already in absorb mode and bulk has finished. possible your charger cables are too small if its switching too soon. As it’s based on charger voltage not battery voltage. Unless your charger has a V sense line. Most do not.

Bulk time is completely related to the size of charger and battery.