it works very badly
first many chargers like this in series dont always DEPEND on the v-Drop, look hard enough and you can find that many dont even recognise one when it is simulated.
They often depend more on the voltage max, which is not so bad as it seems.
The rate slows down as the battery voltage increases, if one cell finishes before the other, the charged cell is just overcharged till both cells reach the voltage, then they are both held at the voltage which eventually charges them both. the Rate during any overcharge is important.
Or
the rate itself is just low (which probably doesnt apply with your 900ma rating stuff).
|-{====]--{====]-|
|-----2.8v---------|
Temperature waits or stops are tossed on the side to avoid disaster, but are (usually) not used for anything else, after all when used in different temps and situations, they are not effective anyways.
then they toos in Timing on the side, just so it eventually terminates over time when/if nothing ever finishes, if it is a voltage max then they dont worrry so much about termination on time, they can just keep floating.
A person prefers to use the batteries in teams, and charge the batteries as a team in the series type chargers.
Other methods are, it just pulverises all the cells till the whole rack of them shows a single v-drop, then finishes by topping off. that is a complete mess, but can still pull off the charging. i have one of those, and it is very mean if the cells are not close in charge to eachother.
They COULD check each battery voltage for the drop, but i havent seen that method used on Series chargers, so to detect the drop it is via the voltage of both cell items. (or in the case of 2-4-6-8 ones the voltage of the whole set)
It can also be usefull, with Series styles to discharged the cells singularly prior to charging, JUST so they are all at the same capacity prior to starting a series charge. It is still best to do series charging with cells that were used together to begin with. That is one solution though , to get them similarly discharged, then they will mostly similarly charge in series.
So to discover all that, all you have to do is a quick ampmeter testing, put on a low cell and a high cell, wait a few minutes, then check the actual current flow to the batteries. if the current flow when overcharing the already charged battery isnt terrible, then it will survive.
IF
The current is staying way high like over 500ma and not going down, then you look to see if it will detect a v-drop, or if it will just timeout eventually, basically hard overcharging the cell enough to ruin it. If it is depending on v-drop the one cell will still be going up while the other is going down, and it cant see the drop occuring. and even if it detected the drop on the ONE, the other one wont be charged fully.
each of these chargers have thier little cheap tricks to keep from blowing the top off of batteries
and doing thier charging, usually it works, even if it is not ideal. The quantity of damage is relative to the Rate of overcharge and the length of time at that rate.
Checking the rates is the easiest way to tell , if charged batteries (even one of an offset pair) are being hit too hard with current (at overcharge), then it sucks, and you should do something to address the problem. Just using the batts as a team, or having them really close, or getting a single channel charger to replace it for that use.
How does this actually work? Wont there be 2x signals?
yes (usually tries to read the series set voltages)
Or will the depleted cell charge harder and catch up? Balance out?
it doesnt catch up like one would think. Current through the set is the same, the high cell gets overcharged usually , the rate of that overcharge is what counts, usually it isnt real bad. They balance out by continuing the current through the set, the high cell gets overcharge while the low cell is finishing charging.
Will the first cell not show the delta till the other one is at the same level?
the V-drop occurs at the overcharge, a VISABLE v-drop occurs when the rate is high. ONE fully charged cell could be showing a v-drop , but the controller doesn't see it unless the rate is high at the end of charge, and often not till it is a very hard drop for one, or both start to drop.
the v-drop can get quite large , when continuing to pulverise the cell at high rates.
notes: all the above information is useless, if they specifically apply temperature methods, which have thier own issues and ramifications.
