Originally Posted by cmavr8
Ok, I finally found the chance to get my UPS off the grid and try to charge its batteries with the Multi4 charger, using the new settings you created for me!
I experienced something strange though:
Auto cell detection showed 5 cells. Normal charging preset showed 6 cells, which is the correct. Maybe the charger uses the Charge Voltage to estimate/detect cells?
Anyway, changed cell detection form auto to 6 "cells only" but it wouldn't start.
Changed "Stop Cells Change" to No and charge started.
After about 10 minutes I got Safety CODE 120. In the PC software I saw: "SAFETY CODE: Lithium Cell Cnt not Verified".
See first two attached graphs.
Changed "Stop Cells Change" back to Yes and the charge started OK this time!
After a while the 6 cell count became "VERIFIED". See 2nd pair of attached graphs.
Left it charging for 3h. Seems to have worked fine
The 2nd battery is in a very bad condition. Charge started but soon enough I got cell overvoltage error. It gives very strange readings with other chargers, so it is damaged, the charger couldn't help her
Anyway, thanks for the support, the job was done!
Pb batteries do not like to be over-discharged. They must be maintained, or they will go bad. Even if you just let them sit on the shelf for a couple months without ever charging, it's often not possible to recover them. This is why it read a 6 cell pack as a 5 cell. I have often "cheated" in an attempt to revive a Pb. You found one way to do it. But a simpler method is just to use a Ni chemistry preset.
WARNING: YOU MUST PAY CLOSE ATTENTION TO WHAT YOU ARE DOING IF YOU TRY THIS. IF YOU LEAVE A PB ON A NI PRESET TOO LONG, IT CAN EASILY OVER-CHARGE AND EVEN OUTGAS.
The idea is to put a little bit of charge into the Pb, then switch back to the Pb preset and see if it detects the cells properly. One could accomplish the same thing using a Pb trickle charger and then moving over to the Multi4 after a short while. The Ni presets don't care about cell count. They'll put constant current into anything that will actually accept a charge. Basically, you just need something to put a low current through the battery for a short while (maybe 10 minutes) to bring it up enough so it will then charge properly on the Multi4 using the normal Pb preset.
But I'll also add that this is a temporary solution. The battery is likely already spent. It may recover for one charge, but soon, you will find that it no longer has any capacity to speak of. It also doesn't always work. If the Pb is completely shot, it's like trying to charge a piece of wood. I do this procedure usually once a year on my lawn mower starter battery. It delays rushing out and buying a new battery when the grass is already 12" high and I really need to get it mowed. This also works for me when my wife is away from the house, my car won't start because I left the dome light on, and it's too far to walk to the auto parts store and return carrying a 30 lb battery. I can get my car started and drive there myself. Just make sure to take tools with you to swap out the battery in the parking lot, or you may end up stranded.