Varta battery :
OK so it's done charging for the second time.
Started at 18H00 yesterday, C/10 around 11mA.
Within a few minutes voltage rose up to spot on 10 V and stayed there up until 4AM when I went to bed, i.e for 10 hours total.
When I woke up 8+ hours later at 12H45, voltage had gone up a bit, at 11.5V.
So in total it charged for 18H45min at C/10. A bit more than theoretical time, but not much, plus the whole point as I understand it, of charging at C/10, is that it's low enough that you can leave it unattended, it's not gonna blow it.
Anyway, Wilson did a good job and charging current remained close to the set 11mA throughout. It was varying constantly up and down very slowly, but always within reasonable limits : about +/- 0.25mA, happy enough with that.
So when I disconnected it at 12H45, voltage went straight from 11.5V down to 10V where it had been most of its time anyway.
Now 22H45, so after 10 hours disconnected, voltage decreases extremely slowly. Now down from 10.0V to 9.6V.
So looks like 9.6V it will be then.
So, could it be this battery has not 7 but 8 cells ? Like....8x1.2 = 9.6V !!!
The label on the battery is useless, it just says " 9V " battery, it does not state the actual voltage never mind the number of cells in the thing.
So now time to discharge it for the second time !
... but this time won't make the same mistake ! Won't leave it go flat at night while I am sleeping !
Nope... so will wait until tomorrow. Will start discharging it when I wake up tomorrow, so I can keep an eye on voltage regularly throughout the day as it discharges.
Will make sure to write down exact voltage and time, so I can run the numbers and guesstimate the capacity of the battery.... once it reaches 7.0 Volts, as Rob indicated.
So... see you tomorrow for the next and à priori last installment of the Varta saga !