Nice and very helpful advice there
In 2007 I designed a product that uses this battery:
http://shop.lipopower.de/850-mAh-37V-Einzelzelle-1C-38mm-breitThat battery is pretty much what people would have had in their non-smart Nokia phones back then. Like a Nokia BL-5C battery.
Before deciding to use them I did some extensive testing on those batteries that also involved an ELV intelligent battery charger:
This thing can do charge and discharge cycles and log the data on a PC.
So I did cycle some batteries for weeks and found one interesting thing:
1) I set it to 1C and 4.200V and left it for 2 weeks, the battery lost x% of it's capacity (can't remember the figures)
2) I set it to 1C and 4.100V, also left it for 2 weeks, the battery only lost 1/10 of the capacity it was loosing before.
Of course the battery was only charged to about 85-ish% of it's rated capacity, but that was still good enough for me.
The test was done with 4 batteries at the same time. They all showed the same aging effect.
I am sure the mentioned cutoff voltage given on LiPos is that voltage where they have the highest capacity.
So my advice to those who have a less precise power supply would be: Set the cutoff voltage to that value where the tolerance of your power supply would not exceed the 4.200V.
As Dave said in the video: You can terminate charging anytime.
And to those who want a longer lifetime out of your LiPos: Charge them only up to 4.100V.
This is what the product does and about 7 years after release the first and oldest ones started to trickle in for battery replacement. That is very good for Lithium based batteries. Only about 730mAh are used of the 850mAh but the longer lifetimes is worth it.
The supplier I use sort of confirmed my findings, they charge the batteries to about 3.95 V.
That is supposed to be the ideal voltage to store these batteries, so I have been told.
In the meantime there was a design change and the new battery can now be replaced by the customer.
I was never really happy with the built in solution but back then availability was not that good as today.