Could I be briefly educated on Li-ion batteries and the typical relationship between the open circuit voltage and the juice left? I found this table - does it look reasonable?
100%----4.20V
90%-----4.06V
80%-----3.98V
70%-----3.92V
60%-----3.87V
50%-----3.82V
40%-----3.79V
30%-----3.77V
20%-----3.74V
10%-----3.68V
5%------3.45V
0%------3.00V
They’re decent approximations, but they’re still “approximations.”
Chris
What’s the typical LVP threshold? Would 2.8 V be a good guess?
Just look at the discharge curves mooch and others post, that’s pretty much what you’re looking for. Here’s one of mine, only going down to 3.2 as most flashlights start to throttle there for LVP, so for my use case that’s pretty much empty.
Left is voltage over energy, right is voltage over capacity. Slightly different because energy is voltage times capacity. So same information but different representation.
It’s a nonlinear relationship and it is different for every cell. So all “%” based on cell voltage are rough estimates, at best. Voltage also drops heavily under load, so it’s not even possible to tell with reasonable accuracy unless you use a coulomb counter.
I found these tests. I don’t understand the peaks on the graphs - is the battery under load for about an hour, then disconnected momentarily to check the OCV, and put under load again?
If so, do I interpret the V vs. t correctly: the voltage drops by some 0.1 V rapidly when the load connects, but then recovers almost as rapidly when being under load? Why the peaks on the capacity graph are up? Please unconfuse me.
From 3V to 2.6V you can have hours of light . Of course depends on output and batt capacity.
Sofirns HS21 supposedly shuts off at 2.7V. Is this a typical LVP threshold?
Batts can go down to minimum discharge of 2.5V, but not all drivers can do it. And at 2,5V you can get moonlight mode at best if it is not boost driver. So 2.6 - 2.8V just perfect.
Typicaly Li-Ion batteries require discharge cutoff at 2.5V. Some has other values, datasheet of Samsung 35E says 2.65V.
Anyway between 2.5V and let’s say 2.8V there is a negligible amount of energy left so controllers tend to stop discharging earlier to grant better protection for battery. Specific LVP value is up to manufacturer, some devices may stop working at 3.0V.
Most brands aim for 3.0V with stock Li-ION battery.
Many flashlights don’t have a battery percentage indicator, so recharging to 80-90% max to preserve battery life is difficult. But at least it’s easy to avoid the full discharge. What the lifetime reduction loss in these types of batteries when fully recharging all the time? Are there any estimations?
You will find answers in batts datasheet.
