How much do you let the battery go down by before recharging?

Difference between 0-100 and 50 - 100 is that li-ion battery doesn't like to be fully charged or discharged for long period of time. With watch slow discharging, battery will be quite long on 100% or below 40% That's why is better to charge between 40 - 80% but on another hand, who is going to watch the watch and stop charging at 80%? Putting on charger ~40% is much easier. Doesn't have to be exact 40%, I would just avoid to go too low or to 0% and charge either to 100% or stop wherever percentage is after, for example shower.

Thank you very much for this very helpful resource. I particularly liked the article on "Discover what causes Li-ion to age and what the battery user can do to prolong its life". This has basically helped me to understand why my current Fenix 5 battery has degraded as much as it did. I allowed it to get too low then charged to 100%. I will now charge my Epix 2 every time I take it off to have a bath when it is below 50% or so.

I see people here discussing the death of the battery but that is not the real problem that we all face, it is degradation to the point of significantly shortened life. My Fenix 5 initially gave me 14 days, I now get closer to 5 or 6 days. This is after 2 and a half years of use. I want to protect my new Epix from this fate and prolong, not just its life, but its ability to hold a charge for as long a time as possible.

A week later and I am convinced Z is right.  It is best to charge the watch when it drops to 40% and then unplug it at 80 to 85%.  No doubt Garmin knows this.  During most weeks this is not a problem.  Just charge when the phone drops to 40% if you aren't on some extended recording session.  The problem is stopping at 80%.  No one is going to sit there and watch it.  Garmin needs to give us a charging option to charge the watch to 80% and stop.  I bet that is easily done with the next firmware.  

Exactly...if i have to check when to recharge and when to stop the charging it starts to be a nightmare.

Looking also at the article from RonHi i guess that starting to recharge the battery, daily, during showers, once reached 40-50% should be the ideal...hopefully it will not recharge too much during 10-20 minutes of the shower 

In any case, once reached 90% or lower, the charge is a lot slower and that's one of the methods to try to avoid charges to 100%...also we just see a number on the watch but are we sure that 100% is the real 100%? 

Thanks 

edit.

probably can't do it everyday as the charge in 10-20 minutes is greater than the discharge during the 24 hours....even with the Epix 2 and AOD.

Isn't the number of times you charge a battery a determining factor in this too?

So charging it at 40% and only charging it to 80% means you will have to charge it close to 3 times the number of times as you would charging it at 10% to 100%.

I'm just going to charge mine at 10% or lower, and fully charge it, because I think less number of times charging also equals better battery longevity.

Why should we care? I think I agree with you related to what's best for the battery. On the other hand: Charging from 40% to 80% means you're effectively using just 40% of the capacity. How many cycles will it take to tear down the battery to a capacity of 40%? I guess after 1000 cycles, you'll end with 70%. So after 2000 weeks, you still have roughly twice the capacity you typically use. Doesn't seem to be worth the effort to me.

Please don't be offended, just my thoughts....

My first thought too...i have a smartphone that i recharge daily and sometime twice in a day(it's not from 0 to 100% but i still charge it more than once) due to using it a lot for playing games and after 1 year and half it's still decent. I can't imagine having problems with a watch that i recharge once in a week or, in case of Fenix 7 users or people that don't keep AOD on the EPix2, once every 2 weeks or even less...be it from 40 to 80 or from 5/10 to 90.

I'm discovering new stuff following threads like this and i'm grateful for all the inputs...but i guess i'll just recharge it when i can after i get the notification from the watch(should be around 10% and after that the watch can last more than 24 hours).

I've had Garmin watches since the FR305 and have always charged whenever I feel like it without any concern about the charge level. That said, I rarely let the battery get too low as I always want to ensure I have plenty of charge for any activity. There is so much information (some contradictory) out there that it's hard to sort out the useful from the not so useful.

My suggestion? There's more important things to worry about than the battery charge level when charging the watch. Use the watch. Charge as required to fit your use case.

Bottom line, question was how to prolong battery life. You don't have to follow 40 - 80% rule and it's ok to charge/discharge from time to time. Personally, I'm just charging when drops somewhere below 50%. For example when I come home from biking, I put watch on the charger, take a shower, maybe a bit longer (charging not showering :D). If I forget to take it of the charger and charged to 100%, that fine too.