18650- LI-ION ,longevity question

[rumme]

Lets say you are using good cells, { Samsung 22p} and you have a battery built for 72 volts and capable of 100 amp continuous - 150 amp max bursts and you use that battery to those limits . Generally the battery would be rated for about 500 complete cycles , before it started to noticeably degrade ?

What if you take that same battery , and do not stress it to its amp limit and instead ran it at 50 amps continuous and 100 amp bursts . Would the battery possibly now handle 1000 complete cycles before it started to noticeably degrade ? This is assuming in both scenarios, you have a BMS cutoff of 60 volts so the battery is never undercharged.

 

[Hillhater]

impossible to say without testing, but it should have a longer useful life.
Charge rate, temperatures, time kept fully charged, etc,...all have a big influence on cycle life and capacity retention.
there are a few threads testing cycle life vs discharge and charge rates,....try a search

 

[spinningmagnets]

For max life, never charge to 4.2V per cell. 4.1V is much better, and 4.05V is better still. Discharging to 3.0V is better than a lower LVC, and 3.3V per cell is even better than that.

3.0V to 4.1V per cell is good.

3.3V to 4.05V per cell is better.

Tesla uses Panasonic cells, readily available on the web [no secret sauce], they have an eight-year warranty (2000+ cycles?), and recently a taxi driver put over 300,000 miles on a 2-year old Tesla, and it still provides over 90% of its rated new capacity.

 

[DVDRW]

My data so far:
Panasonic NCR18650PF grade C
From 2016 april
Discharging ~0.7C
Charging 0.15C
Cycling 20-90% (3.3-4.1V)
~150 cycles
Battery degradation less than 1%

No BMS, still balancing not needed (22s18p pack)
https://i.imgur.com/Q46QiKh.jpg

 

[Pajda]

Hillhater is right, it depends..

From my experiences if we are talking about "reasonable" loads (up to 1C average discharge) the most important parameter is an absolute Depth of Discharge. In my cycle life test of modern 18650 cells I am charging the cells to almost fully charged 4,2V with 100mA cut-off current at 0,5C rate and discharge them with 1C discharge rate down to 50% DoD (3,6-3,45V) and after 1000cycles most of them have more than 90% of their intitial capacity. I believe that if I change the test condition to 4,1V-3,35V (still 50% DoD - I will do this test in next months) I will get only slight better result. But on the other hand it cost me an emergency range because I always charge battery only to about 85-90% of its full capacity. But there comes another significant parameter into the game, and it is cell calendar life because this 1000 cycle test tooks "only" about 3 months. So I am trying to say that long term storage voltage will probably have bigger influence on cell aging than absolute value of charging voltage.