How to tell what a Li-Ion bike battery's capacity is?

[PeteCress]

Sounds like an Li-Ion battery is good for about 800 charge/discharge cycles before 10AH capacity becomes more like 8.

But how does one tell how far along that deterioration slope a battery is?

The agenda being to avoid getting caught with a dead battery 5 miles and 1,000 feet downhill from home without having to carry a backup battery.

Figuring on:

• Cycle Analyst 3
• Infineon 12 FET Controller
• Li-Ion "Shark" from Luna Cycle. 11.5 ah, 14S 4O Panasonic 18650 cells, 30 amps continuous

 

[markz]

https://ebikes.ca/shop/electric-bicycle-parts/test-equipment.html

 

[goatman]

end of ride
30 amps continuous
volt sag will probably trip the lvc
enter panasonic ? at 7.5 amps into the lygte comparator and see
https://lygte-info.dk/review/batteries2012/Common18650comparator.php

 

[fatty]

Sounds like an Li-Ion battery is good for about 800 charge/discharge cycles before 10AH capacity becomes more like 8.

This depends greatly on the specific cell model, and is specified in the cell datasheet.

But how does one tell how far along that deterioration slope a battery is?

Test capacity when new, then test capacity when used. 1 - used capacity/new capacity = deterioration.

The agenda being to avoid getting caught with a dead battery 5 miles and 1,000 feet downhill from home without having to carry a backup battery.

As always:
Get as much battery as you can afford and/or fit
Find your round-trip distance in miles
Divide your battery Watt-hours by your distance to find Wh/mile
Find the speed that matches this Wh/mile
Keep your speed below that target speed, and you won't get caught with a dead battery

More directly, CA3 allows you to set this range requirement and limit your power and thus speed accordingly.

 

[john61ct]

Capacity testing just requires a constant current dummy load, precise voltage measurement and precise timing.

Usually done at the ten hour rate for LI

Get a benchmark at commissioning time during your break in period

then SoH% snapshots, every 100 cycles, or annually, whatever.

Standard for EoL in industry is 80%, but consumers often push to 75% or 70%