command: sudo tlp-stat -b
output:
— TLP 1.6.1 --------------------------------------------
+++ Battery Care
Plugin: generic
Supported features: none available
+++ Battery Status: BAT0
/sys/class/power_supply/BAT0/manufacturer = DP
/sys/class/power_supply/BAT0/model_name = bq20z451
/sys/class/power_supply/BAT0/cycle_count = 666
/sys/class/power_supply/BAT0/charge_full_design = 6330 [mAh]
/sys/class/power_supply/BAT0/charge_full = 5043 [mAh]
/sys/class/power_supply/BAT0/charge_now = 4936 [mAh]
/sys/class/power_supply/BAT0/current_now = 0 [mA]
/sys/class/power_supply/BAT0/status = Full
/sys/class/power_supply/BAT0/charge_control_start_threshold = (not available)
/sys/class/power_supply/BAT0/charge_control_end_threshold = (not available)
Charge = 97.9 [%]
Capacity = 79.7 [%]
my take:
this is an apple battery, meaning this command won’t load it up to a threshold I choose (not available)
charged currently at 97.9%, even if the gui says it’s 100%
capacity is 79.7%, what for me is a very high value, considering this is a 10 year old notebook (maybe it hasn’t been used much?)
your take?
I’d recommend a full battery calibration before running the command one more time, if you haven’t already (charge the battery fully, leave it on the charger at 100% for a while, then fully discharge until it shuts itself off, leave it for a bit, then fully recharge while off). If the calibrated values line up with a full:design ratio of ~80%, especially with a 10-year-old battery with almost 700 cycles on it, my take is that’s pretty great.
That said, I think the best way to get an accurate feel for the health of an old battery is to put it through one full cycle of normal use and time how long it takes to die.
The best way would in fact be testing it with an electronic load that applies a precise and well known load to the battery and integrates capacity until a matching shutoff condition is reached.
However, the majority of people do not happen to have access to such an instrument, so I’d say your suggestion is a close approximation of the best way, which could be augmented by adding simple measurements, which can be done by most people at home for a reasonable, quantifiable judgment.