How does Coconut Battery measures battery health

Hello,

I'm using coconut battery to monitor the health of my A1286 MBP battery which at the moment shows 98% health (6866/7000mAh). How does the utility come to this calculation? I'm asking as I'm doubting the battery capacity of 6866mAh as the laptop barely stays on for an hour under normal usage, including watching some non hd videos on youtube.

To investigate the issue I've used CB's 'discharging with' value, which seems directly connected to 'Amperage' shown in the battery section in system report as a metering of the discharge rate of the battery. Since I believe this measurement comes from the shunt resistor of the battery's output that's to me the truest indication of power being output (as well as battery voltage) and it averages 13/30W.

For a battery which is rated at 77Wh at 100% health, even during high usage it should last at least 2.5 hours (77wh / 30w ) while mine is definitely less than an hour under normal load.

Battery manufacture is ANSANOR so I believe it could be a 3rd party cheap battery problem. But even so how are both system report and coconut battery getting wrong informations?

Or am I completely off with the calculations?

Small note, the laptop internal GPU is disabled..

Cheers,

Alex