How to calculate power (charge up)?

So, just a question I've been curious about for a while, and I was wondering if anyone knew a formula for figuring this out.

Anyhow, assuming that efficiency is maintained at 100% and charge is accepted at a constant rate at all battery %, how would I calculate the amount of time required to charge something in say, this scenario:

Empty 24,000mah Power Bank
Micro-usb input
2.4A charger

As far as I can tell wattage doesn't have fixed time units, which makes it sort of strange to me.... Does anyone know how I would calculate the rough amount of time it takes to charge this?
 
Solution
I believe all Li-ion batteries have built in charging circuits, which regulate the current flowing into the battery. Hence why devices with the same battery capacity can take different amounts of time to charge, or how you can speed up charging by turning on 'quick charge' in some devices. Because of this, I'm not sure it's possible to calculate how long it would take to charge.

In theory, if you wanted to calculate how long it would take to charge a 24000 mAh (24 Ah)battery charging at 2.4A:
Total charge in a 24000 Ah battery = 24 * 3600 = 86400 C
Time to charge @ 2.4 A = 86400/2.4 = 36000 s = 10 hours.

TJ Hooker

Titan
Ambassador
I believe all Li-ion batteries have built in charging circuits, which regulate the current flowing into the battery. Hence why devices with the same battery capacity can take different amounts of time to charge, or how you can speed up charging by turning on 'quick charge' in some devices. Because of this, I'm not sure it's possible to calculate how long it would take to charge.

In theory, if you wanted to calculate how long it would take to charge a 24000 mAh (24 Ah)battery charging at 2.4A:
Total charge in a 24000 Ah battery = 24 * 3600 = 86400 C
Time to charge @ 2.4 A = 86400/2.4 = 36000 s = 10 hours.
 
Solution