i have a battery charger (DC1.5 550mAX4) In how much time will it charge a battery(1.2v 2000mAh)?

Question

Please give the calculations

Answer 1

Depends on the charger. Is it a current source, or voltage source? This can be calculated, but you are not giving enough information.

My best GUESS would be 8 hours, to a 90% charge state.

Assuming you are only seeing half the current 550mA/2 = 275 mA. Take your (2000mAh/275mA) /0.90 efficiency = 8 Hours

If it were a constant current source, then you could simply divide the capacity by the charge current. Say you have a 200 mA constant current source, then your charger would charge the battery in 10 hours, assuming 100% efficiency. At C/10 (Capacity divided by 10), charge efficiency is typically only 90%, so you 10 hours needs to be divieded by 0.9, yielding 11.1 hours.

Most inexpensive devices initially put out a high current, then drop down. You can determine the charge time, by measuring the current over time. Say you start charging the battery, and take current readings every minute. If you took 60 of those readings, you could determine how much you have charged the battery in the first hour.

One other aspect, is how do you define charged? That is not as simple as it sounds, as most chargers can not attain a true 100% charge state, especially quick chargers.