How many hours of 5v 2A charding can one get from your 2A and 4A batteries?
Do you have an example of how many full charges to an iPhone each battery can do?
A 4Ah battery means it has enough capacity to provide 4 amps of power per hour. The batteries are 18 volts, so the battery capacity in Watts is (4 * 18 = ) 72 Whr (watt hours). The USB charger supplies power at 5 volts & 2 amps, so converted to Watts that's (5 * 2 =) 10 Watts. So an 18v 4Ah (72 watt hour) battery would take the charger a little over 7 hours for the USB charger to drain it. If your USB device uses less than 2 amps of power, it'll take longer to drain.
Date published: 2017-09-06