How to calculate the charging time of aa batteries?

LED Flashlights – General Info
1

there is a formula from google site I found:

charging time(hours)=(capacity of battery mAh)*(1-charging efficiency)/current being used to charge the battery mAh
for example:
If charging a 2000mAh AA battery with a current of 1000mAh and an efficiency of 90%, the charging time would be
(2000mAh*(1-0.9))/1000mAh=200mAh/1000mAh=0.2 hours or 12 mintues

how about if I charging 2pcs/8pcs aa battery together? how long the time will takes?
how to know the current and efficiency?

If anyone have ideas?

2

also battery calculator online, but different results

2000mAh battery , 1000mah current, but 20% efficiency loss, final: 2.4hours

:smiling_imp:

3

12 minutes is not correct.

Ignoring losses, a 1000mah current will charge a 2000mah cell in 2 hours.

A 2000ma current will charge in 1 hour.

A 200mah current will charge in 10hours.

If you’ve a battery pack (cells connected), then same applies, just use the total capacity of the battery and the charging current.

Edit to add: whats this for? No good charger uses time alone to charge, most use dV/dT or similar.

4

I find the easiest way is to see if anyone has reviewed the charger and then just use their data, for example:

https://lygte-info.dk/info/indexBatteriesAndChargers%20UK.html

I use this IKEA chrager for my AA NIMH so I can look up the data:

https://lygte-info.dk/review/Review%20Charger%20Ikea%20Ladda%20YH-990BF%20UK.html

For a 2000mah Eneloop it takes just over 120mins at 1000ma charge current, actually very efficient. And because it has 4 bays which each charge at 1000ma it will take the same time whether it is 1 or 4 AA being charged.

5

thank you.

yeah, 12munites is not correct. :weary:

I understand as like this, of correct?
same 4pcs 1.2V aa ni-mh batteries, 2300mah.
and charger specification:
DC 1.2V 1000 mA
D/C/AA/AAA *1: 1000mA (850mA-1150mA@1.2V)
*2/*3/*4: 2000mA (1700mA-2300mA@1.2V)

charging current: 2000mah/4=500mah, 500mah current will charge 2300mah in 4.6 hours
ingnoring losses, 4pcs aa ni-mh battery will takes 4.6 hours to charge.

I use ebl 906 battery charger:Buy Smart Battery Charger for C/D/AA/AAA/9V Batteries – EBLOfficial

6

the data seems too professional, I can’t know them well. :person_facepalming: Thank you anyway

7

li ion will usually take at least 6 hours to full charge

[assuming they were empty at the start]

the first 80% might go in, in 30 minutes

after that it has to slow down or the volts get too high

8

That site gave you a bad formula. The charging efficiency is the portion of the energy delivered by the charger that the battery retains, so it effectively reduces the charge rate. The formula should be:

. . . . T = C / (╖ * I)

or in long form:

. . . . Charge Time (hr) = (Battery Capacity (mAh)) / (Charge efficiency * Charge Current (mA))

For your example:

. . . . T = 2000mAh / (0.9 * 1000mA) = 2.22 hours

The efficiency is difficult to know since manufacturers don’t publish it, and it decreases as the cell ages and its internal resistance goes up. I’m not sure if it might vary depending how deeply discharged the battery is, too. 80-90% seems like a reasonable estimate, but do be aware the calculation will be approximate. This is fine if you just want an idea how long you are going to be waiting.

If you want to use this formula to decide when to terminate charging, it is not advised to do so for high charging currents. It should be ok to do so with NiMH batteries for low currents (below 0.25 C rate). The official test for NiMH cycle life (IEC 61951-2) actually moderately overcharges the batteries, but does so at a relatively low rate.

However, since your EBL 906 is a smart charger, which is good, it uses a method called -dv/dt termination to detect when the battery is full, instead of estimating it based on time or voltage. You should not need to decide yourself when to stop charging. Just remove the batteries once the charger indicates it is done.