# How long does it take to change up

#### Albinoni1967

##### Enlightened
On average assume if if I charge up a flat 18650 battery how long does it take. Would you say 1, 2 or 3 hours.

#### MBentz

##### Enlightened
Depends on the battery and the charger. If your charger charges at 1 amp and you have a 3000 mAh battery, it will take three hours.

If your charge rate is .25 amps and you're charging a 2000 mAh battery, it will take eight hours.

#### Albinoni1967

##### Enlightened
Ok I'm getting a Xtar VP1 charger and my batteries are 3400mAh, but I'm not sure what rate the VP1 charges at.

#### Curious_character

##### Flashlight Enthusiast
Depends on the battery and the charger. If your charger charges at 1 amp and you have a 3000 mAh battery, it will take three hours.

If your charge rate is .25 amps and you're charging a 2000 mAh battery, it will take eight hours.
Sorry, it doesn't work that way for Li-ion batteries. The constant current is delivered only until the cell voltage reaches 4.2. After that, the charge current slowly drops. The cell isn't fully charged until the current drops to a very low value. It typically takes about 3 hours to fully charge a Li-ion cell at 1C. That is, a 1 amp charger takes about 3 hours to fully charge a 1 Ah cell.

This is the standard charge algorithm, but not all chargers follow it. See HKJ's reviews for actual measurements of actual chargers.

c_c

#### MBentz

##### Enlightened
Sorry, it doesn't work that way for Li-ion batteries. The constant current is delivered only until the cell voltage reaches 4.2. After that, the charge current slowly drops. The cell isn't fully charged until the current drops to a very low value. It typically takes about 3 hours to fully charge a Li-ion cell at 1C. That is, a 1 amp charger takes about 3 hours to fully charge a 1 Ah cell.

This is the standard charge algorithm, but not all chargers follow it. See HKJ's reviews for actual measurements of actual chargers.

c_c

Charging my 5000 mAh R/C batteries at a 1C (5 amps) rate takes a little over an hour, according to the digital display on the charger.

I have never timed how long it takes to charge one of my 3400 mAh 18650s in an i2 or i4 charger, but it certainly is not an all day affair. According to you it would take well over 9 hours to charge, and that had not been my experience. Perhaps my two chargers are sending more current to the batteries? According to my DMM, they come off the charger at ~4.21v.

#### Norm

Charging my 5000 mAh R/C batteries at a 1C (5 amps) rate takes a little over an hour, according to the digital display on the charger.

I have never timed how long it takes to charge one of my 3400 mAh 18650s in an i2 or i4 charger, but it certainly is not an all day affair. According to you it would take well over 9 hours to charge, and that had not been my experience. Perhaps my two chargers are sending more current to the batteries? According to my DMM, they come off the charger at ~4.21v.

What is the state of charge at when you start to charge your cells? They may well be a long way from fully discharged.

Norm

#### MBentz

##### Enlightened
What is the state of charge at when you start to charge your cells? They may well be a long way from fully discharged.

Norm

Good question. Currently I'm only using one light with rechargeable batteries. The next time I charge the batteries I use in the SX25L3 I'll report back.

#### Curious_character

##### Flashlight Enthusiast
A good explanation of the Li-ion charge process is at http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries. The lengthy process I described is for a full charge. If you simply charge at 1C for a little over one hour and terminate the charge when the voltage first reaches 4.2 volts/cell, the battery ends up about 85% charged -- it's the remaining 15% that takes the extra two hours. Some chargers probably cut off somewhere between the 85% point and full charge, resulting in charge times between 1 and 3 hours at 1C. The charger reviewed by HKJ in the link he provided does this.

c_c