About 18650 Li-Ion Battery Chargers Pt.2 of 4, How fast a charger charges the battery

About 18650 Li-Ion Chargers - Pt.2 of 4, How fast a charger charges the battery

It does not mean the higher the charging current the better. Yes the higher charging current charges the battery faster but to prolong lifespan and ensure safety, the standard charging current in the industry is 0.2C to 0.5C (C here means battery capacity).

For example, the charging current for 18650 3000mAh battery is 600mA (0.2 x 3000) to 1.5A(0.5 x 3000). But normally the maximum charging current should not be larger than 1C and best within 0.2C to 0.5C.



I will talk about the common chargers available in Singapore – Nitecore and Xtar. These 2 are good chargers commonly used for charging Li-Ion and other batteries. In this article I will only talk about 18650 Li-Ion batteries. How fast a charger charges depends on the charging current per slot.

The Nitecore i2 and D2 charger;
When 1 or 2 batteries are charged at the same time, each charging slot will receive a maximum output current of 0.5A.




The Xtar SP2 and VP2 charger;
The SP2 charger has one button that is used to select charge current of 0.5A, 1A and 2A. The selection affect both slots. Maximum is 2A per slot. When using 2A, it is more suitable for IMR type of battery as it's too high for normal battery.


In  VP2 you have the option of selecting 3 charging current of 0.25A/0.5A/1.0A. Maximum is 1A per slot. 




The Nitecore i4 and D4 charger;
When 4 batteries are charged at the same time, each charging slot will receive a maximum output current of 375mA.

When one or two batteries are charged, each slot will receive a maximum output current of 750mA.
Note : The charger has 2 channels, one channel is handling slot #1 and #3, the other channel is handling slot #2 and #4. When charging cells in both slots for a channel, time division is used to distribute the charge. Sounds complicated right?

If you want to charge two cells independently of each other (i.e., each charged at the full 750mA current the unit is capable of), you need to place the cells in slots #1 & #2, #2 & #3, #1 & #4, or #3 & #4.

If you place the cells in the paired slots  #1 & #3, or #2 & #4, the charging current will be split between the cells. Rather than just cutting in half (i.e., 375mA per bay), the current remains at 750mA for each bay – but it alternates charging by cycling off/on once every second for each battery. This effectively results in the same thing, but the cell is actually being charged at 750mA for a 1sec on, 1sec off, cycle. 

The end result of all of the above means that it takes a little longer to fully charge your cells. Some said for one 18650 2200mAh cell (or two cells in independent channels), it takes at least 5 hours charging time from fully depleted and some even complain that four 18650s would take 10+ hours on the i4.

This is the main setback of this i4 charger, you need to take note of which slot you put in the battery if you are charging 2 batteries. So take note of this.



The Xtar VP4 charger;
Many thought that VP4 is a good upgrade from VP2, but got disappointed in the charging current of the VP4. In  VP4 you have the option of selecting 3 charging current of 0.25A/0.5A/1.0A but only 2 charge slot can support 1A charging current.

If a battery is in slot 2 or 3 (the centre 2 slots), then the maximum charge current is 0.5A per slot. So even if you are not charging 4 batteries at the same time, if you put 1 or 2 batteries in slot 2 or 3, the charging current is limited to 0.5A per slot.


Summary : When only slot #1 and/or slot #4 is used the maximum current is 1A. If there is any batteries in slot #2 or #3 the maximum will be reduced to 0.5A per slot.


The Nitecore UM10 and UM20 charger;
UM10 is single slot while UM20 is a 2 slots charger.

In the specifications, it stated Output Current: 1000mA / 500mA for both UM10 and UM20. The current output depends on the input source, which is not provided as it uses a USB 5V cable (only the USB cable is given). If you use a High Power USB 5V 2A adapter like the newer handphone adapter, it may get 1A  per slot for UM10 and UM20. But if you use a older Low Power USB 5V 1A adapter, of course you may only get 0.5A per slot for UM10 and UM20.

Since the 5V USB power adapter is not provided by Nitecore, how efficient is the input source is questionable. Personally I do not like the idea of using a third party power source not supply with the charger. Neither do I like the idea of using the PC to power the UM10 or UM20.  So though it has the convenience of using the same 5V USB charger as your handphone, but many end up buying another high power 2A adapter as you do not want your handphone to fight for the same adapter (so additional cost involved).


The Xtar VC2 and VC4 charger;
The Xtar VC2 is a 2 slots charger while the VC4 is a 4 slots charger.

The VC2 automatically adjust suitable charging current from 0.1A to 0.5A.

The VC4 automatically adjust suitable charging current from 0.1A to 1.0A and maximum up
to 0.5A x 4 slots or 1.0A x 2 slots. So if you are charging 4 batteries, the maximum charging
current per slot is 0.5A, only if you are charging 2 batteries then it's 1A per slot.

Again you have to remember which slot to put your batteries to achieve what charging
current in VC4 : The outer 2 slots are 1A, and the inner 2 slots 0.5A. It means if you put
3 to 4 batteries, it will be 0.5A per slot.


…contd Pt.3