CHG IN Pin current handalling capability

I want to know if anybody has used to charge battery using a charger gretter than 850mA (as mentioned in PTS of Q2686)…I have a cherger which can provide 3A. What will be the result?


I have built a power supply to supply 2A to the Li-Ion charging circuit on a Q2686 - all seems to work OK.

However, the Q2686 PTS notes that the charging circuit on the Q2686 ONLY regulates the voltage to the battery, the power supply has to regulate the current. This maximum current is dependant on the battery being used.

ciao, Dave

Hi ciao,
Thanks for the reply. I will try with my 3a supply and post the result.

Please don’t just “try” :exclamation: :open_mouth:

Please take great care to ensure that you correctly design your charger to safely charge your battery.

Li-Ion batteries are extremely dangerous when incorrectly charged :exclamation: :open_mouth:

For example, look at this video:


I have the same problem. Is there any problem to use an 1A power supplier? because mine is 500mA, and I think it doesn’t work correctly.



I can’t understand what is the function of this charger. First of all, my power supplier in CHR-IN, is Iout=500mA and Vout=5V, but when the module starts the charger, the current is 820mA at 4V. If I connect, another 2.5A power supplier and I don’t limit the current, then the module takes the current it needs, because of my battery is 3.75V an 2.2Ah, it takes 2.5A. Does it mean that the module doesn’t control the charger current?
Can anybody explain how does it work. Please.
Hi, I c

It is clearly described in the Product Technical Specification (PTS):

That’s all it does - just turns the switch ON or OFF:

  • When the switch is ON, the power supply (at CHG IN) is, effectively, connected directly to the battery;
  • When the switch is OFF, the power supply (at CHG IN) is, effectively, disconnected from the battery.

Clearly, when the switch is ON, it will pass whatever current the power supply can give - that’s why it is essential that the power supply limits its own output current to the maximum value stated!

As stated, it doesn’t control its magnitude - simply switches it ON or OFF.

When designing-in any electronic device, it is always important to carefully study all the documentation provided by the manufacturer!

In addition to the PTS, you also need to study the Wismo Quik Q2686 Customer Design Guidelines:
Reference : WM_PRJ_Q2686_PTS_003
Revision : 003
Date : February 9th 2006

It clearly illustrates the charging arrangement:
[attachment=0]Q26 Charging Circuit.gif[/attachment]

Sorry but I don’t have this document Q2686 PTS, Ref wm_prj_q2686_pts_001, Rev 008, 25 Oct 200, I can’t find it in the Wavecom website, and in my supplier. Could you send me the document, please?

Another doubt, is about the charger, I don’t have a AC/DC Charger, because my design is for an AVL, so it’s a car battery connected to the step-down and then to the chg-in, is there any problem with this configuration?

Thank you for your help.


Ok, I have it.

Thank you.


A what :question:

Not if it meets the stated specifications!

The “configuration” is irrelevant - so long as it meets the stated specifications!

The Q26 (like any other device) neither knows nor cares how you achieve the stated specifications - it just requires that you do meet them :exclamation: