Battery subject


Hi everyone,

I am searching the appropriate LI-ion battery to use in my Q2686 Wireless CPU PCB but I am not completely sure about some things, so I would be very grateful if somebody can help me out!

First of all, I think I don’t have a complete idea about what a NTC is. Until recently I thought that it was the middle pin that mobile batteries give, so that the mobile can measure their temperature while charging them. But since I’ve read Q2686_CDG_revision4.pdf specification datasheet, I am not really sure. What is this pin and is it absolutely necessary to use with my Q2686? I have asked a lot of battery suppliers in my country but nobody offers a battery with NTC…

Last, I have read in the same datasheet that " Li-ion batteries must be used with the embedded PCM"… Does it mean that this PCM is embedded IN the Q2686 or it should be offered by the battery, because some suppliers from China provide batteries with PCM as well…

Please somebody help me clear all these out!



NTC = Negative Temperature Coefficient; in this context it means an NTC thermistor - which is, indeed, so that the charger can sense the battery temperature.

Not so long as you keep everyone far enough away during charging to be well clear of any flying debris when the battery explodes due to overheating… :open_mouth:

No - it means that the PCM must be embedded within the battery pack.

Take a look at


Thank you awneil for the information! This site isreally useful but the company does not have any Li-ion batteries! Do you know any other comapnies in Europe to do so?

Thanks a lot!


they do, i’ve got two on my desk
there is no thermistor inside though. so you’d have to add one yourself.


Ok I send them an inquiry about a Li-ion battery with 3.7V and over 1500mAh.
How can I add a thermistor? Is it bulky because the PCB should be as small as possible and so should the battery… Does it have an embedded PCM?


Isn’t Varta’s “Lithium-Polymer” just their particular style of “Lithium-Ion” :question:




I don’t think so! When I searched for batteries in a battery company in China, they told me that they do have Li-ion batteries but they suggested me to buy Li-Polymer batteries which perform better but they are not the same! Has anybody tested Li-Polymer battery in his/her wavecom’s product and worked ok?


Although I joked about it earlier, battery charging - especially Lithium-Ion - is a very serious matter, with potentially very serious results if you get it wrong. :exclamation: :open_mouth:

Therefore, you should not rely on internet forums for your design guidance - speak to your local Varta representative.They do have very detailed technical information on the correct handling of their batteries…



Don’t know about Varta’s nomenclature - but in general Lithium-Polymer (LiPo) and Lithium-Ion (LiIon) are two different battery technologies.

They each have similar charging characteristics - and some charging IC’s will do both but they are NOT the same!.

The Aircraft Radio-Control community has taken to using LiPo batteries in their electric model aircraft as some new generation batteries will deliver up to 50C (that’s 50 times their rated current capacity) for short periods of time, and will accept large charge currents - thus leading to short recharge times.

There’s a nice post here with a FAQ on using LiPo batteries - with links to videos of what happens when charging goes wrong…

BTW, there are also two different types of LiIon batteries - one cell type has an charging endpoint of 4.1 Volts, and the second 4.2 Volts. You’ll have to check the datasheet of the battery that you are using to ensure that you charge the battery correctly. I suspect that charging a 4.2 Volt cell to 4.1 Volts is not going to upset things - but the opposite is probably not true.

Also note that there is a Low Voltage cut-off for LiIon and LiPo batteries - usually around 3V. Discharging the battery below this point will usually cause irreversable damage to the battery. The PCM that is installed in a lot of batteries will do a low-voltage disconnect - but this is for the protection of the battery. Don’t rely upon the PCM to sense when the battery is flat - do it yourself. The Q26xx has this facility in the battery management module.

If you are using the Q26xx to do your battery charging, you will have to check that all the battery parameters are correct. See the AT+WBCM section in the AT Command Interface Guide.

In short, check the battery data sheet/talk to the manufacturer before finalizing your design. There are NO short-cuts when using LiIon or LiPo batteries.

ciao, Dave


I stand corrected. :blush:



Sometimes it’s hard to work out if terminology has been mangled by the Marketing department before it gets to the engineers!

From the discussions in this and other threads, I suspect that there’s probably a place for a sticky on the forums somewhere about batteries and using them with the Q26xx modules.

ciao, Dave


Searching for the appropriate battery for my Q2686 device, I have contacted VARTA and talked with the people there. They confirmed that some Li-Poly batteries with Li-ion system DO work just fine with my Q2686 module.

My problem is that I didn’t find there any batteries with as small as possible dimensions and quite high capacity (mAh)… I have seen in another device EEMB’s LIR103450A battery but I couldn’t find anywhere a supplier in Europe but only in China.

I would like to ask anybody who knows any suppliers in Europe not only for this specific battery but any Li-ion or Li-polymer batteries except VARTA.

Thanks and sorry if this post is a bit irrelative with Wavecom’s forum. Although I think there must be a special subject for batteries used with Wavecom’s products.

Thanks in advance!



Most batteries include integrated circuits to prevent overheating/overcurrent and deep discharge. This applies to all batteries for mobile phones.

The middle pin in mobile phone batteries is used by the phone to detect what type of battery it is.


for packaged battery’s, yes. but for seperate cells, not necceseraly.

also, not necceseraly. if you have a three contact battery-pack, this third pin usually is connected to an NTC. with four pins, there is possibly also ID information available.