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I was looking through a very legitimate well known product, noticed the battery pack is stamped with 4.4V. I think this is actually the nominal voltage it provides.

The reason I think that is that this is a $100MM+ company, and I know from professional experience, LiPo battery markings and regulatory compliance has gotten extremely tight in the last few years when you ship batteries in products. These guys ostensibly are dotting all the i's and crossing all the t's.

The 4.4V stamped battery, has a much higher mAh stated amount than any corresponding 3.7V LiPo, on a volume basis, then we've ever been quoted.

Is there such a thing as a 4.4V LiPo?

PICTURE AS REQUESTED:enter image description here

Leroy105
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  • They have two cells connected together in some way. Maybe the marking is for the nominal voltage of the pair? – Leroy105 Oct 19 '17 at 19:34
  • I'm assuming the marking is per cell, I have to cut them apart. These things are 350 mAh at 4.4V, and are 25mm x 14mm x 5mm. I think the regulatory requirement is a marking on each cell.... – Leroy105 Oct 19 '17 at 19:41
  • Strange. They don't tolerate 4.4 V very long without damage. – winny Oct 19 '17 at 19:43
  • Maybe they are custom made to be 4.4V. My question is why take on the extra cost, do you get extra mAh at higher voltages in a cell dimension? – Leroy105 Oct 19 '17 at 19:45
  • If they had a formula for a different battery chemistry with higher voltage, they would be billionaires and you would know about it. Measure the actual voltage and you will find something more of a normal 3.7 V nominal LiPo. – winny Oct 19 '17 at 19:48
  • I can't measure it, I gutted the board in a teardown and killed the charging contacts. The battery is now dead. It'd be a serious science experiment to hook it up and charge it separately. – Leroy105 Oct 19 '17 at 19:51
  • No no. Your regular laboratory power supply would suffice. Heck, a voltmeter, reststor and USB charger would do the trick. What does "dead" mean? – winny Oct 19 '17 at 19:54
  • No -- I have to desolder this battery from the board, desolder a header on a board with a charging IC, solder the battery onto the charging board, etc... If this is not something obvious or known, I can give a holler to our battery factory who produces actual cells and just let them run with it... Dead = a reading of 0V currently. Maybe the 4.4V is the maximum voltage value, and there is some regulatory carve-out for stating the max -- but I've only ever seen the nominal operating voltage. – Leroy105 Oct 19 '17 at 19:58
  • 0 V is pretty dead. -0.5 V is the final nail in the coffin. – winny Oct 19 '17 at 20:06
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    @winny There are, in fact, a recent generation of "High Voltage" LIPOs with different construction which are *marketed* as being suitable for a 4.35v charge termination. And charger ICs for that voltage exist. Type "LiHV" into your favorite search engine. – Chris Stratton Oct 19 '17 at 20:22
  • @ChrisStratton Sure, but that makes it a ~3.8 V nominal voltage battery, not 4.4. – winny Oct 19 '17 at 20:26
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    It's become customary to speak of these by their charge termination voltage. The middle voltage isn't really very meaningful - in higher drain applications by the time you see an unloaded reading of 3.7 or 3.8 volts it's nearly time to start thinking about finding the charger. But no, 4.4 (or more realistically 4.35) isn't a counterpart to the 3.7 number, it's a counterpart to the traditional 4.2 charge termination. – Chris Stratton Oct 19 '17 at 20:30
  • I saw the 4.4V max voltage later on, and thought it might be these. I wonder what the price premium is for these. – Leroy105 Oct 19 '17 at 20:40
  • Bah! Some top level management deciding to inflate the numbers. – winny Oct 19 '17 at 21:34
  • @winny, regarding "management deciding to inflate the numbers", no, this is a matter of trade-off, see this answer: https://electronics.stackexchange.com/a/317798/117785 – Ale..chenski Oct 19 '17 at 21:54

1 Answers1

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4.4 V and 3.7 V here refer to different characteristics.

  • 3.7 V is the nominal voltage (average voltage during a complete discharge) of a "traditional" LiCoO 2 -based lithium ion cell. Such a cell typically has a minimum voltage around 3.0 V, a maximum voltage around 4.2 V and a nominal voltage between 3.6 and 3.7 V.

  • 4.4 V refers to the maximum voltage of cells with an improved anode that can endure higher voltages. These cells tend to have a similar minimum voltage, but the maximum voltage is between 4.35 V and 4.4 V. Since they can be charged further, the nominal voltage is also increased to around 3.8 V. This improvement is achieved with silicon and graphene -containing additives

In the radio control world these are explicitly marketed as "LiHV" etc, but they are increasingly common in all sorts of products like mobile phones.

There are several research papers on the subject, e.g. http://m.jes.ecsdl.org/content/164/1/A6075.abstract

jms
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