#20V LITHIUM BATTERY PORTABLE#

The laptop market drove most of the volume for high-capacity 18650 cells in the past, but the shift to lighter/thinner form factors has shifted things to prismatics and pouch cells. In any case, I wonder what the future holds for the 18650. Of course, I saw another talk by a researcher who contradicted that. My understanding from a talk by some guy at HP is that all things being equal, pouch packs tend to be more durable because they can dissipate some of the mechanical stress from deformation of electrodes during charging. In comparison, OEM batteries for your laptop are unlikely to lie about capacity. The fun part is that differing discharge curves between various Li-ion chemistries mean that even if you compare two bare cells with the same mAh rating and differing chemistries, you'll get different total energy numbers in watt-hours, especially as you go up in current.Īlso, remember that as those packs get cheaper, the manufacturers are more likely to lie about the specs. Given this, direct-drive off Li-ion is quite rare, with almost everything having a DC-DC converter between the cells and the load to deal with that curve and to create the voltage the device uses internally.

The voltage vs charge state curve at any given current load has some shoulders at the start and end, but does have a distinct slope down instead of a plateau with a sharp drop-off. those that use Ni, Mn, and/or Co oxides for the positive electrode instead of FeP oxides) have a just-charged voltage of usually 4.2V (though some high-capacity cells pump that up to 4.35V), and a discharged voltage of 2.5V to 2.8V.

#20V LITHIUM BATTERY PORTABLE#

If they actually were all labeled like the Poweradd sort of is that Paltival linked, in watt-hours, they'd actually be bearing a useful number for comparisons.Īs a clarification for what Deffexor posted upthread, most Li-ion chemistries used in portable batteries (i.e. 3.7V nominal) wired up in parallel, and not the actual amp-hour capacity of the pack at the voltage you're using it at. It's pretty amusing that all those battery packs are using an amp-hour number based on the lithium ion cells they contain (i.e.

20v lithium battery