winny wrote:
"Will all the respect, I would not agree with you on the first one. The nominal voltage is the midpoint of the discharge curve without any load. To say what the voltage is under load is less useful since it's hard to calculate worst case scenarios from it.
The second part is also of a similar matter. If you have a transistor for instance that will blow at 4.1 V and your battery will drop down to 4.0 V when loaded with the circuit in question, the capacitance/chemistry slowness will very likely blow the transistor before the voltage drops down to 4.0 V."
Thank you for the clarification and correction.
Here's what the BatteryUniversity.com says to confirm what you posted -
QUOTE:
"
[font=Verdana, Arial, Helvetica, sans-serif]Confusion with voltages
For the last 10 years or so, the nominal voltage of lithium-ion was known to be 3.60V/cell. This was a rather handy figure because it made up for three nickel-based batteries (1.2V/cell) connected in series. Using the higher cell voltages for lithium-ion reflects in better watt/hours readings on paper and poses a marketing advantage, however, the equipment manufacturer will continue assuming the cell to be 3.60V.
The nominal voltage of a lithium-ion battery is calculated by taking a fully charged battery of about 4.20V, fully discharging it to about 3.00V at a rate of 0.5C while measuring the average voltage.
Because of the lower internal resistance, the average voltage of a spinel system will be higher than that of the cobalt-based equivalent. Pure spinel has the lowest internal resistance and the nominal cell voltage is 3.80V. The exception again is the phosphate-based lithium-ion. This system deviates the furthest from the conventional lithium-ion system[/font]
[font=Verdana, Arial, Helvetica, sans-serif]
Prolonged battery life through moderation
Batteries live longer if treated in a gentle manner. High charge voltages, excessive charge rate and extreme load conditions have a negative effect on battery life. The longevity is often a direct result of the environmental stresses applied. The following guidelines suggest ways to prolong battery life.
-The time at which the battery stays at 4.20/cell should be as short as possible. Prolonged high voltage promotes corrosion, especially at elevated temperatures. Spinel is less sensitive to high voltage.
-3.92V/cell is the best upper voltage threshold for cobalt-based lithium-ion. Charging batteries to this voltage level has been shown to double cycle life. Lithium-ion systems for defense applications make use of the lower voltage threshold. The negative is a much lower capacity.
-The charge current of Li-ion should be moderate (0.5C for cobalt-based lithium-ion). The lower charge current reduces the time in which the cell resides at 4.20V. A 0.5C charge only adds marginally to the charge time over 1C because the topping charge will be shorter. A high current charge tends to push the voltage into voltage limit prematurely."
[/font]
[font=Verdana, Arial, Helvetica, sans-serif]
Page ref: [/font]
The high-power lithium-ion (BU5A)
The ideal charge voltage from above for colbalt based Li-Ion seems to be
3.92V which is way below the oft quoted 4.2V,
my charger (NanoCharger) seems to charge to
4.09V - so I don't see 4.2V on any of my RCR123's - but it is rated to 4.2V (marked on charger) and when I measure it open-circuit - it does measure 4.2V -
so perhaps the charger may make a difference?
Thanks,
[font=Verdana, Arial, Helvetica, sans-serif]
[font=Verdana, Arial, Helvetica, sans-serif][/font]
[/font]