Corbin,
Be aware I am pulling numbers out of the air to make this illustration easier to understand, I'm learning this as well. the numbers are just for illustration and don't reflect an actual battery (as far as I know).
If I understand this lithuim stuff at all, you are not leaving 16% when you charge to 3.8 volts in a 4.0 volt battery. You have to look at the charge curve of the battery. Lets call this 3.8 volts you give the knee of the curve 90+% of the battery power is contained within the flat area of the discharge curve. From 3.8 volts to 4.0 volts might be only 5% of the total power stored. From 3.8 to (lets grab a figure for illustration purposes of 3.0) 3.0 volts might be the other end of that 90% of the battery power, then you his the low voltage knee where it drops from 3.0 volts to 2.8 volts might be again 5% of the power contained in the battery.
For a crude exercise take a piece of paper, turn it landscape and draw 2 verticle lines 10 inches apart 3 inches tall and call the space between them 100% of your battery power now draw a line from one verticle to the other at the 1.5 inch point of the two verticle lines. we will say that line represents 3.2 volts and 100% of the battery's power. Now erase a half inch of each end of the horizontal line. Then connect the left end of the remaining horizontal line to the top of the left line, then connect right end to the bottom of the right verticle line mark the top of the left line 4.0 volts and the bottom of the right line 2.8 volts.
You now have a VERY rough representation of a lithium charge graph. To be truely accruate the horizontal line would slope from about 3.6 to about 3.0 volts but for illustrations sake this will do.
So from 4.0 volts to the central 96% of your power (that 5% we were talking about earlier) the voltage drops fast then hits what is called a KNEE of the curve then you are in the long haul of the discharge till yo get to that 3.0 volt knee at the other end where a last 5% remains, you will drop fast to 2.8 volts and 100% DOD.
If you push a battery above 4.0 volts or below 2.8 volts you can cause irreversble damage. I don't know what the damage will be but I'm told there will probably be damage.
This is why they tell you should short charge the battery and never over discharge the batter. There is really so little power in the area above and below the knee it isn't worth going there and letting a slip of attention or equipment failure cause damage.
Then you have to worry aput the variation between cells. If you charge your lowest cell to max you might drive your best cell over the top.
Please tell me if what I wrote helped you. I drew that graph a while back and it sure helped me when I next looked a t a battery data sheet.
Jim
Be aware I am pulling numbers out of the air to make this illustration easier to understand, I'm learning this as well. the numbers are just for illustration and don't reflect an actual battery (as far as I know).
If I understand this lithuim stuff at all, you are not leaving 16% when you charge to 3.8 volts in a 4.0 volt battery. You have to look at the charge curve of the battery. Lets call this 3.8 volts you give the knee of the curve 90+% of the battery power is contained within the flat area of the discharge curve. From 3.8 volts to 4.0 volts might be only 5% of the total power stored. From 3.8 to (lets grab a figure for illustration purposes of 3.0) 3.0 volts might be the other end of that 90% of the battery power, then you his the low voltage knee where it drops from 3.0 volts to 2.8 volts might be again 5% of the power contained in the battery.
For a crude exercise take a piece of paper, turn it landscape and draw 2 verticle lines 10 inches apart 3 inches tall and call the space between them 100% of your battery power now draw a line from one verticle to the other at the 1.5 inch point of the two verticle lines. we will say that line represents 3.2 volts and 100% of the battery's power. Now erase a half inch of each end of the horizontal line. Then connect the left end of the remaining horizontal line to the top of the left line, then connect right end to the bottom of the right verticle line mark the top of the left line 4.0 volts and the bottom of the right line 2.8 volts.
You now have a VERY rough representation of a lithium charge graph. To be truely accruate the horizontal line would slope from about 3.6 to about 3.0 volts but for illustrations sake this will do.
So from 4.0 volts to the central 96% of your power (that 5% we were talking about earlier) the voltage drops fast then hits what is called a KNEE of the curve then you are in the long haul of the discharge till yo get to that 3.0 volt knee at the other end where a last 5% remains, you will drop fast to 2.8 volts and 100% DOD.
If you push a battery above 4.0 volts or below 2.8 volts you can cause irreversble damage. I don't know what the damage will be but I'm told there will probably be damage.
This is why they tell you should short charge the battery and never over discharge the batter. There is really so little power in the area above and below the knee it isn't worth going there and letting a slip of attention or equipment failure cause damage.
Then you have to worry aput the variation between cells. If you charge your lowest cell to max you might drive your best cell over the top.
Please tell me if what I wrote helped you. I drew that graph a while back and it sure helped me when I next looked a t a battery data sheet.
Jim