I think the only way to get 10.8v and 5800mah is 2p3s.
ohaya, has your machine reported capacities on the discharge cycles? I imagine they may be lower in the first cycle or two, but it would be nice to know.
EDIT: Cross posted with your pic. Thanks for sharing that.
So the total mAh/Ah rating of the pack is determined by the number of cells in parallel, right? I thought I had it figured out, then got confused somewhere, trying to get back to where I was before... :Sp
Sorry, I was so flustered by the voltage thing, that I didn’t bother to note the discharge results :(… I know you all are probably getting tired of hearing that, but trying to be candid here.
If you google the NCR18650 and MH12210, it looks like it comes up with a Panasonic 2900 mAh battery, with same wrapping style, so I think that that’s what these batteries are.
One last question ohaya. Sorry for all the questions. I’m wondering if the “C 9907” is date code. Usually the date codes are in faint characters that are formed by perforations going lengthwise on the side of the cell. Usually the last part is a date code. Do you see anything like that on the side of the cells?
They will be much newer. The letters stand for the month and year. Y will be pretty recent, but I don’t have the date codes in front of me. I will get back on that.
I just looked through the Panasonic data sheets and such on these cells. They have all kinds of warnings, but not one mention of taking cells to low voltage being dangerous. The closes thing I could find was the following:
“Overdischarge can damage the performance of the battery. Equip the unit with a mechanism to
prevent overdischarge, especially in situations where the user may forget to turn the equipment off.”
I’m assuming that discharge protection would have been in the Fujitsu battery pack circuitry?
I don’t think these have individual protection circuits. The wrappers on the negative end don’t go “around” to the flat part of the negative end, but only down the side, to within a couple of mm’s of the bottom, so I’m pretty sure about that.
Yes the pack's circuitry handles the protection function, and also does the balancing for charging - that's all the crazy little wires going every which way inside.
Looks like I was wrong about the letters being the month and year. That must be for Sanyos or some other maker. The four numbers are the date. Looks like yours were made in September 2009. Check out post #66 here:
I don't know if I'll buy any of those batteries, but I might buy some other Fujitsu stuff. Maybe another tablet to add to my pair of Fujitsu tablet pc's. :)
I bought some unused versions of these cells a while back. They have a “2525” code and C9V (the 9 is above the V). The 99xx code is most likely a date code, I don’t think that 99xx can be assumed to be 1999 or 2009.
Charging new li-ion batteries is a completely different animal than charging li-ion batteries that have been repeatedly discharged too much. I believe 1.9v is the optimal voltage for factory fresh batts before their first charge. There is a white paper pdf floating around on the net about this. From Moli corp or panasonic or someone similar.
As I understand it (from the nasa white paper i believe), the danger of crystal formation occurs after REPEATED overdischarge below 2.5 volts and then recharging. If the batteries are indeed new (and that’s a big “if”), then there is NO danger of crystal formation because there has NOT been repeated OVERdischarge cycling. Crystal formation needs mutiple cycles to form. And as we know, the crystals form, rip the interior catalyst bag and then the dreaded venting with flames occurs. So if there has NOT been repeated overdischarge, you SHOULD THEORETICALLY be safe and fine. Whether the cells are capable of a full charge is another story.
In fact, NASA found that overdischarging SINGLE cells and then recharging did not produce venting. Venting occurred with PACKS containing multiple cells.
I am NOT a battery engineer, so this info should not be considered completely accurate. I could have misread or misunderstood something I read.
I’ve taken a couple of batteries through charge-discharge-charge-discharge-charge cycles. At the end of the 3rd charge, the batteries were at 4.15 - 4.20V.
I then did another discharge test @ 1A discharge on both batteries. I don’t know if I’m doing something wrong (I’ve only had the Accuccel for a couple of weeks now), but when I did those batteries, I got 633 mA, and 849 mA.
That doesn’t seem right? Too little, since these are supposedly 2900 mAh batteries?
Jim
P.S. The 2 batteries that I charged last night/this morning (losing track of days and nights here :laughing: have been holding their voltage. Both of them are about the same voltage as after the final charge that I did last night/this morning.