Some time ago, I lost the charger for my Ixus camera. I hadn’t used it for a while, and sort of presumed that it was dead. However, after several months of no charging, I was amazed after when I picked it up one day, and it fired up with enough charge to take several flash photos.
It has a Lithium ion battery that’s barely bigger than the tiny memory card. Which got me to thinking…does anyone know why is it so difficult to get rechargable Li-ion batteries in AA or AAA size? You can get Ni-MH and Ni-Cad batteries in standard sizes in any electrical, music or photo shop, but I can’t find Lithium rechargables anywhere.
I’d love to get a few sets for my big, power-hungry digital SLR, but can’t find any.
Seems to me they should be the logical successor for NiMH batteries that are around: after all, I’ve had a Li-ion battery in my mobile phone for at least six or seven years.
Any ideas as to why they can’t be got? Does such a thing exist? If not, why not? If it does exist, why are they so hard to find?
I think it’s because the volatges aren’t the same. Ususally a given kind of battery will have one voltage for a single cell, and batteries are made in different voltages by combining multiple cells.
In a word, Voltage. Normal disposable battery chemistry results in cells with ~1.5V. NiCads and NiMH give ~1.25V per cell…pretty close, and will usually work fine as disposable batterys are below that level well before they are dead.
Lithium chemistry yields at least 3V per cell, and in some cases closer to 4. So replacing a normal battery with a lithium rechargable overvoltages the device by at least twice. Thus manufacturers don’t want to make them available as “average” consumers are apt to burn things out.
If you take pains to get them, you can get lithium chemistry cells in traditional packaging, but they will probably never be available through consumer channels.
Ni-Cd and Ni-Mh cells have nominal volage of 1.2V, so they work as drop-in replacements for alkaline AA/AAA cells. A Li-Ion cell has a nominal voltage of 3.6V.
Li-Ion has safety issues as well. From Wikipedia entry on Li-Ion:
By the way, there are low self discharge Ni-Mh AA batteries available. They are even sold pre-charged. One example is the Sanyo Eneloop; I have several sets and been pleased with the performance.
Primarily because lithium-ion batteries are incredibly fragile, and dangerous. If you discharge one too much, you might damage it. If you dent one, you might damage it. If you overcharge one, or try to charge a damaged one, it might explode spectacularly.
Thus, they require special charging and discharging circuits, as well as pressure sensors and other fail-safe devices in order to work safely.
Devices that accept ordinary AA batteries do not have the appropriate fail-safes, so they would have to be integrated into the battery - taking up space in the AA case, and costing money.
Wow! With them being so commonplace in mobile phones, I never imagined that safety would be an issue. I guess the device being powered has to be designed for the higher voltage involved and have specific safety features to cope with the battery’s chemistry.
Thanks to all for the quick replies. scr4, thanks for the info on the low self-discharge NiMH: I didn’t know about them, and they sound like exactly what I need. My main problem is picking up my “good” camera for a quick snapshot, and finding dead batteries. It seems like a set of those should sort my problem out.