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Forum: Pentax Camera and Field Accessories
02-10-2020, 02:49 PM
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As I've had a dead DSTE D-Li90 clone knocking about for a while, I thought I'd open it up. Externally it claims 2800mAh, internally it has two 1400mAh cells in series. So claimed capacity = lie. Or miscalculation, if you want to be generous :p... On the assumption the Newmowa one you tested has the same level of economy with the truth, I'd expect it to have 1200mAh cells in it, and thus be about 2/3 of the Pentax capacity. Which is your observation when you tested it, so it's probably reasonable to expect an exaggerated claim to be about 2x the actual capacity, when the battery is new. The internal protection circuit in the DSTE would appear to be OK, preventing over- and under-charging, dead cells, overheating and protecting against short circuits. (I couldn't test it as it's corroded and the cells are leaky, but it appears to be an implementation of the standard Ricoh circuit plus a thermal sensor. This circuit is shown in the data sheet linked from R5460 Series 2-Cell Li-ion Battery Protection IC) .
I'd count myself lucky to get 3 years' use out of a lithium battery pack, in general. Quite how Pentax achieve 5 or 6 years is a bit of a poser, but may be down to sourcing high-quality cells which are designed for the job in hand, and users typically using only the supplied charger. It'd be interesting to hear from people who've used only the Pentax charger on 3rd-party batteries, and vice versa.
Today I could pick up a pair of DSTE clones (which now appear to show 2100mAh on the label) from a well-known supplier, for £14.49; a single Pentax D-Li90 is £59, so I could get roughly 8 clones for the cost of one OEM. If the clones die after 3 years, not 6, that's still 1/4 the cost to me, with the minor inconvenience of changing batteries a bit more often, and maybe carrying one more spare (if I'm not carrying all of them anyway). And I won't mind nearly as much when they stop working, as long as I still have some that are OK. Please note that I Am Not A Serious Photographer (i.e. my livelihood doesn't depend on it) - YMMV.
Cheers
Jonathan
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