The Sigma BP-41 battery is identical to the Ricoh DP-65, but while they both match a million others in voltage, their pin-out is reversed ( - T + instead of + T -). Is there an adapter that is compatible? Also, is there an adapter that accepts DC coming from a solar battery via a USB cable?
That’s frustrating. You could use something like the PIXO C-USB which auto detects pin voltage and charges from USB. You have to fiddle with the connections a bit, but it works. We should have them in stock next week or you can check on eBay.
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