RX100 Generic 1600 mAh NP-BX1 Battery Review

Started May 4, 2013 | Discussions thread
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Ron AKA
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RX100 Generic 1600 mAh NP-BX1 Battery Review
May 4, 2013

I asked about experience with this generic battery in this thread a while back, and decided to take a chance on it. I ordered it off eBay from Unplugdaily. It has the following identifying numbers:

Box: 28735 BSONBX1XLI01 [D 553]

Battery: N28735

And looks like this:

N28735

It arrived reasonably charged up to 3.7 volts. I put it in the RX100 and charged it until the charge light went off. The voltage was now 4.2 volts. This is the same voltage I get when I fully charge the original Sony battery. This all looks good.

The dimensions are the same and there are four contacts labeled the same as the original Sony:

C - T +

Through a bit of research I determined the T terminal is for an internal thermistor which changes resistance as the temperature of the battery changes. I believe the RX100 uses this to shut the camera down if the battery overheats. In cell phones it is sometimes used to prevent charging if the temperature drops below freezing. Not sure if Sony uses that or not.

At room temperature (70 deg F) the original Sony battery measures about 104K ohms from the T to - terminal. After a half hour in the freezer it increased to about 330K ohms. And warmed up to about 85 deg F the resistance dropped to about 75K ohms.

At room temperature the generic measured about 75K ohms. When I put it in the freezer and when I warmed it to 85 deg F the resistance never changed. I concluded that there is no thermistor in this battery pack and there is just a simple 75K ohm resistor. The net result is that the RX100 will think the battery temperature is at 85 deg regardless of what temperature it is really at, and there is no high temperature protection.

The lack of protection is not that good, if you are going to shoot long movies. From other posts I gather that the battery may heat up under a long continuous shoot. If you shoot long bursts of movies then it would be prudent to pull the battery a few times to see how hot it gets. Movie mode is not my main purpose so I will either use the Sony battery for that, or check this generic if I use it.

There is also a contact marked C. It appears to be not connected to anything and is not used in the camera. There are only three terminals and a spring in the camera. The spring would not likely reliably connect to that C terminal. So I have no idea why the C terminal is provided and what use it could be.

On another Sony camera I have that uses a NP-BN1 battery, it has three terminals with no T terminal, but has the C terminal. It is used by the camera (W570), and I measure a reduced voltage at it. When the + voltage is 4 volts this C terminal measures about 3.7 volts. Again no idea what this is about, but it does not appear to be for temperature measurement. Perhaps it assists in determining charge level??

That is about it for now. Will try to post back when I get some feel for the capacity of this generic compared to the original Sony (1240 mAh). If anybody has any idea what those C terminals are about, I would be interested in your thoughts... In a Google search I have come up dry. It does not even seem to be covered in this Technical Manual  from Sony.

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