Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Heat pumps behave like bidirectional refrigerators: they cool the building by heating the outside air or heat the building by cooling the outside air. In relatively mild, dry weather, this works perfectly.
Here in the Northeast US, it’s not such a bright idea. For about half the year, the ambient temperature is low enough and the humidity high enough that pumping heat out of the exchanger drops its temperature below the dew point, whereupon ambient moisture condenses on the fins and, given the temperature differential between ambient and coil, freezes solid.
In that situation, the efficiency of the heat exchanger drops well below zero: it turns on electric resistance heating bars to warm the inside air and runs a defrost cycle on the exterior heat exchanger.
Just for curiosity’s sake, I applied a slitting saw to the oldest defunct generic NP-FS11 battery pack, cutting carefully along the bonded joint between the two parts.
No coolant, 1000 rpm, 200 mm/min, the saw is 22 mm diameter. Much slower than you’d use if you were in production, but I’m not.
First cut all the way around at 0.5 mm inside the case, then another pass at 1.0 mm. The second cut went ting as it passed the tabs at the base of the cells, so I knew the halves were released.
Inside we find a pair of 14430 Li-Ion cells, wired in parallel, with a little protection circuit board just jam-packed with teeny parts. One may reasonably assume the circuit controls over-charge and over-discharge, as well as current limiting.
Pack opened
So a reasonable (or, perhaps, amusing) thing to do would be to buy raw cells from a nominally reputable supplier, do a heart transplant, and see if that improves the situation.
Protection Circuit – Outboard
Photos of the protection PCB, showing the cell connections. Positive end of the cells is toward the PCB. I think there’s enough clearance in the camera’s battery compartment to allow a wrap of tape around the case in lieu of re-bonding the plastic together.
Sony no longer offers the NP-FS11 Li-Ion batteries required for my DSC-F505V camera, so I’ve been using “generic” replacements for quite some time. My experience has been mixed: some batteries provide a reasonable amount of run time, others provide almost none.
Feeding the appropriate keywords into Froogle gives you a range of battery suppliers, with offerings from, as of this writing, $3 to $103. Perhaps not surprisingly, the image for a $70 battery exactly matches the one on my desk that cost perhaps $15 a few years ago… although I’m certain that the actual battery you’d get wouldn’t match that picture.
I just bought three NP-FS11 batteries from the usual low-buck Hong Kong eBay supplier: six bucks apiece, shipped halfway around the world. The eBay listing claimed 1800 mAh, which seemed aggressive, and the batteries sport a 3900 mAh label, which is flat-out impossible.
Frankly, I didn’t expect much and here’s the discharge test graph to show I wasn’t disappointed. I used a 1-amp rate as a reasonable guess at the camera’s peak draw, although that might be a touch high for a continuous discharge.
Generic Sony NP-FS11 Li-Ion Batteries
The top blue curve is from a two-year-old literally no-name battery (no logo, no nothing!) that still provides decent run time; it’s the one matching that $70 battery. It provides about 1100 mAh, reasonably close to its 1300 mAh rating.
The middle curves, black and purple, are two of the new cells that provide about 900 mAh: half the as-listed-on-eBay capacity, 25% of the absurd label value. Their very low terminal voltage during most of the discharge says that these won’t provide much run time at all.
The green curve piddling off on the bottom is the third new cell, which is obviously defective. As I said, I didn’t expect much and I certainly wasn’t surprised.
The red curve is an old and completely defunct batteries.com offering that never provided good service.
Here’s another plot of three successive charge-discharge cycles for just the three new batteries. The first curves (at 1.0 A) correspond to what you see above, the remaining two sets (at 0.5 A) are the next two cycles. Batteries G and I have improved, H remains a dud.
MaxPower NP-FS11 Battery Tests
Given the varied offerings on the Web, I believe that there is no way to ensure you’re getting a known-good battery from a reputable supplier. It’s absolutely certain that price does not correlate with quality; the ones I bought simply establish that low-end offerings are crap.
The purchase was worth it for the amusement value alone; I don’t expect any action from the vendor, although I did send a copy of that graph with some explanatory text. The question is whether I should give them a five-star rating for prompt delivery…
As it happens, there’s enough room to slide a standard CR123A-size cell into the battery compartment. I think a bit of Quality Shop Time applied to a dead NP-FS11 battery case (and the vital Sony “Infolithium” DRM module) will provide a baseplate with all the proper connectors. Perhaps I can conjure up a “battery” containing a single cell of known-good quality?
Primary CR123A cells supply only 3 V, not the 3.6 V the camera really wants, so I can’t use disposable cells.
The Smell of Molten Projects in the Morning 