Short answer: to judge whether an FW50 is a counterfeit, work through four steps — check the shell’s mold lines and finish, check the printed type and its position, check whether the camera recognizes the pack and reports charge reliably, and weigh it against a known pack. If two or more of the four come up wrong, it is almost certainly a fake. One distinction first: a legitimate third-party pack such as the YO TNP-FW50 clearly labels its own brand and does not pretend to be Sony, whereas a counterfeit carries the SONY mark and imitates the original. Those are entirely different things.
The FW50 attracts fakes because it has had a long production life, huge installed base, low unit price and steady demand. The counterfeiter’s goal was never to make a good battery but to make you believe you bought an original. So the question is not whether the pack performs well — it is whether it lies about what it is.
Step one: shell and mold lines
An OEM FW50 shell is a two-shot molding, and the parting line is fine and even, almost imperceptible under a fingertip. Fakes are limited by tooling precision and cost, so the line is usually coarser and rougher and catches a fingernail. Check three places: the long edges on both sides, the bottom corner nearest the contacts, and around any port cover or interface opening.
The material differs too. The OEM shell is fairly matte with a faint frosted texture, and after long use it goes uniformly glossy; fakes often use regrind, look gray or yellowed, develop shiny patches and tend to crack at the latch.
One more point that gets missed: the contacts. OEM contacts are gold-plated, warm in tone, evenly spaced and consistent in spring force. Fakes are often nickel-plated or bare copper, white or reddish, and show obvious scoring after a few insertions.
Step two: printing and typeface
Printing is the cheapest thing to fake and the easiest place to give yourself away. OEM print is crisp and sharp, set in a custom typeface with even letter spacing; fakes usually use a generic font, and under magnification the edges are soft and the stroke weights uneven.
| What to look at | Genuine | Typical fake |
|---|---|---|
| Letter edges | Sharp, no ink spread | Soft, feathered or doubled |
| Model and capacity text | Fixed position, aligned to a baseline | Offset, crooked, not centered in the recess |
| Certification marks | Correct proportions, even line weight | Distorted proportions, lines blurring together |
| Serial number | Laser-marked with depth variation | Ink printed, rubs off |
| Origin and warning text | Airy layout, sensible line breaks | Crammed together, typos or odd phrasing |
The last row deserves its own note. Fake warning text is often copied from a different model, so you see small slips such as “lithium battery pack” where it should read “lithium-ion battery pack”, or the voltage given as 7.4V instead of 7.2V. The FW50 is rated 7.2V / 1020mAh / 7.7Wh; if those three numbers do not line up, stop there.
Step three: decoding and camera communication
This step needs a camera. Fit the pack, power up and watch three things: whether a battery-related message appears, whether the charge indication moves continuously, and whether low battery still triggers a normal shutdown.
A genuine OEM pack and a properly made third-party pack both behave consistently on all three. Fakes typically show one of these: the gauge sits at 100% for a long time and then jumps to 10%; or the number leaps when you power off and on again; or the camera shuts down with plenty of capacity apparently left. All of these mean the decoding chip is only reporting numbers rather than reading the cells.
Bear in mind that older bodies (the NEX series, the first-generation A7) may show a message with third-party packs in any case, so this step has to be read alongside the specific model — it cannot be generalised. Model-by-model notes are in the TNP-FW50 compatibility section; if you are more interested in the OEM specification, compare against the ratings in the NP-FW50 battery section.
Step four: weight and feel
The hardest part to fake is the cell. An OEM FW50 bare pack usually comes in a little over 40 grams, and a gram or two either way is normal. Fakes cut cost with low-density cells and often feel clearly light; occasionally it goes the other way, with a steel slug added inside to give heft, taking the weight over the norm.
So compare rather than trusting your hand. Take three packs of the same model, weigh each on a kitchen scale: within 3 grams of each other is fine, more than 5 grams apart is worth suspicion. A rattle when you shake it also suggests poor assembly.
Feel includes the damping as the pack goes into the camera. A genuine pack slides in with even resistance and the latch clicks home; a fake is either loose enough to shift or so tight it needs force, which over time wears the latch in the camera’s battery bay.
Combine the four into one quick list to run through before you buy:
- Are the mold lines fine and even, the shell matte, the contacts gold-plated?
- Is the printing sharp, and do 7.2V / 1020mAh / 7.7Wh all agree?
- Does the camera recognize it consistently, is the gauge smooth, does low-battery protection work?
- Does it weigh a little over 40 grams, and do same-model packs sit within 5 grams of each other?
Two or more failures across the four is enough to call it. Conversely, if you bought a compatible pack that clearly states its own brand, it should not carry a Sony mark at all, and holding it to a “looks like the original” standard is unfair — what you are judging is whether it is honestly labeled and works reliably.
FAQ
Is a pack without a Sony logo automatically fake?
No. A legitimate third-party pack should not carry a Sony logo, and printing one would be infringement. The test is whether it impersonates, not whether it comes from a third party.
Is a very low price a sure sign of a fake?
Not necessarily. Compatible packs are legitimately much cheaper than OEM, which is a property of the category. The real red flag is a fake sold at OEM money, or a price so low it defies reason alongside a claim of being genuine original stock.
Can a fake damage the camera?
The risk sits mainly with the pack itself: inconsistent cells and a crude protection board can cause abnormal heat or sudden cutouts. The camera usually has its own protection, but using poor packs long term is not a good habit.
Is a used OEM pack worth buying?
Look at cycle count and age. The FW50 starts with modest capacity, and a worn pack may be down to sixty or seventy percent, so a low price may still not be good value. A new, properly made compatible pack is more predictable by comparison.