Short answer: capacity loss in a pack like the NP-FW50 is irreversible. The freezer trick, deep discharge and so-called pulse revival that circulate online cannot restore capacity — at best they can temporarily restore communication on a pack with dirty contacts. Two hard numbers decide whether to replace it: whether a full charge now delivers less than 70% of the rated shot count, and whether the casing has swollen or deformed. The first decides whether it is still useful; the second decides whether it is still safe. Once a pack swells, it is out of service whether or not the camera still powers up.
1. First: is the pack worn out, or is it a false fault?
Plenty of people fit a new pack and find the problem unchanged, because the problem was contact resistance all along. After years of use the metal contacts on an FW50 oxidise, collect dust, or loosen at the latch, and the symptoms look identical to a dead battery. Sort it out with these checks first:
- A different pack behaves normally: the fault is in that pack — read on for the capacity test.
- A different pack misbehaves too: inspect the contacts in the body for a dark oxide layer and wipe them with a cotton swab (never sandpaper), then check whether the bay is loose.
- The gauge jumps but shooting is fine: usually poor contact on the communication pin, or a worn cell whose voltage curve has steepened. The first can be cleaned; the second cannot.
- It drains while sitting unused: self-discharge is clearly fast, which points to an aged cell or a leaky protection board. That is genuine wear.
One more case is easy to misdiagnose: shooting outdoors in winter and watching the gauge fall from 50% to 10%. The pack is not failing; cold raises internal resistance. Put it back in an inside pocket to warm up and most of the reading usually returns. For how cold affects usable capacity, see the site’s -10°C cold test written around the NP-FZ100 — the mechanism is identical on an FW50.
2. Three steps to estimate what your FW50 has left
You do not need lab equipment; the camera itself gives a rough but usable reading. Run the test on the same body with the same settings so the numbers are comparable.
- Do one full charge and discharge: charge in a dock charger (an original unit such as the BC-VW1) until the indicator goes out, then shoot continuously until the camera shuts itself down. Do not recharge in between and do not leave it idling.
- Record two numbers: the total frame count, and the elapsed time from power-on to shutdown. For video, record the minutes of continuous recording instead.
- Compare against a baseline: use the body’s official CIPA figure, or a pack you know is healthy. Above 80% remaining is normal ageing; 70-80% starts to affect real work; below 70% it is time to replace.
In practice, an FW50 under normal use reaches the 80% mark somewhere around 300-500 full cycles, which maps to three to five years for a typical owner. If you shoot only a dozen times a year, a pack may still hold decent capacity at five years, but self-discharge will be faster, so top it up before every trip.
3. Swelling: the signal to take seriously
Swelling means gas has formed inside the cell, and it is irreversible structural damage. Being “still working” does not make it safe. The test is simple: lay the pack flat on a table and press gently on the corners. If you feel it rock, or if it takes force to push into the bay and drags on the way out, it has already swollen.
There is one rule for handling it: stop charging, stop using it, do not open it, do not puncture it, and do not put it in household waste or near fire. Keep a swollen pack on its own in a metal or ceramic container away from anything flammable, and get it to a collection point that handles lithium-ion cells as soon as you can. Do not take the risk for the sake of a few more shoots, and do not tape it flat — clamping the casing presses on the internal separator and actually raises the short-circuit risk.
Some conditions also mean immediate retirement: cracks in the casing, a smell of electrolyte, abnormal heat during charging (clearly above room temperature), or a charger that keeps reporting an error. All of these are far more serious than a drop in capacity.
4. Replace or keep: a decision table
| Symptom | Still usable? | What to do |
|---|---|---|
| Above 80% capacity, no obvious faults | Yes | Keep using, top up every three months |
| 70-80% capacity, drains a bit fast | Yes, but not as a primary | Demote to backup, leave it behind for important work |
| Below 70%, or falls from 60% to 10% | Not advisable | Replace; keep the old one for short pickups |
| Hot after charging, charger keeps erroring | No | Retire immediately and recycle |
| Swollen, deformed, or smells odd | Absolutely not | Retire, isolate, take to a collection point |
On the subject of revival, one thing needs saying clearly: the only thing that can genuinely be improved is contact quality. Cleaning the terminals, tightening a loose latch and replacing a tired charger can genuinely bring a falsely faulted pack back to normal. But if capacity has actually gone, no software or folk remedy will help — the lithium ions in the cell are partly inactive, and that is a chemical loss. Consumer “battery rejuvenators” do essentially nothing for camera packs and carry an overcharge risk, so they are not worth trying.
In practice, there is no need to insist on an original when replacing an older body. The FW50 has been out of production for years, and plenty of “new original” stock is old inventory or refurbished. A third-party pack with honest ratings and a temperature-sensing contact is better value — the YO FW50 is one of that kind, typically priced well under a hundred yuan, which is enough to keep an older body going. To see how other owners of the same bodies build their kit, browse the NP-FW50 category.
Finally, a habit question: do not store a pack you are not using at full charge, and do not run it to shutdown before putting it away. 40-60% is the most stable state, topped up every three to six months, and that can add a year or two to a pack’s service life.
FAQ
Can freezing an FW50 restore its capacity?
No, and it carries risk. Cold does not bring inactive lithium ions back, and condensation after removal can damp the protection board. The idea has some history from the nickel-metal-hydride era; it does not apply to lithium-ion cells.
The gauge says 30% and the camera shuts down. Why?
Most often the cell has aged and its voltage curve has steepened, so the remaining-charge estimate is off; cold weather or higher contact resistance can do the same. Clean the contacts, warm the pack and retest, and if the behaviour persists treat it as capacity loss.
Can a swollen pack stay in the camera as a ballast weight?
Not advisable. A swollen pack is under internal stress, and any pressure or temperature change can make it worse — it is a hazard even when it is not charging. The right move is to get it to a collection point promptly rather than store it at home.
Do third-party FW50 packs last less long than originals?
It depends on the cell, so no blanket answer applies. Good third-party cells can come close to original cycle life, while cheap products may fade noticeably within a year or two. Judge by whether the rating is plausible and whether protection circuitry is present, not by the brand label.