Start with the answer. In our testing, a third-party NP-FZ100 after a normal year of use keeps roughly 85%–95% of its original usable capacity, meaning a loss of around 5%–15%. That lands in the same band we record for Sony’s own pack under comparable workloads. There is no widespread pattern of third-party cells collapsing inside a year. Three things separate a healthy pack from a tired one: how many cycles it has run, how you charge it, and where it spends its downtime. Below you’ll find the retention figures sorted by workload, our test protocol, and a clear line for deciding when to retire a battery. To run the same check yourself, follow the steps in how to spot a fake capacity rating.
What one year costs you, sorted by workload
Capacity doesn’t fade on the calendar. It fades with cycles plus storage conditions. Two packs bought on the same day can age very differently: one belongs to a commercial shooter who has run it through a hundred-plus cycles, the other sits in a weekend bag with a few dozen. The table below comes from our year-long tracking of a single batch of NP-FZ100 compatible batteries. Figures are given as ranges rather than precise single values.
| Usage level | Approximate cycles in year one | Capacity retained (range) | What it feels like in the field |
|---|---|---|---|
| Light: weekend walks, occasional top-ups | Around 20–40 | 95%–99% | Basically indistinguishable from new |
| Moderate: one or two shoots a week, two packs in rotation | Around 50–80 | 90%–96% | Tight at the end of a long day; bring a spare |
| Heavy: weddings, commercial work, frequent 4K | Around 100–150 | 85%–92% | One pack won’t cover half a day; rotate three or more |
| Poor storage: left full, cooked in a hot car | Unrelated to cycles | Possibly below 85% | Noticeably short; replace early |
One caveat worth more than the rows themselves: variation between two individual batteries inside the same row is often wider than the gap between rows. Two packs from the same batch, one living in a camera bag and one baking on a parcel shelf, can end the year more than ten percentage points apart.
Where the capacity goes: four main drivers
Cycle count does most of the work
Chemical aging in a lithium cell is tied to charge and discharge cycles. The industry shorthand is straightforward: expect roughly 80% remaining after 300–500 full cycles. That works out to a few percent lost per hundred cycles, which lines up with what we saw across the year. The full breakdown by stage is in what's left after 100 cycles.
Storing it full, and storing it hot
Leaving a pack parked at 100% in a warm place — a car in July, a sunny windowsill — accelerates the decline noticeably. This is also why a battery that “hasn’t been used much” can still test low. The damage came from the shelf, not the shutter.
High current draws add stress
Fast burst shooting, 4K and high-frame-rate recording, heavy use of IBIS and live view: all of it pulls more current, which means more heat and faster wear. Owners of high-speed bodies like the A9 series and A1 tend to notice it sooner.
Running it down to zero every time
Discharging until the camera shuts itself off, then charging back up, is a deep cycle and it costs the cell something. Shallow top-ups age far more slowly than full drain-and-fill habits.
How we measure: our lab protocol
We keep the conditions fixed so numbers stay comparable. Here’s everything that shaped the ranges above, so you can judge how far they transfer to your own kit.
- Temperature: discharge tests run at room temperature, around 25°C. Cold weather behaves differently.
- Method: constant-current discharge down to cutoff voltage, then compare the delivered charge against the original rating.
- Sample size: multiple packs from the same batch are tracked together, and we report the observed range. A single outlier never becomes a conclusion.
- Reporting: ranges and “around” only. Cell consistency varies batch to batch, so single-digit precision would be neither repeatable nor useful.
- Cross-check: findings are confirmed in-camera, since what shooters actually care about is frames per charge, not milliamp-hours.
Treat these numbers as a way to judge whether aging is normal. They are not fine enough to rank brands against each other.
Third-party vs Sony: is there a real difference in the curve?
Under matched workloads, we have not observed any systematic fast-fade behavior unique to third-party packs. Both curve shapes look alike: gentle at first, steeper later. When an individual sample drifts off, the cause points back to cell batch or handling habits rather than to whether the pack came from Sony.
In fairness, batch-to-batch and environment-to-environment variation is real, so read this as a trend rather than a controlled head-to-head verdict.
Four signs it’s time to replace
- Runtime drops to roughly 70% of a new pack. By then a full day is a gamble, and a replacement costs far less than a dead camera mid-shoot.
- Around the two-year mark. Even with decent capacity left, internal resistance has usually climbed, and high-current work (bursts, 4K) will cut out early.
- Any swelling. Stop using it. No charging, no discharging. Take it to a hazardous waste or battery recycling point; never puncture or burn it.
- Full charge to half-empty in minutes. That points to internal resistance or a confused fuel gauge. Run one full charge-discharge cycle to recalibrate; if nothing changes, replace it.
FAQ
Is 10% loss in a year a defect?
No. Against the 80%-after-300–500-cycles benchmark, losing 5%–15% in twelve months is normal. If a pack falls below 80% within six months, and you can rule out heat and deep discharges, contact the seller for a check.
Do third-party packs always fade faster than originals?
Matched for workload, we don’t see a meaningful difference. Cycle count, time spent at full charge, and ambient temperature are what move the needle.
Does an unused battery degrade on its own?
It does, and storage habits matter a lot. Aim for 40%–60% charge, keep it cool and dry around 15–25°C, and top it up every three months. Both fully-charged and fully-empty storage age a cell faster.
Can lost capacity be restored?
No. Chemical aging is one-way, and “revival” tricks don’t work. What you can do is run a complete charge-discharge cycle so the remaining-charge display reads honestly again.
How should I dispose of a degraded pack?
Not in household trash. Drop it at a local hazardous waste or battery recycling point, ideally with tape over the terminals.
Bottom line and what to buy
Condensed: after one year a third-party NP-FZ100 usually still measures 85%–95%, which is normal wear. Think about replacing it around two years in, or once runtime falls near 70%. If your body belongs to the NP-FZ100 camp — A7 III/IV, A7R III/IV/V, A7S III, A9 series, A1, A6600, A6700, A7C series, FX3, FX30, ZV-E1 — add a YO NP-FZ100 compatible battery (2280mAh / 7.2V / about 16.4Wh) at around $17.89, or step up to the TNP-FZ100 (2400mAh / about 17.3Wh) at around $19.66 for a little more headroom. Kits run about $22.93 for one battery with a charger and about $36.74 for two batteries with a charger. Sony’s original NP-FZ100 sells for $70 and up. For day-to-day upkeep, the checklist in five habits that extend NP-FZ100 life covers the basics. Studios, rental houses, and resellers buying 100 units or more should reach us through the wholesale inquiry page for volume pricing.