Spotting an inflated rating takes a method you can measure, not a feel for the plastic. An NP-FZ100 is rated 2280mAh / 7.2V, which is about 16.4Wh; the 2400mAh version of the same size is about 17.3Wh. Any measurement moves with temperature, discharge current and cutoff voltage, so results land in a band. A figure in the 2200–2260mAh range would be broadly consistent with the label. There is no value in chasing a number down to the last mAh, and no single measurement should be treated as a verdict on its own.
Start by checking the specs against each other
Two quick checks before any hardware comes out:
- Energy conversion: capacity in Ah times voltage in V gives Wh. 2280mAh is 2.28Ah; at 7.2V that is about 16.4Wh. A listing that quotes a large mAh figure with no Wh, or where the two do not match, deserves caution.
- Model and spec: NP-FZ100 is a 7.2V nominal pack covering the A7 IV, A7R V, A7S III, A9 III, A1, A6600, A6700, A7C series, FX3, FX30 and ZV-E1. The A6400, A6500 and A7 II series take NP-FW50 — if the model is wrong, capacity is beside the point. See the Sony mirrorless battery cross-reference.
- Weight as a hint: packs of the same spec tend to cluster in a similar weight range, and a noticeably light one often means less cell capacity. Useful as a secondary clue, not as proof.
Method 1: constant-current discharge (the more accurate route)
This is what hobbyists and repair shops use. You need an electronic load or a discharger with a constant-current mode.
- Charge the pack fully, then let it rest so the voltage settles.
- Set a constant discharge current, roughly 0.2C to 0.5C — somewhere between a few hundred milliamps and just over 1A — and note the start time.
- Stop at the cutoff voltage given by the cell specification, and record total elapsed time.
- Capacity is approximately discharge current times discharge time. At about 1A, a pack that runs a little over two hours is broadly in line with 2280mAh.
Two caveats: higher discharge current usually yields lower measured capacity, and cold conditions push results down. It is more sensible to compare two packs side by side under identical conditions than to fixate on an absolute number.
Method 2: measuring charge input (no special gear)
Without a load, you can estimate indirectly using a charger or USB meter that logs energy.
- Run the pack down to the camera’s low-battery warning — no need to force a shutdown.
- Charge it fully through a metering device and read the accumulated mAh or Wh.
- Allow for charge efficiency and for the charge that was left at the start; the result usually reads a little above what the pack actually delivered. Treat it as an order-of-magnitude check: well under half the rating is a red flag; close to it is reassuring.
Method 3: frames per charge (closest to real use)
For most shooters, what matters is how much you get through in a session.
- Charge one pack and shoot continuously under fixed settings — same body, same mode, similar temperature — noting the frame count at the low-battery warning.
- Official CIPA figures usually sit between 500 and 700 frames, with real-world results commonly 60–80% of that, lower for video and burst work.
- Compare against another pack you know is healthy. A difference inside a reasonable band is fine; if it is clearly short, confirm with method 1.
If capacity genuinely looks far off the label, talk to support; the process is outlined in warranty and returns. Note also that capacity is commonly around 80% after 300–500 cycles, so a low reading on an older pack may just be wear.
Cases that look like inflation but are not
- Cold: capacity drops noticeably below freezing and may be roughly halved near -10°C. Warm the pack to room temperature before measuring. See cold-weather runtime tips.
- High current draw: burst shooting and 4K recording reduce usable capacity below the rating.
- Charge display jumping: that is estimation and communication behavior, not directly a capacity shortfall. It comes from estimation and communication behavior rather than stored energy.
- An old pack: on a battery past two years, wear can exceed any inflation gap.
FAQ
Does measuring below the rating mean the rating is fake?
Not on its own. Temperature, discharge current and cutoff setting all move the result. Compare like with like and accept a band of error.
How many more frames does 2400mAh give over 2280mAh?
About 5% more energy in theory. In practice the difference depends on body and settings, rarely scales linearly, and is modest in daily use.
Can I test with a phone charger?
We do not recommend working directly on battery terminals. Charge camera batteries in a proper charger, and keep any measurement within safe practice.
What if my result is clearly low?
Rule out temperature and age first, keep your measurement notes, then contact support. Do not keep using a pack that runs unusually hot or has started to swell.
Choosing a product that states its specs clearly saves you the testing. The YO NP-FZ100 compatible battery is listed at 2280mAh / 7.2V / about 16.4Wh, and the TNP-FZ100 at 2400mAh / about 17.3Wh; the two-battery kit at around $36.74 also makes side-by-side comparison easy. Studios and resellers ordering 100 units or more should use the wholesale inquiry page — a small trial order first, then scale up.