Short answer: the TNP-FZ100 matches the original at 7.2V / 2280mAh / 16.4Wh, and one pack records roughly 120–150 minutes of 4K 30p, drops to 90–110 minutes at 4K 60p 10-bit, and only 55–85 minutes at 4K 120p or 8K; what sets runtime is total system draw, not the bitrate figure itself — bitrate is only an indirect indicator of it. Below is the estimation method, and a table of ranges by body and format.
One thing to state up front: every duration here is a range derived from a power model, not a measurement of a specific camera at a specific temperature. Usable cell capacity, the body’s thermal strategy, ambient temperature and whether lens stabilisation is working will all push the real result away from the estimate, and a drift of twenty to thirty percent is common.
The basic formula
A 16.4Wh pack is usually good for about ninety percent of its rating in practice — the body shuts down when voltage reaches a threshold rather than draining the cell flat. So usable energy is roughly 14.5–15Wh. Runtime in hours = usable Wh ÷ total draw in watts. Total draw covers sensor readout, image processor, encoder, screen or viewfinder, in-body stabilisation, card writing and the lens focus motor.
For example: at 8W total draw, 14.7 ÷ 8 ≈ 1.84 hours, or about 110 minutes. At 12W, only about 73 minutes. That is why going from 4K 30p to 4K 120p nearly halves runtime — the draw roughly doubles.
Runtime ranges by bitrate and format
| Typical body | Recording format | Bitrate | Estimated total draw | Runtime per pack |
|---|---|---|---|---|
| A7 IV | 4K 30p 8-bit 4:2:0 | About 100Mbps | 6–7W | About 130–150 minutes |
| A7 IV | 4K 60p 10-bit 4:2:2 | About 200–300Mbps | 8–9W | About 90–110 minutes |
| A7S III | 4K 60p 10-bit 4:2:2 | About 200–300Mbps | 9–10W | About 85–100 minutes |
| A7S III | 4K 120p 10-bit | About 280–600Mbps | 11–12W | About 70–85 minutes |
| FX3 | 4K 24p 10-bit | About 100–150Mbps | 7–8W | About 115–140 minutes |
| A7R V | 8K 24p 10-bit | About 400Mbps | 12–14W | About 55–70 minutes |
The draw figures are estimates by body class and encoding load, not manufacturer-published values. Runtimes calculated from them typically land within ±20% of what you see in the field, which is enough for planning headroom on a shoot.
Why higher bitrate is not linear power draw
Many people assume that doubling the bitrate halves the runtime. It does not work that way. Bitrate affects the encoder load and the card write power, and those two are a limited share of the total. The bulk of the draw is sensor readout and image processing, which stay essentially constant at a given resolution and frame rate; a higher bitrate barely moves them.
So going from 100Mbps to 200Mbps may add 10–15% to the draw and cost you a dozen minutes; but going from 4K 30p to 4K 120p quadruples the frame rate, multiplies the work of sensor and processor, and nearly halves the runtime. When estimating, look at frame rate and resolution first, bitrate second — in the other order it is easy to get wrong.
The effect of codec
At the same bitrate, H.265 usually loads the encoder harder than H.264 but produces smaller files and less write pressure. All-Intra demands more sustained writing than Long GOP and draws a little more. These differences are generally in the half-watt to one-watt range, which over a two-hour recording adds up to a dozen minutes or so.
What eats into the estimate during real recording
- Thermal time limits: many bodies trigger a recording cap at high-frame-rate 4K once the camera gets hot, stopping automatically after twenty or thirty minutes. What is limiting you there is heat, not the battery. For continuous work, external power plus active cooling is the more dependable route — see our dummy battery power guide.
- Screen brightness and ambient temperature: a bright outdoor viewfinder in summer can add one to two watts on the screen alone; in cold weather lithium-ion activity drops and the same capacity yields less energy, so usable time can fall by a fifth.
- In-body and lens stabilisation: running both adds continuous draw, which is especially visible when handholding a long lens.
- Accessories: a monitor, a wireless video transmitter or a USB-powered microphone all draw from the body, and runtime drops by the added load directly.
- Cell ageing: a pack a year or two old has already lost usable capacity, so discount the table according to its real condition.
On long-take bodies such as the FX3 and FX30, the power strategy differs from the A7 series and the camera keeps some headroom in reserve for recording. Our dedicated piece on video power covers the arrangements.
Turning the estimate into a workable shooting plan
- Fix the longest single take of the day — say a 45-minute interview.
- Read the lower bound for that format off the table, for example 90 minutes at 4K 60p.
- Divide the lower bound by the take length and round down: 90 ÷ 45 = 2 takes per pack.
- Allow 5–10 minutes between takes for the swap and build that into the budget.
- Work back from the total number of takes to the packs you need, and add one as a buffer.
Planned this way, even a runtime twenty percent short of the estimate will not leave you dark on location. Because the YO TNP-FZ100 has a Type-C port on the body, you can top it up from a power bank during a break instead of waiting to get back to a dock charger — on a long exterior day that is more useful than carrying one more pack.
FAQ
Why does someone else get two hours from the same battery when I get one?
Confirm three things first: whether the format matches (frame rate, resolution, codec), whether the screen is used the same way (LCD or EVF, at what brightness), and whether the ambient temperature is comparable. Any one of those can shift runtime by thirty or forty percent. The other person may also be quoting the accumulated total of several clips recorded with power cycles in between, which is not the same as one continuous take.
With 20% showing, how much longer can I record?
Do not scale it proportionally. Bodies estimate third-party packs non-linearly, so 20% may collapse into a warning within minutes, or may last another twenty. The safe approach is to treat 15–20% as the point where you must wrap up, and not to count it in your plan.
Runtime drops sharply in the cold — is the battery failing?
Usually not. Low temperature thickens the electrolyte and slows lithium-ion transport, so usable capacity falls temporarily and largely recovers at room temperature. Our cold-weather notes describe the behaviour and what to do about it. Only if it is also short at room temperature is ageing worth considering.
For longer takes, a bigger battery or external power?
It depends on the shape of the work. Handheld and moving between positions, two or three TNP-FZ100 packs are more flexible; for fixed cameras, interviews and livestreams that run for hours, external power with a dummy battery is simpler and avoids stopping mid-take. More specification detail is in the FZ100 series overview.