Batteries and USB Power

The light comes up over the marsh a little after six, and by then the camera has been on the tripod for twenty minutes, the Nikkor Z 180-600mm f/5.6-6.3 VR aimed at a line of posts where a kingfisher was seen the day before. Nothing happens for an hour. Then the bird arrives, and the next ten minutes produce several hundred frames.

By early afternoon the second battery is down to its last bar, and nobody counted the shots. The useful question is not how many frames remain but how many hours, and whether the two packs left in the bag will reach the evening light. It can be answered the night before, from a few numbers Nikon prints and some arithmetic.

Page numbers in parentheses point to Nikon's Z6III Reference Guide, edition 09, which matches firmware 2.00.

01.The EN-EL15c and the Packs Before It

The Z6III runs on one EN-EL15c, a rechargeable lithium-ion battery of about 80 g (p. 1010). One comes in the box with a USB cable that has a Type-C plug at each end, but there is no charger (p. 35), and the battery ships partly charged (p. 995).

Its label carries two numbers. The voltage, 7.0 V, is the electrical pressure that drives current through the camera. The charge, 2280 mAh or milliamp-hours, says the battery could in principle supply 2,280 milliamps, which is 2.28 amps, for one hour (p. 1010). What a battery can actually do depends on its energy, the product of the two, counted in watt-hours, where one watt-hour is one watt kept up for an hour:

$$E_b = V \times Q = 7.0\ \text{V} \times 2.28\ \text{Ah} = 15.96\ \text{Wh} \approx 16\ \text{Wh}$$

Here $E_b$ is the energy of one battery, $V$ its voltage and $Q$ its charge in amp-hours. Heat, Power and Recording Limits starts from the same 16 Wh. Watt-hours are the unit to carry through this chapter, because they compare batteries and power banks that work at different voltages.

Nikon names two older packs that the Z6III will run on, the EN-EL15b and the EN-EL15a, and says both give fewer pictures per charge, without saying how many fewer (pp. 969, 1008, 1016). The camera charges an EN-EL15b over USB but not an EN-EL15a, which needs the MH-25a charger (pp. 91, 974). The original EN-EL15, with no letter after the number, is missing from every list of power sources for this camera, and Nikon mentions it only to say which charger takes it (p. 977). With no statement that the Z6III accepts it, I would not put one in.

A genuine EN-EL15c carries a Nikon holographic seal, and Nikon warns that counterfeits can overheat, ignite, burst or leak (p. 45). If the camera shows a message saying a battery cannot supply it with data, Nikon gives three possible causes: a fault for a Nikon service centre, a third-party battery, or a genuine battery that is almost empty (p. 926). Charge it before deciding it has failed.

02.Charging in the Camera or in a Charger

First-Day Setup covers charging inside the camera: with the camera off and a USB source on the supplied cable, the lamp glows amber, and on Nikon's EH-8P adapter an empty EN-EL15c fills in about two and a half hours (p. 91). It also gives Nikon's 27 W minimum for other makers' adapters. The author's 100 W USB-C wall adapter, which came with a NEEWER NW-F4 charger, clears that minimum, though Nikon gives no charging time for a third-party adapter. A computer can stand in for the adapter if it stays awake, since charging pauses while it sleeps, and if the cable runs straight into it rather than through a hub or a keyboard. Even then charging may be slower, and some computers supply no power at all (p. 92). Whatever the source, let a battery that is hot from use cool first, or it may charge only partly (p. 995).

Charging in the camera takes one battery at a time, and the heat chapter works out that four packs charged that way take about ten hours. That is the case for a separate charger.

Nikon's Chargers

Nikon lists two. The MH-25a, which the author owns but cannot plug in until its missing mains cord is replaced, takes every pack in the table (pp. 974, 977), but the Reference Guide gives no charging time for it. The MH-34 runs from an EH-8P adapter over the supplied C-to-C cable and fills an empty EN-EL15c in about 2 hours 30 minutes and an EN-EL15b in about 2 hours 50 minutes (p. 976), but it takes neither the EN-EL15a nor the EN-EL15 (p. 977).

Chargers From Other Makers

The author charges with two third-party units instead. The llano 20 W two-bay USB-C charger takes two EN-EL15c at once from any USB-C source at up to 20 W, and the Koah dual USB-C charger, which came bundled with one of the four batteries, shows each slot's charge on an LCD display. The Reference Guide says nothing about either. Nikon's general position is that the EN-EL15c is meant for Nikon products, that Nikon accepts no responsibility for faults arising with chargers not compatible with the battery, and that damage traced to non-Nikon accessories is outside the warranty (p. 45). The 27 W figure does not decide the matter, because it describes a source plugged into the camera (p. 92), not a charger that holds the battery itself.

Nikon's warnings for any charging still apply. Stop charging a battery that has not finished in the expected time, stop using one that changes colour or shape (p. 41), and do not leave a full battery on charge (p. 996). With those habits, the two two-bay chargers hold all four of the author's batteries at once, which turns the ten-hour job into one evening.

03.Running on USB Power While You Shoot

USB power delivery, ON by default (p. 807), lets the camera draw on a connected USB source while it is on, and while it is off but still busy with a Bluetooth upload or a lit card access lamp (p. 856). Nikon names three sources: its EH-8P adapter on the supplied cable, a computer's Type-C port, and a third-party portable charger, usually called a power bank. A battery must be in the camera, and an icon in the shooting display and on the control panel shows when outside power is in use (pp. 856, 932, 942).

First-Day Setup sets out the rule that decides between powering and charging: with the camera on and the standby timer running, the source powers the camera, and once the timer has run out or the camera is off, it charges the battery (p. 857). The standby timer is the countdown, 30 seconds by default, after which the camera turns its displays off to save power (p. 89). At OFF, the camera takes nothing while awake but still charges once the timer runs out (p. 857).

For stills, the charging half of that rule matters most. A recording keeps the camera awake, so outside power only slows the drain, as the heat chapter explains. A stills photographer on a tripod spends much of the day waiting, and Nikon's table counts every wait longer than the standby timer as charging time (p. 857), though its accessory list says the camera does not charge while on (p. 969). Confirm it at home: switch on, let the timer run out, and check Battery info (p. 855) after a few minutes. Nikon says a power bank that meets its conditions can charge the battery as well as power the camera, without guaranteeing that every one will (p. 92). If the test shows the charge rising, a power bank in the bag turns the quiet stretches at a hide into charging time, though the cable ties the camera to the bag.

Nikon also recommends a full battery or outside power for long exposures (p. 148) and the interval timer (p. 524), which Long Exposure and Night and Silent Shooting, Timers and Time-Lapse cover. Setting USB in the network menu to iPhone or USB-LAN blocks USB power altogether (p. 900), so leave it at MTP/PTP, the default (p. 871).

Reading a Power Bank's Label

Nikon's conditions for a power bank, USB Power Delivery at 27 W or more on a C-to-C cable (p. 92), are in the heat chapter. What they leave open is how far a power bank will go, and its label invites a mistake. Suppose one is marked 20,000 mAh at 3.6 V. Dividing charge by charge, $20{,}000 / 2{,}280 \approx 8.8$, suggests nearly nine batteries' worth, which is wrong, because the two ratings belong to different voltages. In energy the power bank holds

$$E_{pb} = 3.6\ \text{V} \times 20\ \text{Ah} = 72\ \text{Wh}, \qquad \frac{E_{pb}}{E_b} = \frac{72\ \text{Wh}}{16\ \text{Wh}} = 4.5$$

where $E_{pb}$ is the energy stored in the power bank, so it gives at most about 4.5 full charges. Some energy is lost as heat on the way to the battery, and neither label says how much. The author owns no power bank, so these numbers illustrate the method and describe no product.

04.How Long a Charge Lasts

Nikon's stills figures come from a standard test set by CIPA, the Camera and Imaging Products Association (p. 1016), and a standard test is what makes figures for different cameras comparable. The camera takes one picture every 30 seconds at default settings, here with the Nikkor Z 24-70mm f/4 S, a lens the author also carries, Nikon's MC-CF660G card and a room at 23 °C, give or take 2 °C (p. 1016).

The video figure, about 100 minutes (p. 1016), belongs to the heat chapter. Nikon also lists what shortens battery life in real use: holding the shutter-release button halfway, focusing again and again, NEF (RAW), slow shutter speeds, Wi-Fi and Bluetooth, attached accessories, repeated zooming and cold (p. 1016).

Turning Shots into Hours

A shot count hides the quantity that matters on a long day, which is time. The 360 shots of the Viewfinder only row with energy saving off, taken 30 seconds apart, span

$$t = N \times \Delta t = 360 \times 30\ \text{s} = 10{,}800\ \text{s} = 3.0\ \text{h}$$

where $N$ is the number of shots, $\Delta t$ the interval and $t$ the length of the test. One battery spread over those three hours gives an average power of

$$P = \frac{E_b}{t} = \frac{15.96\ \text{Wh}}{3.0\ \text{h}} \approx 5.3\ \text{W}$$

where $P$ is the average rate at which the camera drew energy, including whatever it did between frames. The heat chapter's figure for video is about 9.6 W.

My reading, which Nikon does not state in these words, is that battery life follows how long the camera stays awake more closely than how often the shutter fires. Nikon's notes support it: endurance varies with the interval between shots, a half-pressed button and repeated focusing cost battery without taking a picture (p. 1016), and a longer standby timer shortens battery life (p. 661). A thirty-frame burst adds only seconds of waking time, so a day of bursts can pass 360 frames easily, while a morning half-pressed over an empty perch can fall well short. Pre-Release Capture, which shoots into the buffer for up to about 90 seconds of each half-press (pp. 664-665), is the extreme case. Plan in hours, not shots.

Settings That Cost Battery

Energy saving (photo mode), OFF by default (p. 807), dims the display about 15 seconds before the standby timer runs out and may lower its refresh rate (p. 858). From the table, it adds

$$\frac{380 - 360}{360} \approx 5.6\%$$

in Viewfinder only and $(410 - 390)/390 \approx 5.1\%$ in Monitor only. Viewfinder and Monitor Displays keeps it off for action because of the slower refresh, and this chapter agrees: one extra shot in about twenty is a poor trade for a less fluid viewfinder as a bird takes off.

Custom Setting c3 Power off delay includes the Standby timer, 30 seconds by default (pp. 89, 624, 661), and Nikon says plainly that longer delays shorten battery life (p. 661). Silent Shooting, Timers and Time-Lapse sets it to No limit in theatres, because the timer makes a sound, and carries a spare to cover the cost. Everywhere else I keep the default.

Wireless links cost battery too (p. 1016). Airplane mode at ON switches off Bluetooth and Wi-Fi and drops the link to Nikon's ML-L7 remote (p. 872). The author's Hanpusen wireless remote stands in for the ML-L7, so test it with Airplane mode on before counting on both. Upload while off is ON by default and keeps phone uploads running after switch-off (pp. 869, 880), and First-Day Setup turns Auto select for upload off to save battery. SnapBridge and the Cloud covers both.

05.Reading the Battery

The battery indicator sits in the shooting display and on the control panel (pp. 89, 932, 942). At its lowest level, have a charged spare ready. Once the battery is spent the camera will not fire and shows "Shutter release disabled. Recharge battery." (pp. 89, 926).

Battery info gives three readings (p. 855). Charge is the level as a percentage. No. of shots counts shutter releases since the last charge, including releases that record nothing, such as measuring a preset manual white balance. Battery age runs from 0, a battery in full health, to 4, one at the end of its charging life that should be replaced.

Two of those readings give a personal battery figure. Suppose that after a morning at a hide the battery reads 60% with 520 shots on the counter. It has spent 40% on 520 shots, so

$$\frac{520\ \text{shots}}{40\%} = 13\ \text{shots per percent} \quad \Rightarrow \quad 100 \times 13 = 1{,}300\ \text{shots per charge}$$

for that style of shooting, between three and four times the CIPA figure. The numbers are invented to show the method, and the result is rough, because the level display also falls in the cold without energy being spent (p. 995).

Nikon gives two signs of a worn battery: an age of 4 (p. 855), and a clear fall in how long a full battery lasts at room temperature (p. 996). A new battery charged below about 5 °C can show an age of 1 for a while, which clears after a charge at about 20 °C or warmer (pp. 855, 995).

06.A Battery Budget for a Long Day

Take a wildlife day of ten hours, first light to last, and suppose the camera is awake, with its displays on or its standby timer running, for half of it, so $t_a = 5$ h. That share is an assumption. Long waits at the viewfinder push it up, and a walk with the camera off between sightings pulls it down. The author's four EN-EL15c batteries supply

$$E_s = n \times E_b = 4 \times 16\ \text{Wh} = 64\ \text{Wh}$$

where $n$ is the number of batteries and $E_s$ their combined energy. The demand depends on the power the camera draws while awake, which the Reference Guide does not give for this kind of shooting, so two rates bracket it. The low one is the CIPA average above, $P_{lo} = 5.3$ W. The high one, $P_{hi} = 10$ W, is my own planning convention: the heat chapter's video figure rounded up, standing for a hard day of half-pressing, focusing and bursts (p. 1016). The day needs $E_d = P \times t_a$, which gives

$$E_{d,lo} = 5.3\ \text{W} \times 5\ \text{h} \approx 27\ \text{Wh} \approx 1.7\ \text{batteries}$$

$$E_{d,hi} = 10\ \text{W} \times 5\ \text{h} = 50\ \text{Wh} \approx 3.1\ \text{batteries}$$

At the low rate two batteries would do. At the high rate three fall short, since $3 \times 16 = 48$ Wh is 2 Wh under the 50 Wh needed, while four cover the day with $64 - 50 = 14$ Wh, nearly one battery, in reserve. Turned round, four batteries keep the camera awake for $t_{max} = E_s / P$, which is between $64/10 = 6.4$ h and $64/5.3 \approx 12$ h.

The budget leaves out three things that each tilt it the wrong way. The CIPA rate was measured at 23 °C (p. 1016), and capacity falls in the cold (p. 995). An ageing battery holds less, which Battery age tracks (p. 855). And Nikon gives no figure for the 180-600mm. Four batteries leave room for these, and three do not. Change batteries at the lowest level rather than at the lockout, for the reason Changing a Battery gives below.

07.Cold Weather

Long Exposure and Night covers the core: cold cuts capacity, the level display drops even on a full battery, a partly charged battery may not work, a cold battery can recover some charge once warmed, and the battery will not charge below 0 °C (pp. 995-996). What it leaves out is the rest of Nikon's charging ranges, which the figure puts side by side.

The camera and battery work from −10 to 40 °C (pp. 995, 1009-1010). Charging should happen indoors with the room between 5 and 35 °C, the battery takes no charge when its own temperature is below 0 °C or above 60 °C, and from 0 to 15 °C or 45 to 60 °C it charges more slowly and holds less (p. 995). So a battery carried in from a freezing car charges slowly, or not at all, until it warms.

Nikon suggests charging one battery fully and keeping another warm on cold days (p. 996). On a wildlife day the battery in the camera takes the cold and the spares ride in an inside pocket. Condensation, when the camera moves between cold air and a warm room, is covered in Cleaning and Weather (p. 991).

08.Storage and Long-Term Care

Nikon's advice separates two time scales. For use, charge close to the outing, because a charged battery left unused loses charge (p. 1016). For storage, take the battery out of the camera, keep it dry at 15 to 25 °C, and leave it near half charge rather than full, bringing it back to about half at least yearly (p. 995). Charge the night before, and store at half.

An empty battery reaches about 50% in about half the time it needs for 100% (p. 995). In the camera, where a full charge on the EH-8P takes about 2.5 h (p. 91), that is

$$t_{50} = \frac{t_{100}}{2} = \frac{150\ \text{min}}{2} = 75\ \text{min}$$

where $t_{100}$ is the time to a full charge and $t_{50}$ the time to about half. Confirm the result in Battery info.

Do not leave batteries in the camera or the charger, both of which draw a tiny current even when off, enough over time to leave a battery unusable (p. 995). Charge a fully flat battery before use rather than switching the camera on and off on it, which shortens its life (p. 996). Keep the terminal cover on a loose battery and the contacts clean (pp. 995, 1016).

A body put away for a while should also have its battery out, so a leak cannot damage it, and Nikon suggests a monthly battery-in session of a few shutter releases (p. 993). Keep camera and batteries out of a closed car on a hot day (pp. 993, 995), and tape a dead battery's terminals before recycling it (pp. 41, 996).

The Clock Battery

The clock runs on a small battery charged from the main one, which lasts about a month once full (p. 101). A body stored without a battery for longer can lose the date and time, so after a long rest look for the flashing clock icon that First-Day Setup describes (p. 101).

09.The MB-N14 Power Battery Pack

The Reference Guide covers one grip, the MB-N14 power battery pack, which the author does not use. It holds up to two EN-EL15c batteries, about $2 \times 16 = 32$ Wh by my arithmetic, accepts the EN-EL15b and EN-EL15a with fewer shots, and adds controls for upright shooting (pp. 969, 1008). An EH-8P can charge the batteries in it or power the camera through it (p. 970), and Power battery pack info, an item that can be added to the i menu, shows their state, with the details in the pack's own Reference Guide on Nikon's Download Center (p. 702). Custom Controls lists which of its grip controls can be reassigned.

10.Changing a Battery

Turn the camera off before taking the battery out (pp. 88, 995), and never pull it while the card access lamp is lit, because pictures still being written can be lost and the camera or card damaged (pp. 45, 992). After a long burst the camera will not switch off until its buffer is empty, and if the battery runs out first the shutter locks while the waiting frames are saved (p. 155). A battery can be hot after heavy use, so take care lifting it out (p. 995).

11.Recommended Settings

12.Beginner Mistakes

Comparing milliamp-hours across voltages. A power bank's 20,000 mAh at 3.6 V is not 8.8 batteries' worth. Convert both to watt-hours first.

Charging an EN-EL15a in the camera. The camera will not do it, and the MH-25a will (pp. 91, 974).

Charging a battery straight from the cold or straight after heavy use. It charges slowly or partly, and below 0 °C not at all (p. 995). Let it reach room temperature.

Storing batteries full, or in the camera. Store at about half charge, out of the camera and charger, at 15 to 25 °C (p. 995).

Pulling the battery while the card access lamp is lit. Wait for the lamp to go out and switch off first (pp. 45, 155, 992).

13.Related Chapters

• Heat, Power and Recording Limits: video battery life, power banks while filming and the EP-5B mains connector.
• First-Day Setup: charging in the camera, the 27 W rule and the clock battery.
• Viewfinder and Monitor Displays: monitor modes and why energy saving stays off.
• Silent Shooting, Timers and Time-Lapse: the standby timer in theatres and power for time-lapse.
• Long Exposure and Night: batteries in the cold and power for long exposures.
• Release Modes, Frame Rates and the Buffer: why a flat battery stops the shutter while the buffer empties.
• Pre-Release Capture: the shooting style that keeps the camera awake longest.
• SnapBridge and the Cloud: background uploads and their battery cost.
• Cleaning and Weather: condensation and storing the camera.