Battery guide for photographers
Modern photo equipment require electric power to work. A number of the different components that make up a modern digital camera system (e.g. autofocus, stabilisation, the LCD for preview and review, power zoom, and of course the image sensor itself) will not work without electrical power. If you use external flash units, you will find that they too consume a lot of electrical power. Choosing the right batteries for your camera and flash will not only save you money, but it will also prevent you from missing shots because your flash is recharging or you've run out of power.
There are different kinds of batteries in use today. We usually classify them according to the chemistry they use. The chemistry determines their other characteristics, such as the amount of power they can supply, how they behave under load, and whether they are rechargeable or not. Below is a list describing the major chemistries of interest to photographers.
Alkaline batteries in the shape of standard AA disposable cells are cheap and ubiquitous. They have low self-discharge and can be stored for a long time. They will also last for a long time when used to power low-current devices such as TV-remotes and alarm clocks.
The chemistry of alkaline batteries is a reaction between zinc and manganese dioxide (Zn-MnO2). Their nominal cell voltage is 1.5 volts.
Unfortunately, Alkaline batteries are not well suited for use in digital cameras and modern flash units. Because they rapidly drop their voltage under load, they will give you very few shots for the money. They can be pressed into service in an emergency, when you are out of more suitable batteries. (And after a set of Alkaline batteries no longer work in your flash or in a camera, it will usually work fine for a long time in any device that only drains a low current.)
Nickel Oxyhydroxide (NiOx)
Nickel Oxyhydroxide are disposable (non-rechargeable) batteries designed to replace alkaline batteries to power digital cameras. Manufacturers claim that in when used to power digital cameras, they last twice as long as alkaline batteries, and tests confirms this. They have low self-discharge, so they can be stored in unused condition for a long time.
Used in low-drain applications, such as TV-remotes and alarm clocks, they do not last any longer than standard alkaline batteries. Used in a flash like the Nikon SB-910, they are outperformed by rechargeable NiMH by a large margin, both in how long they last, and in how fast the flash recycles.
NiOx batteries initially has a higher nominal voltage (1.7 volts) than alkaline batteries (1.5 volts) which can cause problems in certain products, such as equipment with incandescent light bulbs (e.g. torches), and devices without a voltage regulator.
The Panasonix Oxyride is sold with the following warning:
CAUTION: This battery has an initial voltage of 1.7 volts. User must ensure that each circuit in their application is designed to accept the higher initial voltage and is safe and otherwise completely appropriate for the desired application.
Lithium batteries are disposable (non-rechargeable) batteries.
The term “lithium battery” refers to a family of different chemistries, comprising many types of cathodes and electrolytes. Common for all is that they have a low self-discharge rate, and, unlike Alkaline batteries, they pack a lot of power in a compact and light-weight package. Nominal cell voltage can be from 1.2 volts to about 3.8 volts, depending upon chemistry.
The most popular Lithium batteries come in the shape of flat button cells, such as the CR2032. Lithium batteries are also offered in other standard sizes such as PP3, CR-V3, AA, and AAA.
Disposable Lithium 1.5 volts batteries may be used as a light-weight and high-capacity replacement for disposable Alkaline batteries, provided the equipment has been designed to be fitted with a Lithium battery. This is usually explained in the manual.
So called “high-power manganese batteries” are based upon a reaction between lithium and manganese dioxide (Ln-MnO2). They have a nominal cell voltage of 3.0 volts. They can damage equipment if they are used to replace 1.5 volts alkaline manganese cells.
A too-rapid discharge of a Lithium battery can result in overheating of the battery, rupture, and even explosion (consumer Lithium batteries usually incorporate thermal protection in order to prevent this from happening). A modern battery powered flash unit may impose very high current drains on the batteries. When used for flash, lithium batteries tend to become very hot compared to any other chemistry. Lithium batteries should not be used to power flash units unless the manual explicitly says that Lithium batteries may be used.
Mercury batteries are non-rechargeable batteries that is no longer available because mercury is a very toxic substance.
Mercury batteries have a open circuit voltage of 1.35 volts and low self-discharge. Since their voltage remains almost constant (within 1 %) for several years at light load, mercury batteries were frequently used to provide a constant reference voltage in stand-alone and integrated light meters manufactured before mercury batteries were banned in 1991.
The legal substitutes for mercury batteries today are silver-oxide and zinc-air batteries. For a in-depth discussion of how to replace mercury batteries, see The mercury cell problem and its solutions (pdf) by de Gruijter.
Silver-oxide batteries are non-rechargeable batteries that may replace banned mercury batteries in some equipment. Like mercury batteries, silver-oxide cells have a low self-discharge and constant voltage over time. However, their open circuit voltage is 1.55 volts, higher than the 1.35 voltage of mercury batteries.
This can either be resolved by recalibrating the light-meter to work with the higher voltage, by modifying the camera by inserting voltage regulation in the light-meter circuit, or by inserting the silver-oxide battery in a special adapter that uses a diode to drop voltage to simulate a mercury battery. Note that since the voltage drop is a non-linear function of the current flow, a voltage dropping diode is not a very accurate solution.
Zinc-air batteries are non-rechargeable batteries that may replace banned mercury batteries in some equipment. Like mercury batteries, zinc-air cells have a constant open circuit voltage of 1.35 volts.
Zinc-air batteries have three disadvantages: 1) They require air to operate, which means that you may have to drill holes in the battery compartment, and you may need to use spacers to allow air-flow if cells are stacked. 2) They do not work well in a dry climate. 3) Their lifespan is limited to 2-4 months, so they tend to be expensive.
Most of you know Lead-acid batteries in the form of standard 12 volts car batteries.
The nominal cell voltage is 2.1 volts. A 12 volts car battery consists of 6 cells.
This chemistry makes a cheap and simple rechargeable battery with a low self-discharge rate and a high tolerance for abuse.
This is a mature technology that is not much used in photo equipment, but you may find in the proprietary power packs for professional cameras and lighting kits where ruggedness and durability is more important than weight.
Lead-acid batteries contains toxic lead and acids, and should be disposed of safely.
Nickel Cadmium (NiCd)
NiCd batteries are rechargeable.
The nominal cell voltage is 1.2 volts.
This chemistry dates back to the 1950ies and has a number of limitations, such as the so-called “memory effect” (NiCd batteries must be fully discharged before recharging or they will deteriorate rapidly). Overcharging will also ruin a NiCd battery. It contains Cadmium, which is highly toxic. NiCd batteries should be disposed of safely.
Newer battery types, in particular NiMH and Li-ion, has made NiCd redundant. Avoid.
Nickel-Metal Hydride (NiMH)
NiMH batteries are rechargeable and come in a number of standard sizes including AA. One AA cell typically stores up to 2900 mAh.
The nominal cell voltage is 1.2 volts.
Being rechargeable, they work out cheaper than disposable Lithium batteries for digital cameras that use AA-sized batteries.
They have low internal resistance and is capable of powering high-drain devices such as modern flash units. Their main drawback is a high self-discharge. They will typically lose around a third of their capacity after one month. This means that you should make sure your NiMH batteries are freshly charged just before use.
They also have a low tolerance for overcharging, have some “memory effect”, and may lose capacity from various abuse, such as “quick charging” and being stored without a charge too long. Reconditioning it in a suitable charger may restore most of the lost capacity.
NiMH does not like being stored in a state where its open circuit voltage drops below 0.7 volts. This may cause crystals to form which will eventually destroy the battery. For best battery longevity, re-charge NiMH in storage at least once a month.
If you let NiMH batteries lie around unused for three months or more, you may experience that crystallisation has created high internal resistance and decreased battery capacity. If you experience this, applying a “forming charge” to the battery may help.
However, if this process is too far gone, the battery may be past recovery. I have some NiMH batteries that I've kept in storage too long. My Maha MH-C-9000 reconditioning battery charger refuses to touch these. It simply rejects them with the message message “high”. For the record: These batteries can be charged with my Vanson intelligent charger, and after charging and resting them for one hour, a digital multi-meter indicates a healthy 1.4 volts open circuit voltage, my Digicam Power EC-741 battery tester says they are fine, and they will power any low drain device, such as a torch, for hours. However, when I pop these freshly charged cells in my Nikon SB-910 Speedlight, the low battery symbol lights up and they are useless.
Low Self-Discharge Nickel-Metal Hydride Hybrid (LSD NiMH)
In 2005, an improved version of the NiMH rechargeable battery was introduced. This version used a new and larger separator between the electrodes that reduces self-discharge. These cells are marketed as “hybrid”, “ready-to-use”, “pre-charged” or “low self-discharge” NiMH rechargeables.
Their chemistry is similar to standard NiMH batteries. They have the same 1.2 volts nominal cell voltage, the same low internal resistance and the ability to power high-drain devices. They can be charged in standard NiMH chargers, and most of the things said about NiMH batteries in the previous section apply LSD NiMH. They have a slightly lower capacity than NiMH, one AA cell typically stores 2000 mAh.
The advantage of the new design is that they can be stored for much longer in the shop or in your camera bag without discharging. Manufacturers of LSD NiMH claim that after one year in storage at room temperature, an LSD NiMH should retain 70-85 % of its peak capacity
Like regular NiMH, LSD NiMH will self-destruct when stored for a long time with a too low voltage. However, since their self-discharge rate is lower, this is less likely to happen if you remember to always top them up after use.
The best known LSD NiMH brands are Sanyo Eneloop (2000 mAh, 1500 recharge cycles, retains 75 % charge for three years); and Sanyo XX (2500 mAh, 500 recharge cycles, retains 75 % charge for one year). For newer XX version has higher capacity than the original Eneloop battery, but has a slightly higher self-discharge and can only accept a third of the recharge cycles.
NiZn batteries are rechargeable, but trickle charging is not recommended. Because of this, you need to use a special charger that cuts off charging when the batteries are fully charged.
The NiZn chemistry has been known for over 100 years, but only recently (2009) has NiZn rechargeables become available as standard AA size cells.
NiZn cells have an open circuit cell voltage of 1.85 volts when fully charged and a nominal cell voltage of 1.6 volts. Due to tolerances NiZn will usually work as an replacement for products that are designed to use alkaline AA cells (1.5 volts), but the higher voltage may confuse monitoring circuits about the state of the batteries, so you will not get any warning about batteries that are running out of juice.
One NiZn AA cell typically stores up to 1500 mAh, which means that they have lower total capacity than NiMH and LSD NiMH. They have a self-discharge rate similar to NiMH, so you should make sure you use freshly charged cells if you decide to use NiZn. Their main advantage is that with a very low internal resistance, they are able to deliver a lot of current in a short time. This, together with their 1.6 volts nominal voltage, means that they provide shorter recycle times than any other AA-battery when used to power a modern flash unit. In fact, they provide so short recycle times that you risk frying your flash if it doesn't have built-in thermal protection.
One the positive side, NiZn batteries are cheaper than other types of rechargeable batteries, they do not suffer from any memory effect, pose no chemical hazard, and both nickel and zinc is easy to recycle.
In the past, NiZn batteries has allowed fewer recharge cycles than, for example, NiMH batteries, making them more expensive in the long run despite lower initial cost. However, better materials and other improvements seem to be closing this gap.
The best known NiZn brand is PowerGenix.
Lithium Ion (Li-ion)
Li-ion batteries are a new type of batteries that was first introduced in the 1990ies. This chemistry is still improving. Most propriety batteries supplied with digital cameras these days are Li-ion batteries.
The nominal cell voltage is 3.6 or 3.7 volts.
In addition to the odd-sized proprietary Li-ion batteries, you can buy a 3 volts Li-ion battery called “RCR-V3” that is shaped like two AA-batteries. This can be used in many (but not all) digital cameras that take AA-type batteries as a direct replacement for two AA cells.
Li-ion batteries are a rechargeable, have a low self-discharge rate, do not suffer form the “memory effect”, and packs a lot of power in a compact package.
They have, however, a high internal resistance and is less suitable for high-drain devices such as electronic flash units.
Unlike NiMH and NiCd rechargeable batteries, they do not tolerate trickle charge. Always use the charger supplied with the battery to recharge Li-ion batteries. If they overheat, they may explode. For this reason, Li-ion batteries are usually fitted with a protection circuit. This protection circuit may, however, be missing from some aftermarket Li-ion batteries.
Li-ion batteries degrade with time. This happens whether the battery is used or not. However, they degrade much faster if stored in high temperatures, so keep unused batteries in a refrigerator. They are best stored fully charged. If a Li-ion battery becomes depleted below its low-voltage threshold, the battery may not accept charge because its internal protection circuit disables charging.
If you read up the specifications of a particular battery, you will usually find two numbers: Its capacity (measured in mAh), and its voltage (measured in volts).
The meaning of mAh
The total capacity if a battery (under ideal conditions) is listed in its specifications as mAh (milliAmpere-hour). This number is supposed to indicate for how long a battery can deliver a given current. A battery with a capacity of 2000 mAh should be able to supply a current equal to 200 mA for 10 hours. (200 mA x 10 h = 2000 mAh). The higher the mAh-number is, the higher, in theory, is the capacity of the battery.
However, the mAh that is given in the advertising copy for a battery is measured using a method prescribed in IEC 61951 that puts a low continuous load on the battery. This may not be the conditions you use the battery under.
For instance: An Alkaline battery may be rated at 2700 mAh as long as the load current is low, but the capacity could appear to be as little as 400 mAh if this battery is used to power a device like a modern flash, that draws a high current (peaks at 12 ampere and average more than 4 ampere) when charging its capacitor.
It should also be mentioned that some manufacturers cheat when reporting the mAh number. No-name brands rated at 2700 mAh by the manufacturer may only measure 2200 mAh when I test their capacity according to IEC 61951 standard, while premium brands actually measure up to their rated capacity.
When buying batteries for your camera or your flash, you should not only look at the mAh-number, but also make sure that the other characteristics of the battery matches your intended use.
Voltage is a measure of electrical potential between two points. The higher the voltage, the higher the potential, and (provided resistance is constant) the higher the current.
The nominal cell voltage depends on the battery's chemistry and is a number that is computed from equilibrium conditions. The nominal cell voltage cannot be directly measured, but can be found in the manufacturer's specifications for the battery.
The open circuit voltage is the voltage that can be measured between the two poles of the battery when fully charged and allowed to rest for one hour, when there is no load on the battery. For most batteries, it is very close to the nominal cell voltage, but NiMH rechargeables tend to have a open circuit voltage that is slightly higher than their nominal voltage.
A common misunderstanding is that the voltage of Alkaline batteries “are 1.5 volts”, and that the voltage of NiMH batteries are “are 1.2 volts”. Because the former chemistry has a higher voltage, the argument goes, it is more powerful and delivers a shorter recycle time. However, he actual voltage output by a battery under load is a function of several parameters, including its internal resistance and its discharge cycle. This means that Alkaline batteries that are connected to a high drain device such as a recycling flash unit will deliver less than 1 volt most of the time. Those interested in the details should read this technical note by Roy Lewallen. Anyone that has tested out Alkalines vs. NiMH hybrids in a modern flash such Canon's 580EX Speedlite knows that a “1.2 volts” Sanyo Eneloop rechargeable is superior to a Duracell “1.5 volts” Alkaline. Lewallen will show you why.
Determining battery capacity
The international standard IEC 61951 put out by the International Electrotechnical Commission describes, among other things, how to determine the capacity of Portable sealed rechargeable single cells.
The charge and discharge currents to be used in this procedure are expressed in a fraction of C, where C is the rated Ampere-hour capacity of the battery. For instance, if a battery is said to have a rated Ampere-hour capacity of 2400 mAh, a charge of 0.1C means to charge with a current of 240 mA, a discharge of 0.2C means to discharge with a load that results in a 480 mA discharge current, and so on.
The procedure that apply to NiMH cells (both ordinary and LSD NiMH) is as follows:
- The battery shall be charged until it is fully charged according to the specifications given by the manufacturer. [For AA-sized cells, a 16-hour 0.1C charge is adequate.]
- After charging, the battery shall be stored allowed to rest in an ambient temperature of 20°C ± 5°C for not less than 1 hour and not more than 4 hours.
- The battery shall then be discharged in an ambient temperature of 20°C ± 5°C at a rate of 0.2C. This test shall continue until the battery pack reaches its end of discharge voltage. [For NiMH cells, this is 1.0 volt.]
- During this period, voltage shall be logged, integrated at the end of discharge, and multiplied by the discharge current to obtain battery energy.
- This procedure may be repeated a maximum of 5 times, with the best result being chosen as the final measured energy value.
For instance, if step 3 in the procedure took 5 hours to complete, and the discharge current was 480 mA, the total energy (capacity) of the cell is 480 x 5 = 2400 mAh.
If you plan using your digital camera or flash on a regular basis you should invest in a good set of rechargeable batteries. While rechargeables are more expensive up-front than disposable batteries, they can be recharged and used over and over again. This will work out cheaper in the longer run.
Batteries for a digital camera
For a digital camera, I think the best choice is a Li-ion battery. If your camera has a proprietary battery, this is also probable your only option.
However, if your camera uses a proprietary battery there will be the “original” battery sold by your camera manufacturer and several aftermarket alternatives that usually cost a lot less. However, according to this story in Engadget, there are cases where aftermarket Li-ion batteries have exploded inside the camera.
Given the complexity of the Li-ion chemistry, I prefer to buy “original” batteries just for the peace of mind. However, I have friend who claims that aftermarket batteries perform just as well. Nikon has the following advisory about counterfeit batteries.
If your camera accepts AA-batteries or any other standard size, I would recommend using RCR-V3 if these batteries is listed in the manual as compatible. They are expensive, but light, provide the greatest number of shots per charge, and have low self-discharge. It may also be a good idea to purchase a set of disposable NiOx AA-batteries and keep those as a spare set in your camera bag as an emergency back-up.
If a proprietary Li-ion battery or RCR-VR3 batteries are not an option, the obvious choice is LSD NiMH batteries. While LSD NiMH batteries have a higher price-tag and slightly lower capacity that regular NiMH batteries, the added convenience of charge-and-forget more than makes up for it.
Battery grips for DSLR cameras sometimes come with optional trays that lets the photographer choose between several battery types.
Some of these offers a higher frame rate when fitted with certain batteries. For instance, with the Nikon MB-D10 Multi Power Battery Pack for the Nikon D300 and D700, the photographer may fit a proprietary EN-EL3e Li-ion battery, the proprietary EN-EL4a, or eight AA-type NiMH batteries. The EN-EL3a provides lighter weight and the greatest number of shots per charge, the two others provide a higher weight and a higher frame rate (increased from 6 fps to 8 fps). In this case, it is your call which of the alternative batteries to pick.
Other battery grips, such as the Nikon MB-D80 Multi-Power Battery Pack for Nikon D80 and D90 provides a similar choice between the proprietary Li-ion battery or six AA-type NiMH, but without any increase in frame rate. In this case, the proprietary Li-ion battery is probably the best choice.
Batteries for flash
Photographers like powerful flashes that recharge fast. A top-of-the-line flash such as Nikon SB-910 may draw as much as 12 ampere at peak moments, and 4 ampere on average.
Lithium batteries (both disposable and Li-ion rechargeables) are not designed to supply currents as high as this and may in worst case overheat and explode. Lithium batteries are therefore fitted with a thermal protection circuit that is supposed to shut down the battery before this happens. If the protection circuit is damaged, the battery may explode and damage the flash and injure the photographer. Since the protection circuit usually works, this is not a very likely scenario. However, because of the explosion hazard, I believe lithium and Li-ion batteries should be avoided as a power source for flash units.
All my flash units use AA-type batteries. Because of their low internal resistance and ability to stand up under load, I think LSD NiMH is the best choice as power source for portable flash units. The added convenience of charge-and-forget more than makes up for the higher price and slightly lower capacity of LSD NiMH batteries.
If you want the fastest possible recharge time, the best solution is to use an external battery pack. However, you can also cut recharge times to one third by using NiZn rechargeables. You need to be careful when you do this. Most modern flash units are not designed for machine-gun style use. NiZn stores less charge than both regular and LSD NiMH, so you need to carry more spares with you if you opt for the NiZn route.
In an emergency, disposable Alkaline batteries may be used to power a modern flash. Alkaline batteries poses no explosion risk, but they have a high internal resistance and does not stand up well under load. My experience with Alkaline batteries in modern flash units is that I get relatively few pops from a set before flash recycle times becomes very slow.
The table below is copied from page F-21 of the Nikon SB-900 manual, and shows what recycle times and the number of firings at full output to expect from different chemistries:
|Min. number of flashes*/|
|Alkaline-manganese (1.5V)||4.0 sec.||110/4.0-30 sec.|
|Lithium (1.5V)||4.5 sec.||230/4.5-120 sec.|
|Oxyride™ (1.5V)||3.0 sec.||125/3.0-30 sec.|
|Ni-MH (2600 mAh)||2.3 sec.||190/2.3-30 sec.|
|Ni-MH (eneloop)||2.3 sec.||165/2.3-30 sec.|
|* When firing the Speedlight at full output once every 30 seconds (120 seconds with lithium batteries).|
While AF-assist illuminator, power zoom and LCD panel illumination are off.
With fresh batteries. Performance may vary depending on battery freshness or battery specifications.
The table is not entirely realistic, because Nikon allows recycle times as high as 30 seconds (and two minutes for Lithium!) before considering a set of batteries spent. Most photographers will replace the batteries when recycle times exceeds 10 seconds. But the table confirms my gut feeling that NiMh is the best type to use in a modern flash unit.
While I have not had good experienced when using Alkaline batteries in modern flash units, I have noticed that some older flash units, in particular vintage versions of the Vivitar 283 produced in the 1970ies, are very sensitive to voltage. My old Vivitars (I have a few) won't recycle if I install NiMH batteries. I've found that the old Vivitars work best with four 1.6 volts rechargeable NiZn or 1.5 volts standard Alkaline batteries in the battery tray.
Batteries for wireless triggers
Battery powered wireless triggers are low drain devices and works very well with alkaline and lithium batteries.
Some models that use AA or AAA batteries are sensitive to voltage, and becomes unreliable when rechargeable NiMH or LSD NiMH cells with a 1.2 volts nominal voltage are used. This, however, is mostly the case with older designs. Newer models seem to be designed to work equally well with both 1.2 volts and 1.5 volts cells.
Battery packs for flash
If your flash has a battery pack connector, you can speed up flash recycle time by adding an external battery pack that applies voltage directly to the capacitor. Note that even when you use an external battery pack, you need to have batteries in the flash to power the flash's control circuit.
There are four types of external battery packs:
- High voltage packs
- Inverter packs
- Premium low voltage packs
- Simple low voltage packs
Each type is discussed in more detail below.
High voltage packs
High voltage battery packs are fitted with a proprietary rechargeable high voltage and high capacity battery that supplies a constant voltage of abouts 300-330 volts directly to the capacitor of the flash. High voltage battery packs reduce the flash's recycle time, and also extend the number of flashes you can fire without having to replace the battery. Examples:
- Nissin PS-300 for Canon (search Adorama, Amazon USA, Amazon UK, B&H, eBay).
- Nissin PS-300 for Nikon (search Adorama, Amazon USA, Amazon UK, B&H, eBay).
- Quantum Turbo 2x2 (search Adorama, Amazon USA, B&H, eBay).
- Quantum Turbo 3 (search Adorama, Amazon USA, B&H, eBay).
- Quantum Turbo SC (search Adorama, Amazon USA, B&H, eBay).
- Quantum Turbo QTB (search Adorama, Amazon USA, B&H, eBay).
Quantum power cables for the Turbo packs:
- Quantum CZ2 for Canon (search Adorama, Amazon USA, Amazon UK, B&H, eBay).
- Quantum CKE2 for Nikon (search Adorama, Amazon USA, B&H, eBay).
Because there is no inverter in these packs, there is no need for it to be connected to the pc-socket of the flash.
According to user reports, the Nissin PS-300 do not work if the flash is powered by alkalines, you must use NiMH rechargeable batteries.
Using a high voltage battery pack may cut your recycle time for a full recharge down to as little as 1 second. This may sound like something you may want to do, but most portable flash units are not constructed for this type of use. If you fire a full discharge every second or so with a small plastic flash that has no cooling, it will become very hot. The Nikon SB-800 have no temperature monitoring and no protection against overheating. It will break if you abuse it in this way. The Nikon SB-900 and Nissin Di866 has built-in overheat protection, and will shut down after about 40-50 cycles (or less) if you fire as fast as the battery pack let you. You will then have to let it cool for ten minutes or so before you can resume shooting. The Nikon SB-910 has an overheat protection system that will make recycle times longer when the flash heats up, cancelling the effect of the high voltage battery pack.
In short, if you want to fire your flash very frequently, a battery pack may not be all you need.
Quantum makes some flashes that can fire away all day without overheating. They are built to dissipate more heat, and are also a lot bigger and a lot more expensive than other shoe mounted flash units. If using a battery pack makes your flash overheat, you may need to invest in Quantum flash units.
Inverter packs use ordinary AA type batteries for power, put uses an inverter to “pump up” the voltage to 325 volts. With fresh batteries, they reduce recycle times just like high voltage packs. However, because they are powered by standard batteries, recycle times will become longer as the batteries run down. Unlike high voltage packs, they do not extend the number of flashes you can fire without changing batteries significantly.
Inverter packs are the most common type of external battery pack for flash. Examples:
- Canon CP-E4 (search Adorama, Amazon USA, Amazon UK, B&H, eBay).
- Nikon SD-8A (search Adorama, Amazon USA, Amazon UK, B&H, eBay).
- Nikon SD-9 (search Adorama, Amazon USA, Amazon UK, B&H, eBay).
- YongNuo SF-17 for Canon (search Amazon USA, eBay).
- YongNuo SF-17 for Nikon (search eBay).
- YongNuo SF-18 for Nikon (search Amazon USA, eBay).
If the inverter had been constantly engaged, the batteries would run down fast. To avoid this, the Nikon SD-8A (and similar) must be connected to the pc-socket of the flash. The pc-signal is used to activate the inverter when needed. This means that the pc-socket is not available for connection the flash to external radio triggers such as PocketWizard, Skyport or CyberSync. To get around this, you can use a pc splitter (search eBay), or a FlashZebra Nikon 3 Pin to Miniphone Mono cord. The Canon CP-E4, and the Nikon SD-9 works differently, and do not need to be connected to the pc-socket.
The Nikon SD-8A and YongNuo SF-17 can also be used with the Nikon SB-900 and SB-910. However, the Nikon SD-9 and YongNuo SF-18 can not be used with the Nikon SB-800.
There has been user reports that the YongNuo power packs SF-17 and SF-18 behave erratic when the flash is used off-camera. Until this is sorted out, DPanswers do not recommend the YongNuo power packs.
Premium low voltage pack
A premium battery pack is a proffesional grade pack using custom batteries that will supply a constant output of 6-12 volts. Example:
Provided the pack is fitted fit a high capacity custom battery, this type let you fire a high number of full power flashes without having to replace the battery. But unlike high voltage and inverter packs, they do not reduce recycle times.
Simple low voltage packs
A simple battery pack is a battery pack that accepts six or eight standard AA akaline batteries that will supply a constant output of 7-12 volts. Example:
This type of pack must be loaded with an even number of standard AA akaline or NiMH batteries (the number is usually six or eight, depending on model). Having more batteries available than what fits into the battery compartment of the flash lets you fire a higher number of full power flashes without having to replace the battery. But unlike high voltage and inverter packs, they do not reduce recycle times.
I regard the simple low voltage packs as an alternative to your camera bag as a compartment for carrying spare batteries. The only difference between carrying spare batteries in such a pack, instead of in your camera bag, is that having them in the pack only saves you from pausing shooting to load fresh batteries into the flash's own battery compartment when you run low.
These units tends to be very cheap. However quality and reliability also tend to be on the low side. To avoid these issues, I prefer carrying the spare batteries in my camera bag.
Guide to good battery-keeping
When you use rechargeables, you should buy them in sets of four (provided your flash takes four batteries – as most flash units do these days). Then, always charge and use the same set together. Mixing batteries of different brands, capacities and ages may result in shorter life-span for the batteries. To keep each set together I use a battery case that holds four batteries.
I will not recommend using a so-called “quick charger” to charge NiMH rechargeables. To make your batteries last, you should use an intelligent charger with an individual circuit for each cell that uses 2 hours or more to recharge a set of batteries. Charging NiMH batteries in a quick charger is possible, but this may damage the battery and it will also reduce the overall lifetime of the battery.
A slow, “intelligent” charger that monitors the charge of each cell individually should be used if you want long-lived rechargeable NiMH-batteries.
For optimum results, a reconditioning chargers such as the La Crosse BC-700 or Maha MH-C9000 (shown right) is recommended.
Both will do a good job analysing and reconditioning your batteries, but the one I recommend is the Maha. It is slightly more expensive than the La Crosse, but the user interface is much simpler and more intuitive than the user interface on the La Crosse.
My only gripe with the Maha is that the LCD-display is of a cheap type that does not let you view it from an oblique angle. You need to position your face straight in front of the unit to read the display. Otherwise it works very well.
The Maha MH-C9000 has four slots for AA and AAA NiMH batteries (including LSD NiMH batteries). Each slot has a separate circuit. The following operation modes are available:
- Charge. This mode does what every NiMH charger does. However, with the MH-C9000, you can also set the desired charge rates from 100 mA all the way up to 2000 mA. A charge rate of 200 mA gives longest battery life, but you may want to use a greater charge rate with good batteries when in a hurry.
- Refresh & Analyze. First recharges the battery, rest for one hour, discharge, rest, then recharges again. Charging and discharging rates are programmable. Reports the discharge capacity in mAh at the end of the cycle. Will recover lost performance. Recommended once every 10 cycles for NiMH batteries.
- Break-in. This mode applies what is known as a “forming charge” and should be used with brand new batteries to make sure they have optimal performance. The process requires 39 to 45 hours to complete. It reports the actual capacity in mAh at the end of the cycle, measured according to the IEC 61951 standard for determining battery capacity. This mode may also be used to save batteries that cannot be rescued by the Refresh & Analyze mode. Recommended once every 30 cycles for NiMH batteries, or if batteries has been in storage for more than 3 months.
- Discharge. In this mode, the charger will discharge a battery and measure how much power it was storing. The battery is not charged at the end of the cycle. This mode lets you test both NiMH or Alkaline batteries to see what their actual capacity is.
- Cycle. Performs a charge-discharge cycle for the programmable number of times. Charging and discharging rates are also selectable. At the end of the cycle, a final recharge is applied. This mode can be used to “exercise” a tired battery to improve its performance.
The break-in mode of the Maha MH-C9000 is superb. Some of my batteries had decayed to the point were they only had a fraction of their original capacity of 2400 mAh. The one in worst shape had an effective capacity of 278 mAh. Three rounds in the break-in mode took the best part of a week, but at the end, they had been reconditioned to more than 1900 mAh.
The Maha MH-C9000 is fastidious about what batteries it will charge. It will measure the internal resistance of a battery, and if it find its internal resistance too high, it will just display the message “high” and refuse to charge the battery. While batteries rejected by the Maha can be charged with other chargers, they no longer work well (if at all) in any high drain device such as a flash, so they should be recycled.
Below is a summary of the how to take care of your rechargeable batteries to make them last.
- Make sure you insert the batteries correctly into the camera or flash.
- Never mix used and unused batteries.
- Never mix different types of batteries.
- Store and use your batteries in “sets” that makes sure each battery in a “set” is of the same age and has seen the same number of recharge cycles.
- Take care not to overcharge rechargeable batteries. Use an “intelligent” charger with an individual circuit for each cell.
- Use a reconditioner periodically during the life of a battery.
- Do not use a so-called “quick charger”. For NiMH, it is better to use a charger that uses 2 hours or longer to recharge a set of batteries.
- Don't expose your batteries to extreme heat or cold. However, it is OK to store Li-ion at +4°C.
- Don't leave batteries inside the camera or flash for an extended period of time. Batteries might leak and damage your equipment.
Some components, such as the colour LCD or a stabilisation system, are putting a high drain on the batteries. The tips below will help you preserve battery power:
- If you are going to take lots of photos in a short time, don't switch on and off for each shot. Restarts uses more power than having the equipment sitting idle for some time.
- Use the the colour-LCD on the back of your camera sparingly. Use the optical view-finder rather than live-view to compose. Turn off automatic review.
- Turn off vibration reduction / image stabilisation when you do not need it.
- Use an external card-reader, rather than the camera, to transfer photos from your digital camera to your PC.
Applying a “forming charge” to a NiMH battery is a way to restore to (almost) former glory batteries that have lost a significant part of their capacity.
To apply forming charge, proceed as follows:
- Apply a 16-hour 0.1C charge.
- Let the battery rest for 1 hour.
- Apply a 0.2C discharge until the battery reaches its end of discharge voltage of 1.0 volt.
- Determine capacity in mAh by multiplying discharge current with the time it took the previous step to complete.
- Let the battery rest for 1 hour.
- Apply a 16-hour 0.1C charge.
- Determine capacity, and repeat from step two until no further improvement is detected in capacity.
A single cycle (steps 1 to 6) normally takes 39 to 45 hours to complete. With a battery in really bad shape, it may require as many as five repeated cycles before capacity is optimal.
If, after five repeat cycles, the battery is still unable to hold a usable charge, this usually means that the battery can't be fixed.
The simplest method for applying a forming charge reconditioning charger to automate the task.