Normally a speedlite will hold 4 AA batteries. A battery pack will allow you to connect extra batteries to your speedlite. This gives the advantage of more flashes per set of batteries and faster recharge times. Now you can take more photos and not have to wait so long between shots for the speedlite to recharge.
The battery pack is designed for speedlites that already have a suitable socket. Nothing else is required.
Brief Operation of a Speedlite
A Flash Gun uses a very high power but very short duration flash of light (see? the clue was in the name). Normally, belting out that amount of light would require a lot of power and create overheating problems. But as the light duration is measured in milli seconds the heat does not get a change to become a problem. As the flash is only required for such a short period, the battery to drive is can be very small. In fact a capacitor is used instead of a battery.
The tube used is a Xenon tube. The flashgun will energize it with a high voltage that will strike a plasma in the tube releasing the light.
So the speedlite needs a high voltage (about 300v) and a method of storing this until it is needed (a capacitor). It is only required to connect the capacitor to the tube at the right time to get the light you need.
The speedlite uses a high voltage generator to convert the 6v volts from its batteries to the 300v needed for the flash tube. When you switch on the speedlite and you hear that whine? That’s the high voltage generator running. When it has almost filled the capacitor, it doesn’t have to work so hard and the whine starts to get quieter.
This is the high-voltage end. This is what I like to call the ‘business end‘.
The other end is the control functions. This is the part where you can set the trigger channel, what power setting you want, etc.
How does the Battery Pack work?
As I said before, there are two parts to a normal flash according to the voltage they operate at…
1. The controls (5v)
2. The flash (300v)
The Battery Pack is a high voltage generator. It will drive the 300v side of the speedlite. It can generate a higher power 300v supply than inside the speedlite. The speedlite is restricted by the heat generated so it’s 300v source is of a lower power. This means it takes longer for the speedlite to fully charge the capacitor using its own power. Using the external pack allows the capacitor to charge much faster. In the time it takes you to compose your shot the flash is ready.
The connection from the Battery Pack to the speedlite has three pins. Only two are necessary for the 300v. One is the +300v and the other the 0v pin. The third pin is to communicate between the speedlite and the battery pack. If the pack is connected, the speedlite will not charge the capacitor – it will leave this to the Battery Pack. If you disconnect the Battery Pack, the speedlite will detect this and once again take over the charging of the capacitor.
How to use the Battery Pack
Leave the Battery pack connected but switched off. Does the speedlite work as normal?
Disconnect the pack while it is driving the speedlite.
Connect it up as normal. Then unplug when expired – assistant to replace the batteries. Then plug back in. All that happened was a short slow-down in the photography.
Which Speedlites can accept the Battery Pack
I’m only looking at manual speedlites here. The YN560iii, YN560iv, YN660 all accept the external battery packs.
I will update this list over time as I get the extra information.
The Battery Pack connector
Some people might ask why the connector is so large. It would be much better to use a smaller connector in such a small speedlite. If you use a small connector for 300v there is a higher risk of dirt, or skin-oil, etc. creating a low resistance path between the pins of the connector. The further these pins are apart, the less is this risk.
The reason the pins are exposed on the speedlite and hidden in the connector for the Battery Pack is that the exposed pins on the speedlite carry no voltage when they are exposed. The voltage is carried in the Battery Pack connector – which is shrouded.
The middle pin (0v) in the speedlite connector is longer than the others. This means that when you connect the Battery Pack, the 0v line is connected first. By the time the 300v pin is connected, the plug has already entered the socket and so there are no exposed high voltages. Eve.
The connector has a key-way. This means it can only be connected one way – a safety measure. It also means you must buy the proper one according to whether you are using Canon, Nikon or Sony, flashes or their compatibles. Because why make them exactly the same when you can make them different.
What battery packs are available
| Manuf | Model # | Qty Batteries |
| Yongnuo | SF-18C | 8 |
| Aodelan | P12 | 12 |
| Canon | CP-E4N | 8 |
What other types of battery pack are available
The normal DIY battery packs tie in to the speedlite’s 4xAA batteries by bypassing them or substituting them for dummy batteries. Then a larger external battery will be connected. This increases the flash available power from about 2,500mA to about 10,000mA or even higher.
This is fine for increasing the number of flashes available from a set of batteries, but will not increase the recharge time. Whatever recharge time you will get from a fresh set of batteries – then that is the best you can hope for using this DIY approach. But if you’re not so interested in this and just want more flashes, and are handy with a screwdriver and a soldering iron, then this approach could suit you very well.
Precautions when using the Battery Pack
Don’t fire too many flashes in quick succession – the speedlite could overheat. Part of the design of a speedlite monitors the temperature rise using the fastest flash rate possible under normal conditions. The design will be modified if necessary to ensure overheating is not an issue. But by adding a Battery Pack you are upsetting these design criteria.It is your responsibility to ensure the speedlite does not suffer as a result of adding this extra power to it. In fact, Canon have added extra circuitry in their latest flashes that will throttle them back in the event of overheating. This will manifest itself to the photographer in that the flash will start working for a while. Frustrating, but done for the best of reasons.
Take care of the Battery Pack output lead – it can have 300v at its plug.