mAh, Eneloops and battery packs.

Started Oct 31, 2013 | Discussions
PP2K New Member • Posts: 15
mAh, Eneloops and battery packs.

This may be a silly question, but it's something that's been bothering me for a long time. Mind you, my knowledge of watts, amps and volts, is miniscule. For me, it's always been enough just to know how many pops a given battery can give me.

So, I do some of my stuff with speedlights and been looking at these external battery packs. Let's say, I put 8 AA Eneloops inside my speedlight, 1900 mAh each, and they give me, say, 250-300 full power pops. Then there's this external 2000 mAh pack, that gives 320 pops. Then there's another 4500 mAh pack that says 1800 pops.

Ahem... 8 x 1900 is 15 200. And why does the second pack advertised, give so much more pops than the first one? What's the math here, between mAh's and volts and all that shizzle?

dad_of_four Veteran Member • Posts: 8,448
One word - Marketing

PP2K wrote:

Your cannot multiply the 8x1900 to get your total amperage available. Each battery supplies 1.2 to 1.5 volts, putting them together in series yields 12 volts needed for your speed light, but your capacity is still approx 1900 mAh.  Your speedlight is configured like the bottom image.  You'll get 6 volts, but only 1900 mAh

You 4500 mAh pack is probably already wired at 12 volts, so its available capacity is the full 4500 mAh. It  could be wired as a combination of the two images.  Several batteries in Series to get to your operating voltage, then several of those Series packs wired in parallel to get the desired mAh

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OP PP2K New Member • Posts: 15
Re: One word - Marketing

Aha! So that's the deal. Makes sense to me. It seems I wrote this wrong to begin with – of course I don't have 8 Eneloops in the speedlight, but instead, four But, I get the idea now. Thanks D-O-F!

WFulton Senior Member • Posts: 2,697
Re: mAh, Eneloops and battery packs.

PP2K wrote:

This may be a silly question, but it's something that's been bothering me for a long time. Mind you, my knowledge of watts, amps and volts, is miniscule. For me, it's always been enough just to know how many pops a given battery can give me.

So, I do some of my stuff with speedlights and been looking at these external battery packs. Let's say, I put 8 AA Eneloops inside my speedlight, 1900 mAh each, and they give me, say, 250-300 full power pops. Then there's this external 2000 mAh pack, that gives 320 pops. Then there's another 4500 mAh pack that says 1800 pops.

Ahem... 8 x 1900 is 15 200. And why does the second pack advertised, give so much more pops than the first one? What's the math here, between mAh's and volts and all that shizzle?

We don't have any clue what flash and what external power pack we are discussing... It may have more battery cells in it?

Four AA NiMH cells ought to give 150 to 250 full power flashes, but of course it will depend on how much power the flash can use. With the same batteries, a small flash can do more of its full power flashes than a bigger flash will do. The purpose of the larger flash is to use more power in each full power flash.

Putting four cells in series to be 6 volts does multiply the voltage, and does leave the mah capacity unchanged, but it also delivers 4x more power (than one cell). Power is voltage x current.  Capacity is current x time.

The typical flash uses four AA cells, but they have an internal power converter to raise this to be 300+ volts to charge the flash capacitor, which drives the flash tube. The recycle time is the time to recharge that HV capacitor. High current ability of the NiMH is a big plus there.

The 1900 mah is a total capacity, milliamp hours, not a rate. The bigger speedlight flash will draw 6000 or 7000 ma  for the few seconds that it is recharging the capacitor. Then it eases off to vastly lower current, to only keep it charged, and to power the other electronic chips.

The external power packs are also power converters, outputting the 300+ volts direct to the capacitor through a special port for the purpose.   Around 325 volts is common.

The overall number of maximum flashes depends on the power of the flash, and also depends on how much capacity it can get from the number of cells attached.  More cells is more power.

Only if it is the same flash and same conditions and same number of cells, then the mah number can be compared more meaningfully.  But it is a capacity, not a rate.

NYCphotoman Regular Member • Posts: 134
Re: mAh, Eneloops and battery packs.

I would not think in terms of capacity, but in terms of recycle time. Certain batteries and packs recycle the flash faster then others. Capacity discussion is a moot topic in any event because the more a battery is drained the greater the recycle time. Once the batteries are drained past 50 percent the recycle time is too great.

Keep in mind that no one operates their flash at full power. Most of the time a flash goes off at a 1/4 power or less. So 300 pops might translate to 1200 pops.

White 2000 mah Eneloops are proven to be the fastest to recycle the flash. Just carry spare AAs in your pocket. The professionals will switch the batteries out with fresh ones well before they reach the limit.

Suntan Veteran Member • Posts: 5,915
Re: mAh, Eneloops and battery packs.

NYCphotoman wrote:

White 2000 mah Eneloops are proven to be the fastest to recycle the flash.

Where has this been proven vs. all of the dedicated flashgun battery packs on the market?

-Suntan

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OP PP2K New Member • Posts: 15
Re: mAh, Eneloops and battery packs.

My thanks to Mr Fulton as well. A bit too detailed for me, yet loads of info

Suntan, I think NYCPhMan meant that those specific Eneloops are faster when compared to other rechargeable high capacity NiMh AA's.

Suntan Veteran Member • Posts: 5,915
Re: mAh, Eneloops and battery packs.

Well first of all, the OP was specifically asking about dedicated external battery packs.

Second of all, ok I'll play along, where is the proof that the enloops recycle faster than all other AA batts available?

-Suntan

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razorseal Regular Member • Posts: 117
Re: mAh, Eneloops and battery packs.

Well first of all, the OP was specifically asking about dedicated external battery packs.

Second of all, ok I'll play along, where is the proof that the enloops recycle faster than all other AA batts available?

-Suntan

What is this a courthouse and there is an indictment?its just one of Accepted standards. Many people use it because they're fast.

Jesus... People always wanting hard effing proof with raw data scores and crap

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Phil
Phil Veteran Member • Posts: 3,142
Re: mAh, Eneloops and battery packs.

Suntan wrote:

Well first of all, the OP was specifically asking about dedicated external battery packs.

Second of all, ok I'll play along, where is the proof that the enloops recycle faster than all other AA batts available?

-Suntan

I'd have to take some data for you. I have 4 speedlights (holding 4 pre-charge AA) with 4 external battery packs (each holding 8 cells NIMH, not pre-charges).

I very routinely get 1 second recycles (a 1,000 count) not a stop watch. The bad news in my case is my speedlights have no thermal cut-outs. So I'm on my own when it comes to a melt down.

I'll do ten shoots and then talk to the subjects about the next set-up and then go back to shooting.

The other thing I can do is double up flash heads on the main channel to cut the required power from each. Of course at that point its no longer full power dumps and I start ignoring my 10 count. I never worry about the fill or key lights keeping since their power is way down.

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NYCphotoman Regular Member • Posts: 134
Re: mAh, Eneloops and battery packs.

The battery packs which accept the AA batteries are the best for Speedlites and in that case white Eneloops are the best AA to use in terms of recycle time. The reason why I say this is because its the most serviceable pack on the market. You dont have to send it in to anyone to get it re-celled.

In terms of all out speed the packs which use NIMH sub-cs seem to be the fastest. I havent seen any tests but that is my observation. However whenever you use an NIMH or Lithium pack its a pain getting it serviced. You cant do it yourself.

Therefore in terms of battery packs my opinion is the packs which use the sealed lead acid cell are the best. The original Quantum Turbo is the best. You just take out three screws and the cell comes out. Sometimes its difficult getting it out and I have damaged packs doing it but it can be done easily at times.

If you are buying a second hand Turbo then get one with a later serial number. One which has 4 green lights on top versus the older models which have a red and 3 green. I have several turbos and some from the 90s which work very well. Ive had some issues with Quantums 2x2s. The NIMH sub Cs work very well at recharging the flash but eventually after 2 busy wedding seasons they die.

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