Keeping track of my dozens of AA's drives me nuts--I'd be happy to switch to a single rechargable Li-ion battery--like the one in my camera or a tiny version of the one in the Vagabond I just picked up. Will we see proprietary Li-ion power packs instead of AA's in the near future? If not, why?
The problem is one of scalablility. It would be possible to power your speedlighti with a Li-ion battery if you wanted to haul around a unit the size of the vagabond pack, but a Li-ion batttery scaled down to fit inside a speedlight wouldn't be able to deliver the current needed to power a flash.
Google "Battery University" for more info on Li-ion and other battery types.
Kisutch wrote:
The vagabond is an 8ah 12V--that's a lot more than 4aa's.
Assuming 2500mah AA cells:
10 AAs in series at 1.2 volts = 12 volts and 2.5ah
3 of the above series in parallel (36AAs) = 12 volts 7.5ah
And I've read battery university many times and there is no reason lithium batteries could not be scaled down to fit inside a speedlite. They power cell phones almost exclusively so why not a speedlite. I personally would love to get rid of multiple set of nimh batteries for my flashes.
jeraldcook wrote:
[Li-ion cells] power cell phones almost exclusively so why not a speedlite.
Those two devices have quite different power requirements, so I don't see how that's a valid comparison. Comparing a cellphone to a camera, yes, but a cellphone to a flash, no.
There are non-rechargeable AA lithium batteries, and while I understand the reason why there are no rechargeable lithiums in the AA-format, it seems to me that the existence of AA non-rechargeables lithiums is evidence that it's not a cell-size to performance problem.
BrianO wrote:
Those two devices have quite different power requirements, so I don't see how that's a valid comparison. Comparing a cellphone to a camera, yes, but a cellphone t o a flash, no.
The purpose of using the cell phone example was to demonstrate scalability; perhaps it was a bad example but my position stands. All batteries have a stated discharge rate as a multiple of their capacity(C). A 1ah battery with a 1C discharge rate can safely be discharged at 1ah and will discharge completely in 1 hour. A 1ah battery with a 2c discharge rate can safely be discharged at 2ah and will discharge completely in 30 minutes. Most lithium-ion cells have a C rating of 1-2C which is more than enough for a flash.
Cell phone batteries on the other hand are lithium-polymer batteries where discharge rates are usually around 10C, but can be as high as 50C. That means you could safely discharge a 2.5ah battery at 125amps in 1.2 minutes. Clearly either technology could be used in speedlites.
RDKirk wrote:
I'm questioning that, too.
There are non-rechargeable AA lithium batteries, and while I understand the reason why there are no rechargeable lithiums in the AA-format, it seems to me that the existence of AA non-rechargeables lithiums is evidence that it's not a cell-size to performance problem.
The non-rechargeable AA lithiums have a different chemical makeup than most lithium-ion and lithium-polymer batteries, specifically, they're lithium/iron disulfide. This is why other lithium batteries have a cell rating of 3.7 volts and the AA lithiums are only 1.5. Energizer lithiums have a maximum discharge rate of only 2 amps. And since the capacity of a Energizer lithiums is 3000mah, that give a "C" rating of only 1.5, which is no different than lithium-ion batteries and way below the lithium-polymer batteries found in cellphones, MacBooks, iPads, etc.
A camera manufacture could make a battery pack for a speedlite if it wanted to do so. Lithium battery packs have built in PCB boards that prevent overcharging/discharging/exploding while individual cylindrical batteries generally do not which is why you never see individual lithium rechargeable batteries.
jeraldcook wrote:
The non-rechargeable AA lithiums have a different chemical makeup than most lithium-ion and lithium-polymer batteries, specifically, they're lithium/iron disulfide. This is why other lithium batteries have a cell rating of 3.7 volts and the AA lithiums are only 1.5. Energizer lithiums have a maximum discharge rate of only 2 amps. And since the capacity of a Energizer lithiums is 3000mah, that give a "C" rating of only 1.5, which is no different than lithium-ion batteries and way below the lithium-polymer batteries found in cellphones, MacBooks, iPads, etc.
A camera manufacture could make a battery pack for a speedlite if it wanted to do so. ...Show more →
That is my point.
Lithium battery packs have built in PCB boards that prevent overcharging/discharging/exploding while individual cylindrical batteries generally do not which is why you never see individual lithium rechargeable batteries.
As I said before, I know why they don't make rechargeable lithium batteries in the AA format.
RDKirk wrote:
As I said before, I know why they don't make rechargeable lithium batteries in the AA format.
Because there doesn't exist a battery composition that produces both 1.5 volts and is rechargeable. And with the new nimh being low-discharge there probably isn't much incentive to spend the funds researching such a technology.
p.1 #10 · Why no Lithium batteries for speedlites?
Be careful what you wish for.
If proprietary Li-ion battery packs were available for flashes you'd probably complain about the price because they would likely be 2-3x the price of a set of 4 AA Eneloops.
Also the fact you can go into any convenience store anywhere in the world and buy AA's in an emergency is a plus. I've found myself doing that a few times when forgetting to bring along enough rechargeable batteries.
The care and feeding of AAs is simplified with good 8-cell charger like the MAHA and wrangling them is made easier by purchasing 4-cell plastic cases from sources like Green Batteries or Thomas Distributing.
p.1 #11 · Why no Lithium batteries for speedlites?
It sure is a nice idea, imagine if your 5D3 and 600EX took the same battery, that sure would be convenient!
I wonder if it has to do with discharge properties required. A camera or cell phone pull a slow, steady draw, but a flash pulls it in large, quick bursts.
p.1 #12 · Why no Lithium batteries for speedlites?
jeraldcook wrote:
Because there doesn't exist a battery composition that produces both 1.5 volts and is rechargeable. And with the new nimh being low-discharge there probably isn't much incentive to spend the funds researching such a technology.
They do, just that they aren't much better than NiMH based AA, in terms of size vs. capacity. http://amzn.to/GBbG2h
It's much more of a hassle to implement a 4-cell AA size Li-Ion pack for the flash, while a high current PCB is also required for flash use. Why 4-cell? Because general consumers would like to use regular AAs in their flash too.
p.1 #13 · Why no Lithium batteries for speedlites?
brett maxwell wrote:
It sure is a nice idea, imagine if your 5D3 and 600EX took the same battery, that sure would be convenient!
I wonder if it has to do with discharge properties required. A camera or cell phone pull a slow, steady draw, but a flash pulls it in large, quick bursts.
That would in fact be fantastic.. I don't know enough about batteries to comment, but that would be a dream.
I do know of video lights, that take Canon batteries / Nikon batteries.
p.1 #14 · Why no Lithium batteries for speedlites?
Lithium Ion cells are pretty finicky and generally do not like heat. A high end camera mounted flash is going to draw about 6-8 amps at 6 volts peak. This is within the specs for a 18650 cell (Li-ion) but that cell is about 4.7V when fully charged. You need 2 of them to get a 9V (nominal) system and that would mean 6AA cells. Not compatible.
The issues are with charging -- Li-Ion charging is tricky; many, many fires and explosions have been documented, particularly in series connected cells (even during discharge with series cells).... Engineers are trying to "idiot-proof" such systems -- GM has spent many millions on the Volt's power pack and fully 85% of the computer monitoring of that pack is related to "Safety" with only 15% to charge state and performance -- on the other hand regardless of how well we engineers idiot proof our products the competition is building better idiots even faster!
p.1 #15 · Why no Lithium batteries for speedlites?
larkinsg wrote:
...regardless of how well we engineers idiot proof our products the competition is building better idiots even faster!
So true.
I heard someone the other day propose the theory that there is only a fixed amount of intelligence in the universe, and so as the population increases, the per person average IQ decreases.
One has only to turn on the television or drive on the highway these days to see that it seems to be true.
p.1 #16 · Why no Lithium batteries for speedlites?
larkinsg wrote:
Lithium Ion cells are pretty finicky and generally do not like heat. A high end camera mounted flash is going to draw about 6-8 amps at 6 volts peak. This is within the specs for a 18650 cell (Li-ion) but that cell is about 4.7V when fully charged. You need 2 of them to get a 9V (nominal) system and that would mean 6AA cells. Not compatible.
The issues are with charging -- Li-Ion charging is tricky; many, many fires and explosions have been documented, particularly in series connected cells (even during discharge with series cells).... Engineers are trying to "idiot-proof" such systems -- GM has spent many millions on the Volt's power pack and fully 85% of the computer monitoring of that pack is related to "Safety" with only 15% to charge state and performance -- on the other hand regardless of how well we engineers idiot proof our products the competition is building better idiots even faster!
...Show more →
Max and nominal voltage for Li-Ion cell is 4.2V and 3.7V, while LiFePO4 is 3.6V and 3.3V respectively. The LiFePO4 is a good substitute although it's still over voltage. In addition, for size like AA, LiFePO4 an NiMH aren't whole lot different in terms of size vs. capacity.
On a different note, a 2P Li-Ion configuration should work for 6 AA based high voltage battery pack (7.4V nominal and 8.4V max). Same can be done for 8 AA pack with 3P or 4P Li-FePO4 cells (9.9V or 12.8V). The 2S2P (2 18650 Li-Ion in series, then 2 of them in parallel-7.4V 4000mAh) in my Sunpak TR2000 pack lasts forever on the 580EX.
p.1 #18 · Why no Lithium batteries for speedlites?
ASI uses Metz's that are powered with RC car lithiums on brackets...sure it's a bit bulky, but you can knock off a few thousands frames before any noticable recycle lag...
