# Rechargeable battery in your speed lights?



## ecphoto (Apr 9, 2014)

I've been wondering if its a good practice or not. I know that the voltages are slightly different on rechargeables 1.2v compared to something like a Duracell with 1.5v. I would be using them on a regular speed light and maybe a power pack too. Till now I've just been using regular Duracell's. I was just wondering if they perform well or if the affect your recycling or power.


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## ronlane (Apr 9, 2014)

I have seen a lot of people talk about using Eneloop rechargeable batteries in their camera gear, including speed lights.


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## ecphoto (Apr 9, 2014)

ronlane said:


> I have seen a lot of people talk about using Eneloop rechargeable batteries in their camera gear, including speed lights.



Do you know if they get less or more battery life?


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## Derrel (Apr 9, 2014)

I use the SB 800 with the fifth battery compartment added...it might not seem like much, but that FIFTH battery with that one, extra 1.2 volt, 2500 milli-ampere hour rechargeable Ansmann battery really makes a difference in recycle times....

I shoot most indoor flash at ISO 250,320,or 500 "most" of the time, so that also helps a bit. It has been so long since I used 4 or 5 AA-alkalines that I no longer have any basis for comparison between 1.5-volt batteries and 1.2-volt AA rechargeables.

If I need to shoot a LOT of flash pics, or have a gig where I know that I might get like ONE chance to shoot and absolutely MUST make the most of a few-second span, I still rely on an ancient Quantum Battery 1...


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## Gavjenks (Apr 9, 2014)

They won't explode or anything. Whether they last less time or achieve slower cycling, I can't say for sure, but if so, it's a small enough difference that I've never just intuitively noticed it. Maybe if you have a stopwatch, it will be there, but it's not anything as dramatic as like 50% longer or shorter or anything like that.


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## Overread (Apr 9, 2014)

Some thoughts:

1) Use Rechargeable batteries which retain charge between uses. Sanyo Eneloop were the first but Duracell and others now have similar lines out as well. These batteries will hold a charge even when left in a unit for months at a time; traditional rechargable batteries would drain out when left in a unit, meaning that the fully charged flash at the start of the week could be far lower by the end even if you'd not used it (which made for erratic reliability when you reached for the flash).

2) Use a good quality recharging unit. The typical ones sold with batteries are fast chargers - 30 mins or faster. These are BAD. They are bad because the faster you charge a battery the less charge it holds and the quicker its capacity degrades; with flash batteries able to be drained so fast that they could be on daily cycles these fast chargers will quickly cripple your batteries.
A slower charging unit (say overnight) is far superior. Maha/Powerrex make a good series of units that can be used to charge batteries with slower charging times. An 8 cell is ideal for charging groups of batteries; whilst their 4 cell C9000 can even be used to recondition batteries to get more recharge and new life out of them (rechargable batteries only of course). 



Rechargeable batteries, used and recharged right, are a very worth while investment. You'll save a fortune on batteries by using them; otherwise you might find that you can easily go through 2 or 3 blocks of 4 AA per flash on a day of good use - do that for a fe days and you've spent quite a sum of money if you were buying AAs. 

I keep mine in those little 4AA plastic holders that are around, keeping them in sets so that the whole set is charged and drained at the same time and rate. I also use a PIXEL battery pack that holds two groups of 4 AA Batteries which boost the recharging rate of the flash units (check your unit, not all flashes can take them an there are different PIXEL packs for different flash types).


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## ecphoto (Apr 9, 2014)

Overread said:


> Some thoughts:
> 
> 1) Use Rechargeable batteries which retain charge between uses. Sanyo Eneloop were the first but Duracell and others now have similar lines out as well. These batteries will hold a charge even when left in a unit for months at a time; traditional rechargable batteries would drain out when left in a unit, meaning that the fully charged flash at the start of the week could be far lower by the end even if you'd not used it (which made for erratic reliability when you reached for the flash).
> 
> ...



I think I'll look for some soon. I'm down to my last 8 of a 48 pack and I might buy a couple of sets of rechargeables instead of plunking down the cash for another 48 pack lol.



Derrel said:


> I use the SB 800 with the fifth battery compartment added...it might not seem like much, but that FIFTH battery with that one, extra 1.2 volt, 2500 milli-ampere hour rechargeable Ansmann battery really makes a difference in recycle times....
> 
> I shoot most indoor flash at ISO 250,320,or 500 "most" of the time, so that also helps a bit. It has been so long since I used 4 or 5 AA-alkalines that I no longer have any basis for comparison between 1.5-volt batteries and 1.2-volt AA rechargeables.
> 
> If I need to shoot a LOT of flash pics, or have a gig where I know that I might get like ONE chance to shoot and absolutely MUST make the most of a few-second span, I still rely on an ancient Quantum Battery 1...View attachment 70666



I think I'll look into it. If it works for so many of you it must work pretty well.

Is there another brand other than the Sanyo ones that is good and maybe less than $5.00 per cell?


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## Overread (Apr 9, 2014)

Quantum battery packs are not cheap, the PIXEL is a cheaper reliable option for general speedlite use. Really gage it on the amount you use and need your flash as to which is the most cost effective approach.


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## ecphoto (Apr 9, 2014)

Overread said:


> Quantum battery packs are not cheap, the PIXEL is a cheaper reliable option for general speedlite use. Really gage it on the amount you use and need your flash as to which is the most cost effective approach.



I would probably get a compatible Yongnuo pack since they are way cheaper. I'm sure not better than the quantum, but in my budget.


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## ecphoto (Apr 9, 2014)

I found this on the Sanyo Eneloop site, it explained the difference pretty well. I guess the NiMh are the newer cells that work better than what they used before, or cheaper brands still do use.


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## Scatterbrained (Apr 9, 2014)

ecphoto said:


> I've been wondering if its a good practice or not. I know that the voltages are slightly different on rechargeables 1.2v compared to something like a Duracell with 1.5v. I would be using them on a regular speed light and maybe a power pack too. Till now I've just been using regular Duracell's. I was just wondering if they perform well or if the affect your recycling or power.


   You're not going to notice a real difference unless you get cheap rechargeables.  I remember getting so annoyed with my light that I bought the external battery pack, only to still see ridiculous cycle times.  I switched from the "house brand" I had gotten from Adorama to the Energizers and the cycling is instant.  I don't even use the powerpack anymore, I just carry a few extra batteries in the bag.  Just bear in mind that the higher the power rating of the battery, the quicker it will lose it's charge when stored.   In a controlled test the Energizers and Powerex actually outperformed the Eneloop (not enough that it'd really matter), but the Eneloops held their charge the best over time.    All three were fairly close.


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## ecphoto (Apr 9, 2014)

Scatterbrained said:


> ecphoto said:
> 
> 
> > I've been wondering if its a good practice or not. I know that the voltages are slightly different on rechargeables 1.2v compared to something like a Duracell with 1.5v. I would be using them on a regular speed light and maybe a power pack too. Till now I've just been using regular Duracell's. I was just wondering if they perform well or if the affect your recycling or power.
> ...



I just checked out those energizer ones on Amazon. They are half the price of the Eneloop ones.


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## TheFantasticG (Apr 9, 2014)

I use Eneloop XX batteries now-a-days. Just recently bought a few extra sets.


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## ecphoto (Apr 9, 2014)

TheFantasticG said:


> I use Eneloop XX batteries now-a-days. Just recently bought a few extra sets.



I've heard the XX version has more capacity, but 1/3 the life(500 cycles) according to their website.


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## TheFantasticG (Apr 9, 2014)

Meh, worth the trade off. I can go an entire day doing macro with a set in my sb700 so it just might even out in my case.


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## table1349 (Apr 9, 2014)

ecphoto said:


> Overread said:
> 
> 
> > Quantum battery packs are not cheap, the PIXEL is a cheaper reliable option for general speedlite use. Really gage it on the amount you use and need your flash as to which is the most cost effective approach.
> ...


 
I think you are a bit confused.  The Quantum Battery pack mentioned is not at all like the Yongnuo.  The Quantum is expensive because it has it's own battery and voltage regulator.  It is not a compartment that holds batteries like the Yongnuo.  The Quantum will out perform the standard battery packs like the Yongnuo in number of flashes and recharge time.  That is what you are paying for.  The confidence that if you are shooting a 7 hour wedding and reception or some other long event, you will have the power to shoot from beginning to end with no worries.


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## Derrel (Apr 9, 2014)

gryphonslair99 said:


> ecphoto said:
> 
> 
> > Overread said:
> ...



JUST as an aside...this Quantum was bought brand new in 1985. Nineteen hundred and eighty-five! It was used regularly (every-other weekend, sometimes 2 events in one weekend) until 1990. It was then neglected until 2005 or so. I shot indoor H.S. basketball with it for the 2005-2006 seasons, powering two, 285 HV flashes from the balcony railings. Since then I have shot a few parties, and one wedding with it. It is on its ORIGINAL lead acid cell. This thing the last time I shot it heavily, fired 366 frames over a 2-hour party. This thing is TWENTY-NINE YEARS OLD!!!!! I bought this when I was a college kid. I am now a middle-aged man. The Quantum Turbo battery I bought one year later, in 1986, was DEAD-dead-dead when we moved into our first house in 1991. I am incredulous that this thing STILL holds a good charge and still recycles FAST.


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## ecphoto (Apr 9, 2014)

gryphonslair99 said:


> ecphoto said:
> 
> 
> > Overread said:
> ...



You've made an excellent point. I know that they are two vastly different pieces of technology, I'm not confused about their capabilities respectively. Rather I know the budget I'm working with, it won't allow for all the stuff I want. A cheap Chinese made battery pack is all I can afford right now.


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## Derrel (Apr 9, 2014)

Those Chinese battery packs actually look pretty good, considering the price, size, and the ease of use as far as just popping in freshly-charged batteries. Sure, not as much "oomph" as a heavy lead-acid battery, but also a lot less money, cheap for the batteries, you know...really...a pretty good ancillary power source that beats just 4 x 1.2 volts in AA's...


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## astroNikon (Apr 10, 2014)

When looking at rechargeables also look at their voltage
For instance the all silver energizers are 2300 mAh
The light green top energizers are 1400
Rayovacs are 1600
Etc


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## Edsport (Apr 10, 2014)

I use 3800 mAh in my speedlights. Lots of storage power and very cheap...

Cfl rechargable aa | eBay


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## Big Mike (Apr 10, 2014)

Plenty of good info here already, but here is my two cents.

There are a few different types of AA batteries that you might choose:

The most common is the standard Alkaline. The benefit is that they are easy to find and cheap to buy and most importantly, they will hold their charge for years.  The bad news is that they are not rechargeable and unless you send them to a facility that can recycle them, they most likely end up in a landfill, which is terrible for the environment.  Another issue with alkaline batteries is how they perform in a flash.  Typically I've found that the recycle times for a flash will start to drop fairly soon, maybe at 50% capacity, and they continue to get longer as the battery looses more charge.  Many times I've found that alkaline batteries become practically unusable for a flash, but I can still take them out and put them into something like a remote control, and get months of use out of the remaining power.  In summary, alkaline batteries are bad for the environment and don't perform well in a flash.  

The typical rechargeable battery type is NiMH (nickel&#8211;metal hydride).  Nickel&#8211;cadmium was standard 20+ years ago, but I don't think they are used today.  NiMH batteries are more expensive to purchase (plus you need a charger) but they can recharged many, many times which makes them much less expensive than disposable batteries.  NiMH batteries perform much better in a flash.  I've found that they give you a more consistent recycle time over the life of the charge, and when they start to slow down, they are almost drained.  The problem with 'standard' NiMH batteries is that they don't have a great shelf life.  They will loose their charge just sitting around.  

There is a somewhat newer version of NiMH that been able to mostly overcome the self-discharge issue.  The most popular ones are the Sanyo Eneloops.  They hold their charge longer, thus acting more like alkaline but they still perform very well in a flash.  These are the ones that most people would recommend if you are going to buy new batteries.

Another type of battery to mention is Lithium.  They are not rechargeable and are rather expensive so I don't recommend them.  Their only advantage is that they are very light weight compared to the other types.  Note that these are not Lithium-ion, which is the type of batter that your camera & cell phone likely use.  They don't make Lithium-ion batteries in AA form (as far as I know).

Another thing to consider when buying rechargeable batteries is a good charger.  I typically like to avoid the cheap (one hour) type chargers as they can really make the batteries hot and that isn't great for the life & health of the battery.  I prefer a charger that allows me to choose the charging rate.  Slower is better, as long as you have the time.  Some chargers will also have options to discharge and cycle the batteries and a select few will have a 'break in' mode which conditions the batteries to hold a full charge...it can even be used to give new life to old (worn out) rechargeable batteries.


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## Tinderbox (UK) (Apr 10, 2014)

Edsport you have bought fake ni-mh batterys they take a low 1000-1500mah AA battery and stick a label with 3800mah on it, so far there is no AA ni-mh battery over 2900mah that i have seen.

A quick and dirty way to check the capacity is to compare the weight of the new battery with a branded version of an AA battery, if the 3800mah battery is lighter than a branded 2100mah battery it has to be fake.

I have been a member of the website below for years and they test all battery types for capacity, and the fake capacity battery`s on ebay are notorious.

Flashlight Electronics - Batteries Included

John.

EDIT : I am busy testing the capacity of some cheap third-party battery`s for my Fuji X-E1 3x battery`s for £11.80 when an original goes for £40+



Edsport said:


> I use 3800 mAh in my speedlights. Lots of storage power and very cheap...
> 
> Cfl rechargable aa | eBay


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## WayneF (Apr 10, 2014)

gryphonslair99 said:


> The Quantum Battery pack mentioned is not at all like the Yongnuo.  The Quantum is expensive because it has it's own battery and voltage regulator.  It is not a compartment that holds batteries like the Yongnuo.  The Quantum will out perform the standard battery packs like the Yongnuo in number of flashes and recharge time.  That is what you are paying for.



This not correct information about the Yongnuo external battery pack.  It is NOT merely a AA battery compartment, far from it. 

Speedlights do use AA batteries, typically four to output 6 volts.   These AA batteries go into a AA battery compartment.  The speedlight necessarily also builds in a power converter and voltage regulator to convert 6V to around 325 volts to directly charge the flash capacitor that powers the flash tube.    This power converter current is the whine we sometimes hear at recycle.

Some speedlight models have* another high voltage connector *where an external battery pack can be plugged in.  The battery pack also includes a similar power converter and voltage regulator which outputs* around 325 volts*, and this high voltage connector goes directly to the flash capacitor.  Now there are two voltage sources, internal and external, two 325 volt sources, charging the flash capacitor, for faster recycle and larger longer battery capacity.  The original 6 volt AA cells also powers the rest of the electronics, so the AA batteries have to be there too.

The Yongnuo SF-18 battery pack plugs into the Nikon speedlights using the SAME high voltage connector that the Nikon SD-8 and SD-9 battery packs plug into.   Canon is the same deal.   That external connector is a 325 volt connector.    The external package is NOT merely a battery compartment.  If it were merely a battery compartment, it would have to plug into the speedlight battery compartment, which it does not.


I know little about Quantum, but the specs make it obvious that some Quantum batteries are 6V lead acid, but others use a NiMH battery pack.   I don't know how the Quantum NiMH batteries connect, but the 6V lead acid has to be connected into the flash AA battery compartment, replacing the original AA batteries, and simply furnishes 6V with a much longer capacity duration (a bigger 6V battery).    Lead acid batteries also have a much lower internal impedance, and so recycle (from the flashes own power converter) can be much faster recycle using 6V lead acid instead of 6V of AA alkalines.  Rechargeble NiMH batteries are about twice as fast as alkalines, but not as fast as lead acid.

For example, another source of such replacement 6V lead acid battery pack is the Al Jacobs Black Box:  PRODUCTS and SERVICES | www.ALJACOBS.COM which necessarily plugs into the flash AA battery compartment (typically using Quantum cables and connectors, because they are available).    Longer life, faster recycle than AA batteries, but is still NOT a high voltage power pack like the Yongnuo SF-18.   In this sense, the lead acid batteries are merely another battery compartment.

The Yongnuo SF-18 battery pack uses AA NiMH, *but it definitely outputs 325 volts* to charge the speedlight flash capacitor directly.
It will work with alkaline AA batteries too, but alkalines will recycle much slower than NiMH or lead acid (alkaline is high internal impedance).


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## EIngerson (Apr 10, 2014)

I run the Eneloops in everything. Flash, triggers, you name it. I have zero complaints about them.


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## ecphoto (Apr 10, 2014)

WayneF said:


> gryphonslair99 said:
> 
> 
> > The Quantum Battery pack mentioned is not at all like the Yongnuo.  The Quantum is expensive because it has it's own battery and voltage regulator.  It is not a compartment that holds batteries like the Yongnuo.  The Quantum will out perform the standard battery packs like the Yongnuo in number of flashes and recharge time.  That is what you are paying for.
> ...



Good to know!


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## WayneF (Apr 10, 2014)

Tinderbox (UK) said:


> Edsport you have bought fake ni-mh batterys they take a low 1000-1500mah AA battery and stick a label with 3800mah on it, so far there is no AA ni-mh battery over 2900mah that i have seen.



Some reports are even lower, closer to only 500mah.   

You will surely want to trash those fake 3800mah AA batteries.    Some chargers have options to test batteries by discharging them, to determine how much mah they can actually provide.   At least find a friend with that, and check them.

This 3800mah myth is everywhere if you search around on the internet.  Even Amazon is victim:
Amazon.com : Rechargeable 1.2V "3800"mAh AA NI-MH Batteries Battery (Pair) : Camera Flash Battery Packs : Camera & Photo

See this about fake Sonys:  CountrySelector - Sony


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## Tinderbox (UK) (Apr 10, 2014)

Ok, my test is complete the third-party battey that cost me £3.93 has a capacity of 1079mah it was supposed to be 1300mah.

The OEM battery that costs £45.00 to buy on Amazon UK, had a capacity of 1163mah and it was supposed to 1260mah.

That is only an 7.8% difference in capacity between the third-party battery and the oem battery, but the oem battery costs 11.45 times more 

john.



Tinderbox (UK) said:


> Edsport you have bought fake ni-mh batterys they take a low 1000-1500mah AA battery and stick a label with 3800mah on it, so far there is no AA ni-mh battery over 2900mah that i have seen.
> 
> A quick and dirty way to check the capacity is to compare the weight of the new battery with a branded version of an AA battery, if the 3800mah battery is lighter than a branded 2100mah battery it has to be fake.
> 
> ...


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## table1349 (Apr 10, 2014)

WayneF said:


> gryphonslair99 said:
> 
> 
> > The Quantum Battery pack mentioned is not at all like the Yongnuo.  The Quantum is expensive because it has it's own battery and voltage regulator.  It is not a compartment that holds batteries like the Yongnuo.  The Quantum will out perform the standard battery packs like the Yongnuo in number of flashes and recharge time.  That is what you are paying for.
> ...



I understand that however to me an average of 200 flashes from a Yongnuo with NiMH batteries and an average of 1050 flashes with a Quantum T3 is a significant difference as is being able to supply power to a camera body at the same time and still supply an average of 600 flashes from the T3 or two flashes at the same time.  To me, that is a significant difference.


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## ecphoto (Apr 10, 2014)

I went into a local hardware store and found their house brand selling for $1.50 per battery and the charger for $5.00, I figure for $11 I've got nothing to lose.
They are 2000mah NiMH and according to the package they are good for 800 recharge cycles.







Sent from my MB886 using Tapatalk


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## Overread (Apr 11, 2014)

Dump the cheap charger and get one of these Maha C800S-U 8-Cell Smart Charger from mahaenergy.co.uk


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## Edsport (Apr 11, 2014)

Tinderbox (UK) said:


> Edsport you have bought fake ni-mh batterys they take a low 1000-1500mah AA battery and stick a label with 3800mah on it, so far there is no AA ni-mh battery over 2900mah that i have seen.
> 
> A quick and dirty way to check the capacity is to compare the weight of the new battery with a branded version of an AA battery, if the 3800mah battery is lighter than a branded 2100mah battery it has to be fake.
> 
> ...


I don't know if they are fake or not but i've done a couple weddings using them and they just won't quit. I've had them a few years now and they are still holding up. For under a buck each i figure i got my money's worth either way...


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## WayneF (Apr 11, 2014)

gryphonslair99 said:


> I understand that however to me an average of 200 flashes from a Yongnuo with NiMH batteries and an average of 1050 flashes with a Quantum T3 is a significant difference as is being able to supply power to a camera body at the same time and still supply an average of 600 flashes from the T3 or two flashes at the same time.  To me, that is a significant difference.




OK, I was not discussing the Quantum, but no dispute that it is a larger battery. The T3 costs $600 and weighs 2 pounds, and its battery is not user replaceable.   You ought to get something for that.  

I was just pointing out that the Yongnuo for $49 was a whole lot more than just the battery compartment that you said.  It does what it needs to do.  The flashes own four AA batteries ought to do 200+ full power flashes, and the external battery pack increases that capacity, probably in ratio with battery count.   It may not reach $600 worth however.


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## table1349 (Apr 11, 2014)

WayneF said:


> gryphonslair99 said:
> 
> 
> > I understand that however to me an average of 200 flashes from a Yongnuo with NiMH batteries and an average of 1050 flashes with a Quantum T3 is a significant difference as is being able to supply power to a camera body at the same time and still supply an average of 600 flashes from the T3 or two flashes at the same time.  To me, that is a significant difference.
> ...



The thing that struck me funny was that Yongnuo's site listed approximately 200 flashes using NiMH batteries.  I would have thought it would be better than that.


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## WayneF (Apr 11, 2014)

gryphonslair99 said:


> The thing that struck me funny was that Yongnuo's site listed approximately 200 flashes using NiMH batteries.  I would have thought it would be better than that.



I would think so too.  I don't have the battery pack, but my YN565EX does about that by itself, no external battery.


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## Tinderbox (UK) (Apr 11, 2014)

The best charger for your battery`s, it`s proven to treat them kindly to  make them live as long as possible and fill them right up to the top and the price is great, two different version, the Accumanger 10 for AA and AAA and the Accumanger 20 for AA AAA C D and PP3.

John.


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## table1349 (Apr 11, 2014)

Can't be beat:  Maha 8-Cell Combo NiMH/NiCD Charger for AA/AAA/C/D (MH-C808M)

Not just a charger but a deep cycle conditioner as well.


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## Overread (Apr 11, 2014)

gryphonslair99 said:


> Can't be beat:  Maha 8-Cell Combo NiMH/NiCD Charger for AA/AAA/C/D (MH-C808M)
> 
> Not just a charger but a deep cycle conditioner as well.



And (whilst their C9000 is a great charger) 8 cells is far more practical - that's 2 sets of flash batteries being charged at once. That doesn't sound much; but when you have them on an overnight cycle that's 2 sets of batteries ready for the morning instead of 1 from a regular 4 cell charger


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## ecphoto (Apr 11, 2014)

What about this charger?
http://www.amazon.com/EBL®-Version-...d_sim_e_5?ie=UTF8&refRID=1G362FBSKRCHMK4H3X5T


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## table1349 (Apr 11, 2014)

Quick and rechargeable batteries never go in the same sentence.  Quick chargers cook batteries.  Cheap chargers also generally cook batteries.  They do not have the kind of circuitry that can read and adjust to a batteries needs.  I have eneloops  that are at least 5 or 6 years old that will take as much charge as when I got them.  I was wishing they would start to die just so I could switch to the eneloop XX's.  Maybe next year,


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## table1349 (Apr 11, 2014)

Overread said:


> gryphonslair99 said:
> 
> 
> > Can't be beat:  Maha 8-Cell Combo NiMH/NiCD Charger for AA/AAA/C/D (MH-C808M)
> ...



I was going to buy the C800 when but found the C9000 on sale.  If I had been smart I would have got two for the very reason you mention.  This one interests me, but I would like to know from users how well it works. http://professionalbatteries.com/product.sc?productId=16


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## Tinderbox (UK) (Apr 12, 2014)

Hi.

It looks like it charges two battery`s at a time, as it only has 4 charging led`s

You need a charger that charges them individually. 

John.



ecphoto said:


> What about this charger?
> Amazon.com: EBL® 808A(Latest Version) 8 Bay/Slot AA AAA Ni-MH Ni-Cd Quick Charger Smart Battery Charger for Rechargeable Batteries: Electronics


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## WayneF (Apr 12, 2014)

Tinderbox (UK) said:


> Hi.
> 
> It looks like it charges two battery`s at a time, as it only has 4 charging led`s
> 
> ...





Appears to be a $11 knockoff of the $95 Maha 808.   There might be some differences.  



The cheap chargers are of a few types. A few just always charge at a low  slow rate and never shut off. Some shut off after a constant time  period, regardless of the battery size or previous charge state. Other  faster ones shut off when the batteries get too hot, which implies  charged. 

The better chargers have computer circuits to monitor* actual battery voltage  and state*, and shut off when the battery is actually full. This is not  just some simple maximum voltage like car batteries, instead the voltage curve  has a little hump after which the voltage falls slightly (called Delta  V), and this is much less pronounced in NiMH than in NiCd, and also  temperature dependent (see Eneloop data sheet).  It's not real simple, relatively difficult, and good performance  requires some smart. 

Even if the better design, some of these cheaper ones  monitor and control a pair of two batteries combined (without seeing  individual cell detail). The cheapest charger is really NOT what you  want today, at least not for maximum battery performance.  If it charges X batteries, you want X status LEDs, and specifically, the capability to charge only one battery.


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