Experiment: 2000 mAh Eneloops vs 2700 mAh PowerExs

[Aquanaut]

I was over in a photography forum, and it was claimed: " I get more than double the amount of flashes out of a set of PowerEx 2700s vs my new, but well conditioned eneLoops."

He was referring to an external camera flash unit where electrons are transferred from a battery pack (4 X AAs) to a high voltage capacitor which is then discharged across a flash tube. The DC voltage is stepped up by a DC to DC converter. I believe he is sincere in his experience, but I cannot understand it from a scientific point of view. Can anyone explain what is happening?

Except for flashing my flash a few hundred times with Eneloops and with PowerExs, is there a less extensive experiment I can try to prove or disprove the claim?

 

[45/70]

This probably isn't going to help you much Aqua, as while I have been an amateur photographer for many years, I've always tried to avoid using flash, whenever possible. Therefore, my personal experience doesn't include cycling a camera flash unit.

Where I noticed the difference between, in my case, Sanyo industrial 2500's and sanyo 2700's compared to eneloops, is that initially, the high cap cells did perform better at medium to high current loads. After 25 cycles, or even less however, the eneloops would start to outperform the high caps. I attribute this to the more fragile components used in the high cap cells being more easily damaged under higher current loads. I still have my original batch of 20 eneloops, and they perform quite well. The high cap Sanyo's on the other hand, are long gone.

Dave

 

[SilverFox]

Hello Aquanaut,

I would be skeptical of the "more than double" comment if all the cells are in good condition.

2700 mAh cells usually test out to around 2500 mAh. The Eneloop cells come in at around 1950 mAh. If you are using the cells right off the charger and using their total capacity in a single day, the 2700 mAh cells should give you around 1.3 times as many shots.

The advantage of the Eneloop cells would factor in if you shot a few shots, then stored the flash for a few weeks before using it again. Then with that type of use cycle, the Eneloop cells would come out ahead because of their low self discharge properties.

Tom

 

[Battery Guy]

Hello Aquanaut,

I would be skeptical of the "more than double" comment if all the cells are in good condition.

I have to say that I am in full agreement with Tom on this. I simply cannot conceive of an application where any 2700 mAh NiMH cell would outlast an Eneloop by a factor of 2 or more. While I have not tested the PowerEx 2700 cells, I have tested the Sanyo 2700 cells and the results are posted in my AA Ragone Plot thread here, along with Eneloops. It is very unlikely that the PowerEx 2700 would have a higher power capability than the Eneloops, unless the Eneloops were bad, fake, or old and very heavily used.

Aquanaut: I would humbly suggest to your friend that he either has bad Eneloops, very old and heavily used Eneloops, or that the Eneloops were not charged properly prior to this trial.

Cheers,
BG

 

[InHisName]

But what if it works like my frustrating video camera?

I have LOTS of battery power when my camera gives up and quits.

Say for instance the eneloops have 1700mah (because they are used a long time) and the flash stops at 5.2v so maybe it only gets 30% of the eneloops. That comes to 510Mah. For 2500, being fresh and below the 25 cycles you know, you might get 50% out of them. That comes to 1250Mah. So in this example, you see 2.5x !

Then like the others note, after 25 cycles they equalize then after that eneloops are better for the rest of the time.

 

[fabienne]

Well I have 2000 mAh Eneloops, 2700 Maha Powerex and 2100 Maha Imedion (Maha LSD version). Out of three, I always use the 2700 for my flash (Canon 580EX II + Battery Pack CP-E4) total 12 batteries, because of higher capacity and I've been using them almost every week, so I prioritize having higher capacity over low self-discharge rate advantage.

As for my battery grip of Canon 7D (BG-E7), I use the Maha Imedion and Eneloop interchangably because I don't charge them every week, since it serves as my backup battery.

So if you value the LSD, get eneloop but if you need higher capacity, get 2700 powerex. It's worth-it for me at the same price.

 

[Battery Guy]

But what if it works like my frustrating video camera?

I have LOTS of battery power when my camera gives up and quits.

You probably have lots of battery capacity, not power, when you camera quits.

Say for instance the eneloops have 1700mah (because they are used a long time) and the flash stops at 5.2v so maybe it only gets 30% of the eneloops. That comes to 510Mah. For 2500, being fresh and below the 25 cycles you know, you might get 50% out of them. That comes to 1250Mah. So in this example, you see 2.5x !

Then like the others note, after 25 cycles they equalize then after that eneloops are better for the rest of the time.

Eneloops and PowerEx 2700 are both NiMH cells, and it is almost for certain that the Eneloops have a lower internal resistance and will have less voltage "sag" during discharge at high rates compared to the PowerEx 2700. This is because as the capacity of the cell increases, the thickness of the electrodes increase and the electrode surface area decreases. It is a rule of battery design that cannot be avoided, and it is why high power cells always have lower capacity compared to standard cells of the same chemistry.

So your scenario does indeed work if the Eneloops are old and have developed a high internal resistance. Like I said in my previous post, if the Eneloops are old, fake or heavily used, you could have a 2x difference. However, Aquanaut did not indicate that his friend was comparing new PowerEx with old Eneloops.

Cheers,
BG

 

[45/70]

......Like I said in my previous post, if the Eneloops are old, fake or heavily used, you could have a 2x difference. However, Aquanaut did not indicate that his friend was comparing new PowerEx with old Eneloops.

That depends a lot on what "new, but well conditioned" means. If it means running 4 eneloops down in series, until a cell or cells are reverse charged multiple times during the conditioning, then the eneloops could very well be in the equivalent condition as old/heavily used. That part of what his friend is quoted as saying bothers me a bit, as the meaning is unclear. I doubt that is the situation, but still......

Dave