Are Eneloops still the best?

Started Jul 25, 2011 | Discussions thread
ComputerDork
Regular MemberPosts: 225
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Re: Are Eneloops still the best?
In reply to Graystar, May 27, 2012

I recently bought 16 Maha Imedion cells, figuring that they were the same as current gen Eneloop with a bit higher capacity. They aren't that bad, but aren't equivalent and waste more energy as heat, it looks like.

Here's the rather extensive testing I found:

http://www.candlepowerforums.com/vb/showthread.php?298090-The-AA-NiMH-Performance-Test-Thread

Seems like the Eneloop XX hold their voltage a lttle better under 10A load than the Imedion. Under 1A load the Imedion supply higher voltage. The Immedion are the worst in that test when it comes to maintaining their capacity, as a percentage of their maximum, at different loads. (For example, at 10A constant drain they only supply 1700mAh not 2400. They really only get 2400mAh at 1A constant discharge rate .) While the Elite seem to be the most efficient as a % of maximum capacity, followed by the XX.

So basically, under high load, the Elite 2000 do a way better job of maintaining their capacity especially at 3+ amp loads. They're the most efficient due to lower internal resistance and thus less power lost as heat at high current loads, from what I can tell.

This seems like the best for flash, but does a camera draw enough current to need this?

I can't figure out what the current range "per shot" is for my D7000, but the manual says that the EN-EL15 LiON battery is 1900mAh at 7V and that according to the CIFA tests this gives you "1050 shots" (where a shot is once every second, involving zooming/autofocus, and the in camera flash is fired half the time).

If I understand the math then that means that

(1900mAh / 1050) / 30 seconds = 217mA average over the 30 seconds

That's a bit pointless though because there's going to be some sort of spike of current drain during the shutter release that won't last too long, so lets say the spike lasts 4 seconds and the majority of the current is used during that time:

(1900mAh / 1050) / 4 seconds * 90% = 1466mA average over 4 seconds

So IF the camera is suckiing current at about 1.5A in spikes, and something like 0.2A on average over the whole time, I'm still not sure what that means for battery efficiency since I don't know how the battery reacts to spikes and for all I know there's some 1 second or less spike of 5A or something that some point. But maybe, if I had to guess, the battery drain rate efficiency would be in the 1A or 2A sustained range. So efficiency related to current drain doesn't seem like it should matter too much (if spikes don't have some special effect.)

For flash use, this testing suggests that the Powerex 2700's are significantly better than the Eneloop 2000 when it comes to flash recycle time:

http://photography-on-the.net/forum/showthread.php?t=677074

With the amount of current that the Goal Zero Elite 2000's can supply though, I wish this testing included those.

Anyway, from reading all of this my best guess at some conclusions are:

  • Since these constant current drain tests pretty much represent flashlight-type loads, not camera or flash load patterns, it's hard to know how well they apply to real world use in camera equipment.

  • Some evidence suggests that Powerex 2700 are good for flash, but maybe even better for cameras due to their efficiency drop at higher current drain. Of course they aren't LSD so won't last on the shelf that well, etc.

  • The Imedion seem like, at least, a reasonable alternative to the Eneloops or even XX (aside from lower capacity) in cameras, assuming that current load and spikes in cameras is similar to 1A or 2A continuous loads. The graphs seem to suggest that the Imedion are probably substandard for recycle time in flash.

  • The XX looks like it should be better for recycle time than almost anything else, not by much, except for the Elite which ought to blow everything else away.

  • It doesn't seem to me like the amazing advantages of the Elite are all that important in cameras (unless maybe using the in camera flash), however they ought to make a massive world of difference in flash units.

I'm sure I've gotten something wrong here since I don't understand this stuff that well, and its kind of complex anyway, but what all this suggests to me is that I should:

  • Continue using the Powerex 2700 I already have in my camera where I cycle them rather constantly, and often have lots of low current standby time.

  • Keep using the Powerex 2700 in flash units until I get to play with some Goal Zero Elites.

  • Not use the Imedion in flash units if possible.

  • Use the Imidion batteries as extra backup in bags where they may not get used as much and I'm too lazy to take them out and rotate them though usage like I should. Also use them in other devices that drain batteries really slowly.

  • Get some Elite 2000's and use them in my flash units, but there seems to be no point in using them in a camera (lower capacity and no real advantage).

If I've gotten anything wrong here please tell me because I will seriously appreciate it.

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