Questions about AA in MB-D10 (D700)

Started May 31, 2011 | Discussions thread
Billx08 Forum Pro • Posts: 11,373
Re: Questions about AA in MB-D10 (D700)

agc1976 wrote:

Thanks all for the replies. Another question, is the battery meter accurate when running off of AAs from the grip? I doubt it but I have to ask.

It depends on the batteries. Alkaline batteries show significant voltage drops when they're used heavily (actually shooting) and very heavily (shooting using the built-in flash). In time, the voltage will creep up again. NiMH AA batteries start with a lower voltage, but have a much flatter output voltage that doesn't drop much with heavy current loads. They start out fully charged at slighly above 1.2 volts per cell and by the time they are almost completely dead are supplying about 1.0 volts. Fresh alkalines start at 1.5 volts, and by the time they're 95% depleted can be supplying only 0.5 volts. This may work for low powered LED lights and small portable analog radios, but most digital devices, especially cameras, need approx. 1.0 volts per cell or the camera will power off. So many times the supposedly "dead alkalines" you throw away may actually have 30% to 50% of their capacity remaining, but they're just not usable by digital cameras that have minimum voltage requirements.

I once tested a Fuji camera with alkaline AA batteries using one of the same types of tests that the manufacturers use (CIPA, with 50% of the shots using full powered flash) and it did slightly better than the camera was rated for, which had been showing a battery warning, and finally powered off due to "dead" batteries at somewhere between 210 and 220 shots. The camera was rated at 200 shots using alkalines and 400 shots using NiMH batteries.

Knowing about alkaline's ability to "rebound", I gave it about 30 minutes of rest and then continued shooting without using the flash. I shot in batches of about 20 to 50 shots at a time, and over the next couple of days got the total up to over 600 shots before stopping the test. I'll never know how many more shots the camera could have gotten from those alkalines. For the MB-D10, the best AA batteries to use might be lithium AA's. They have the highest voltage, and under significant load are able to supply 1.4 volts per cell. They also have the relatively flat voltage curve of NiMH batteries, but are better in that by the time they're nearly dead, they're still supplying about 1.2 volts per cell. Since the frames per second shooting rate in the MB-D10 starts to decline once the voltage drops to a certain level, the lithium AA batteries should shoot at the maximum frame rate until they're getting near to their end of life (they aren't rechargeable). They should also last a lot longer than alkalines but they have one drawback. They do run hotter than other AA battery types. In the MB-D10 where they aren't inside the camera, this may not be a problem. It could also be an advantage if you shoot in very cold temperatures (40 deg. below zero), where lithium AA batteries would be able to continue working if only the cameras weren't too cold to function. I'd try a set of Sanyo Eneloops first, but if the frame rate drops too soon, would switch to lithiums.

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