# Canon moves to SD from CF for Canon S2 IS

Discussion in 'Digital Photography' started by Siddhartha Jain, Jun 22, 2005.

1. ### Skip MGuest

You should see our family room before a shoot...3 phones hooked up to
chargers, one dual Canon charger with BP-511As on board, at least two
Quantum Turbo batteries and attendant chargers, and 2 NiMH chargers with 4
AAs each. And we wonder why our electric bill is so high...

Skip M, Jun 28, 2005

2. ### Dave MartindaleGuest

It's unlikely to be the battery chargers. Really.

For example, suppose you're charging 4 NiMH AAs. Suppose they are
completely discharged, and their capacity is 2500 mAh. The total amount
of energy in the charged cells is 4*2.5*1.2 = 12 watt-hours. Now
suppose that the charging process is only 50% efficient - this includes
electrical losses in the wall wart and charger circuits, and electrical-
chemical losses in the cell itself. Thus, one full charge cycle for
these cells will draw 12*2 = 24 Wh from your house electrical system.

Now, suppose the amount you pay for extra electrical consumption is 10
cents per kilowatt-hour. \$0.10 per kWh is 1 cent per 100 Wh, so the 24
Wh calculated above costs 1/4 cent.

The BP-511A's have a capacity of about 8-11 Wh (depending on mAh rating)
so they cost the same or less to charge. I found a web page somewhere
quoting the Quantum Turbo energy as 20 Wh, so it's about double the set
of 4 AAs.

Suppose that each phone battery pack has about the same energy as the
4 AAs. I estimate a total battery energy of about 100 Wh in your list
above. Again assuming 50% charging efficiency and 10 cents/kWh, the
total cost in electricity from charging all of these batteries is about
2 cents.

Another way of looking at it: you can charge all these batteries once for
about the same cost as running one average PC for an hour or so.

Dave

Dave Martindale, Jun 28, 2005

3. ### Skip MGuest

Thanks for the explanation, but I was only kidding! ;-) The main threat is
from tripping over the plethora of cords running this way and that.

Skip M, Jun 29, 2005

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