Presented
at the
Georgia Geocachers Association January 2007
Meeting
in Atlanta
by –
CharlieP
Everything You Ever Wanted to Know about Batteries and More
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Characteristics of AA Cells |
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Characteristics |
Alkaline |
Nickel Metal Hydride |
Lithium |
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Voltage Range |
1.5 to 0.9 |
1.4 to 1.1 |
1.5 to 1.3 |
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Discharge Curve |
linear |
flat at 1.25 volts |
linear |
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GPS Application |
Very Good |
Very Good |
Very Good |
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Digital Camera Application |
Poor |
Very Good |
Very Good |
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Capacity |
2200 mAh |
1300-2400 mAh |
2800 mAh |
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Hours of Use @ 120 mAh |
18 |
11 to 20 |
23 |
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Use Cycles |
1 |
300 to 1000 |
1 |
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Shelf or Service Life |
4 years |
4 years |
10 years |
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Self Discharge Rate |
Negligible |
70º F - 1st day 5% then 1% per day. 100º F - double the 70º rate |
Negligible |
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Cost per cell |
$0.50 |
$2.00 |
$2.00 |
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Cost of Charger |
$0.00 |
$5 to $40 |
$0.00 |
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Economics for Heavy User - 2 AA Cell GPS @ 120 mA used average of 80 hours per month - 4 years |
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Alkaline |
Nickel Metal Hydride |
Lithium |
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Cells Used |
418 |
4 |
330 |
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Cost incl. Charger |
$209.00 |
$13 to $48 |
$660.00 |
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Economics for Light User - 2 AA Cell GPS @ 120 mA used average of 10 hours per month - 4 years |
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Alkaline |
Nickel Metal Hydride |
Lithium |
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Cells Used |
52 |
4 |
40 |
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Cost incl. Charger |
$26.00 |
$13 to $48 |
$80.00 |
Slow or Overnight Charger - Will charge depleted cells in 10 to 20 hours. Pros - low cost, small and easy to carry, not likely to damage cells. Cons - takes time to charge cells, no 12 volt capability, no trickle charge.
Fast Dumb Charger - Will charge depleted cells in 2 to 5 hours. Pros - faster charge rate. Cons - may damage cells by overcharging. Not recommended.
Fast Smart Charger - Will charge depleted cells in 1 to 2 hours and reduce charge rate when cells are charged. Pros - fastest charge rate, easy on cells, may have trickle charge feature, 12 volt capability, and ability to charge AAA and other types of cells. Cons - higher cost. Rayovac and Maha make some good smart chargers.
NiMH Battery Management and Safety
Mark cells in pairs (or sets of four) and always use them and charge them together.
New NiMH cells may not have full capacity until 3 to 5 FULL charge/discharge cycles. GPS will fully discharge cells (to 1.1 volts) but digital cameras may only use 50% of capacity. NiMH Cells may require a full discharge every few months to maintain capacity, but do not discharge NiMH cells to zero voltage (completely dead) as this may damage them.
Do not carry cells loose in pocket or pack, use insulated wrapping or container, e.g., paper or plastic. Maintain outer plastic covering and repair if damaged. Short circuited NiMH cells can burn skin or damage your GPS or camera !!!
Pack a set of lithium cells for backup for both your GPS and camera. Carry spare AA cells in a small flashlight. Some NiMH batteries may not fit in some devices - do not remove covering!!
Thanks to CharlieP for this handout on Batteries