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Discharge data on 4/3 Fat A NiMH
Cells |
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Custom
design and manufacture of state-of-the-art battery
chargers, UPS, battery packs and power supplies for OEMs in a Hurry
This graph shows the effective capacity of two
NiMH 4/3 Fat A cells. The PowerStream has a rating of 3850 mAH, and the
Panasonic has a rating of 4500 mAH. As can be seen, the effective capacity of
the Panasonic drops quickly as the discharge current increases. The PowerStream
cells do not have such a severe drop off. The point is, that at low currents
the difference between the cells is 650 mAH, at 3.5 amps the difference is only
200 mAH.
The reason for this is simple. In order to squeeze more capcity
into the cells, Panasonic used thinner foil electrodes, which increased the
impedance (resistance). At higher currents the voltage drop through the
electrodes is severe. This is a good tradeoff if you are drawing low currents,
but if you are drawing high currents, you might be better off buying the less
expensive PowerStream cell.
This curve shows the PowerStream 4/3 Fat A NiMH
cell in a 12 volt, 10 cell pack. It shows the useful discharge time you can
expect at different discharge currents. The end-of-discharge condition is
usually considered to be 1 volt per cell, or 10 volts for this pack. You can
see that there isn't much capacity left between 1 volt and zero volts per
cell.
PowerStream 4/3 Fat A:
| Current |
Nominal Rate |
Measured run time |
Expected run time |
Ratio |
Equivalent AH |
| 0.525 A |
C/7 |
440 |
440 |
1 |
3.85 |
| 1.02 A |
C/4 |
226 |
226 |
1 |
3.85 |
| 1.5 A |
C/2.5 |
150 |
153 |
0.98 |
3.78 |
| 2.0 A |
C/2 |
114 |
115 |
0.99 |
3.80 |
| 2.5 A |
C/1.5 |
91 |
92 |
0.98 |
3.79 |
| 2.98 A |
C/1.3 |
75 |
77.5 |
0.97 |
3.72 |
| 3.5 A |
C/1.1 |
64 |
66 |
0.97 |
3.73 |
| 4.0 A |
C/1 |
56 |
57.8 |
0.97 |
3.73 |
| 4.5 A |
C/0.86 |
50 |
51.8 |
0.97 |
3.72 |
| 5.0 A |
C/0.77 |
44 min |
46.2 |
0.95 |
3.67 |
In this chart the "expected run time" is what
you would expect if you took the capacity measured at a C/20 discharge rate and
divided it by the the discharge current. You can see that even at 0.77C, the
PowerStream cells are still up to 95% of their 20 hour capacity. This indicates
a high quality, well constructed cell that was designed for high current
capability.
A similar chart shows the PanaSonic 4500 mAH 4/3 Fat
A
Panasonic 4/3 Fat A:
| Current |
Nominal
Rate |
Measured Run Time |
Expected Run Time |
Ratio |
Equivalent AH |
| 0.9 |
C/5 |
300 |
300 |
1 |
4.50 |
| 1.49 |
C/3 |
178 |
181 |
0.98 |
4.42 |
| 1.98 |
C/2 |
128 |
136 |
0.94 |
4.22 |
| 3.51 |
C/1.3 |
70 |
77 |
0.91 |
4.10 |
As you can see, at C/1.3 the capacity is
already down to 91% of the rated capacity, whereas the PowerStream has 97% at
C/1.3, and still has 95% at C/0.77.
For a chart of the sizes and weights of cylindrical
batteries click here:
For more battery engineering resources click here:
Note: We don't
inflate our specifications as many companies do. The capacity in amp-hours is
guaranteed, and will be exceeded most of the time. "Usable cycles" is a
guideline, but not guaranteed because we have no control over abuse of the
cells. |
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PowerStream Technology:
140 South Mountainway Drive, Orem Utah 84058
Phone: 801-764-9060, 9062, 9063, 9064
 Fax:
801-764-9061 |
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PowerStream
Technology
140 South Mountainway Dr.
Orem,
UT 84058
Phone: 801-764-9060, 9062, 9063, 9064
Fax: 801-764-9061
Map & Directions
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© Copyright 2000,
2002, 2004 Lund Instrument Engineering, Inc. All rights reserved
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