REFERENCE
POWERmini USB User Guide 2.1.0A
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TECHNICAL REFERENCE
Battery Types
For best results you should be sure to set the charge and cut-off parameters to suit the battery chemistry
that you are going to use. POWERmini allows you to save settings for the maximum and minimum battery
voltages separately for different types of batteries.
Different types of battery chemistry have different voltage vs capacity characteristics. The characteristic
Capacity (Ah) vs voltage curves of three popular battery types are shown in Figure 11 below.
Figure 11 Comparison of battery characteristics for different battery chemistry
The three types of batteries shown in the chart above are Lithium Iron Phosphate (4 cell), Lead Acid (6
cell) and Lithium Polymer (3 cell). Notice that the curves are similar in shape but have very different
values for the fully charged and depleted states.
•
Lithium Iron Phosphate battery
The LiFePO4 battery a higher maximum voltage (100% charge level) and a relatively flat discharge
curve. These batteries can also provide very high output currents relative to their Ah rating.
•
Lead Acid battery
The battery a lower maximum voltage, a steeper discharge curve and a lower cut-off voltage.
•
The Lithium Polymer
This is popular in car jump start battery packs and cell phones because it has a higher per-cell
voltage. The 12V jump start version uses only 3 cells, resulting in a battery that has an even lower
maximum voltage and a lower cut-off voltage than Lead Acid batteries
Also, beware - the surprisingly low capacity of the battery shown in the orange curve above is
because the 7Ah manufacturers rating applies only to the battery USB charge port not the 12V
battery output.
Although some QRP radios work well with this battery type, the low nominal terminal voltage of this
battery is problematic for other radios, many of which require a battery voltage of over 12V to function
normally.
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Ba
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Ah
Battery Comparison (Ah vs Battery Voltage)
Lithium Iron Phosphate
7.5Ah
Lead Acid 7Ah
Lithium Polymer (3 cell)
'7Ah'