Is it possible that a battery booster could work?
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Here are the voltage specs for a Midland STP105B approved radio
http://midlandusa.com/wp-content/uploads/2013/07/STP-Series-P25-Operation-Manual_Ver6_0.pdf
Is there enough energy below 1.0 v to be boosted to 1.0 or above to provide more energy ?
Looking at the specs of that device, it uses perhaps 200mA when receiving and perhaps 1.5A when transmitting. The batteriser boosts to 1.5V, so even if it were 100% efficient, that would need 2.25A at 1V cell voltage for transmit and 3.21A at 0.7V. Now, if you look at the typical battery boosting inverter chip, its efficiency usually falls off dramatically at low voltages so it is common to get maybe 65% efficiency at 1V and maybe 40% at 0.7V.
Using these guestimate figures, that would mean that to counteract the inefficiency, you would need 3.5A at 1V cell voltage and 8A at 0.7V. Anyone who has ever tested an AA battery knows that if the battery is at 1V and you try and draw these currents, the battery voltage will be in freefall. You might get 5 seconds out of it. Basically with these radios, you will get less life with the Batteriser as the higher battery voltage probably means the transmitter runs at a higher power but for a shorter time. The Batteriser will also lose maybe 10% of the power through converter losses when the batteries are still fresh so that will shorten the life further. Without the batteriser, the transmitter will keep working for longer but the transmit power will be a little lower.
The story actually gets worse since there is no way the Batteriser can seriously maintain input currents of 3.2 A at 1V or 8A at 0.7V. Again, if you look at typical battery boosting ICs, the peak output current drops of quickly as the battery voltage drops. So even if the converter can do 2A at 1.4V, it may only do 1A peak at 1V and 500mA at 0.7V.
So the end result is the batteries will not last as long, you cannot really use the energy when the battery voltage gets near 1V, and worse of all, the battery meter on the radio will indicate a full charge until the random point in time that the radio goes dead. No warning of the radio shutdown to the emergency workers who may be in a dangerous and critical situation at the time.
If these services are using so many batteries, it is probably because they have a policy to always send emergency workers out with a new fresh set of batteries, and the Batteriser would have no effect on a policy like that.