FYI. The GD77 battery will go flat even if the radio is turned off
Posted: Thu Jan 14, 2021 6:50 am
Guys,
This is nothing to do with the firmware, but recently bought a "battery eliminator" and have modified it, so that I can supply power directly to the radio from an external PSU.
What I found suddenly quite interesting, is that the radio takes 0.7mA even when turned off.
I have checked why this is happening, and its because the power latching circuit, uses a high current FET, which has a 10k resistor as a pullup on its gate.
But when the radio is turned off, the gate is connected to ground, via the volume / on-off control on the radio.
This means that the battery is constantly discharged by a 10k resistor.
0.7mA may not sound like much, but the battery capacity is around 2200mAH when the radio is completely new.
So even if the radio is brand new, the battery would go flat in 130 days, which is around 4 months.
After just 1 month, the battery will only be 75% full. 20 months 50% etc.
So if you have more than 1 GD-77 (or DM-1801 or RD5R) and don't use the other radio that much, or if the GD77 is not your main radio, I recommend you remove the battery when not using it.
Because eventually the 10k resistor may flatten the battery so much that it damages the chemistry of the battery .
This will also apply to the Baofeng DM-1801, but not the Baofeng RD-5R
This is nothing to do with the firmware, but recently bought a "battery eliminator" and have modified it, so that I can supply power directly to the radio from an external PSU.
What I found suddenly quite interesting, is that the radio takes 0.7mA even when turned off.
I have checked why this is happening, and its because the power latching circuit, uses a high current FET, which has a 10k resistor as a pullup on its gate.
But when the radio is turned off, the gate is connected to ground, via the volume / on-off control on the radio.
This means that the battery is constantly discharged by a 10k resistor.
0.7mA may not sound like much, but the battery capacity is around 2200mAH when the radio is completely new.
So even if the radio is brand new, the battery would go flat in 130 days, which is around 4 months.
After just 1 month, the battery will only be 75% full. 20 months 50% etc.
So if you have more than 1 GD-77 (or DM-1801 or RD5R) and don't use the other radio that much, or if the GD77 is not your main radio, I recommend you remove the battery when not using it.
Because eventually the 10k resistor may flatten the battery so much that it damages the chemistry of the battery .
This will also apply to the Baofeng DM-1801, but not the Baofeng RD-5R