I am sharing Alexander Fedorov's tutorial on Facebook in case you don't have access to it.

FatShark googles are not using full capacity of the Li-Ion 18650 batteries, because the low voltage alarm goes off too early at 6.4V while these batteries can be safely discharge much lower at 3V (6V for 2 cells). 

The low voltage alarm can be changed by a resistor divider (R45 and R46 on the picture).... 





Those are 10k each, so voltage divided by 2. 

If R45 is replaced with 7.5 kOhm - goggles will only start to beep around 5.95 volts. So, packs can be used or quite extra time

just replace r45 with 7.5K and leave r46



PS it cannot be done with firmware update
PPS it will be not good idea if you use LIPO 2s packs

Before the mod, low voltage alarm triggers at 6.4



After the mod, it triggers at 6.0

Cool mod. Although I will probably not do it. Now I know I can run li-ion just a bit more after the low battery warning.

sorry, but this mod just doesn't work, at least not as you claim on my HD3's (which have the same pcb) I used an adjustable resistor to test this and it will reduce the voltage it alarms you at from 6.8v to 6.4, but adjusting any lower will just not set off the alarm at all. Not sure why as the voltage divider stuff all sounds right but it just doesn't work

What is voltage across the resistors ? Is it directly the battery voltage, across the 2 resiators, so that the alarm starts, when there is 6.4/2 = 3.2 V over the R45 ?

----- Edit
I see the calculation, it seems to support the above assumption, but I would like to confirm.

(07-Feb-2019, 04:29 AM)jdigi78 Wrote: sorry, but this mod just doesn't work, at least not as you claim on my HD3's (which have the same pcb) I used an adjustable resistor to test this and it will reduce the voltage it alarms you at from 6.8v to 6.4, but adjusting any lower will just not set off the alarm at all. Not sure why as the voltage divider stuff all sounds right but it just doesn't work

Hi, I am very curious about why that doesnt work. Have you found out ? Is there any other observation ? Have you measured the voltage across the resistors, when the alarm was suppose to go off ?