I am soldiering on with my trusty RU990 as I can't find anything better at a sensible price and in all honesty it does exactly what I need.....
I know this has been raised many times but I've never seen a definitive answer......battery life with 4 AAA ni-mH was abysmal - typically lasting less than one day - so with some minor battery compartment modifications I managed to squeeze a 5th battery in and added a diode in series so as to limit the voltage gain to around 0.7V, I also made a delta-V cut off charger to suit the higher voltage.
But even though the battery voltage is 6.0V the display icons are down to 2 bars and as soon as it drops to around 5.4V the bars are either 1 or "LOW" and it switches off / re-boots.
I've removed one of the motion sensors so it only switches on when shaken rather than just touched and the batteries are definitely not discharging as they re-charge very quickly and yes, I have tried more than one set of new batteries both 900 and 1200mAH capacity.
Current consumption is around 180mA on full brightness and 250uA "off" so 900mAH batteries should last for weeks !
This cannot be right, the problem seems directly related to the battery voltage itself - presumably there isn't an option for selecting primary or ni-mH batteries is there ?
The device shows RU990 v1.0 Application version App. 3.8.17 Database version v3.42 EA Bootloader version Boot V4.31 Free memory 99%
