HP-50G Excessive Battery Drain / Fix?

[HrastProgrammer]

It's a powered USB port where I usually connect external hard disks, so it has plenty of power available. But let's forget USB ... Should 50G drain all batteries during 7 days @ 2-3 hours work each day (just normal work, no overclocking etc.)? This is not normal.

I have an 12 years old HP-49G+ (CN33... with crappy cash-register keyboard) and 3 batteries (compared to 4 in 50G) last much, much longer. On 50G I expected at least 2 months with average usage, especially because it is powered over USB while connected (during file transfer, for example).