Make sure your battery selector in "setup" is set for NIMH instead of alkaline. Also if these are brand new rechargeables they won't reach their full capacity until after a few charge/discharge cycles.
Most people are finding that in v2.85 the battery meter has seen a vast improvment on accuracy. As far as battery life you should see anywhere from 10-16 hours depending on your usage of the compass, backlight, waas, etc.
Also the temperature was below 0 Celsius and I recently read that NiMh don't like the cold.