On Sunday, September 23, 2012 3:15:04 PM UTC-7, Mike McCarron wrote:
Help!



I have carefully measured my current draw in my glider at .8 amp. l would

like to know if there is any reasonable explanation for why a 9 amp hour

battery goes from 13 volts open circuit fully charged to 11.6 volts in 4

hours.



MC

Would need to know a lot mo Fully charge the battery and then let it rest off the charger for 12 hours. If it measures 13 V, then either your battery, charger, or DVM is bad. It should read about 12.6 - 12.8 depending on the technology assuming some sort of lead acid. Then run the battery for 4 hours with your 0.8A load. Then remove the load and let rest for several hours, then measure. Should measure about 12.1V or so. Measuring just after removing the charger, or under load, or just after removing the load will give you erroneous results, if your goal is to use voltage as a state of charge indication.