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#1
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Battery Power
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 |
#2
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Battery Power
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. Short answer: 9AH is the nominal capacity, the actual capacity depends on temperature, discharge rate and battery age.. Long answer: have a look at the graphs in, for example, http://www.standbattery.com/linkfiles/Technology%20Manual.pdf |
#3
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Battery Power
At 23:10 23 September 2012, Tom Gardner wrote:
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. Short answer: 9AH is the nominal capacity, the actual capacity depends on temperature, discharge rate and battery age.. Long answer: have a look at the graphs in, for example, Could not find the graphs. Brand new battery and very reliable battery charger. |
#4
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Battery Power
At 23:10 23 September 2012, Tom Gardner wrote:
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. Short answer: 9AH is the nominal capacity, the actual capacity depends on temperature, discharge rate and battery age.. Long answer: have a look at the graphs in, for example, Could not find the graphs. Brand new battery and very reliable battery charger. |
#5
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Battery Power
Also, 0.8 amps is about double the load the battery is rated for. The capacity of your 9 A.h battery should be about 10 hours at 25 degrees C. Your battery sounds cold or tired or both!
Plus, do you ever use your radio? Mike |
#6
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Battery Power
On 9/23/2012 4:32 PM, Mike McCarron wrote:
At 23:10 23 September 2012, Tom Gardner wrote: 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. Short answer: 9AH is the nominal capacity, the actual capacity depends on temperature, discharge rate and battery age.. Could not find the graphs. Brand new battery and very reliable battery charger. Fully charge the battery, then do a discharge test at about 0.8 amps. Even a new battery can be defective, so I always do a discharge test on new batteries before using them in the glider. It could also be the charger. Have you tested it's charging ability recently? -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) |
#7
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Battery Power
At 23:34 23 September 2012, Mike the Strike wrote:
Also, 0.8 amps is about double the load the battery is rated for. The capacity of your 9 A.h battery should be about 10 hours at 25 degrees C. Your battery sounds cold or tired or both! Plus, do you ever use your radio? Mike Where does it say that I should only draw 400 ma? The battery is brand new and fully charged. Open circuit wasr 12.0 to start. What is the problem? Mike |
#8
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Battery Power
At 00:07 24 September 2012, Mike McCarron wrote:
At 23:34 23 September 2012, Mike the Strike wrote: Also, 0.8 amps is about double the load the battery is rated for. The capacity of your 9 A.h battery should be about 10 hours at 25 degrees C. Your battery sounds cold or tired or both! Plus, do you ever use your radio? Mike Where does it say that I should only draw 400 ma? The battery is brand new and fully charged. Open circuit wasr 12.0 to start. What is the problem? Mike As a correction to the above I meant to say the open circuit voltage was 13 volts when I started everything up. I do use the radio as little as possible. |
#9
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Battery Power
On 9/23/2012 5:07 PM, Mike McCarron wrote:
At 23:34 23 September 2012, Mike the Strike wrote: Also, 0.8 amps is about double the load the battery is rated for. The capacity of your 9 A.h battery should be about 10 hours at 25 degrees C. Your battery sounds cold or tired or both! Plus, do you ever use your radio? Mike Where does it say that I should only draw 400 ma? The battery is brand new and fully charged. Open circuit wasr 12.0 to start. 800 ma isn't too much to take from the battery. It will reduce the capacity about 10% from the 400 ma, ~20 hour rate used to measure the rated capacity. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) |
#10
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Battery Power
The 9A.h batteries I use would have a rated capacity of about 8A.h at a current of 0.8A - that's about ten hours' worth. Dropping the temperature to freezing will drop that to about 7 to 8 hours - still more than you're getting.
Also remember that the current drawn by some devices may increase as the voltage drops. I'd suggest checking your current draw at a range of battery voltages. If your charger's ok, it sounds like your battery isn't. Mike |
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