Re: question on deep cycle battery use

Don Anderson

Hi Suresh
A 65 ah battery designation means that the battery technically is capable of delivering 65 amps for 1 hour or 32 1/2 amps for 2 hrs or 16 1/4 amps for 4 hrs etc etc. However if the full capacity was actually used that would kill the battery completely. Doing this would damage the battery. Deep cycle batteries although more robust than car batteries should not be drained more than about 50% of their capacity and probably less if you want it to last. For your battery 50% is about 32 ah.
Lets get back to your original question which is how much time do I get out of my battery with my only my ccd connected. You say your ccd camera is rated to draw 13 watts. To figure out how much time your battery will give you at the above mentioned 50% battery drawdown, you need to convert the camera draw into amps. There should be a spec in the manual that shows how many amps your camera draws; if not you can figure that out with the simple electrical formula P= A x V where P= power in watts, A= electric current in amps and V= voltage. Transposing the formula to convert watts (P) into amperage draw (A) the formula now looks like this A = P/V. Using this formula, your ccd camera draw works out to be  A= 13w/12v (battery voltage) = 1.08 amps. Now that you know the amperage draw you can figure out how long your battery should last to 50% drawdown which is 32 amp-hrs/1.08 amps = 29.6 hrs. Suresh, none of these calculations are exact since battery voltage begins to drop almost immediately as you start draining it but it is close and gives you a fairly good idea.
You can keep tabs on your remaining battery capacity with a simple volt meter. The voltage of a fully charged battery in good condition will vary depending on its temperature as well as other variables such as the rate of drawdown. Fully charged the battery should read about 12.5V. A completely dead battery will show about 10.5V while a 50% discharged battery should read approximately 11.0-11.5V.
Suresh, the above is meant to give you a rough idea only but the answer to your basic question is with your camera only attached to your battery if it is in good condition, you should get a full day of imaging time.
Hope I didn't lose you with all of this. There is a wealth of information on the web on how lead-acid batteries work and how to take care of them.
Don Anderson

From: "Suresh Mohan Neelmegh drsureshmohan@... [ap-gto]"
To: "ap-gto@..."
Sent: Tuesday, April 4, 2017 9:12 PM
Subject: [ap-gto] question on deep cycle battery use

i run a 65 ah battery for my mount.,ccd ,and dew heater (occasionally)).My ccd uses 13 watts of power at 50% cooling. Does this mean if i used the battery for ccd alone, i would only get 5 hrs of ccd working? Could someone explain

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