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CG5-Amp Hours-Batteries

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#1 LateViewer



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Posted 13 October 2012 - 05:02 PM

Hey guys,

I have been reading a bunch of old threads on making a battery power system for the CG5. 33AH, 22AH, 17AH. How many hours to run the CG5 for a night and possibly add a dew heater. 2 nights in a row max.

I use a 12AH battery to power the fans on my dob and that has always been sufficient.

I am trying to get away with as small a battery that is reasonable.



#2 dr.who


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Posted 13 October 2012 - 07:10 PM

Assuming a amp draw of 1.5 with both motors engaged on the mount and a .6 amp draw when tracking and a 10 hour night... That would be a blended draw of 1 amp. So you would need a minimum of 20 amp hours for two nights. You need to factor in the additional amp draw of a dew heater which is usually 1 amp plus how low you can discharge the battery before damaging it (I would recommend one of those powered scooter batteries which can be drawn all the way down and recharged without damage).

This is just a rough estimate by the way but should put you on the right track. If you spend more time looking at an object than slewing to it then the number of amp hours does go down. Same with the running time on the dew heaters.

#3 Eddgie



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Posted 13 October 2012 - 10:12 PM

The dew heater may be a bigger drain than the CG5.

The CG5 will track on less than an amp. When slewing it draws a couple of amps, but typically a slew will only last from a few seconds to maybe 30 seconds. If you slew a lot, then you won't get nearly as much time as you will if you do a lot of observing between slews, or tend to make shorter slews to stay in one area of the sky.

Dew straps are another issue entirely. My 6 amp supply for my CGE (which only uses a bit more to track and slew than my CG5) is hard pressed to just run the tracking and the dew strip for my C14, If I slew the mount while the dew strip is in a heat-on mode, the slew will be bogged down because I am drawing over the rated power of the supply. If the heat element kicks off, the mount will speed back up to normal slew rate.

So, depending on the dew strap draw (about 4 amps for the C14), you could run though a battery pretty quickly.

Determine the draw of the dew strip to get a real feel for what you will require. If you have to have a dew strip on high (the only thing that changes is the duty cycle.. the controller alternates the power on and off, but when it is on, it will draw max), then it will be on a lot and draw the rated current for that time.

For example, if I have to turn the dew strip on high for the C14 to clear dew, it draws 4 amps continously.

Once it is heated up, I can dial it back to about 30% to keep dew off (heater is running at full 4 amps for 30% of the time).

So for me, that would mean that if the dew strip draws 4 amps, but is only running about 30% of the time, you would need 1.2 amp hours in addition to the .8 amps that the mount draws to track.

But if your dew strap needs to run a lot more than this, it can really start to make a big demand on your power source.

If it were just the mount, it would be a bit easier, but you need to determine the current draw of the dew strip and the percentage of time it is on.

#4 rmollise



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Posted 14 October 2012 - 11:55 AM

It depends on how much slewing you do, but if that's a moderate amount, a 17ah job will do it.

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