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Problem with maintaining power using a 12 volt pack

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I have a 12 volt power pack for my NexStar SE 8 and always have it fully charged. It seems to work fine after the first alignment but picks up inaccuracy the more it slews. The pack shows the yellow needs recharging light after about an hour, though it does keep going. I have tried re aligning but the longer I use it the more inaccurate it gets and I think the motor is just losing power. I cannot connect directly to the mains. Does anyone have any suggestions?

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As the charge drops, so does the output voltage.

That impacts on the power to the motors, less power, the less they can move as quickly as you ant.

What power pack are you using? I don't have one of these mounts, but I think that they can run from internal AA batteries?

To match that you probably need a 12V 7Ah power pack as a minimum.

Are you using that same power pack for your camera, any dew strips or other accessories? These all drain your power pack. 


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What kind of innacuracies are you talking about? The Nexstar SE is renowned for backlash and I find mine rarely nails a goto dead centre, but it's good enough to get the object in FOV.

As iapa says, a 12V battery will most likely be running less than 12V after a while, which is why you see the recharge light illuminate on your pack. The internal AA option is generally regarded as a waste of time for the same reason.

I recently contacted FLO about an issue with my Nexstar SE mount and they were quite explicit about the requirement for a good power supply of at least 12V, preferably 13.8V!

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I have the 8SE.  My power pack is a 17Ah Phaze from Halford's.  I charge it after every use, and it has never failed in use.  As others have said, forget about batteries.

If the motors slow a bit, I wouldn't have thought that would make GoTo get less accurate, so are sure you have entered lat/long, date and time correctly?  And two known star alignment or three unnamed star alignment should be used in preference to just one star alignment.  



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Up in The Boarders it is going to be cold at present and temperature will drop the battery performance off. Also the small ones are a bit susceptable to "damage". If they drain - fairly easy to do - then the plates inside them never quite work efficently again. "Drain" does not mean it gives up and supplies nothing, it means get about half empty.

The other aspect is a battery starts up at peak voltage then drops rapidly off this peak, but it is advertised as this peak. Another recent post showed the characteristics of a Lithium battery - it started at 12v and after 20 minutes was down at 11.5 volts and keeps heading downwards. So this 12v battery was a 12v battery for about 20 minutes or less only. A car battery is stated as 12 volt but it reality is they are 13.2 volts.

Powering a scope outside is getting to be a bit of a problem, many solve it by building their own - smallish battery and some wiring ability, the battery is best if a deep cycle type. Others go down the larger Lithium route, get LiFe (lithium Iron) based ones. But that is somewhat costly. As are most aspects of astronomy.

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