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OJ87

Power supply for my new EQ6R mount

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Hi everyone , I'm beginning my first tour in DSO astrophotography and I bought the Skywatcher EQ6R as mount and planning to buy a SkyWatcher  Quattro Newtonian 10-Inch, which will bring the mount (plus photography accessories ) to its limits. So I want to buy a power tank to operate in field. I see a lot of  experienced astrophotographers use car batteries as power supply for their mounts and  seems it works perfectly. Could you tell me what I need to build a good power supply for my new friend? (Battery Capacity, accessories or any other things to guarantee a stable 12V current for the hole night). The mount  requires 12V as manufactures says. 

Thank you very much, 

Best regards 

Edited by OJ87

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The mount should be able to handle the normal voltage from any 12v car battery (nominal 13.8v fully charged).  The spec of the mount suggest 2A ad the current draw,  so in theory a 40 A/h battery would last 20 hours before being completely flat.  But the voltage will also drop as the current drops, so in real terms it may last 10-15 hours.  To be safe, if you can afford a 70 A/h battery then this should cater for all your needs for a full night, but also note that a battery will perform better in a warm environment, but at cold winter temperatures, the coldness can have an effect on the duration / capacity.

 

Hope that helps 

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You spent a lot of money on yopur equipment so far, so I sugest you buy a good battery as well. The best ones are the LiFePO4 batteries.
The voltage does not drop after a while like with lead/acid batteries, they handle temperature a lot better, and they have a much longer productive life.

Here is some interesting info about them:  https://www.victronenergy.com/upload/documents/Datasheet-12,8-Volt-lithium-iron-phosphate-batteries-EN.pdf

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The Quattro is a lovely scope but I wouldn't consider it a first scope. Being a fast scope finding and keeping focus will be a fairly daunting task. A small refractor is a better option and less prone to wind shake too. 

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I would buy a lithium power pack. They are much more reliable and last much longer (particularly on the shelf) than lead acid.

Just buy something with a reputable name. For example Tracer packs (sold by FLO and others) have UN38 transport approval.
Other manufacturers like PAG are reputable. A Celestron lithium powertank is going to be OK.

An ebay bargain from China may not be the bargain it first seems.

To me, the only benefit of lead acid is that you can buy something way oversize for the application.
For example you might only need 10Ah for a night of mount power. This means a degraded or cold (poorly performing) lead acid will still be good enough.
But do you really want the huge weight of lead acid to add to your scope and mount weight if you are carrying?

Hope this helps, David.

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Thanks guys, I had bought a 100aH lead acid battery with maximal 20A as output. I know it's huge load of weight (15kg), but it's ok, since I'm planning to run my laptop also from this battery, it'll handle it for the next couple of years, then I hope other form of batteries will be cheaper with better performance and more capacity. 

Best regards 

 

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2 hours ago, OJ87 said:

Thanks guys, I had bought a 100aH lead acid battery with maximal 20A as output. I know it's huge load of weight (15kg), but it's ok, since I'm planning to run my laptop also from this battery, it'll handle it for the next couple of years, then I hope other form of batteries will be cheaper with better performance and more capacity. 

That will be fine. I assume it's a 'leisure' type battery given the 20A max output which is much better than a 'normal' car battery for your astro use. As long as you don't let it drop below about 50% capacity, recharge it after use and every month or so if not used, it will last for many years. I have a 110 AH leisure battery with 1 kW inverter as a standby in case of power cuts and that is now 8 years old. I test it occasionally and it's still fine. My car battery (in the car) is entering its 10th year now and is a little sluggish in the winter but hasn't failed to start yet. :D If the weight is not a problem I'd choose lead acid over other forms still.

Alan

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