[Chaos-l] Fw: 12v battery recommendations

[Robert Nielsen]

Jeff,

I can assure you that there will be plenty of power (and outlets) at the star party for charging batteries.   And yes, there is also power available on a large majority of the field.  So you very likely can run your mount off of 120V, if you like.

Concerning batteries, I don't know if you can figure out the amount of electricity (in amps) that your mount pulls when (a) tracking, and (b) slewing ... sometimes these figures are listed in the manuals for the mount.   You also should determine how much it takes to power your dew heaters and any other accessories you may use.   You can then use those figures to determine how "big" (in capacity, not physical size) a battery you need.   

For example, let's say your mount uses 0.6A when tracking, and 1.2A when slewing.  You want to observe from sundown at 8:00 until 2:00 AM, and you will look at 60 targets (meaning you will slew 60 times, 30 seconds each time).  Tracking for 6 hours will be 6 X 0.6A or 3.6 amp hours.  The slewing will be 60 X 30 seconds, or 30 minutes ... so 0.5 hours times 1.2A or 0.6 amp hours.  Together this makes 4.2 amp hours for the night.   

You shouldn't drain a battery more than half it's capacity ... so you need at least an 8.4 amp hour battery.   But note that dew heaters take much, much more power. So you probably want a 20-33 amp hour battery.

I've found AGM batteries give that amount of power for the least amount of weight.  And I've also found that a no-name replacement battery did as well as the brand name original.     So my recommendation is to make sure it is an AGM battery, make sure it has enough amp hours, but don't really worry about the brand.

Robert

On Sep 20, 2012, at 5:02 PM, "Mark Montazer" <mark at montazer.org> wrote:

> Great question, and one that's certainly been on my mind recently. My first
> question is, how accessible will power be on the field? Jayme,  I believe
> you mentioned there may be _some_ power available. Can you elaborate on
> that?
> 
> My second question is, will there be enough power during the daytime to
> charge all of these car batteries? I imagine there will be a dozen or so
> going at once by the 2nd day.
> 
> Mark
> 
> 
> -----Original Message-----
> From: chaos-l-bounces at rtpnet.org [mailto:chaos-l-bounces at rtpnet.org] On
> Behalf Of Tony Rice
> Sent: Thursday, September 20, 2012 3:39 PM
> To: CHAOS
> Subject: [Chaos-l] Fw: 12v battery recommendations
> 
> 
> 
> -Tony
> rtphokie at gmail.com
> 
> 
> Forwarded message:
> 
>> From: Jeff Charles <jmc51 at ix.netcom.com>
>> To: Help at chaosastro.com
>> Date: Thursday, September 20, 2012 2:48:13 PM
>> Subject: 12v battery recommendations
>> 
>> I am a member of the Club and recently got my first GEM. I am trying to
> get ready for the Star Party in Oct. and want to make up a battery box. From
> what I read I assume that I want to buy an AGM deep cycle battery. Can
> someone recommend a brand that Club members have had luck with? Local
> availability would be a plus. Thanks in advance.
>> 
>> Jeff Charles, Durham 
> 
> 
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