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dave b
Carpal Tunnel
Reged: 05/10/05
Posts: 2460
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http://www.windsun.com/Batteries/Battery_FAQ.htm
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dave bonandrini
30" f/5.2 Dobsonian
President of GCAC
Astromart Moderator
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keef95
member
Reged: 04/16/08
Posts: 18
Loc: My Own Private Idaho
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I don't know much about amp/hrs and such but thought I'd chime in on the "Power Tank" portion as I used to have one...
I bought a 17 amp/hr Celestron six months ago. Shortly after getting it, I read a couple of reviews about it's poor quality and features not working and thought to myself, "not mine...mine's a good one". Well I spoke too soon...I went to plug in my dew heater a couple of weeks ago and one of the power points has quit working. The radio knobs always spun on the stems (which I never cared about so didn't sweat it) and the spot light had quit.
I opened it up, saw nothing obvious so I salvaged the battery and tossed the rest. I bought a 3 way power point from Target and use one of my motorcycle battery tenders to charge it. It's 1/2 the size and works like a champ.
My point is: What ever battery you decide to use, put together your own and you'll be money ahead.
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Obsession 18"/OMI primary
CPC1100 w/Moonlight Focuser
Zhumell 8" Dob
Baader 5,8,13,17,24 & 36mm
Ethos 8mm & 13mm
UHC-S,O-III,M&SG,Vari Polarizer
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calan
sage
Reged: 06/16/07
Posts: 245
Loc: Oklahoma City, OK
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ummm... why doesn't Celestron, orion, etc. make one of these units that is actually usable?
I mean you'd think that with all these problems with the "Power Tank" units, they'd build one that is deep cycle and reliable...since that IS what they are being marketed and used for.
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Orion XT10 (completely rebuilt, DOB or GEM mountable)
Meade LXD75 6" Newt w/mods
Nikon 10x50 AE Extreme
Hyperion 21mm and 8-24mm Zoom
Astrotech 38mm Titan II
BO/TMB 6mm
Various Plossls
Time flies like an arrow, but fruit flies like a bannana.
The trouble with most jobs is the job holder's resemblence to being one of a sled dog team. No one gets a change of scenery except the lead dog.
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trumpetjazz
journeyman
Reged: 03/09/08
Posts: 5
Loc: Surrey, B.C. Canada
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Hey dvb:
I will also be attending the Merritt Star Quest during the first weekend, see you there!
I have exactly the same issues with power so this thread is very handy indeed. Based on what I've learned here I will likely go with a Nautilus deep cycle battery from Canadian Tire. There is one model for $89.99 Cdn that has a 93 amp hour rating. I'm thinking this should easily power scope, laptop, & dew heaters all night and I'll recharge via generator during the day.
Josh, I'd be interested to know what you finally settled on and if you have any field testing results.
Terry
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Celestron CPC 1100 "El Gato"
SkyWatcher 102mm f10 refractor
Denk 2" PowerXSwitch Diagonal S2
Kendrick Digifire 10
Antares W70 5.7mm, 8.6mm, 14mm, 19mm
Televue 32mm plossl
GSO 10:1 SCT Crayford Focuser
ADM counterweight system
Bausch & Lomb Legacy 10x50 Binocs
Starizona Piggyback PP
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Kolenka
professor emeritus
Reged: 06/01/08
Posts: 600
Loc: Seattle Area, WA, USA
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Quote:
Speaking from my electrical engineering background, load current does not determine the wattage that any device uses. The current and the voltage together determine that. Again, if you have a device that needs 1.3 amps, you need to know if that is what it needs from a 12V supply or a 120V supply.
I would agree, the point of measurement is very important. But I don't think we can auto-assume a wall measurement off of 1.3A, the effect of the transformer when then calculated leads to unreasonable results. 156 Watts sounds like it would be powering my "Everything and the kitchen sink" Xeon workstation at idle, and then some. Then again, 1.3A doesn't sound like peak for a reasonable laptop either internally OR at the wall, which lead me to assume it was an idle power reading effectively taken at the point of entry into the main laptop circuit.
The reason why this muddies the water a bit is that draw of a properly regulated electronic device uses a fixed voltage for most of the components, and while you can dip below that (which is very bad), you won't be running voltages higher than that. This distinction is an important one, and lets us operate with some simpler math if the measurement is not using an at-the-wall measurement. If we are talking at-the-wall, yes, you are right that wattage needs to be used so we can actually get a more realistic current draw from the laptop's DC power source.
My main nit is that you brought in the at-the-wall math on a reading that very likely wasn't at the wall unless we are talking about one of those Alienware systems that actually uses desktop CPUs and GPUs in an oversized laptop case.
I may be a bit rusty on my EE, but you are in similar company. 
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Meade 10" LX200R
Orion 80ED
Nagler 7T6, 9T6, 13T6, 17T4, 26T5
Canon XSi (Modded), TIS DMK 31AF03
Northwest Astro Photoblog
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dvb
Carpal Tunnel
Reged: 06/18/05
Posts: 1924
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Quote:
Hey dvb:
I will also be attending the Merritt Star Quest during the first weekend, see you there!
I have exactly the same issues with power so this thread is very handy indeed. Based on what I've learned here I will likely go with a Nautilus deep cycle battery from Canadian Tire. There is one model for $89.99 Cdn that has a 93 amp hour rating. I'm thinking this should easily power scope, laptop, & dew heaters all night and I'll recharge via generator during the day.
Terry
Keeping my fingers crossed for clear skies and no forest fires!
I was also checking out the Canadian Tire batteries; they also have an adapter from terminals to cig lighter. I haven't found a cheap float charger yet - lots of trickle charges for about $40.00.
I'm also checking out Battery World in Burnaby, which stocks Trojan
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Skywatcher 10" f/4.7 Newt on Matilda
Skywatcher 10" f/4.7 Collapsible Dob
Meade 8" SN f/4
Celestron C8 SCT
Celestron C6 SCT
Skywatcher ED100
Skywatcher ED80
EQ6 Pro "Matilda"
AT Voyager
Skymaster 15x70
Mallincam HyperColor Plus
Edited by dvb (08/20/08 10:33 PM)
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Midnight Dan
professor emeritus
Reged: 01/23/08
Posts: 619
Loc: Brockport, NY
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Quote:
My main nit is that you brought in the at-the-wall math on a reading that very likely wasn't at the wall unless we are talking about one of those Alienware systems that actually uses desktop CPUs and GPUs in an oversized laptop case.
Hi Kolenka:
Of course, you're right that the 1.3 amps at 120V infers a 156 watt rating which is MUCH more than most laptops require. But 1.3 amps at 12 volts is only 15.6 watts which is much LESS than most laptops require.
It is true that at idle, 15 watts *might* be a reasonable power drain. And if the OP was to cut his power cord to the laptop and insert an ammeter, or otherwise try to directly measure the current draw, he might see that kind of a reading (although I still think it would be somewhat higher). Since most people don't do this, I thought it was much more likely that he just read the 1.3 amps off of the power brick. If that's the case, he'll be grossly underestimating the time he'll get out of a battery supply.
Keep in mind that just because the power brick is designed to produce up to 156 watts, doesn't mean that the laptop needs that much. Most laptops are in the 45-80 watt range and even that is likely to be only when it's running everything. More likely, it will be using in the 30 to 60 watt range most of the time. Still considerably more than 1.3 amps at 12 volts.
My main point was to warn the OP that if he's reading that value off the power brick (fairly likely) he'll be overestimating the time he'll get out of the power supply. And that's why I asked him to double-check that rating. I also suggested a example current draw based on 60 watts (5 Amps at 12V), not the the 156 watts of the power brick, and suggested de-rating that to 3-4 amps for normal usage. So I think that's a more reasonable guess at the power needs.
-Dan
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Scopes: Celestron NexStar 8, Orion EON 72mm ED/APO on Astroview mount (EQ3)
Eyepieces: Celestron 40mm, 25mm, Baader Hyperion 13mm, 8mm, 5mm
Other: Telrad, 2x Barlow, 0.63x Focal Reducer, Dew-not strips, DewBuster controller
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gripweed44
scholastic sledgehammer
Reged: 02/12/05
Posts: 905
Loc: PDX
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Hi
what AH draw does a Celestron CG-5 mount have when its only being used to track the sky? No goto's
Anybody know?
Thanks
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John
Omega Centauri is the finest Globular I have seen with my own eyes.
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dvb
Carpal Tunnel
Reged: 06/18/05
Posts: 1924
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"DC 3-OUTLET RECEPTACLE 2701555 $0.96 orig. $14.99
15A, 12V DC triple accessory outlet with illuminated green ring in the centre socket. With screws, adhesive tape and wire harness. Inline fuse added."
Couldn't resist this option from "The Source" (Canadian Version of Radio Shack) with the built-in fuse -- altho it's a 15 amp / 125V fuse, that I'll probably replace with a 10 amp 32V DC fuse. At 96 cents for the receptacle, the fuse will be twice the cost! (This deal is only available in-store in Canada, as supplies last.) I'll add on a pair of clips or rings to attach it to the battery terminals.
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Skywatcher 10" f/4.7 Newt on Matilda
Skywatcher 10" f/4.7 Collapsible Dob
Meade 8" SN f/4
Celestron C8 SCT
Celestron C6 SCT
Skywatcher ED100
Skywatcher ED80
EQ6 Pro "Matilda"
AT Voyager
Skymaster 15x70
Mallincam HyperColor Plus
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Skylook123
Post Laureate
Reged: 04/30/05
Posts: 3974
Loc: Tucson, AZ
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Quote:
ummm... why doesn't Celestron, orion, etc. make one of these units that is actually usable?
I mean you'd think that with all these problems with the "Power Tank" units, they'd build one that is deep cycle and reliable...since that IS what they are being marketed and used for.
I've been using an Orion 17 AH Power Tank for over 2 1/2 years. The scope goes out two or three times a month, plus three Grand Canyon Star Parties for a week each, plus five weekends for All Arizona events. Haven't had any trouble with it yet. I only use it for the Atlas mount, and rarely a laptop at the same time.
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Jim
A Bad Night With A Telescope
Beats A Good Night Doing Anything Else
Tectron 18" Truss Dob/Sky Commander DSCs, "Derrick"
Meade 10" LX-5 SCT/Atlas-G "Ol' Blue Eye"
Orion 90mm refractor,
Meade 10" Starfinder Newt/JMI NGCMax DSCs,
Celestron 10x50 Ultima Pro
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DaemonGPF
Pooh-Bah
Reged: 03/22/08
Posts: 1472
Loc: New Mexico
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Ok I finally went out and gathered up the components. Found a 125 amp hour deep cycle marine battery for $80, terminal rings $3, plug adapter $8, inline fuse holder and a box of blade fuses $5. It should give me more than enough juice for two nights. I also have two brand new extended life batteries for my laptop, so I can draw from them until they drain out and recharge them by day in the Jeep. It should keep my laptop off the marine battery for several hours each night.
What I cannot find locally is a float charger that isn't rediculously priced. I just need a basic cheapo one. Most online places are quoting me 3 weeks shipping time which will give me zero time to test this setup. Tried Sears, Checker Auto, Walmart, Autozone.. Suggestions?
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-Josh
*Orion Starblast Imaging 150mm OTA
*Orion Starblast Imaging 114mm OTA
*Meade 50mm AR short tube OTA
*Meade DSI Pro IIc
*Orion Starshoot DSCI
*CG5 mount
http://cleardarksky.com/c/AlbuqNMkey.html
My Messier Project Gallery
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cvedeler
Carpal Tunnel
Reged: 12/20/05
Posts: 1525
Loc: Scottsdale, AZ
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I just bought a 115 amp hour deep cycle battery at Walmart for $58. It is a beast (about 45 - 50 lbs), but being ultra conservative, should provide me enough power for two full nights running the whole show with plenty of reserve. I also have an Orion 7 amp hour power pack and a Black and Decker 19 amp hour power station.
I tried to run my laptop off of th 19 amp hour system with its built in inverter and it ran for about 4 hours before the battery system failed! I had no idea a laptop drew so much power. I could have gone for about another 1 - 2 hours running on the laptop battery, but there was to be no surprises there. So much is lost to heat in the conversion of 12v DC to 115v AC back to 18v DC. If you don't believe me feel the heat coming off the little fan cooling the inverter, not to mention how hot the little power supply gets. I bet at least half the power is lost to heat, probably more.
Best advice - add up all the maximum power draw in amps from all of your gear and double it. Multiply that by the number of hours you plan on using it and double that. Buy a battery system that will supply that number of amp hours and you should be good to go.
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Chris Vedeler
Astro-Physics 160EDF
Astro-Physics 900GTO
Orion 80mm Guidescope
Canon EOS XT modified with Baader filter by Hap Griffin
Meade DSI Pro / Philips SPC900NC webcam
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www.aznightsky.com
Scottsdale, AZ
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cvedeler
Carpal Tunnel
Reged: 12/20/05
Posts: 1525
Loc: Scottsdale, AZ
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Quote:
Ok I finally went out and gathered up the components. Found a 125 amp hour deep cycle marine battery for $80, terminal rings $3, plug adapter $8, inline fuse holder and a box of blade fuses $5. It should give me more than enough juice for two nights. I also have two brand new extended life batteries for my laptop, so I can draw from them until they drain out and recharge them by day in the Jeep. It should keep my laptop off the marine battery for several hours each night.
What I cannot find locally is a float charger that isn't rediculously priced. I just need a basic cheapo one. Most online places are quoting me 3 weeks shipping time which will give me zero time to test this setup. Tried Sears, Checker Auto, Walmart, Autozone.. Suggestions?
I just bought one at Walmart for $27. It is 6 amps and has a 2 amp trickle float charge function too. It clams to be "smart" and monitor the charging. I can't find it on their webpage but it was at my local store.
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Chris Vedeler
Astro-Physics 160EDF
Astro-Physics 900GTO
Orion 80mm Guidescope
Canon EOS XT modified with Baader filter by Hap Griffin
Meade DSI Pro / Philips SPC900NC webcam
----------------------------
www.aznightsky.com
Scottsdale, AZ
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dvb
Carpal Tunnel
Reged: 06/18/05
Posts: 1924
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My Orion power tank packed it in last night after a couple of years of use.
Bought a Trojan deep cycle 24 that will run for 20 hours before needing a recharge. Weighs about 47 lb.
Also a Schumacher Charger, which can charge at just 2 amps. I also could not find a cheap float charger locally.
Also picked up a couple of battery terminal clips that I've attached to a fused 12v DC receptacle. I hope to try it out tonight.
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Skywatcher 10" f/4.7 Newt on Matilda
Skywatcher 10" f/4.7 Collapsible Dob
Meade 8" SN f/4
Celestron C8 SCT
Celestron C6 SCT
Skywatcher ED100
Skywatcher ED80
EQ6 Pro "Matilda"
AT Voyager
Skymaster 15x70
Mallincam HyperColor Plus
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Paul G
Carpal Tunnel
Reged: 05/08/03
Posts: 1766
Loc: Freedonia
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Quote:
What I cannot find locally is a float charger that isn't rediculously priced. I just need a basic cheapo one. Most online places are quoting me 3 weeks shipping time which will give me zero time to test this setup. Tried Sears, Checker Auto, Walmart, Autozone.. Suggestions?
Get a Battery Tender Junior, good quality and only $39.95:
Battery Tender Jr
The local Pep Boys auto store has them in stock for $35.00.
I use two Optima blue top AGM batteries.
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Gus
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DaemonGPF
Pooh-Bah
Reged: 03/22/08
Posts: 1472
Loc: New Mexico
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Found me one online that ships in one business day. Should have it by end of week, which will give me roughly 3 weeks to test everything out before the star party and make sure this battery will hold.
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-Josh
*Orion Starblast Imaging 150mm OTA
*Orion Starblast Imaging 114mm OTA
*Meade 50mm AR short tube OTA
*Meade DSI Pro IIc
*Orion Starshoot DSCI
*CG5 mount
http://cleardarksky.com/c/AlbuqNMkey.html
My Messier Project Gallery
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DaemonGPF
Pooh-Bah
Reged: 03/22/08
Posts: 1472
Loc: New Mexico
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Just wanted to say thanks for the info everyone. I stress tested my 125 amp hour marine battery this past weekend and ran just fine with all equipment powered up and operating for at least 5 hours per night, 2 nights in a row with no signs of it dying on me. I kept it constantly slewing around and driving imagers. The $7 float charger from e-bay worked just fine, ended up being the same one for sale at harborfreight.
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-Josh
*Orion Starblast Imaging 150mm OTA
*Orion Starblast Imaging 114mm OTA
*Meade 50mm AR short tube OTA
*Meade DSI Pro IIc
*Orion Starshoot DSCI
*CG5 mount
http://cleardarksky.com/c/AlbuqNMkey.html
My Messier Project Gallery
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