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Franky
member
Reged: 03/11/09
Posts: 49
Loc: Europe, Slovakia
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Hello guys. I'm looking for a battery, to take my mount and scope to remote locations, but I am not sure about the choice:
1) I want to power mount (MI-250), heaters, notebook, SBIG camera, guide camera, USB hub.... When I've summed all that up, it was somewhere around 30 Amps @ 12V. So if I want to stay out in the dark for 8 hours, does that mean I'll need 240 Ah battery? (8x30=240). I'll use the battery in cold weather (between 0 and -10°C).
2) What technology do you recommend? It must be a cyclic battery, that will handle deep dischardges, cold weather, etc. Should I buy AGM or Gel battery? Or something else?
Thank you so much for your help ;-)
Frank.
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Celestron C14 on Mountain Instruments MI-250
Meade 5000 ED APO 80mm on Celestron CG4
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4593
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Quote:
Hello guys. I'm looking for a battery, to take my mount and scope to remote locations, but I am not sure about the choice:
1) I want to power mount (MI-250), heaters, notebook, SBIG camera, guide camera, USB hub.... When I've summed all that up, it was somewhere around 30 Amps @ 12V. So if I want to stay out in the dark for 8 hours, does that mean I'll need 240 Ah battery? (8x30=240). I'll use the battery in cold weather (between 0 and -10°C).
2) What technology do you recommend? It must be a cyclic battery, that will handle deep dischardges, cold weather, etc. Should I buy AGM or Gel battery? Or something else?
Thank you so much for your help ;-)
Frank.
Got no idea what a "cyclic" bat'ry is. Deep cycle battery?
That is what you need, and the bigger the better. The SBIG's Peltier will suck down a low-capacity in a right-quick hurry. Think a 100ah range marine battery...I don't believe you be constantly consuming 30amps with your rig...but bigger _is_ better.
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Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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AlanT
sage
Reged: 08/20/07
Posts: 488
Loc: 122º36' W, 47º37' N, WA USA
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Your math is good enough (actually you'd want more AH because you never want to fully discharge the battery)... BUT... I can't believe 30A... That's huge.
Mount: Don't know the MI-250 but I bet it's less than 0.5A most of the night. It should only be drawing high current while slewing fast.
Laptop: I measured my full size laptop. averaged 2A
USB hub, could be up around 2A, if all 4 ports are used. (500mA/port max)
SBIG: I'd guess about 2A average, assuming you're already in cold weather so the TEC isn't working to hard. My St-2000 uses less than 2A average.
Guider: If powered from USB, then 0.5A.
Heaters: That I don't know, but I keep my gear dew free on less than 1 A. YMMV.
So these numbers are < 10A. Are you sure you're up to 30?
Personally, I use two batteries (easier to lug, and can be configured to minimize potential for ground loops). I use a 40AH for the mount and heaters, and an 80AH for the rest of the gear. I've never done it, but I'm sure I could go two nights on 'em. However, I've never used them for long nights below about -5C, so I can't comment on really cold performance. Both are deep cycle. Ones a Diehard Marine battery, the other from a supplier of wheelchair/scooter batteries. If you poke around the net you can find lots of good info on the differences between the types of batteries, and on care and maintenance. I chose regular deep cycle batteries for price vs use over expected lifetime.
Just my 0.02
al
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al
Meade 80mm APO
Celestron 6" SCT
CGE, GM-8, & CG-5 GT
ST-2000xcm, DSI Pro II, DSI Pro
( www.alberts-astro.com/astro )
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mclewis1
Thread Killer
Reged: 02/25/06
Posts: 3955
Loc: New Brunswick, Canada
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I second the idea of two batteries ... put your voltage sensitive stuff on one (mount SBIG imager, guider) and put the less sensitive stuff on the other (laptop because it is probably running through a DC-DC adapter, USB hub and the dew strips). Put the extra money into a quality battery for the sensitive stuff and go with a bit more brute force for the less sensitive battery. The idea is that you can probably "abuse" (take it down below 50%) this battery a bit more without worrying about it causing problems (the devices mentioned are not as sensitive to lower voltages which occur when you seriously deplete a battery).
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Mark
C11, C6, APM/TMB115, and AT80ED - Tandem mount CGE and CG-5A, WO EZ-Touch and AT Voyager
25x100s and 8x56s, T-Mount Light, Mark 1 eyeballs - Modded 350D, DSI-P, SPC900, Mallincam
Just because you can doesn't necessarily mean that you should
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Billydee
super member
Reged: 01/23/08
Posts: 186
Loc: Winter Haven, FL
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Look at the suggested Marine batteries and another type is the ones made for RVs both of these are deep cycle and can be taken as low as 40% of their rated amp hour. This means 60 amp hrs is about all you should go without damage to the batteries. 60ah/8hr = 7.5 amps per hour average use. This is a resonable usage for your setup. When everything is using power at the same time you would get up to about 10 amps but that happens for very short periods and most times you will draw much less than 7.5 amps. If you want to test it put an amp test meter in series with one post on the battery and all the load after the meter (most stores have this for testing batteries in cars). Then run your gear one piece at a time and then keep adding to the load one more piece of equipment. I think you will be shocked (pun) at how little you use under full load. There are Very Deep Cycle batteries but they weigh 75lbs for a 120 amp/hr type and can cost more than $500. That does not include the small horse you will have to buy and feed to haul it. The suggestions about more than one battery are great. Less weight and split loads. The major problem is heater strips and mount/ccd cross feed. The spikes when a heater strip lights off do wild things to other items on the same circuit. Remember that the laptop has an internal battery and it can run up to 5 hrs before needing a recharge (HP sells high amp/hr units for about $192) so for 5hrs you will have 2amp/hr less drag on the main ones.
Luck, Bill
Edited by Billydee (11/07/09 04:28 PM)
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Franky
member
Reged: 03/11/09
Posts: 49
Loc: Europe, Slovakia
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Thank you guys for wonderful suggestions.
You wrote that the two batteries can be configured to minimize potential for ground loops. How do you do that? I am not very experienced in electronics, so this is an "unknown island" for me.
So far I thought that everything that is interconected by data cables (mount -> laptop, cameras -> laptop, etc) should be connected to same ground to prevent ground loops. Two batteries represent two grounds, right?
So putting notebook to one battery and mount/cameras to another battery might represent a potential for ground loops. Plus I'am not sure what role will a USB hub play in ground loops theory. This is how I understand it, so if I'm wrong (I guess I am :-), please enlighten me :-)
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Celestron C14 on Mountain Instruments MI-250
Meade 5000 ED APO 80mm on Celestron CG4
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AlanT
sage
Reged: 08/20/07
Posts: 488
Loc: 122º36' W, 47º37' N, WA USA
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With regard to ground loops.
With two batteries, one ground can float with respect to the other, so a "loop" won't form.
Say you use one source. From that you power your mount and mount electronics, and you guide from your laptop via a parallel port to the mount st4 port. Now there is a potential ground loop. The mount electronics can return to ground through the mount power, or return via the st4/laptop connection. Typically, opto-coupling isolation would be used in the connection to the st4 to avoid the loop, but just in case you don't have the right cable, don't allow the grounds to meet.
I might be wrong (or over cautious), but that's how I've got it worked out in my head.
al
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al
Meade 80mm APO
Celestron 6" SCT
CGE, GM-8, & CG-5 GT
ST-2000xcm, DSI Pro II, DSI Pro
( www.alberts-astro.com/astro )
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cdndob
professor emeritus
Reged: 07/28/06
Posts: 658
Loc: The Great White North
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Frank,
While two batteries might be better I'd start off with one good sized deep cycle battery. I've been using a 115ah marine deep cycle bettery since last year to power my EQ6, 3 dew heaters, DSLR battery charger, GPS on USB power, full sized laptop via a AC power inverter and a guide camera on all nighters without any problems. Never had an issue with ground loops so I can't comment on what the issues are with that.
Also, I agree with what others have posted, a 30amp draw seems far to high for the equipment you've listed.
Steve
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Franky
member
Reged: 03/11/09
Posts: 49
Loc: Europe, Slovakia
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Thank you guys for great help.
So I've ordered Varta (brand of Johnson Controls in EU) 90 Ah AGM battery. I'll see what happens and if any problems occur, I'll by one more battery. This unit cost 235 €, and for less sensitive equipment I might buy Exide AGM 95 Ah for 113 €.
BTW, as for the AGM vs. GEL batteries topic. I found out that AGMs can go into deeper discharges, handle temperatures below 0°C better and can be charged using conventional car battery charger at higher voltages, and thus faster. Therefore I've chosen AGM technology.
Clear skies,
Frank.
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Celestron C14 on Mountain Instruments MI-250
Meade 5000 ED APO 80mm on Celestron CG4
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stevecoe
"Astronomical Tourist"
Reged: 04/24/04
Posts: 2648
Loc: Arizona, USA
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I taught electronics at DeVry Institute in Phoenix for 26 years. I can promise you that you are not pulling 30 amps from a conventional battery with the size cables that come with a modern telescope. More like 5 Amps total, except when slewing to another target, then maybe 7 to 10 amps for a short while.
I think you have made a good decision;
Steve Coe
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TeleVue 102 refractor on CGEM mount
10 inch f/4.7 Newtonian
Author "Deep Sky Observing" Springer-Verlag
Author "Nebulae and How to Observe Them" Springer
Canon Xt astrocamera with Hutech modification
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Gregk
Pooh-Bah
Reged: 11/19/06
Posts: 1453
Loc: Gilbert Arizona
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I powered my Celestron ASGT Mount and laptop IBM T40 (screen turned down to minimum for 4.5 hours using a Celestron Power tank 17 amp hours..Mount draw 2 amps non slewing Laptop 2.5 amps with led screen down low.....
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www.azspaceblog.com/
Orion Star Shoot Pro OSC
Oiron Star Shoot II OSC
Celestron Cg-5 ASGT mount
Celestron ED80 Piggy back with william Optics 66mm APO
Celestron 6" SCT Piggy Back with william Optics 66mm APO
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blueman
Vendor Blue Sky Accessories
Reged: 07/20/07
Posts: 1433
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I found that Marine Deep Cycle Batteries are the best way to provide all night power for imaging. You can get a 115-140 amp hr battery for $70-90 and they will run things for many hours. I have a 115 amp and a 140 amp. I use the smaller for the mount, focuser and GPS, then the large one for the Laptop and camera. This works pretty well and I can run 2-3 nights without recharging. I do recharge every day with my motorhome generator though, because I want to maintain the charge and not have low voltage at the end of the night.
Blueman
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14.5" Starmaster with ServoCat and Argo Navis
AT 8" RC
TV NP101 f/5.4 APO Telvue .8 Focal Reducer
WO 80mm f/6 APO Televue .8 focal reducer
SBig ST2000xm with CFW-9 filter wheel
Astrodon Gen2 filters RGBL
Baader HA,O-III, H-Beta, S-II Filters
Losmandy G-11 Gemini Auto-guided
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johnnyha
Pooh-Bah
Reged: 11/12/06
Posts: 1137
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Great battery, AGM is the way to go, it will last you a decade and more. And try the CTEK 3300 charger if you're looking for a great charger.
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Johnny
Spicewood, TX
Sherman Oaks, CA
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