12 volt power supplies

[trufflehunter]

Hi folks! I'm looking around for one of those 12v rechargeable power pack thingies. Just pulled the latest Supercheap Auto cattle-dog out of the mail box and they've got a couple of models on sale: a 12AH red job and a 17AH yellow one. I figure the 12AH model is all I'd really need to run an LX90, and at the "special" price of $38 I'm sorely tempted. Here's a link to those items on their web site:

http://www.supercheapauto.com/www/index.cfm?itemid=34

Any thoughts? Any better suggestions? There's a beer in it for ya! :cheers:

vielen dank and thanks heaps too...

[Striker]

there a good price...I have the 24amp but its much more expensive.....you could get 3 of these for the price I paid for my 24amp.....

[trufflehunter]

Thanks guys! Just another quickie which may sound really dumb: can I also use it to power a laptop? (ducks)

It's a Compaq Presario, but its AC adaptor is rated at 18V (ducks lower)

Please note: I am electronically dyslexic.

[RAJAH235]

Truf, you can get a dedicated laptop power supply from Jaycar.
Part# MP-3462. Variable volts out @ up to 3 Amps. My old cat. price is $89.50. but may have changed since 04.
(www.jaycar.com.au) in power supply section.
HTH. :D L.

[Striker]

definetly dont mix 12 volt with 18 volt....amps dont mean much... more amps just means it will last longer....but different voltage means...Booooooom.

[Astro_Guy]

The Gel cells in most field batteries shouldn't be drained below 40-50% of their capacity. This means that a 17Ah battery really has a useable capactity of about 9Ah. Assuming that the LX90 pulls 1 AMP, that would give you 9 hours of use before the battery should be recharged. I think the LX90 pulls about 750mA, which would extend your time to 12 hours.

[[1ponders]]

I've used a 15A jumpstarter pack to power both my LX200 and my laptop (with an adapter) but not at the same time. It ran both with no problems, the laptop for over 7 hours taking avies and processing them.

[RAJAH235]

TO ALL CONCERNED. The item stated is a converter. It is designed to put out variable voltages ABOVE 12 volts input to between 15 volts & 24 volts, @ up to 3 AMPS.
TRUF, please look in Jaycar cat. as I suggested. This is the cheapest and best way to run your comp. :D L.
ps. Tony?????

[Astro_Guy]

I should have pointed out that it is possible to draw all 17 Ah from a 17Ah gel cell battery; however, this will significantly reduce the battery life. One thing I have noticed is that the Auto jump start batteries in the 17Ah class usually have a starting current rating of 500 amps, whereas the Celestron 17Ah Power tank (sold elsewhere under a variety of names) has a starting current rating of only 250 amps. This would imply that the auto batteries have thinner plates and will wear out sooner. Personally I've been using one of the 17Ah auto batteries for about three years. Unfortunately I only get to use it about six nights per year, so that doesn't represent much of a field test. OTOH, I have used it to jump start about a half dozen cars.

[RAJAH235]

If you have a 100 a/h battery, you can draw 1 amp for approx. 100 hrs. but you will NOT be able to draw 100 amps for 1 hr. Not capable! :D L.

[iceman]

I'm interested in something to run the laptop in the field too, I don't need to worry about something for my non-motorised scope :)

So the Jaycar thing is the way to go?

[Starkler]

Yep amp hour ratings are usually based on a 20 hour discharge, ie 100a/h = 5 amps for 20 hours.

[trufflehunter]

Thanks, guys, for all of your input.

I think I'll forget about powering the laptop for the time being, because it looks like I'd have to run two power sources. It'll run for about 3hrs from its own internal battery anyhow. I'll just concentrate on running the scope.

Rajah, was your comment about the item being a CONVERTER, referring to the Jaycar item for running the laptop? Not a reference to the Supercheap Auto item? Would you give me the 'go-ahead' to grab the Supercheap Auto 12AH power source? Or is it a resounding "No, Truffo, get something else!" ?

I'm thinking (ignorant of such things as I am, so it makes my brain hurt!) that if the LX90 is nominally rated at drawing (is that the right word?) 1amp, surely that would be at 'maximum slew'. Most of the time it would be drawing (there's that word again) much less than that just driving the scope sidereally. So, here's where my feeble brain pipes in, wouldn't a 12AH source run the scope for many, many hours of 'normal' use?

Anuvver fing... the DC input socket on the autostar control box on my old LXD55 AR6 was 'centre positive'. I believe the LX90/200 is the same. Are the plugs on these portable power supplies centre-positive? Is that a 'standard' thing? Or do I run the risk of unknowingly connecting a 'centre-negative' source to my scope and blowing it to smithereens? eeeeeeeeek!

Cheers

[trufflehunter]

Here's Exhibit A, scanned from the current Supercheap Autos catalogue. My first posting of a pic, here goes...

[Howzat]

I think he was saying that the supercheap thingy has 12v output but your laptop needs 18v input

[trufflehunter]

Thanks Phil. I thought that was the case, but just needed to make sure it wasn't a warning NOT to use the 12v unit for powering the scope.

[rumples riot]

I run the Waeco battery system for both the Lx200 and laptop when I am in the field. These batteries are great but they cost over $400. Surveyors and serious campers use them for their reliabililty. It will run a laptop and LX200 for over nine hours without recharge.

Here is the web site it you are interested. http://www.waeco.com.au/products.asp?id=179&cat=2

Good luck with your selection.

[Astro_Guy]

The old LX200 classics had an ammeter on the control panel. My 10-inch LX200 classic draws just under 1 amp while tracking, and over two amps while slewing at full speed. The LX90 should draw a little less current, and 750mA is an educated guess. You could just use the #607 DC power cord that plugs into the cigarette lighter port in your car. Most car batteris have 70 Ah or more capacity.

[Striker]

What you find is that most people will always suggest to get the biggest battery you can afford..specialy with a goto......yes the 12amp will be fine to run for a while but as the battery gets older and you may start to thinking about running accessories of the same battery....(not recommended) but still possible...then the higher amp's will be their to be used....
look for that price...get the battery pack...its a start and its only $38 you cant loose.

[trufflehunter]

Paul, the Waeco battery looks impressive, but, considering I've just forked out for a new scope, not to mention all the accessories beckoning obscenely (as I type I've just ordered 2 Meade QX eyepieces, the 20mm and the 26mm from Bintel)... it's a bit out of my league at the moment. This is the first time I've seriously considered a power pack and riding the learning curve has been fun! I'll certainly keep the Waeco in mind for the future.

Astro, yep, the cig lighter adaptor would be the way to go when I'm using the scope near the car. Which would be most of the time. I'll definitely look at that option. I just know that there will be times when I'll need to separate the scope and the car!

Tony, that's what I wanted to hear! I can't see myself running much else off the battery and, as you say, at that price I've got nothing to lose. The sale at Supercheap runs all week, so I'll think about it... but probably grab one before the sale finishes!

You guys have been most helpful. Much appreciated!

[Mick]

I use 2 x 7 ah gel batteries one for the heater and one for the lx90, I've had the latest set for two years. They are about the same price as 8 c cells.

[RAJAH235]

Truf, What I said was, that the Jaycar converter will run your laptop at the req'd 18 volts. The power pack from supercheap,? more capacity is better. To check polarity of the plugs, use a digital multimeter. Appx $15. from Jaycar. :D :thumbsup: L.

[trufflehunter]

Thanks Rajah:)
Guess what? I think I've got my head around it all now. I'll repeat it back to you so you can check:<ol>
<li>Don't use a 12v power supply to run a laptop requiring 18v!
<li>Avoid running other accessories from the same power supply as the scope!
<li>A cigarette lighter adaptor is a good thing. It will run the scope for ages without flattening the car battery!
<li>The Supercheap models will be fine, but...
<li>Bigger is Better!</ol>
I think I'll just go for the 12AH model and see how it goes. If I find I need it I might go with the Jayco for the laptop as well down the track.

:thumbsup:
Thanks for all your help!

[RAJAH235]

Truf,
1 = True
2 = True
3 = Suggest you do test run, eg; start car every 4 to 5 hrs.?
4 = True
5 = Very true.
:D L.

[Rohan]

Ok, help me out here, im new to astronomy letalone electrical jargin.

Anyway i've got my LX90 arriving tomorrow, and i've got an orion dew zapper. What do i need to run both out the in field for say up to 15hours???? battery for each one? one chunky battery for both? I have no idea and will take what ever is thrown at me so please help. Thanks

PS. I've got the cigerette lighter plug thingy for both the scope & dew zapper. Will i have to get something rewired or are there "packs" that have these plugs on them?

[Brendan]

Truffle,
found this site may be of some interest to you.

http://www.mapug-astronomy.net/AstroDesigns/MAPUG/PowerBox.htm:confuse2:

[RAJAH235]

Rohan, just saw this question. For 15 hrs field use I suggest a very long extension lead. Just not poss. with battery power.
The starter packs usually have 1 or 2 cig outlets as standard.
HTH. :D L.
ps. Bigger,(more capacity), is better.

[Rohan]

noticed supercheap have a 20% off sale tomorrow. Will prob go get some batteries. If anyone can recommend models for 1) LX90 and 2) for dew zapper that would be great.

[acropolite]

Take care if using a long extension lead. Any resistance in the lead will cause appreciable loss in voltage and electronic equipment doesn't like running on lower than specified voltages. Just 1 ohm of resistance in your extension lead will give 2 volts drop at 1 amp current (approx 15%). (Voltage drop=Resistance x Current) Running your toy for long periods on 10 volts may cause damage to the electronics. Resistance isn't so important at 240 Volts because the same 1 amp load only causes 2 volts drop and as a percentage it is less than 1%

[RAJAH235]

Phil,Sorry. I had my tongue in my cheek when I suggested the looooong ext. lead,(240 volt). Rohan wanted 15 HOURS!!!! of use out of battery's?????Don't know if this was a mis print!!!
You simply can't get that much time/current, out of normal 12/24/45/60 a/h units. The t'scope & dew heater take too much current to run for that long. This has been gone over before. You may/???? get 1 amp for around 100 hrs out of a 100 a/h battery, BUT you will NOT get 100 AMPS for 1 hr. NOT POSSIBLE. :D L.
Rohan, get the 25 a/h or bigger. I think Paul & others use these. Check posts. L.
ps. Have a look at this for general idea.

http://www.nlectc.org/txtfiles/batteryguide/ba-char.htm

[Rodstar]

Guys, it has been most helpful reading this thread. Great minds think alike. I am going out to buy a power pack tomorrow! I'll go the 17 ah pack after what I have read.

At the moment it will only be to power the LX200, but I am planning to attach a dew heater soon, which will need some power too. I never have sessions longer than 5-6 hours, so I think the 17ah version should cover all my needs.

Rodstar

[Rohan]

Thanks guys, your help is much appreciated. Only reason i as after something for 15hr was i plan a few weekends away with the scope and won't be able to charge batteries, hence 3 nights @ 5hrs viewing. Oh well will just have to limit the time or chuck some size C batteries in for emergency's.

Will go to supercheap tomorrow to get a battery, BINTEL knocked me up a device that splits a cigerate plug into 2 so i can run the scope and battery. I'm assuming i only need the one battery if i'm getting 25ah. If lower then go for 2 correct?

Once again thanks.

[RAJAH235]

Rohan, There are lots of things that I can suggest, like solar panels to trickle charge your batteries. Either the "C" size ni-mh or "17 a/h" gelcell. Of course they come at a price. Check the (www.jaycar.com.au), site for info.(POWER Section). A small unit will keep your "C" size peaked for emergency use. You'll also need a battery holder for the "C" size.
Solar panel #zm-9016. 12volt @1.2 watts. $39.95 in my old cataldog.
HTH. :D L.
ps. Just remembered, these are all 12 volt battery's we're talking about, right. So why not simply get a "BATTERY ISOLATOR"(# KA-1782 $49.95, in kit form), for the second battery & charge it via the car, while you drive. Same as the 4wheel/caravanners do!

[Rodstar]

Guys, I bought the Supercheap Auto 17ah power pack today. Turns out the plug into the scope is not the right size. I had to go back out and buy a Dick Smith piece to get a plug the right size....cost another $29. Beware of that hidden expense.

Rodstar

[trufflehunter]

Ouch! Thanks for the warning, Rodstar!

[RAJAH235]

What did you have to buy? DC plug adaptors are about $2.00 ea. L.

[Rohan]

yeah which part was the wrong size. I've already got the 12v adaptor so i'd imagine that would fit, i mean a cigerete lighter is a cigerete lighter right. I went to get one but supercheap had sold out. Oh well not in any real rush.

[xstream]

Rod,
I assume you mean the DC plug that comes with the battery for recharging from car cigarette lighter?
If so just make sure the pin is centre positive otherwise you'll cook the electronics in your scope.