power supply

Sgtfretsurfer · #1 05-08-2007, 05:44 PM

Im going to be traveling to a new dark sky location that isnt powered, and i need to be able to use my laptop. So iv had an idea.

iv been running my mount off a 900 amp car jump starter. http://www.rapserv.com.au/category1050_1.htm
Its the yellow one.

Im thinking of buying a double adapter for the 12v cigarette lighter type plug, and having one going from my mount to the power source, and another going from the power source to an inverter, such as this one
http://www.dse.com.au/cgi-bin/dse.st...uct/View/M5150
or this one
http://www.dse.com.au/cgi-bin/dse.st...uct/View/M5300
depending on what my laptop requires (electronics were never my forte')

Iv got a couple of questions for all you electronic wizards out there.
Firstly, will it work??
Which inverter would be most appropriate?
But mainly, will the 900 amp jump starter have enough juice to power a laptop and a mount all night??
If not, any other suggestions?

Any thoughts appreciated
Cheers
Matt

ballaratdragons (Ken) · #2 05-08-2007, 05:47 PM

Matt,

what about one of those tiny quiet generators they make these days. They can power a small caravan with one, so I'm sure it will run a mount and a lappy

Just an idea

Sgtfretsurfer · #3 05-08-2007, 05:51 PM

good idea, u can get them relatively cheap too. But, iv heard that cheap ones produce "dirty" electricity... whatever that means, something about wavering voltages i think..
If i were to do it the way i described, it would be really really cheap. under 100 bucks i think.
But im not sure if itll work, or if it does, how long itll work for lol

ballaratdragons (Ken) · #4 05-08-2007, 06:03 PM

Quote:

Originally Posted by Sgtfretsurfer

good idea, u can get them relatively cheap too. But, iv heard that cheap ones produce "dirty" electricity... whatever that means, something about wavering voltages i think..
If i were to do it the way i described, it would be really really cheap. under 100 bucks i think.
But im not sure if itll work, or if it does, how long itll work for lol

Apparently (i've been told) that the new flashy fan-dangled new mini generators have a fluctuation by-pass or some such name. A device that controls the flow of power out to keep it even.

Sgtfretsurfer · #5 05-08-2007, 06:30 PM

oh ok, that gives me peace of mind. Its nice to know i wouldnt be plugging 4k worth of gear into something thats going to go ZAP! lol

montewilson (Monte) · #6 06-08-2007, 07:50 AM

I ran my set-up on an el cheapo generator for over a year and it worked fine. Switch mode power supplies are quite forgiving.

The unit in question was from Repco and I believe it cost less than $200. I didn't buy it so I can't tell you for sure. Anyway it worked fine running my Tak mount an STL-11000m a desktop computer a computer monitor and two small CRT televisions. It was rated to 1000w peak and could run all that stuff. It was on the limit but did it, so a laptop and mount ect is nothing.

Many gens have a 12v output which is an option for you to charge your batteries during the day and have quiet at night.

I have stepped up to a 2kW unit from Honda which was not cheap but has true inverter sine wave output. I got sick of messing around with 2 stroke oil etc the Honda is four stroke and starts more easily.

Sgtfretsurfer · #7 06-08-2007, 01:49 PM

Interesting. Well what about something like this
http://www.dealsdirect.com.au/p/gene...ed-eagle-blue/

Its pretty cheap, but id wanna be sure that it wont spike and blow the gear or something. Having a generator could be really handy as well, i could power a camp site of it as well as just a laptop and a mount, for not too much more money

Although buying an inverter for 50 bucks would be a pretty cheap way of having power too. Any thoughts on if it would work?

montewilson (Monte) · #8 06-08-2007, 09:03 PM

That Genset is the exact same unit I had before. It works OK but mixing the fuel and oil is a bit of a hassle.

I have never had any spikes or shocks in a year of use (or about 30 nights). An inverter will give better power than a cheap gen but is limited by the battery behind it. Its a compromise you have to decide on.

seeker372011 (Narayan) · #9 06-08-2007, 09:44 PM

a 900 amp car jump starter will not run your laptop for very long at all. It will power your mount all night but I'd give it just over hour or so with a laptop..based on personal experience with a 600amp jump starter which drained in under an hour

You need a 40 amp hour gel battery (or larger capacity, if you want to spend the extra- and also deal with the extra weight, these things get very heavy at this sort of rating). I can go all night with my 40 amp hour battery

asterisk (Geoff) · #10 08-08-2007, 10:25 AM

Hello Matt

Cheaper generators will supply 240v (often ranging between 230 to 250) but the cycle will fluctuate around 50Hz. Usually the more expensive the generator, the more stable the power cycle and the quieter it gets. However, as long as you keep fuel up to it, a generator will provide more power than you will need.

A quieter alternative is a deep cycle battery. The 600 amp battery you mention is usually only about 17 amp - it can deliver 600 for a very brief period, but then loses power quickly after that.

240v inverters are notoriously inefficient - that is, a lot of power is consumed by the inverter to deliver 240v from 12v. A more efficient alternative is a Notebook power supply delivering 15 through 24v at a max of 5 amps. (Jaycar have these)

I am using 2 x 30 amp deep cycle batteries connected through 2 switches/fuses to 4 cigarette lighter sockets housed in a cheap Bunnings tool box.

Deep cycle batteries are designed to run for longer periods without suffering the internal damage that car-type batteries can suffer - car batteries are designed to provide a quick burst of power for starting and are then re-charged by the alternator. Using a car-type battery for long periods without immediate recharging will quickly damage the battery and reduce it's effectiveness.

A laptop will use about 3 amps; dew zappers about 2 amps: total 5 amps. Divide the battery capacity (30 amps) by 5 amps and you can expect to run both for about 5 hours - I know 30/5=6, but total discharge is not recommended - lower the voltage to the lappy so that it is not attempting to recharge it's own battery and you can use a 30amp for longer. Alternatively, calculate your total power use in amps, multiply by the number of hours you expect to use your setup and look for a deep-cycle battery with that amp size.

Good luck

space oddity · #11 11-08-2007, 08:23 PM

SLA batteries are pretty good for keepng their charge. Need a minimum of 40 amp hours, but preferrably much more. Started with a 7 A/H SLA for the ETX, but found it simply did not have enough juice to go more than a couple of hours. I now use a marine grade battery, 75 amp hours. It is rather heavy, but running out of juice is worse. My backup is a 17 A/H booster type for car batteries.17 A/H is just enough to power a scope only for the night. Very important, turn equipment off at the switch before disconnecting the battery- just pulling the plug can give a big power spike, potentially blowing components.

centauri · #12 12-08-2007, 05:44 AM

A couple of things that may help you decide.

I use a Projector brand (Kmart) 12v laptop converter and have for over 12 months and it's brilliant.

You must not discharge your battery below 10.5 volts or it will kill its future performance.(this includes most SLA batteries), I say most, because there are some available that actually like to be discharged but they are WAY expensive.

Deep cycle batteries MUST be charged correctly (14.2vdc to 14.6vdc) for them to be deep cycle, if you don't then they will behave pretty much like a normal car battery.

Normal 12v inverters suck to much juice for what they put out (inefficient). Don't go down this road.

If using a generator, inverter types are way better for sensitive equipment, normal types should really be used for basic stuff like lighting as they can (and most do) have dirty power.

Only charge batteries from a generators 12vdc outlet in an emergency, the 12vdc is VERY dirty as it is normally not filtered and normally only half wave rectified. DO NOT run sensitive stuff from it.

Louwai (Bryan) · #13 12-08-2007, 07:32 AM

Quote:

Originally Posted by Sgtfretsurfer

Im going to be traveling to a new dark sky location that isnt powered, and i need to be able to use my laptop. So iv had an idea.

iv been running my mount off a 900 amp car jump starter. http://www.rapserv.com.au/category1050_1.htm
Its the yellow one.

Im thinking of buying a double adapter for the 12v cigarette lighter type plug, and having one going from my mount to the power source, and another going from the power source to an inverter, such as this one
http://www.dse.com.au/cgi-bin/dse.st...uct/View/M5150
or this one
http://www.dse.com.au/cgi-bin/dse.st...uct/View/M5300
depending on what my laptop requires (electronics were never my forte')

Iv got a couple of questions for all you electronic wizards out there.
Firstly, will it work??
Which inverter would be most appropriate?
But mainly, will the 900 amp jump starter have enough juice to power a laptop and a mount all night??
If not, any other suggestions?

Any thoughts appreciated
Cheers
Matt

Matt, have you thought of just getting extra standard batteries for your lappy. I use a Toshiba Tecra, I have the original battery it came with (4 amp hr) + I also bought an additional 12 amp/hr battery.
When both are fully charged & I use the lappy on my pre-set observing settings, (everything set for maximum battery life) I get a good 6+ hrs of lappy use. The only issue I have is having to shutdown & re-boot when changing batteries.
I mainly use powered sites so it's not a big issue for me, but I'm thinking of getting another standby battery for near future unpowered site visits.

Bryan

g__day (Matthew) · #14 12-08-2007, 10:40 AM

You could always run your generator into a Un-Interruptible Power Supply - UPS, as these tend to have pretty decent line filters and conditioners built in.

centauri · #15 12-08-2007, 03:44 PM

Quote:

Originally Posted by g__day

You could always run your generator into a Un-Interruptible Power Supply - UPS, as these tend to have pretty decent line filters and conditioners built in.

The only trouble with this is that a lot of cheaper UPS units use a stepped output and not true sinusiodal which as a whole is inefficient.

In fact mostly only UPS units that are classed as inline and not standby are true sinusoidal. And then there is the power factor to account for as well.

And something else to bear in mind for generators, inverters and UPS's is that VA does not equal Watts, as a very rough idea take the KVA rating and multiply by 0.7 for watts and then you can work out the max current.
As I said very rough guide so don't flame me for inaccuracies, I know there is a lot more to it than that.