Scope and computer power

[telecasterguru]

I used my EQ6 for the first time on battery on Saturday. I also had my computer (for guiding) hooked up to the battery as well. It is an 18AH battery and with the scope and computer it lasted about 2 and a half hours.
I didn't let it totally run down but it must have been close.
My computer is a brand new ASUS M51V (great computer)
What is the best way to get more power?
Can I hook up two batteries together or should I get a bigger battery?
Any suggestions?
I thought an 18AH battery would have lasted a lot longer.
Thanks
Frank

[sheeny]

G'Day Frank,

I used to have 3 batteries: a 7AH Celestron Power Tank to run the scope, a 24AH jump starter pack to run the dew heaters, and a 38AH jump starter pack to run the laptop.

The computer will be by far the heaviest power user.

After 12 months, my 38AH jump starter pack died... I had simply cycled it too deep too often.

If you want to run your computer from 12V I suggest you get the biggest deep cycle battery you can afford. Don't bother with jump starter packs - they are the wrong type of battery. Deep cycle is what you need.

FYI I haven't replaced the battery for my lappy as I now have the scope setup in the POD, so I put power on to run the lappy.

Al

[Barrykgerdes]

I have given up on batteries for serious work. I got one of the "quiet generator sets and a 50 metre cord and a multi way power block. It runs all night on a tank of petrol and you can't hear it at all at 50 metres. I can have computers and telescopes etc without worrying if the battery will hold out. It even runs the bed warmer in the caravan!

Baz;)

[Glenhuon]

I ended up going with a 1000w gen set too, although it hasn't had a serious trial yet. With 2 lappies, Mount and dew heaters, a 33Ah battery just didn't last long enough and was a pain to move around and keep up to charge. Oh yea, runs the caravan 'fridge too. :)

Bill

[Fox]

Hi Frank

I'm not surprised, an EQ6 it quite a decent mount and will sap the power, so 18 AH is barely enough to drive that, plus if you add dew control then a laptop, it'll run down in no time as you discovered. Petrol generator - wow! that's really serious stuff and not for me.

So I guess you options are limited, you just need more AH. An 18AH SLA is about 6kg, 24AH is around 9kg and 38AH is about 14kg. I steered clear of those power tanks, I decided to go for a quality Yuasa SLA and look after it.

My power needs are much more meagre than yours, but I neatly store my 18AH in one of those very tough, but soft esky cooler packs and that makes it super portable IMHO. Do you think 38AH will do for what you need for an observing session - weight and dimensions are on the edge of portability.

Here's one idea, if you can park close to your observing site, how about leaving the 38AH battery in the boot and just running a long line (with insulated terminal ends!) to where you need it? If that idea works, then you could even go for a 65AH SLA (about 23kg) and leave that in the boot... Fox!

[telecasterguru]

Thanks for all the tips.
I am not sure which way to go except to say it will be more AHs.
The generator sounds perfect but not sure how it would work at a star party when there are lots of people around.
I was talking to my brother today who is into motorbikes and he said to get a deep cycle marine battery.
How much do the generators weigh compared to the batteries?
Frank

[MrB]

Any battery that weighs as much as a generator should be plenty 'nuff.

[h0ughy]

ok i now has 3 x 105 Ah batteries, 2 x 17 ah and 2 x 34 ah oh and i have a 850 watt genny as well, a couple of solar panels and a real love for 240v when i can get it. SPSP only use batteries, IISAC bit of battery and genny, Qld astrofest full 240V

[Brundah1]

Does that mean I can bring my 8KVA Cromelin electric blanket and microwave to Qld Astrofest this year?

Simple math came up with this no 240v senario:
2 x 40Ah AGM batteries 13Kgs each.
Enough for two nights Obs one one battery - scope and heaters.
Other battery should do the small lappy for two nights.
13Kgs each is enough to carry 100M if you have to.
My battery guru says AGM is the best deep cycle / life cycle battery,
until high capacity Lithium Ion prices fall???

Cheers,
David

[marki]

I also use a 1kV generator. It weighs about a third of a big deep cycle battery and is only the size of a shoe box. Exhaust noise is 52dB (bugger all) and you can hold a normal conversation standing right next to the exhaust and when running my laptop, heaters, camera's, mounts etc it just idles away giving 8 hours on a single tank of juice. They cost a little more (if you want the ones with clean enough power to run a laptop/PC) but are far better then any battery option I could find. You can also use it to power a small fridge or kettle or both whilst taking your pics :D. Oh did I mention how quiet they are......

Mark

[Kal]

I recently bought a 12V 10AH Li-ion battery and charger off ebay shipped for $58.

Theoretically it will give the same performance as a 20AH Lead acid battery, since you can only discharge these to about 50% if you don't want to kill it (unless it is a marine deep cycle lead acid battery). The Li-ion batter is also about one fifth the size and weight of a lead acid battery.

I haven't tested it yet, but with battery technology being developed there are some good options out there particularly if you look in the RC world for batteries - the latest LiFePO4 batteries are good for over 2000 recharge cycles for example.

[DavidTrap]

Just a word of warning to anyone planning to use Li-ion or Li-Po batteries.

Please use the correct charger. Lithium batteries are charged with a constant voltage and diminishing current, rather than NiCads & NiMhs that are charged with constant current, but rising voltage (until a delta peak is reached to terminate the charge). If you charge a Lithium battery incorrectly it will explode. Larger batteries will explode with more vigor and have been responsible for burning down houses. If you want to see more, google Lipo fires and I'm sure you'll find some impressive videos.

I use LiPo batteries in RC planes, and have seen examples of them self-destructing when abused. If treated with respect they are great batteries - the power delivery is awesome (42V at 100amps = 4.2kW to lift an RC helicopter weighing ~3-4kg = breath-taking performance)

Just my two cents worth,

Regards
David T

[cfranks]

What brand/model generator Mark? I use 4x 6v 75AH batts in series/parallel and they last one night. They weigh 56Kg too so a gen. is interesting!
Charles

[marki]

G'day Charles, 56kg :eyepop:. This is the one its a great little genset and only weighs about 15kg with fuel and oil. Pretty small as well and has the facility to charge 12V batteries as well as being connected in series to another generator of the same type to give you 2kV output. They cost a bit but are worth the extra. Mine came with a 5 year warranty, try get that with a battery.

http://www.generatorplace.com.au/index.php?option=com_content&view=article&id=12&Itemid=9

Mark

[cfranks]

Thanks Mark, I will look into one.
Charles

[Barrykgerdes]

I too believe in these portable generator sets. I did not get the same brand as Mark but I bought a cheaper one 2.5KVA ($600) on ebay. They are very quiet particularly if you cover them. I keep it about 15 metres from the caravan and during the day I need to go and look at it to make sure it is still going. Mine has a remote start and stop.

I use it at the House at Wiruna to power the caravan, telescope, computers etc. Runs 12hrs on a tank of gas. The remote start is a great feature.

Barry

[lookus]

i have noticed all these people using 100ah batteries and only getting one night. i don't get it.

i have a 75ah thumper battery pack . i run an eq6, 4x dew heaters(one for an 8" mak) 1 ccd and 1 dslr camera, i laptop(13"screen)1x 7port usb hub( with every port in use), 1x red led light, and if i want to run the battery down to a 40% capacity ( which is fairly low but ok for an AGM battery, i will get 2 nights use.( ie 6-7 hrs p/night) I usually recharge after 1 night with solar panels. i runs without a hitch.

[bmitchell82]

its a simple formula really... on your battery packs for the laptops look at the box that is always inline, it will tell you a input and output for the computer.
the output is MAX OUTPUT that means that the laptop will never go above that if it does it would fry it (and that just wouldn't happen).

the EQ6 is max 2amp draw. I know from experience that the EQ6 and Eeepc of mine draws about 1.2 amp when taking images. so if i wanted to keep the Deep cycle battery above 40 percent, then its a easy conversion

2 nights at 10 hours a night (for setup and running times) my eeepc draws max of 2 amps, my eq6 draws a max of 2 amps so that is 4 amps max. 4 times 20 equals 80 amps. then its a conversion of 0.4*battery size + 80a-h = battery size.

that is the 40%+running costs in amps per hour = the size of the battery. try a few numbers and you will get the answer.

in all realistic terms though you wouldn't need this amount of power because there is no way you would be using 4 amps per hour not even if you tried.! more like 1.5amps per hour...

A small word of warning though if you are using PWM dew heaters be sure to run 2 separate batteries. some mounts don't like the power fluctuations!

[mithrandir]

~3.5A for the thinkpad. ~3A for the QHY8, ~2A for the Atik, ~2A for the mount so about 10.5A

135/10.5*0.6 is about 8 hours

And that is without dew heaters.

[bmitchell82]

and now everybody understands why some of us use the EEEpc.! small footprint on power!

Though ide be testing your rig out with everything running youll find that itll be less than you think!