Telescope battery which one?

[icytailmark (Mark)]

hi guys im wondering if anyone recommend what battery to buy for a Losmandy G11 Mount,a pentium 4 laptop,a fan system on the Celestron C11 scope and maybe dew heaters. This will be a astrophotography setup in my backyard. However it wont be in a dome or anything i will be dragging the equipment out each night.

[DavidTrap (David)]

You'll be surprised just how much current that all draws. Are you planning to run the laptop from 12V battery? Are you wanting to use an inverter and the standard 240V plugpack, or a 12V adaptor - the former will consume more power as there are losses with each power conversion.

Dew heaters consume also more than you expect as well.

I'd suggest a 50amp/hr AGM battery (ideally 100amp/hr). Expensive and heavy, but the AGM batteries are sealed, so if you transport it to a distant site, they won't leak acid in your car. You can also discharge them further than a standard deep cycle battery. (A standard deep cycle battery shouldn't be discharged beyond 50% of its stated capacity to prevent early failure - so a 50amp/hr battery is really only a 25amp/hr. The AGM batteries can be discharged much further.)

DT

Cheers
DT

[icytailmark (Mark)]

yeah everything will be 12V thru an invertor but i gotta work out how many watts everything uses.

[mithrandir (Andrew)]

Originally Posted by icytailmark

yeah everything will be 12V thru an invertor but i gotta work out how many watts everything uses.

From your list of parts you want to drive the only one that might need an inverter is the laptop. Everything else will run on 12V.

I have a Targus inverter - comes with more plugs for different voltages than I have laptops - which runs off mains or 12V. Not cheap but handy.

At home I take a 20A lab power supply with a 20 meter extension lead out to where I observe.

Away I have a 130AH dual battery in the Prado.

Andrew

[Geoff45 (Geoff)]

If you are doing it in the backyard, I would suggest buying a laboratory power supply- from $69.95-$199 at Jaycar. I bought one from Dick Smith a few years back, but I can't find it on their site now. It plugs into the mains and produces 13.8v regulated DC, which is good for the G11. So get a looong extension cord and a power board. Computer and lab power supply run off the power board, other stuff (scope, dew heaters) off the DC supply.

I only use batteries when there is no nearby AC.
Geoff

[Barrykgerdes]

Hi
Trevor runs that and more from a 5A 13.8 v regulated supply that I built out of a DS kit (back in the days when it was still DS). Don't muck around with batteries unless you have to. They are expensive and always go flat just when they are needed most.

The standard load:
1 G11 with Gemini
1 set dew heaters (Kendrick type)
2 computers (laptops)
1 camera
1 guider
1 fan on the 8" scope

Barry

[icytailmark (Mark)]

i just worked out my power requirements. To run all the stuff i mentioned it will be around 20 amp/h. However i wont need to run the dew heaters all the time.

[icytailmark (Mark)]

thanks for the input guys.

[OzRob (Rob)]

Is there a reason why you don't run it off the mains? I do it this way but use a UPS. It will be cheaper to buy the required transformer(s) than to buy a good battery.

[hotspur (Chris)]

SLA's are the way to go if you travel along way,and have stuff in car.

If your in your back yard SCA (super cheap auto)have cheap car batteries for around $59,I recently bought one for my boys car they learn to drive in the paddock in,and was suprised at what good value it was,I borrowed it to drive the SS2K,and by golly it had more zip than the crappy 5 year old SLA I bought 2nd hand!

I have a observatory set up so a couple of these cheap car batteries will do very well for goto and dew zappers.

I notice some of the guys that do travel still have these batteries and have special containers for batteries,they come from SCA and about $25 well worth it,really always hand to have a good second car battery.

Cheers Chris

[Brundah1 (David)]

There is a good reason I prefer 13.8V regulated power supplies over batteries whenever 240VAC is available. UPS is an alternative, but again you are dependent on the small battery being in good condition!

Car batteries and OEM long scope leads invariably result in significant voltage drop at the scope end under load. I pulled my new CPC8 long lead (10M) apart and found the + line hanging by 2 strands at the dob of solder - it struggled to get to 10V under load!

I prefer to make my own leads using 3mm twin auto wire, Hela 4914 plugs and 4916 sockets at the PSU or battery end. Make sure you use the correct sized center contact connectors at the scope end - I have seen numerous 2.1mm center contacts - when some scopes require 1.8mm - check your scope specs! An in-line fuse should also be used.

My leads even at 10M vastly reduce voltage drop at the scope under load when a battery source is used, but you are still dependent on the health of your battery and its capacity limits.

BTW Jcar Merit plugs are cheaper than Hela 4914 and are similar quality, Jcar Merit sockets are not Hela quality!

Most 4WDers use Hela plug / sockets for their car fridge, or the small Anderson polarised plugs for higher current load. Hela and Anderson plugs available from Ashdowns and caravan suppliers.

Cigarette plugs just cannot be trusted to maintain good contact.

I now use Manson SPA-8230 13.8V 23A regulated & O/V protected power supplies available from Andrews (were $79 now $99). I discussed these at length with Lee before buying them, he sells lots to hamers, with great reliability reports - few returns. Output from this PSU at 12A is rock solid, no off-on over swing. Should be all Astrophotography rigs require.

No commercial interest yada yada.