Using a car battery for a power supply?

[Monki]

I would like to start using an external power source rather then batteries in my celestron. I know you can get branded power units as such...but i guess the price puts me off when i know i could probably pay half and get a car battery instead.

I just wondered if other people did this? Would i just need the right 'jack' for my telescope and an inline fuse?

Thanks in advance

Sent from a Galaxy S 2 far away.

[StevieDvd]

Rather than trying to condense an answer here if you do a search of the forum for 'leisure battery' you'll find a wealth of info about prices, connections and even diy boxes to tidy up the battery setup.

A search for 'car battery' would probably show far less.

[SaraG]

Until you go to drive home... then the car won't start.

[Tinker1947]

A redundant 12v power supply from old PC scanner's, printers ect, i use a Netgear 12v 5amp from a 16 way switch, extended the 12v cable so the mains side stays in the kitchen with the 12 cable only getting dew'd up, there are these which i have, not got the larg'ish car battery yet.

Astronomiser - Automated Astronomy and AstroImaging Solutions

[Bizibilder]

Car batteries are designed for one big oomph! to get the car started and then for them to be recharged. Leisure batteries, on the other hand, are designed for a constant, slow current delivery over a period of time (for example running the lights in a boat or caravan all evening).

Leisure batteries are initially more expensive than car batteries (and you will need a good charger/conditioner) but they will last for years if looked after and will work out cheaper in the long run.

Their capacity is given in Amp-hours (Ah). A 100Ah battery can provide 1amp for 100 hours or four amps for 25 hours. But (there is always a but!) you should only run your battery down for around half its stated capacity.

You can add up all the bits you run to see what your battery will do: In my case I have:

Mount 1amp (when tracking)

Lappy 3.5 amps

Dew heater 2 amps (when in use)

Total either 4.5 amps or 6.5 amps

So my 75 Ah battery will cope with somewhere between six and eight hours use before I have to recharge it. More than enough for a nights work. (The lappy is a real current guzzler! Without it I can run for 25-30 hours if i needed to).

[faulksy]

i use a 70 a/h 12v car battery of a newish car from the scrap yard only cost a £10. its big enough to power my scope all my heaters and a 12v hair dryer in need be, and never drops below 12v even when used for 5 hours +

[Monki]

That would explain why i didn't get much info when i searched for 'car battery' hehe...

So they are useable, but a leisure battery is preffered? I wouldn't be running anything but my telescope for now and judging from how long my 8 AA batteries have lasted i think if i can get a car battery for cheap like stated above, it might be worth it. I would of course like something neat with a built in red light but since i've been renting a house my funds are very limited ...i guess i'll weigh up the pros n cons first though.

I remember using a car battery to charge my 2000nicad and 3000nimh batteries when i used to race r/c cars It just seemed like it could work for as a telescope power supply too.

Hmmm...unintentional long post.

To save asking about something possibly discussed many times before i will google the rest guys and ask my sparky friend too, thankyou all for the heads up

Edit: and cheers bizibilder for the informative post!

Sent from a Galaxy S 2 far away.

[Bizibilder]

You don't say what mount you have - make sure its not 6volt before you spend your pennies on a 12v battery! The EQ3-2 and EQ5 with motor drives (NOT synscan/syntrek) are certainly only 6v.

[Monki]

Oops, it's just the goto mount that came with my celestron lcm. It is 12v from what i've read

Sent from a Galaxy S 2 far away.

[brantuk]

Most of the commercial mounts are 12V but it's amp hours you want (ah) that last longer on those cold nights. Maplins do some reasonable 17ah power tanks/car starter packs for £35-£55 that are as good as the £100 plus badged power tanks.

Better still - a leisure battery as mentioned above will cost around £80 for 85ah (plus a bit more for a charger). Much better proposition - try local caravan sales stores