17 replies to this topic

[roger94]

Is it possible to use a car battery instead of an expencive powertank? If yes, how?

[Vega]

Yes, I've used one on my EQ6 before by getting crocodile clip > cigarette lighter adaptor from maplins. I also got a 4 point cigarette lighter adaptor to add dew heaters and any other 12v appliances. For the mount I used a cigarette lighter to EQ6 power cable from astronomiser. A word of warning though, car batteries are not deep cycle batteries (they are designed to crank a car from cold rather than prolonged 12v of power). I often found my EQ6 struggling when slewing in both axis after a couple hours use due to the drop in battery juice.

Matt

[red dwalf]

you would be better off with a leasure battery, i.e. the ones for caravans and alike, you can pick up 40 amp versions for about the £40 mark, 40 amps should give you 20 hours service at 2 amp per hour

[roger94]

Thanks for the answers:)

What about a jump starter- battery?

[red dwalf]

there not bad, i think the batteries on these are in between the two. hold charge better than a car battery but not as good as a leasure battery

[Merlin66]

I've been using 20Ah gell cell batteries for the last few years. With a good electronic charger they seem to last forever. One for the scope and one for the "extras"
Pays for itself very quickly.

[ncjunk]

Gotta say any deep cycle battery (marine battery for instance) would be the best choice. A lot of those power tanks are only 17Ah which won´t last too long if you have a lot of things connected.
Also I understand that some Batteries tend to last longer if you don´t fully discharge them, therefore if you take them to 50% of charge and then recharge it will last longer than if you are taking it to 15% of charge and recharging.

Having said all of that I am using a cheap jump starter battery (with the leads and the lights) and it looks like the power tanks you can buy in other places. It is 17Ah and I am using it to power the cameras and the filter wheel.

I will get a deep cycle one when I have the money....and a solar charger...

Neil C

p.s. and in answer to the inital question a car battery is usable but will last less time :-

A car's battery is designed to provide a very large amount of current for a short period of time. This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs, so a car battery may go through its entire life without ever being drained more than 20 percent of its total capacity. Used in this way, a car battery can last a number of years. To achieve a large amount of current, a car battery uses thin plates in order to increase its surface area.

A deep cycle battery is designed to provide a steady amount of current over a long period of time. A deep cycle battery can provide a surge when needed, but nothing like the surge a car battery can. A deep cycle battery is also designed to be deeply discharged over and over again (something that would ruin a car battery very quickly). To accomplish this, a deep cycle battery uses thicker plates.

[roger94]

Thank you guys!

I don't quiet see how to hook up a telescope to a + and a - pole:o
Do you need som sort of adapter?
And how can I charge it?

Sorry for beeing such a noob at this :/

[Vega]

One of these crocodile clip cables will sort the battery end (cheaper from here or ebay though)

then get one of these for the telescope mount.

I also got one of these so I can run dew controllers, camera etc off the battery too

I use a 4.8watt solar panel, 12v regulator and marine leisure battery. Works a treat

Matt

[Milamber]

Any reason why a charger cannot be permanently connected to the battery in use? One would then be using the battery as a giant smoothing capacitor and also it would be on charge all the time - rather like a car battery?

Arthur

[Merlin66]

If you have the correct type of charger this can ( and is) done.
It really needs to be an electronic three stage charger which modulates the charging current and trickle charges without cooking the battery.
We use them all the time on our battery operated semi-mobile equipment.

Guys,
just remember those marine batteries etc are pretty heavy to lug around... you'll soon get fed up with the weight. A couple of gel cell can do the same job, better.

[brianb]

Quote

Any reason why a charger cannot be permanently connected to the battery in use? One would then be using the battery as a giant smoothing capacitor

True, but
(1) your equipment is liable to be wrecked my massive surges which have been known to come down the mains lines

(2) not having a direct connection to lethal voltage AC is IMHO a Good Idea ™ when working outside in the dark dampness.

When you're making up a wiring harness for your battery, try to make the polarity idiotproof - most scopes have no protection against reverse polarity connection, their electronics will be instantly destroyed if you get it wrong. Colour coded croc clips are NOT enough as you will not be able to see the colours when working in the dark by the light of a red torch.

Also be very careful to make it as difficult as possible to short the terminals accidentally, a 12V high current car battery is quite capable of melting a tungsen steel screwdriver blade.

[Psychobilly]

In the OBS I use a 13.8V 20A DC supply which connects to a 110AH Lesiure battery and then run everything of the battery ... Saved me a few times last winter when there were  Short  power cuts and brown outs..

Every few weeks I partially discharge the battery by runnnig the gear for an hour or so without the DC supply switched on ...

Peter...

[Milamber]

brianb said:

True, but
(1) your equipment is liable to be wrecked my massive surges which have been known to come down the mains lines

(2) not having a direct connection to lethal voltage AC is IMHO a Good Idea ™ when working outside in the dark dampness.

Hmm.

1) Hence the "giant smoothing capacitor" that the battery will become, and that also assuming the mains can get to it - see next

2) How will there be a "direct connection" to the mains when the battery charger is supplying 13.8v DC through a transformer?


Arthur

[brianb]

Quote

How will there be a "direct connection" to the mains when the battery charger is supplying 13.8v DC through a transformer?

This depends entirely on how the transformer is wired, how the earth is arranged etc. Lots of cheap equipment most certainly does have a direct connection on at least one of the terminals. Spikes can and do get through.

[Highflight]

Wickes  – Tools, Ladders & Storage – Motoring – Motor Accessories – 12V Power Pack and Compressor  

Hope this helps.

Chris.

[Highflight]

Highflight said:

Wickes *–*Tools, Ladders & Storage*–*Motoring*–*Motor Accessories*–*12V Power Pack and Compressor

Hope this helps.

Chris.

Oops!  Don't bother. Checked this morning and they have sold out. Sorry.

[roger94]

Thank you for all the replies. I bought a Celestron C8 NGT yesterday and I got a really good price at the 17ah powertank so I bought it:p I'm very pleased with my new scope and the powertank never seems to go empty!