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Go To Power - really need some help please.


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I'm using batteries and fed up of them. Scope is a Celestron Nexstar 4SE. I don't understand electricity if it's not mains or a straightforward battery.

I would like to hear from someone who can confirm that if I use one of these

http://www.maplin.co.uk/3-in-1-portable-jumpstarter-383992

that

a) I won't fry my scope

:) I won't electrocute myself accidentally with the jump starter thingies.

Obviously I would vastly prefer to pay £25 than well over £100 for the official Power Tank but if there is any risk of frying the scope or similar, or being underpowered then I will bite the bullet and buy the official Tank.

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sorry for asking a question on this thread .

I was considering buying that one but how do you convert it to give you the plug adaptor for 12 volt on a scope??? do you just strip your 12 volt adaptor down to 2 wires and use the crocodile clips or is there somewhere to plug in an adaptor??[hope that makes sense] i have been using batteries but they only last 2-3 hours so need something better .is there a second 12volt adaptor required ie to go from jump starter to scope

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Thanks Starnut but do you know of anyone who can has used that model with the 4SE? I saw someone refer to it when using the 127 but I'm concerned in case that is not an identical eletrical draw to the 4SE? (milliamps and other stuff I know nothing about)

Scope is 3 weeks old so I'm pretty cautious!

Edited by CFC
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CFC, you'll need to know the amp draw of the scope and put a slightly overrated fuse in-line on the positive as far as I know (and that's not allot) just saying it can be done.

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Thanks Starnut, I appreciate your input. Only thing is - if your equipment needs 750 miiliamps because it's bigger than mine....and the starter pack delivers that and my scope needs 300 because it's small, it's not compatible 'as is', ie it might fry.

I'm only thinking in terms of the equivalent mains power and fuses, perhaps the problem is that I just don't understand this DC stuff.

Edited by CFC
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Thanks Starnut, I appreciate your input. Only thing is - if your equipment needs 750 miiliamps because it's bigger than mine....and the starter pack delivers that and my scope needs 300 because it's small, it's not compatible 'as is', ie it might fry.

I'm only thinking in terms of the equivalent mains power and fuses, perhaps the problem is that I just don't understand this DC stuff.

No matter what rating your telescope is it will only draw the required amount from the power source, so if it is a 2amp current requirement and you have a power supply that is above that rating it will do fine, the more power you have, in what is termed Amp/Hour, (A/h) the longer your telescope will run without recharging, to give you a rough guide, if you draw 2 Amps from a 17 A/h power SLA ( sealed lead acid ) type battery you should get 8 1/2 hours use, but in reality it will be less due to varying factors, but still very good. The concept of using a big power supply for a small unit is often thought of as too much and will fry the unit, when in reality it will last that much longer, the main thing is to have your circuit fused protected to marginally above its power consumption, if you don`t and something happens, as in S... Law you will fry your scopes motors and circuit boards. The popular vehicle lighter plugs that are used normally have cartridge fuses behind the center pin which can be changed to your own requirements HTH :)

John.

Edited by glowjet
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thanks mate but for 14 quid will jury rig my exisitng power lead to the batt connection [will re solder a car adaptor onto my 12 volt scope lead.adaptor

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No matter what rating your telescope is it will only draw the required amount from the power source, so if it is a 2amp current requirement and you have a power supply that is above that rating it will do fine, the more power you have, in what is termed Amp/Hour, (A/h) the longer your telescope will run without recharging, to give you a rough guide, if you draw 2 Amps from a 17 A/h power SLA ( sealed lead acid ) type battery you should get 8 1/2 hours use, but in reality it will be less due to varying factors, but still very good. The concept of using a big power supply for a small unit is often thought of as too much and will fry the unit, when in reality it will last that much longer, the main thing is to have your circuit fused protected to marginally above its power consumption, if you don`t and something happens, as in S... Law you will fry your scopes motors and circuit boards. The popular vehicle lighter plugs that are used normally have cartridge fuses behind the center pin which can be changed to your own requirements HTH :)

John.

Thanks so much John, that really helps. One more question if you don't mind, how do I know what size fuse to put in, sorry to sound like an idiot.

I see the manual says this:

Input Voltage

12 V DC Nominal

Batteries Required 8 AA Alkaline

Power Supply Requirements 12 VDC-750 mA (Tip positive)

Can you translate? And is that the normal milli-ampage of a standard jump starter?

Edited by CFC
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750mA would be .75amps. I guess a 1AH fuse would be ok? Or possibly a .85/.9 if they even do them...you might find with a .75mAH fuse that it blows because of the slightest spike.

In batteries/jump starters, just think of amps/AH/mah whatever you want to call them as the duration of the battery hehe.....more amps=more life. As long as the volts meet the requirements and your amps meet or exceed the requirements you'll be fine :)

Also, jump starters come with different mAH ratings....usually the more mAH it has, the more the battery will cost but the longer it will last.

Edited by Monki
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Exactly. I just buy plain marine batteries without the extras : 90 amp hours and so last for ages. FYI, though, fuses aren't rated in AH. Just in Amps. They come in slow and fast burn varieties, too. If your motors don't draw a high peak current you will probably want fast burn.

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Once you get one it is really important to charge it regularly. If you store it for too long with a low charge it is quite likely that it will die - there are loads of threads on this. I charge mine after every use and at least once a month if I have not used it and it appears to be as good as when I got it a year ago.

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I think our friends have answered your question, if it was me with your unit I would obtain a 1.5Amp quick blow fuse from some TV/Electrical shop that is of the same pattern as the one in your plug, this will allow for any spikes or surges that may occur :)

John.

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