Skywatcher AZ GOTO power supply/battery requirements?

[stonedzep]

It's a cheap multi-voltage I don't think it is output regulated, better trying with the 15v which goes 15.45v output?(that would be regulated but exceedes of little the power needed).

Or better to cash something for a 12v 2A new psu? That looks like the way to go

Btw thanks all for the hints 

[Geoff Lister]

The 12V 2A plug-top supplies, with UK and EU plugs are available, using eBay, in the UK for under £/€ 4.00, or even less if sent from China. They should have a similar price on Capri. I have used ones rated at 1.5A, but prefer the extra margin of the 2A version. They are often sold as supplies for the LED stick-on lighting strips.

Geoff

[stonedzep]

That's it, i am after one of these which I foundon ebay, I am considering also this psu but I am sure would last just 1 or 2 hours, what do you think? 

https://www.amazon.de/2017-New-Kitbox-Uninterruptible-7800-mAh-Lithium-Portable/dp/B06Y2X5CP1

[Geoff Lister]

It is difficult to tell from the advert, whether the 7800mAh is at 5V or 12V. If it is at 5V, the effective capacity at 12V will be closer to 3000mAh. This should be enough for a good evening's observing. I measured the current consumptions of my mounts, as shown below.

Geoff

[stonedzep]

The portable psu I previously linked has arrived, I Will follow up and tell you how long will last. Thanks everyone for the advises and info so far!

[stonedzep]

So far it is three hours and I haven't charged it, two hours yesterday and one at the moment but due to clouds here(!) I paused at the moment, will tell you how much longer it will last soon...or alter...

[Geoff Lister]

I had a decent break in the clouds last night, but it was the rapid cloud build-up, and not battery capacity, that ended the session.

[SilverAstro]

On 8/26/2017 at 08:42, stonedzep said:

Measuring the DC15v 2A gave 15.45voutput hence too much for risking. Then I dusted off a switchable adaptor that goes up to 12v, and measured its output 14.50v(12v setting). I think I Will use this one to power the synscan az goto, but don't know what to think of such high output with every power adaptor...

I have just come across this, sorry to be late on parade   I see by your latest post that you have got what you need, however it may be worth noting the following for future reference :

The output of an unregulated supply can be high when measured open-circuit (ie. not supplying any current to anything) but when it has a load to feed into (when current is being drawn from it ) the voltage will drop to closer to its rated voltage. (may well drop even lower if the load draws more than the rated current)

So, always a good idea to find a dummy load or resistor that will simulate the real load and measure it with that.

 

[Geoff Lister]

There is still the risk that, at switch-on with a high voltage, there is enough energy in the output capacitor, to damage the mount's circuitry, before the voltage drops to the nominal 12V.

[stonedzep]

1 hour ago, SilverAstro said:

I have just come across this, sorry to be late on parade   I see by your latest post that you have got what you need, however it may be worth noting the following for future reference :

The output of an unregulated supply can be high when measured open-circuit (ie. not supplying any current to anything) but when it has a load to feed into (when current is being drawn from it ) the voltage will drop to closer to its rated voltage. (may well drop even lower if the load draws more than the rated current)

So, always a good idea to find a dummy load or resistor that will simulate the real load and measure it with that.

 

Thanks for the headup, a friend of mine that is into electronics told me the same but also told me to be careful as Geoff says otherwise the risk of burning a mount is always there.

So yesterday after few clouds passing I was again out for an other hour and a half, this makes a total so far of 4h30m with the factory charge of that little chinese PSU, and still there is power because the handset backlight did not dim (it should dim when power is running out right?), conclusion:  I am very happy so far and for 25euros on amazon I can only strongly reccomend it, portable, capable and no risk of overpower the mount (outputs are 12v 2A pin jack and 5v 2A usb).

[SilverAstro]

6 hours ago, stonedzep said:

Thanks for the headup, a friend of mine that is into electronics told me the same but also told me to be careful

Absolutely, being careful is what it is always about ! You are unlikely to find a big cap. like that in the little wallwarts that causes surprise and consternation when measured off-load. The simple answer is always to give it a load such as the dew-heater or a battery to be charged. In fact a battery as its regular load while system is in use is a good idea for other reasons.

If it does have big caps it is also likely to be regulated (well regulated ? how does your Mr Average know one of those). Even if well regulated it may not be well designed with over-volt crowbar etc and if it doesnt have that then it is even more dangerous to you dearly-beloved. Because - it will have an even higher-punch available from the primary power side ( to supply the extra volts needed in the regulating electronics.) and when a fault in it develops  it can cause higher volts to be delivered.

So I dont want to worry anyone, we are in danger now of over analysing this, I have on my bench one such example where 21v AC is being o/p where only a variable 0 to 15v DC is desired and it is from a well known and respected suppler.

So belts&braces lads, power up less important devices first and if of nervous disposition hang a volt meter across it. Else pay for the proper job.

[stonedzep]

Ok so yesterday the PSU ran off power, totally I would say it lasted for 5 almost six hours connected to the mount so I am pretty happy with it so far!