Power Issue..?

[daz]

Running the mount from my 110Ah battery last night (along with lappy) and I could not get the mount to align. It missed every alignment star by miles - but when I parked it, it went back home correctly!

I thought the battery might be running low as I noticed the mount power LED was pulsing, not a steady light. But the laptop was still showing as running on AC (via the inverter) and the inverter was not showing any signs of the input power being too low.

I can't say I've seen the power LED pulse before - any suggestions before I chuck it all and buy a dob???

[blinky]

I would still go with the battery, the inverter may be able to cope with lower input voltage than the mount. I am sure if the LED flashes then it is low power.

[barkis]

Sounds an odd one Daz. I would check all your power cables for any sign of corrosion or any bad connection which might result in volt drop due to a resistive connection. If the same battery is supplying power to the Inverter and the mount, connect them individually, and check the terminal voltage across your battery, first with one device connected, then the other. Of course the power drop could be at the plug which goes into the mount, if it a bad connection, and may only manifest itself when on load.

Hope I have not confused the issue.

Ron.

Lead acid batteries can cause wiring to suffer a problem called electrolosis, which can affect cables, and corrode them. You will see this effect on cars usually on the battery terminals. Like a gungy blue crystaline build up.

[beamish]

I am sure if the LED flashes then it is low power.

That's my experience too.

Karlo

[Tinkerbell]

Lo Daz

Have You upgraded the power cable to the mount as the only time we see blinking lights are either the battery is running low or the wrong (original) power cable is being used and the mount is not getting the power it needs to run the motors properly. Also if it is really cold this has an effect on the connections on both ends of the power lead and can cause the power delivery to fluctuate and confuse the controller. :x

[centroid]

Daz, inverters are notoriously 'power hungry' devices.

Why don't you scrap the battery idea, and run a mains extension cable (protected by an RCB) out to the scope.

Then get yourself a regulated 13.8V DC PSU, from Maplins for example:

http://www.maplin.co.uk/Search.aspx?criteria=13.8V%20PSU&source=15&SD=Y

My 4" and 12" dew heater straps, draw about 3 Amps in total, and the 12" LX200R, somewhat less than 1 Amp.

So the 5 Amp PSU (£19.99) would do the job. However, when it comes to PSU's, I much prefer to underun them, and would choose the 7 Amp version (£24.99), which will give you plenty in-hand for any other bits you might want to add in the future.

Dave

[daz]

Hi all - and thanks.

Kev - interesting about the lead. It is the original power lead, had no idea this may be an issue. Off to Andy then....

Did some tests this afternoon. The battery is delivering a constant 11.5v to the controller, so I hooked up the external supply which is not regulated and that fluctuated between 10 and 14 volts!! Never noticed that before!!!

So it could be a combination of things here.

Thanks for the Maplin link Dave, another one on the shopping list......

[James]

...

The battery is delivering a constant 11.5v to the controller, so I hooked up the external supply which is not regulated and that fluctuated between 10 and 14 volts!! Never noticed that before!!!

...

Daz, do you mean the mount controller/hand paddle thingy? (professional terminology here only... ) Although my mount's the goto version and is possible therefore different in its requirements but when the supplied power gets to 11.5v as shown on the handset I know my battery is getting a little low. My usual figures are 12.4v going down to 12.1v after a long session.

When connected to an AC power supply I've noticed the voltage fluctuate a little but we're talking in the range of 13.3v-13.5v.

Sorry if I've got the wrong end of the stick... ?

James

[Tinkerbell]

Lo Daz

If the controller is only receiving 11.5v it will be playing havoc with the motors it sounds as if the power cable (original) is the problem. :?

[MikeP]

I've been reading this with interest. At one point I had what turned out to be a duff battery and had similar problems - go to miles off. I started using a mains PSU and the problem went away.

However, I have examined my cheapo PSU and it says "unsuitable for outdoor use". The Maplin 13.8V regulated PSU looks like a better option, but I'm electrically challenged and have a couple of questions

• 
  [li]Why is it OK to connect a 12V device to a 13.8V supply? What's the significance of 13.8?[/li]
  [li]There have been threads suggesting the mount should have its own battery ie not shared with dew heaters and the like. Would that apply to a mains regulated supply?[/li]
  [li]Assuming it is OK to run multiple devices, could I run an EQ6, two dew heaters and CCD from the PSU?[/li]
  [li]Could I also run the laptop? It is rated at 20V and 4.5A. I have a "thing" that lets me run it from a 12V battery, but it sucks the battery dry in no time.[/li]
  

Thanks

Mike

[daz]

it sounds as if the power cable (original) is the problem. :?

Am coming to the same conclusion now Kev. I ran the lappy off the battery again yesterday, off the inverter, with my three dew straps running as well. Not a peep from anything.

I therefore conclude that the battery is still sufficiently charged and the lead is duff!

Mike (I think we have the same PSU BTW)

1) The regulated PSU CAN deliver a constant 13.8v, but the mount will only draw 12v - it will be a constant 12 rather than the fluctuating 12 (+/- 2v!!)

2) I would think that with the regulated PSU, you can run other stuff through it...

3) Yes

4) Yes

The only thing to watch is the total current requirements. If the laptop is 4.5A, the mount and dew heaters could be another 3 or 4A - so go for the PSU that exceeds your amps requirements.

For the same reasons as you, I'll be getting the 10A version!!

[cygnusx1]

The only thing to watch is the total current requirements. If the laptop is 4.5A, the mount and dew heaters could be another 3 or 4A - so go for the PSU that exceeds your amps requirements.

For the same reasons as you, I'll be getting the 10A version!!

Do you have a link to the item/cost and where to purchase?

[MikeP]

Its the same link that Centroid posted - there are several models with different max outputs up to 10 amps.

Mike

[MikeP]

Daz,

If my laptop is 20V and 4.5A, that rates it at 90W - does that mean that at 12V it will draw 7.5A? If so, even the 10A PSU is insufficient since as you say there is another 3A or so for the other bits. Also, what does "continuous", "50% duty cycle" and "surge" mean? The 10A PSU spec shows 7A, 10A and 12A respectively for these.

Mike

[daz]

Mike

TBH I don't know the answer to the first question - WRT your laptop. I *can* tell you that the transformer on the power lead will convert the 240V AC to 20v DC to the laptop. However, you will also need an inverter to run the laptop from

As for the others:

1) Continuous is the amount of current it will supply continuously!

2) 50% Duty Cycle means that the power is switched off and on (rapidly) - but I would imagine it is smoothed to the output (meaning that you still get the required current draw, but it is delivered by charging and discharging capacitors in the circuit) - but I could be wrong here!

3) Surge is the amount of current the unit can supply in a sudden burst over a very short space of time (i.e. milliseconds) with it shutting down

I'm no electronics engineer, so happy to be corrected - but this is my understanding...

[daz]

Just looked at a laptop PSU here at work.

The input current is 1.5A, the output is 3.6A.

So, my assumption is that (when plugged into the inverter) it will draw 1.5A, but the transformer delivers 3.6A at the other end.

Again, open to corrections from more knowledgeable peeps!!

[cygnusx1]

Interesting thread and discussion....

On the topic of calculating power/current usage can anyone advise

the power and voltage to run a HEQ5 Pro mount?

Also, how does one calculate from the Watt/Amp rating of a device how long it and a number of other peripherals could run on a battery rated at x Watt/ y Amps?

Just trying to work out my requirements to run mount, dew heater and laptop off a mains or battery power supply before i purchase!

[daz]

The HEQ5 needs 12v as well, couldn't tell you the ampage!

Most devices will tell you at least the voltage and current required - using ohms law its then easy to calculate wattage (current ^2 x resistance, resistance = volts / current).

To calculate its running time, you simply divide the battery capacity by the device demands. So a 12v 10Ah battery can deliver 10 amps in one hour, or 1 amp for 10 hours. If your device needs 2 amps then 10/2 = 5 hours running time.

Things like inverters also have a maximum wattage that they can supply (mine is 600w) so again, you just add up the wattage requiresments for all your devices and make sure they don't exceed the rated maximum.

[daz]

I seem to remember the HEQ5 needs 2 amps, now I think about it.............

Oh, and a simple Ohms law calculator is http://ourworld.compuserve.com/homepages/Bill_Bowden/ohmslaw.htm

[blinky]

OK folks,

I feel the need to correct a few of the answers here

Duty Cycle: duty cycle is defined as the percentage of time in a 10 minute period that it can be operated continously before overheating (courtesy of the Wiki!)

If a power supply gives out 13.8v your HEQ5 will recieve that 13.8volts it will not 'draw' only 12volts. The confusion here is that a device will draw the current it needs 1amp 2amps etc but the voltage is constant (this is for non constant current devices BTW but thats another topic!)

When a battery goes flat it's voltage will drop, as far as I can remember if the voltage of a lead acid battery drops to 11.5volts then it's flat (The voltage will drop when a load is applied BTW, you may still find it is 13.8volts with no load)

Daz,

Just looked at a laptop PSU here at work.

The input current is 1.5A, the output is 3.6A.

So, my assumption is that (when plugged into the inverter) it will draw 1.5A, but the transformer delivers 3.6A at the other end.

Again, open to corrections from more knowledgeable peeps!!

The input current is 1.5amps at 240volts

The max output current (Remember a device draws the current it needs) that can be supplied is 3.6A but this is at the lower voltage that your laptop needs. If you drop the output voltage (From 240v to what your laptop needs) then you can up the current, this is exactly how the national grid works, the voltage in those overhead lines is massive (132,000 volts I think) but the current is comparativly low. The transformers at your local sub station take the high voltage/low current supply and transform it to low(er) voltage but a higher current capacity supply.

Hope the above clears up some of the questions!

[daz]

Blinky

Thanks for correcting me

So does the laptop draw 1.5A or 3.6A from the supply?

[Starflyer]

So does the laptop draw 1.5A or 3.6A from the supply?

Hi Daz,

The laptop will draw up to 1.5A from the 240v side of the inverter. I'm not sure what the 12v side of the inverter will draw from the battery but I'd guess around 5A, they're probably only 70% efficient at 'upping' the voltage.

Cheers,

Ian

[daz]

Less than 1.4A (no load) according to its spec.

So, 1.4 for the inverter, 1.5 for the lappy, .35 for the 2" dew strip, 0.5A for the 3", 2A for the mount = 5.75 amps total.

So the 7A version of the above regulated power supply would give me plenty of overhead, even if I added another dew strip of up 1 amp?

[blinky]

BUT did I not see mention of a 50% duty cycle? That means that to supply the 7amps it needs to be off or drawing very little current for 5 out of 10 minutes!

I would suggest getting a bigger supply if this is the case

[Kaptain Klevtsov]

But why oh why have a 13.8V mains power supply feeding an invertor to run the laptop? Surely that means you have to buy a bigger power supply and an inverter? Why not run the laptop off the mains if its there?

Kaptain Klevtsov