View Full Version here: : How much juice do you use

17-10-2017, 09:40 AM
Does anyone know how much power their system uses per hr of imaging ? i assume many of you run off batteries, i am looking to put in an off the grid solar, battery, wind, generator (and probably geothermal by the time i am done with it) and am keen to get an idea of roughly how much ppl use. my thoughts are that the computer is really the primary concern but what % of the power gets used, i am assuming around 200w give or take. other instruments i am running are a microline FLI, a PMX and dew heater. when i run the calcs they dont seem to add up to much. so keen to get the collective wisdom. how much power do you use? or what battery do you use and how long does it last.


17-10-2017, 10:01 AM
I’ve got a 360W Pure Sinwave Inverter running off of a 200AH deep cycle battery. I wouldn’t go below 360W myself but the battery should go for 2-3 nights during winter (longest nights) to get below 50%.

17-10-2017, 12:30 PM
I imagine that your cooled camera may have a surprising draw.

I dont know I must look it up. But cooling and heating are usually responsible for heavy draw on a system.


17-10-2017, 03:04 PM
If you'd like to know more exactly, there's always an AC power / energy meter you could use to measure the power being used. Of course you'd need to plug it all in to AC with their respective plug packs to get an idea. Out of interest, I have one of these on my desktop .. drawing 285 W, with 2 screens, desktop PC + audio amplifier @idle.
https://www.ebay.com.au/itm/Power-Meter-Energy-Monitor-Plug-in-Electric-KWH-Watt-Volt-Monitoring-Socket-AU-/253203759935?hash=item3af41ec33f:g: 3N4AAOSw~g1Z3pgJ

Either that or delve through all the specs for your gear. You could even use your laptop's Indicated battery run-time when fully charged (or better yet test it to FLAT), together with the battery energy storage (usually printed on the battery) to calculate the power used by the laptop.


17-10-2017, 03:54 PM
You're right I think Alex, peltier pads (the cooling thing) pull significant amps. I have a small one I'm playing with that draws 5....plus 2 x cooling fans

17-10-2017, 07:32 PM
That is what i thought, but i do have a meter on my power board and it was giving me readings of not too much above 1amp, it cuts out at 10 so i know htat i draw less than 120 watts (not inc the computer) at any given time. the system i was looking at has 6 200Ah batteries 1.5Kw PV array and i was going to put in a generator to kick in if the batteries ever get too low due to weather. it sounds like that should be more than enough ...

@ Colin, thanks that helps a lot

17-10-2017, 08:58 PM

You have your average power usage which is useful for battery storage and replenishment rates from Solar etc
Then you have your peak loadings - eg if you have an observatory which I assume you will, and both motors operate at the same time then you can have a big power surge.
Most AC motors use about 6 times their power rating in the first few AC cycles of use to energise the windings and spin up to speed.

Most small Inverters up to 600watt may or may not handle this
We tried a number of different Inverters between 400-600w - none managed it reliably.
Motor starts can be quite unforgiving.
I'd start at 1200-1500+ watts, pure sinewave
You might also be better off getting a low power PC device that only draws around 5-12 watts when in use rather than a full PC sized computer that could be drawing 100s of watts.

The other thing is that you dont have to limit yourself to 12v DC - many of these systems can operate at 48v DC and this allows for much cheaper power cabling and typically puts you into the more commercial/industrial quality range and out of the domestic consumer end of equipment that may not have the longevity or duty cycle that you will want.

17-10-2017, 09:15 PM
In Ark we have nominal SOL 2000Ah of battery and 2.1kW of solar panel. The solar panels will degrade, probably faster than what the salesman will tell you!!! The batteries do have a fairly well known degradation curve that depends on DOD and ambient temperature swings (try to minimize both!). IMO you probably have double the battery you really need (not a bad thing at all), and just about right for solar input. It would be a lot easier today than back 7 years ago to have increased the solar power since panels are sooo much cheaper now (so do it if you can), but batteries prices have been pretty stubborn.

The long term average draw is about 2500WHr per day (~100W always on). This is from the computers, network switches, Digital Logger web power boards, weather station, ip cameras, router, microwave radio (or satellite transceiver before that), leak from the AC/DC power adapters, inverter power efficiency and the MPPT charger itself.

When running a dome all night the extra load from the mount, dome motors, TECs etc puts the average daily rate to about 3400Whr (when two domes run it goes to about 4300Whr). Note that everything not required on gets automatically shuts down after dawn flats by ACP (and started up again in the evening 1h before dusk flats).

You will want a BIG inverter, the motors for the domes (or roll-off roof?) need big time current on startup. We tested a 300W and it failed to start the motors., 600W was sorta ok, but if too much other stuff is on at the same time then no good. We settled on a Latronics LS1848 (1800W draw, 5400W peak), Aussie made, it has served us very well.

I made a huge spreadsheet to look at weather variability throughout the year over multiple years (with random numbers to simulate reality) after tabulating the power from all the equipment. The criteria was to stay on with no or minimal solar input for 5-6 days, which was the worst the climate records had shown for that area. The other criteria was to not cycle the batteries more than about 20% DOD during winter (short charging period/long imaging nights). What is your criteria for the worst case scenario?

As you might know it is easier to just over install capacity than to underestimate and have to hack in more stuff later, it also leaves you room for equipment expansion (i.e. other scopes, A/C) later.


18-10-2017, 03:47 AM
so this is what i was thinking


it has a 2.4kw inv which should be fine. the roof is a roll off roof obs, if memory serves me correctly it is a 1.5 kw motor.

i will have a few other scopes in there in the future so i can add to the battery and PV array and add a gen to kick in when power is low

18-10-2017, 06:53 PM
OK sorry I read your post wrong. I thought you meant 6200Ahr of batteries, instead it was 6x200Ahr or 1200Ahr @ 24V (which gives the 14.4kWhr number in the provided link). I should have been more specific in our case we have 12V batteries in 48V chains, total energy capacity is 24kWhr (12V * 20 * 100Ahr). So your system should be just ok but without much spare capacity, depends how much stuff is always on.

A generator is nice, as long as that system can start/stop it automatically, but who is going to fill up the fuel tank? :P

The technical specs at the link you provided are a little thin, i.e. no details about the inverter, it is probably ok powerwise but you should get more info before buying.

Batteries from Alibaba are around the 100USD mark for 12V 100Ahr (1.2 kWhr) last time I looked (doesn't include shipping).


18-10-2017, 06:59 PM
BTW 1.5kW is a big motor. The shutter motor on the Scopedome is 120W, and the azimuth is 80W. Those two combined really strained the 600W inverter we tried (it was a good brand, Projecta, but only made for camping and the like, not industrial).

Good luck,

20-10-2017, 01:21 PM
I have a 120Ah battery that I use at about 4 amps. Except for when I forget to plug the laptop in and then have to charge it too.

That's for camera, mount, laptop, dew heater.

25-10-2017, 02:35 PM
Hi - I use a 24 volt system to run my observatory - 4 x 230 watt 24 volt panels feeding 8 x 150 amp 12 volt SLA batteries in 2 banks of 4. That will run the Mount and Telescope (including the Fan & Heaters), 2 x computer monitors, 2 x 24 watt mini computers, wi-fi router and a 14 watt LED light - for at least 14hrs without dropping below 24 volts - the 4 panels will fully recharge the system the next day.

What you need to understand is that you will only get around 15% to 20% of your batteries Amp hour rating before you start to damage it.

Geof Wingham