Siereal technologt servo controller 2 idlecurrent drain

[muletopia]

Hello Folks,

When  I shut down sitech.exe and leave the controller with power what current is it drawing? my observatory is powered by a 100 watt solar panel charging  2 70 amp hour batteries. How many days of cloud can the system tolerate?

Chris

[Geoff Lister]

Hello muletopia.

The Sitech User Manual (difficult to view from the site) states "Will last several nights on one 7 amp hour Gel Cell on most telescopes." Assuming a 12V battery, that means a 84 watt-hour supply, but used over several nights (assume 2 off, 12 hour nights, as a worst-case of "Several"), this is a continuous power consumption of about 4W. From my understanding of the manual, this is based on a typical mount with a mix of a bit of slewing and mostly tracking.

Now, assuming that you do not want your pair of 70 Ah batteries not to drop below 50% charge, (35 + 35)Ah * 12V /4W, gives at least 210 hours (at 168 hours per week), before the clouds clear. Once they clear, you should have 96W from your panel to recharge the batteries.

Very much a "back of an envelope" calculation, but it may help.

Geoff

[muletopia]

Thanks  Geoff,

But at idle the mount is neither tracking nor slewing so I presume much much less current draw, but how much?

[Geoff Lister]

I did some measurements on my mounts, so this may give you a rough idea

Geoff

[muletopia]

Hello Geoff,

Thank for taking the time to provide your table of current draws, I do appreciate it.

The message I take is that the static (idle) drain is a large fraction of the tracking drain. I will assume that this is also the case for my Mesu mount 200.

Last night, with the controller at static, I measured the battery voltage at 12.75 and two hours later at 12.63 , this after 3 days of solid cloud. As the forecast is for the next 3 days is more of the same I turned the the controller off.

The batteries are a pair of old NZ70 ones that were retired from the farm truck, Given the performance above they may need replacing.

Granted that here in the wheat belt of Western Australia  this is an unusually long stretch of cloudy days it is not something I should have to do often.

As an aside, the Mesu is a shear joy after my synscan mount and much nicer than a Losmandy  G11 I borrowed for a couple of months.

Many Thanks

Chris

[Geoff Lister]

Hello Chris,

As has been mentioned on various previous threads, the battery design for vehicles is based on a short burst of high (starting) current followed by an almost immediate recharge as soon as the engine picks up. The best batteries for mount supplies are the "leisure" style, designed for caravans and the like, where a longer period of modest discharge is to be expected. Although the headline capacity may be the same, the internal plate design is different, and with different proportions of the active compounds.

Geoff

[muletopia]

Hello Geoff,

I am well aware of the battery type issue. My Syntra mount has a nice gel cell deep cycle battery. When I put in the supply to the observatory I had to use what was to hand for batteries, the funds had just bought the Sirius 3.2 m observatory (second hand from Iceinspace classifieds) and the expensive concrete pouring.

Still the truck batteries have lasted a couple of years, the sunshine here is fairly kind to them.

Chris