17 replies to this topic

[clc]

I will be observing most of this fall from a remote location, more than 50 miles from the nearest road or power line (very dark skies).  I have a fairly nice solar system of the cabin, but it really is just enough for the cabin.  My question is how does everyone supply power when you can't plug into the grid, how long does it last, and how much power is really needed?  I have SK EQ6-R with WiFi, a DSLR, and may or may not use an Astroberry.  I don't have the juice to run a laptop more than the internal battery lasts and would have to charge it using a generator.  Access is by aircraft only until there is enough snow on the ground to use a snowmachine, and the rivers have frozen (end of November?).

[Jethro7]

Hello cic 

I use a Jackery Explorer Solar recharging power banks. The size of the capacity will depend on your scope rig and other needs. My little Jackery Exporer 300 powers  my equipment just fine and with a 200 Solar panel charges up fast

 I also have a Jackery Explorer  5000 with two extra 10,000 Watt add on power banks that run everything I need for the night.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro

 

https://www.jackery.com/

Edited by Jethro7, 09 August 2024 - 12:44 PM.

[clc]

Thanks!  I also just found the battery box thread...  good stuff.   I go back to charging.  Solar is good in the summer, but when the best skies are here, there is less than 4 hrs of daylight, and not really enough power in it to charge anything.  I usually shut down the cabin solar system in Oct (really I just shut down the loads...).  Thus charging would have to be with generator.  The EQ6-R claims a 4 amp draw at 12v.  I don't know if that includes the wifi dongle.  Guide camera, DSLR, dew heaters, etc.. are unknowns (for me anyway).  I am a little surprised a 40 ah will last all night though,  if night is longer than about 10 hr.

[clc]

oh yeah,  nobody will ship LiPO batteries up here... too much hazmat tomfoolery to deal with.  Sealed AGM and flooded cell lead acid are about all thats available easily.

[PIEJr]

Hi clc,

Yeah, that's a tough one.

Any chance you could tap a stream for a small hydro-electric?

I've seen and worked on a few in my days.

But up there, I imagine the creeks/streams freeze up, too.

 

To save fuel (and hauling it) you need something small and steady.

 

I'm not sold on wind generation, too unreliable.

 

What about a stationary bicycle generator? Peddle for your pictures.

 

Lots of ways to fix your beans. 

[mclewis1]

A few thoughts on your situation ...

 

"all night" is a broad generalization but I think 8 hrs. would cover what most folks think of as all night. In areas with longer nights it could indeed be 10+.

 

4 amps at 12v sounds like a lot for the EQ6. I get that Synta recommends a 4 amp power supply as that gives them some head room to ensure no voltage drops (sags) in the worst case conditions (power up, continuous slewing, etc.). I think however you can plan on substantially less of a current draw in normal operations (extreme cold would however constitute a worst case condition). Another part of the calculation the mount manufacturer would do is for the continuous slewing on both axis, something you absolutely won't be doing all night (only when you slew to a new object). The current draw when just tracking is much much lower.

 

So for planning with a battery source all night I think you could probably cut that average amperage draw in half.

 

Basic cameras are usually in the few hundreds of milli amps range ( so a few tenths of an amp) but those with cooling onboard can more than double that.

 

Dew heaters are often the big draw on a power source - especially in the larger sizes (for 10+ " scopes) ... often an amp or 1.5amps per hour but this depends on the type of dew heater (resistors, vs. nichrome wires, vs. flat strips). 

 

Powering/recharging a laptop is likely a much bigger power draw. A lot of folks are now specifically using smaller less power hungry laptops for remote operations.

 

Without the laptop involved you'll likely find that your continuous current draw will average around 4-5 amps per hour ... so a 40 ah (amp hour) battery source would likely suffice. You also have to watch the older guidelines that involve 12v lead acid batteries (vs the newer Lithium) as using these older (but popular) batteries will often include a 50% margin (you normally don't regularly deplete these older type of batteries much below 50% - so for a night where 40 ah is required an 80 ah lead acid battery is often recommended). With Lithium battery technologies when you need a 40 ah capacity you buy 40-50 ah batteries.

 

Just be careful with the advertising - Cheap Lithium batteries are often rated in amp hours based on the individual cell voltages (3.7-4.1) and not 12v like the lead acid batteries. This means a blanket statement of "it's a 100 ah battery" needs the additional information of "at what voltage?". A 100 ah lead acid battery will be rated at 12v. A "100 ah" Lithium battery without any other information could really be only a 33 ah at 12v. This is why it's often a good idea to convert everything to watt hours or Wh (calculated by volts x amps). So that mythical cheap 100 ah battery might actually only be a 400Wh power source where the older lead acid 100ah 12v battery would be a 1200Wh. power source ... and that 1200Wh is probably the minimum of what you'll need for your all night sessions.

Edited by mclewis1, 09 August 2024 - 01:43 PM.

[triplemon]

My EQ6 draws around 0.8A average when tracking.

The nameplate amperage of any electrical device is the absolute maximum it could ever draw in emergencies for a short period of time. That is important for sizing fuses and maybe even wireing, but its far, far from typical average power draw.

 

I usually carry a single 85 AHr battery for full three day star parties at 8hr/night, running an EQ6, (low power) laptop, camera, guider and a whole host of LED lights off it, charge my phone and tablet every day. Never even gets close to being fully drained.

 

And as mentioned before - avoid running any 120V stuff through an inverter - that quite often cuts your overall efficiency into as bad as half. Always find "car charger" or "car power supplies' that directly run off 12V.

Edited by triplemon, 09 August 2024 - 02:01 PM.

[TelescopeGreg]

oh yeah,  nobody will ship LiPO batteries up here... too much hazmat tomfoolery to deal with.  Sealed AGM and flooded cell lead acid are about all thats available easily.

Plus you need to worry about the cold - Lithium doesn't like being below freezing.  They can be safely discharged a bit below, but cannot charge at all below 0C.  Some have built-in heaters, but that takes power.  AGMs are pretty much bullet proof in this regard, but they're heavy and you can't discharge them deeply without causing permanent damage.

 

Figure out what you need in terms of amp-hours, then double or triple it for sizing an AGM battery.  If your solar is barely meeting the cabin's needs, get another panel or two and a charger for the telescope.  Worse case, the extra panels can help support the cabin when you're not imaging.

 

As for the current, my setup runs a bit below 3 amps for the core infrastructure (cameras, computer, rotisserie), depending on temps.  The biggest single power consumer is usually the camera cooler.  There's also the Raspberry Pi 4B (running Astroberry) which runs the show at under an amp of 12v, and of course the mount itself.  Add another amp or so for the dew heaters, if they're needed.  I normally do use a laptop to monitor things, but in an energy pinch it can be turned off (sleep mode) since it's only a VNC client to the Pi.  I've had occasion to use my cell phone when the laptop battery died.

[KLWalsh]

For around $500 or $600 USD you can get a generator than runs off a small propane tank of the type used for outdoor grills. -Depending, of course, on what size you want or need.
You can probably find ones that will work to -20C.
You could use it to charge battery/power station for a telescope, and have it run a warming pad to keep the battery from freezing.

[clc]

Temps down to -20C will come pretty soon (mid Sept).  I expect I will be out observing when it is more like -35C.  Even I will just huddle by the fire at -40.  Not alot of available power in any kind of battery at that temp.  The absolutely dark skies, and lack of noise and ground vibration make it worth it.  I should have some photos by the end of Sept when I come back to town.

 

I do wish there was liquid water out there in winter, but if there were I probably couldn't get there on sno-go.  I have thought about putting in a small wind turbine, but haven't done it yet.

 

Mark,  

Thanks for the info, all good stuff and a solid place for me to start planning.  I have been planning on using a rather large deep cycle AGM battery in the 120 ah range and just using the generator to charge it.  Take it into my shop (wood stove heated) to charge after it warms up.

 

TelescopeGreg - 

 That is pretty much what I intend to do also, VNC to astroberry and let it do the heavy lifting for control.  A potential problem is the low temp performance of the Pi... unknown how it will react at -30C.  I'll  let you know when I find out.  I have had arduinos both fail at -40 and continue to work.  seems variable.

 

Thanks for the info! big help!

 

C

[clc]

Triplemon - 

 

good info.  I will run anything that needs 120v off the inverter in the cabin (3kw inverter).  I just don't want to find out that running 120v from the cabin  out to the scope will just tip the batteries inside over the edge.  They will handle charging devices, and Starlink during daylight hours.

 

and just for the record....  bicycling for power??  OFG here,  I'm waaaay past that!  (OFG -- Old Fat Guy).  HaHaHa!

 

c

[astrohamp]

You may find that putting your 'lead' (and even a LiFePO4 battery) into a 'hot box' i.e., cooler, ice chest, 4" thick ridged foam, container with a 4-35+ watt 12v DC plate heater (silicone mat, reptile, pet, seedling/plant, ...) can actually recover/extend the useful life of a discharging battery. 

 

Consider that a 12 watt DC heater full on for 10 hours only consumes 10 amp/hours (120 watt/hours) of a batteries capacity.  I use a Trojan battery spec as example where they say 100% capacity can be had at about 85 degrees F.  For the 105 AH battery pushed hard one could extract 50AH usable. 

 

Capacity drops to about 35% at  0 degrees F, end of graph data, where you hope to still be observing at -30F.  So with the battery cold soaked at 0F, 35% capacity is only 17.5AH usable(.35X50AH).  Best case by heating with a 12watt heat pad (maintaining 80 degrees) would use 10AH (in 10 hours) to yield 40AH usable (50AH capacity usable - 10AH load from heating).  Seems significant to me.  

 

Doing this heating thing with a LiFePO4 100AH battery would produce even better capacity yields.  If only there was a way to have one turn up on your door step some how. 

 

Enjoy the night skies.  My goose down 'suit', heated vest, and so called 'artic' boots couldn't begin to keep me warm at your temperatures.

[TelescopeGreg]

A potential problem is the low temp performance of the Pi... unknown how it will react at -30C.  I'll  let you know when I find out.  I have had arduinos both fail at -40 and continue to work.  seems variable.

Ooh, good point.  The Pi is spec'd at "0-50C ambient", but there is always some self-heating in an enclosure so you can certainly go below freezing a bit depending on the enclosure.  Not sure about getting to -30C, however.  -20C is the low end of the storage temperature; I'd keep the equipment indoors when it's not being used.

 

I was having trouble with my camera hanging up, and thought the cold was getting to the Pi so tried putting it in a foam case, but no change.  The issue turned out to be the powered hub that I was using, and not even temperature related (foam didn't help there either), so I removed it.  The rest of the system has been reliable down to somewhere between 0 and about -5C, which was where I had configured the camera temp setpoint.  The camera temperature started acting funny and I was getting cold, so I packed it all up and went inside to warm up.  I probably could have changed the camera to -20C or so to restore regulation, and the Pi was fine, but I don't like being cold...

 

Do let us know what you find, and remember to set the camera temp lower than ambient by a few degrees so that it can maintain regulation.

[Phil Sherman]

It may be difficult to get LiFePO4 (LiPo) batteries to your cabin but they might prove significantly better than lead acid ones.

Disadvantages:

1. No charging below 32F (0C).

2. No discharging below 0F (-18C)

3. Higher cost per battery

 

Advantages over lead acid:

1. Cold temperatures have less effect on capacity.

2. Much faster charging

3. Much longer service life

4. Almost double the usable capacity of the same sized lead acid battery.

5. Lighter weight

 

There are a number of low temperature mitigations you can use. One of the simplest is to purchase LiPo batteries that have a BMS (Battery Monitoring System) that includes a low temperature charging cutoff. Very inexpensive LiPo batteries usually have a BMS that only includes a low temperature discharge cutoff. An insulated box made from two layers of 2" building insulation styrofoam will do wonders to keep the battery temperatures high enough to allow charging. If additional heat is needed to do this, a 12V pet heating pad inside the box will provide additional heat. Attach this to a mechanical thermostat that turns on the heating pad when the temperature inside the box drops to 35F and you should be set for low temperature use. Thicker or more layers of insulation will help if a double layer box isn't sufficient.

 

An MPPT charge controller will usually be able to charge a battery bank faster than the simpler PWM (Pulse WIdth Modulation) charge controller. When you use an MPPT charger you can wire your solar panels in series or a series/parallel arrangement depending on the number of panels you have. Wiring them in series decreases power losses in the wiring between the panels and the charge controller because these wiring power losses are proportional to the current carried by the wires. Changing two panels wired in parallel to series wiring will eliminate 3/4 of the power lost in the wires between the panels and the controller. These chargers optimize the power drawn from the panels and some of the newer ones also apply this technique to the power fed to the batteries. The higher output voltage of series wired panels may also allow them to produce a little power at the beginning and end of the day when the oblique angle of the sun doesn't have a single panel's output voltage rise enough to activate charging.

 

If you look at the charging cycle graphs of LiPo and lead acid batteries, you'll see that the charge rate of lead acid batteries, as they become closer to full charge, drops off significantly when compared to LiPo batteries. This means that fully charging a lead acid battery takes much longer than a LiPo one having the same capacity. This can be an issue if you're charging with a generator because you'll need to run it for a longer time.

[clc]

Astrohamp - 

 thats a really good idea.  I have not considered a 12v heating pad for the battery box.  seems like it would pay off.  I've been compared to looking like the Michelin Man when suited up for cold.  Bunny boots (army surplus vapor barrier boots), and seriously warm overalls, fur trappers hat.  can stay warm.

 

c

[clc]

Phil - 

 

Good info.  The temps at my cabin won't get above 0 deg F for any significant amount of time after mid Oct until March.  I usually let the cabin cold soak when I'm not there in the winter, it just seems a bad idea to leave an oil stove lit and unattended...  so any batteries I leave there would have to warm before I could get anything out of them.  No real help from the solar system from Oct to March, just not enough sun to charge, maybe a max of 100w/m² for 3 hrs a day.

 

I am going to look for 12 heating pads though....

 

c

[astrohamp]

100w/m2 for 3 hours is not much solar clc yet perhaps could be channeled to warming and trickle charging any battery(s) you leave up there.  The spec I linked lists operating temperature down to -40F and suggests SOC be kept above 60%.  Most likely to avoid freezing and potential damage.

 

Looks like you will be flying in and sno-mowing fuel for generator charging/warming/using.  Doing all at same time upon arrival or/and during observing is possible with AGM as long as the battery hasn't frozen.  But then you already have been doing some of this with any mech you are using up there.

 

Vehicle battery heaters (and oil pan) are common although many are 120v AC not 12v DC.  RV holding tank heaters are typically 12v although can be large in dimensions.  Both can be high wattage which can be reduced in power use by half using two in series which is what I do for my LiFePO4. 

 

I too know the 'Michelin' look and use my Korea (black) and 'Mickey Mouse' (white) boots often.  Heavy and still require more thermal break insoles for my stationary freezy feet.

[Phil Sherman]

Phil - 

 

Good info.  The temps at my cabin won't get above 0 deg F for any significant amount of time after mid Oct until March.  I usually let the cabin cold soak when I'm not there in the winter, it just seems a bad idea to leave an oil stove lit and unattended...  so any batteries I leave there would have to warm before I could get anything out of them.  No real help from the solar system from Oct to March, just not enough sun to charge, maybe a max of 100w/m² for 3 hrs a day.

 

I am going to look for 12 heating pads though....

 

c

This is a situation where you need some actual data. If you solar array can produce 300W/day during the Winter season, it might be enough power to keep a 10-12W heating pad active throughout the time when you're not using the cabin. If you build an insulated box and put it in a freezer with a battery you could monitor the internal temperature of the box to determine the rate of heat loss. Add a thermostatically controlled heating pad and you'll see what its effect is. I also assume that your solar array is angled to produce maximum power when you're using the cabin. Panels angled for the Winter season should produce more power per day than ones positioned for Summer use.

 

When I first joined my (now) off grid observatory partner, he had his solar panels mounted on an adjustable rack with Summer and Winter positions. While these worked fine in the Winter, They were barely able to keep the batteries charged when in the Summer position, I discovered that this was the result of the design of the rack and the shadows it cast combined with the internal characteristics of the panels he used. It turned out that the panels would only produce power for 2-3 hours a day during the Summer. We took the easy fix and left the panels in the Winter position all year long.

 

Grainger Supply sells the EXTECH multimeter with temperature probe. A Google search for "multimeter with temperature probe" found this and some others for less than $50.