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Mobile Power Stations

caller89
09 Jun, 2019 12:14
Hi all

Im looking at purchasing a Tracer 12v 24ah or bigger battery station for when I go to remote dark skies this October.

Has anyone purchased one of these or any other suggestion. if so how many hours do you manage under a single charge?

I need to power the following.
1. EQ6R Pro
2. PC Stick
3. ASI1600MM Cooled Camera
4. Focus stepper motor
5. 2 x 4inch Dew heaters
6. 1 x ZWO camera dew heater
7. Filter wheel.

My ultimate power box data averages about 40 - 45watts during my imaging sessions. The Tracer 12v 24ah data sheet indicates 3 hours for 100watts. however iv seen reviews for the skywatcher power station doing more than one imaging session on a single charge. Im looking at getting 3 nights at 6  hours imaging per night.

Tracer do a larger battery station but a very expensive price tag over £1,000

Look forward to your responses.

Thanks
whwang
09 Jun, 2019 17:42
This won’t help to solve your current problem. However, for people who are determined to do portable imaging, you may want to consider a hybrid for your next vehicle. I drive a Prius, and all I need to do is to plug in a 12V-to-110V converter. It powers my laptop, DSLR, computer, and mount, up to two sets of all these, whole night. The engine automatically turns on probably every half hour for 3 to 5 minutes to charge the battery. Otherwise the car is completely silent. No need to carry and charge additional heavy batteries. Just plug in and enjoy.

The only caveat is that if your equipment really suck lot of power (a huge cooled camera plus a not-so-power-saving laptop, for example), you will need to directly draw power from the 12V battery of the vehicle, instead of using the cigarette lighter, which is typically limited to about 100W.
eigenVector
10 Jun, 2019 02:49
Personally I use independent power bank/laptop usb/cigarette lighter chargers for my gear. Three of those cheaper li-ion batteries on amazon work for me. I use Velcro to attach them to the tripod legs.
caller89
10 Jun, 2019 06:18
Thanks Jonathan

How many sessions do you get from a single charge?
makhlouta
10 Jun, 2019 07:46
I am running a similar setup. CGEM DX, ASI1600 + filter wheel, laptop and dew heater for the guidescope. The easiest (although might be a bit intimidating at first) way and cheapest is to get a car battery. I got a trojan 100ah deep cycle for around 250$ (overpriced in my corner of the planet), a 40% charger and a 200$ powerbox from pegasus. If you can get everything in your setup to DC and avoid inverters, that would be the ideal scenario.

I have a 12V from battery split into 2. One for the laptop (using a DC adapter) and one for the powerbox. The powerbox then takes care of the mount + asi + dew heaters (on auto mode). Last time the asi was running at around 15% power on average during the night, lasted 7 hours and the battery was still around 60-70% charged.

you can consider using solar panels for charging in the future if you're staying 3 days in the field, use a custom battery box and run your own ports, etc…
Edited 10 Jun, 2019 07:48
VicV
10 Jun, 2019 10:57
I've been using Tracer LiFePO4 battery packs for a couple years.
My EQ5 mount is powered by an 8Ah model, and I have a 16Ah unit to power the camera cooler and 2 dew straps, usually set to 30% power. I can comfortably use these for one whole night (6h), with about 30-50% charge remaining in the 8Ah battery. The remaining capacity on the 16Ah battery varies between 35-70% because the power draw of the cooler and heating varies between summer and winter. Power draw is highest during hot, humid summer nights.

With my gear, this 24Ah total capacity is really only enough for 1.5 nights due to a couple reasons:
- You should not discharge batteries below 80% of their capacity, as this significantly limits their lifespan.
- Batteries lose about 30% capacity near freezing temperatures, so you should should keep this in mind during your capacity calculation. This can be mitigated though, e.g. by placing your batteries inside an isolated box during cold winter nights.

It's pretty easy to calculate your total power requirement thanks to the ultimate power box:
We know the exact power draw of your system (45W max), so 3 nights * 6h * 45W = 810Wh total power required.
This needs to be increased to account for maximum 80% depth of discharge (DoD), so 810 Wh / 0.8 DoD = 1012Wh battery
Battery capacity is calculated at a nominal voltage of 12V, so this is equivalent to 1012Wh / 12V = 84Ah battery

A large 12V marine battery would be the most economical option here, e.g. 100 - 120Ah to account for capacity loss due to temperature and aging. Those are much heavier though and require a good automatic maintenance charger to keep them topped off between uses.

Alternatively, you can recharge between each night and buy 2 smaller batteries.
- The mount usually consumes 0.6-0.7A (or 7.2-8.4Wh) during tracking, so that's 43-50Wh for an entire night (6h).
- Subtract this from the 45Wh total power draw and you only need 37Wh of power for all other equipment. That's 222Wh per night.

If we assume that you power the mount separately, you can do one night with these 2 batteries:
- An 8Ah 12V Tracer delivers 77Wh at 80% DoD
- A 24Ah 12V Tracer delivers 230Wh at 80% DoD
Edited 10 Jun, 2019 11:00
caller89
11 Jun, 2019 19:32
Michel Makhlouta
Michel Makhlouta

Thanks Michael. I have been looking at car batteries, so far this is cheapest way iv found. I would prefer to get LifeP04. however these are very expensive.

I do have a pegasus ultimate power box. great bit of kit so no inverters will be required.
caller89
11 Jun, 2019 19:36
Victor Van Puyenb...
Victor Van Puyenb…
Thanks Victor. Your response has been a big help, especially with working out the calculations for how much juice I need and how many batteries I need to use.
Tracer do a 100ah battery case which I'm looking at. however very expensive. alternatively I will be getting two smaller batteries as suggested.
VicV
11 Jun, 2019 21:53
Michael Caller
Michel Makhlouta
Michel Makhlouta
Thanks Michael. I have been looking at car batteries, so far this is cheapest way iv found. I would prefer to get LifeP04. however these are very expensive.

I do have a pegasus ultimate power box. great bit of kit so no inverters will be required.
Be careful, regular car batteries are not designed for deep discharge and will lose a lot of their capacity each time you use them like this. You should look for a 'deep cycle' lead acid battery, e.g. the one Michel suggested. They are more expensive than car batteries but they will also have a much longer lifespan with proper battery care.
Edited 11 Jun, 2019 21:55
makhlouta
12 Jun, 2019 07:05
^^ this is important, deep cycle is the minimum here. i wanted to go with an AGM, much more expensive, but i couldn't figure out its charging or find a charger for it in the market. for my deep cycle, i got a charger specific to it, automatic, slow, takes fewer hours than usual car batteries my fellow astronomers are using.

since you have the powerbox, then you have mostly everything sorted out. it will give you Volts and Amps readings, you just connect it to the battery and you're good to go. that's what i do usually, at home i have an AC adapter for it, in the field i switch to the battery cable (the powerbox comes with one, you just need the cigarette socket plug + clamps).

just keep in mind that the battery cable shouldn't very thin, or very long. or you will see voltage fluctuations. something that took me a while to figure out.
Die_Launische_Diva
12 Jun, 2019 13:50
Just out of curiosity, does anyone uses an inverter generator as a power source?
ruccdu
12 Jun, 2019 14:17
Diva,

I have in the past, but only out of necessity.  When I first started using my current mount, I didn't have a 48v power source, so I used an inverter to go from 12vdc to 110vac to 48vdc, each change resulting in some efficiency loss.  I now use a 12vdc to 48vdc converter with only one voltage change efficiency loss.

Ron
Die_Launische_Diva
12 Jun, 2019 15:23
Thanks for the reply Ron,

I was asking because I accidentally stumbled upon them which as far as I can understand they are more quiet than traditional generators and already provide 12V dc.
UnendlicheWeiten
13 Jun, 2019 17:57
I build a powerbox (230V-version) for my balkony oberservatory.
It is also possible to configure the box for 24V.
If you are interesstet into the setup of my selfmade powerbox, look the following report:
http://www.unendlicheweiten.at/index_htm_files/Selbstbau_PowerBox.pdf
 
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