Power tank advice

[tripleped]

I need to upgrade my power tank. I need something that will run my Dob goto mount, dew controller (multiple strips) and charge my phone for at least 4-5 hour sessions. No astrophotography. Would this be a good choice?  Currently have 2 Celestron power tanks but those drain quickly with all that hooked up  

[Bartman]

It looks almost identical to my Bresser one, just rebranded. If it’s the same spec as mine then it will do you just fine. I use it on my goto scope with 11 inch dew strip, 2 inch eyepiece strip, and heated Telrad. It easily lasts a 4 hours and still has half the battery left. 

[tripleped]

Good to know, thanks!

[Carbon Brush]

Really to properly answer your question, you need to provide numbers.

The (inadequate) Celestron power tanks. What claimed capacity are they?
What battery type? Lead acid or lithium? What age are they? This is so degradation can be estimated.

What is the power requirement on the dew strips?
We have no idea whether you are running a 6" scope with small dew strips or a 24" scope with much bigger strips.
Whether you have dew heaters on all of the main mirror, secondary mirror, finder, eyepiece.

Finally. What is the specification (amp hours) for the proposed replacement?

Firm answers come from firm data.
Guesses result from lack of data.

HTH, David.

 

 

[tripleped]

Ok. Here’s some numbers

 celestron:(about 1yr old)   7 amp hr

      Lead acid.   84 watt

Universal Astro   :   42,000 mAh.   
   Lithium ion.     Capacity 155Wh

             Ac and dc output 100 w each

 

10” skywatcher SynScan goto.   Astrozap dew stripfor 1.25” ep  and 2 for finder scope.   No dewstrips on primary or secondary.  Don’t have data on dew strips at the moment. 
 

 

 

[ONIKKINEN]

I have this one: https://ecoflow.com/products/ecoflow-river-portable-power-station

Has never run out of power during a night so far. I expect it to not last quite so long if its very cold, but at -5C i ran everything for 6 hours and still had some juice left over. I am running a Go-to mount, cooled astro camera, guide cam, 1 small dew strip for the guidescope and a Mini-PC from the power stations USB-C 100W output connection. I used to run my mini-pc from the AC 230V outlet, but that is quite power hungry. Still, if you want to use an AC outlet in the middle of nowhere, you can.

If you're in the US (like in the signature) you also have an option to get a Jackery. Lots of US folks seem to like theirs, and they would appear to be very similar to the Ecoflow river but perhaps cheaper.

[Carbon Brush]

Thanks for the info.

First comment. I'm not surprised the 7Ah lead acid is depleted running dew strips as well as the goto.
When they say 7Ah, they mean 20h @ 350mA. At higher current drain capacity is lower.
Running an amp or two of dew strips the capacity probably drops to around 5Ah.
Don't forget lead acid cells degrade with time, no matter how well you look after them.
The daily loss of capacity starts the day they are assembled at the factory and is temperature dependent.
Few battery manufacturers own up to this. But as the all use the same chemistry........
Your one year old pack may well be getting on for two years from battery build.
This has all been well described in other threads.

Second comment. The lithium pack.
This is almost double the capacity of the lead acid pack. 155Wh vs 84Wh.
So it ought to be very good. In round figures almost as good as both lead acid packs.
In reality lithium cell manufacturers specify capacity/energy under very specific conditions of temperature and constant current discharge.
The chinese manufacturers are very good at playing with numbers and providing misleading information.
For example the 42Ah quoted does not agree with 155Wh on a 12V pack. Unless you add up individual cell capacities🙄.
A bit like saying a car will do 100mph and give 50mpg - but omitting 'not at the same time'.

If you assume use in a pulse current application (dew heaters with controller) you will get 2/3 to 3/4 of the 'on the tin' performance, you won't go far wrong.
So your 155Wh pack is more like 11Wh.

The dew strip consumption is easy enough to establish using a multimeter. Either from resistance or by direct current measurement.
Then you can get a near enough figure for Ah consumption from the duty cycle shown on the controller.

You don't mention a dew strip controller. If you are permanently running these, you will significantly consume battery energy.

As you can see. If you have data on the power supply, and data on the loads, you can calculate performance and avoid the problems you have experienced.
Not everyone chooses to do this.

Now you see why leisure batteries (example 12V 100Ah, or 1200Wh) have been so popular in astronomy.
Even though they degrade with time like all lead acid, they have more than enough capacity for mount + dew even with 33% age related performance.
Unfortunately they weigh a lot more than a powerbank.

HTH, David.