Batteries and power tanks

[footix2]

I've just got myself a Starwatcher Star Discovery with a GoTo mount. 

Looking at getting a power tank for it but the Celestron/SkyWatcher 7Ah or 17ah are out of stock everywhere (shock). 

So with that I mind are there other alternatives I can use that are actually available to buy? 

Also in terms of disposable batteries, what type am I buying? I believe rechargeables are not suitable 

[PEMS]

Many go and purchase the Lithium Ion rechargeables at 12v. They work well. Talentcell seems to be the available one, eBay or Amazon have them. Check Amazon as one seller had the big Talentcell's at a good price. It may be more then you need but the price difference was significant. And the larger would give you a lot more time outside.

I believe the Skywatchers use the almost standard 2.1mm connector so that should not be a problem.

Keep it charged as if fully discharged they never work again, the nature of the battery means it has to always have a small charge present. As they have a small On/Off switch make sure that when you put it back in it's box that the switch is Off. Otherwise the LED drains the battery completely over time. Guess how I know.

Using one does mean that it has to sit somewhere. I do not know the scope/mount you have so look for a good place to secure a small "box" about 12x8cms.

As you rightly say Rechargeable AA's are not sufficent voltage. They supply just 1.2v per battery so 8 makes up 9.6v and the scope will want 12v.

If the option exists in the scope reduce the Maximum Slew rate. Means there is a lower peak current draw and there is no real reason to go at maximum, 7 or 8 will be as good, and might mean you do not have to start the alignment all over again.

[Carbon Brush]

If you have money available and plan for the long term, then buy a professionally built 12V lithium pack. Not necessarily an astronomy pack.

A low cost way into lithium is to use one of the car starter packs, then buy connectors (ebay) and fit fusing.

If you want to spend the minimum, don't mind the weight penalty, don't mind the effort of housing and protection, buy a gel lead acid. Then sort out your own housing connectors, etc.
You also need a charger if you don't have anything suitable around the house.

The attached picture shows a low cost (from Amazon) lithium car starter, with the supplied mains charger.
The connector (ebay) goes into the socket where you normally fit the big croc clips.
Inside the (3D printed) plug housing I have fitted a PTC thermistor for protection.
You can also buy short leads to connect from the starter that terminate into a car cigar power socket.

I use the modified car starter kit to run a goto dob scope. Plenty of life in the battery.

How much you stick with bought in, and how much you do yourself depends of course on what you feel confident handling.

HTH, David.

[Carbon Brush]

Should you choose a NiCd/NiMH rechargeable route, it can be done.

Bear in mind a 12V supply requires 10 cells vs 8 cells for throw away cells.

I would regard AA cells as a last resort. At only 2Ah or thereabouts, they are definte one session before recharge devices.
Also higher capacity cells in a small housing (like AA 2Ah) have a high self discharge. This means if you charge today and go out in a month, you probably won't get a full evening.

Once you start looking at 10 cells and C or D size, you are into building your own package.

[footix2]

I went for the 8300mAh Talentcell battery should get me started at least. Thanks for the help guys

[Old Clive]

On 30/01/2021 at 13:47, footix2 said:

I went for the 8300mAh Talentcell battery should get me started at least. Thanks for the help guys

Hi.

I've got a Star Discovery 150P on order and am looking at a power pack for it.

Are you happy with the 8300mAh Talentcell? I've seen it on Amazon for £62.99, is this where you got yours, and did you need to purchase any cables to go with it?

Thanks and hope you're enjoying the 150P.

[ST_Steve]

I have been using the 6000mAh version (with an AZ GTi) and very pleased with no issues. I have it attached to the tripod leg with Velcro (small and light enough - 360 grams).

Been using since early February and in sub zero temperatures and still four out of five charge level LED's lit. LED's are very small and green on this model and are very subtle so no problems with night vision for me.

You will need an appropriate length cable with connectors to fit your mount. I purchased the 'Lynx Astro Silicone Power Cable 2.1mm DC Jack to 2.1mm DC Jack 1m' from FLO and this is a quality item. Remains flexible even in minus temperatures. The cable will be plugged directly into the power bank - the supplied cable is only useful for charging for use as above.

https://www.amazon.co.uk/gp/product/B0713T4XT9/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

https://www.firstlightoptics.com/astronomy-cables-leads-accessories/lynx-astro-silicone-power-cable-21mm-dc-jack-to-21mm-dc-jack.html

Hope that helps?