Alternatives to Celestron PowerTank?

[jtm92]

Hi guys,

I'm looking at upgrading from my manual dob to a full go-to one. When I emailed Andrews Comm they suggested getting the Celestron 17A/h PowerTank for $249. However, after doing some research about this power supply, it seems that the general opinion has been that it's not worth spitting at.

Some suggestions I've seen for alternatives are to just get a jumpstarter from Super Cheap Auto. Looking at the price difference between this and the "official" power supplies for telescopes, they're pretty attractive. Does anyone have any suggestions or information about what the best option here is? Is there any modding necessary to make one of these compatible with the telescope? And perhaps most importantly, do I run the risk of frying the motors/controllers in the scope?

Cheers

Jarrod

P.S. The scope I am looking at getting is a Skywatcher Black Diamond Flex-Tube 8" collapsible dobsonian.

[Merlin66]

If you have a controlled output ie 12-13.8V your motors and scope will be OK.
I use a car convertor, 12V to 15V, 120w (Jaycar) to power the NEQ6pro.
I've been using 20Ah gel cell batteries for the last seven years (!) no issues, no drama and they are still as good as new.
A proper electronic triple stage charger looks after them.
Check out the golf buggy/ mobility scooter batteries - I strongly recommend them.
I'd even offer - "Satisfaction or your money back"

[multiweb]

That's pretty much what I think about these power tanks having owned two of them.:rolleyes:

I got an AGM gel battery. 75Ah that's still working after years of service. It's about the size and weight of a car battery. Any bigger and it starts to be really heavy (i.e. 160Ah). Worth buying a genie.

[Astro_Bot]

Since you're in Brisbane, I recommend going to YHI Power (in Acacia Ridge) and getting an AGM deep cycle battery - see this thread (http://www.iceinspace.com.au/forum/showthread.php?t=103932) for details, specifically post #20. You can contact Bob (astronobob) for more if you need to. I picked up a 26Ah AGM deep cycle battery, brand new, for $50.

Put that in a plastic box for ~$10 or a specific battery box for ~$25 and then add whatever sockets or lug connections you need. I use a DC-DC convertor to drive the mount and wired that straight to the battery lugs via a fuse - I didn't bother with sockets. As Ken says, there are a few adapters at JayCar, but I got this one (http://www.ebay.com.au/itm/100W-Universal-AC-DC-To-DC-Adapter-Inverter-Car-Charger-Power-Supply-For-Laptop-/281079146234?pt=AU_Laptop_Accessori es&hash=item41719f66fa) off eBay for $16. Of course, with eBay, there's always the risk of getting a dud, but I haven't had any problems so far.

All up, that's less than half the cost of the Celestron Powertank, greater capacity and a better quality battery, too.

[Astro_Bot]

AGM and Gel are two different battery technologies - it has to be one or the other, not both! ;)

[rogerco]

I ran the EQ6 on a jump starter I got on special from Dick Smith for $70 dollars (about half usual price) it worked fine at IISAC. It is 70Ah and very convenient package as it has a smal inverter built it that ran the laptop OK (although the battery went down pretty quick in this mode).

[Larryp]

You can make up a convenient caddy similar to mine, very cheaply. It has an 18Ah AGM battery with a cig. lighter socket, and storage compartments for small tools, fuses, compass, inclinometer etc.

[multiweb]

Brand is AGM :)

[Astro_Bot]

AGM = Absorbed Glass Mat, which is a battery technology produced for many different brands. Having never heard of "AGM" as a brand, I don't suppose you have a link to their site?

[jtm92]

Thanks for all the responses guys,

I've been looking around, and I found a company that sells AGM deep cycle batteries for what seems to be pretty cheap. I'm currently considering this: http://www.solarenergyproducts.com.au/ecommerce/solar-batteries/powersonic-pdc-1270-advanced-deep-cycle-battery.php

I know it's only 7AH, but I'm only planning on running the telescope from it, and I'm looking for portability more than anything; any bigger and it starts to get unwieldy. What are your thoughts on this?

I've also been looking at the Calibre 12V Battery box from Super Cheap Auto, to put the battery in. Does anyone have any experience with this, and its suitability? (http://www.supercheapauto.com.au/online-store/products/Calibre-Battery-Box-12V-Powered-External-Terminals.aspx?pid=12358#Cross)

Finally, a bit of a noob question. What is the best way for me to recharge the battery when it gets low? Are there adapters that I can get that I just plug into the wall to charge the battery? If so, any suggestions on where I can get these and what the best one is?

I'm only a lowly student, so my budget is more $$ than $$$$$$. I don't really want to end up spending more than $150 all up if I can help it.

Thanks again

Jarrod

[Astro_Bot]

7Ah is a bit small, IMHO. To preserve battery life, you shouldn't go beyond 50% depth-of-discharge, even for a deep cycle battery. Deep cycle battery life is rated in number of charge-discharge cycles (e.g. 600 cycles) but that assumes a limited discharge depth (usually <50%) and going below that has a disproportionate effect on life. So, if, say, you want to run an 10" GoTo dob, that draws say 1A average at 12V (that's a guess - I think they draw less than that, actually) and you want to last a 6-hour session, then you should have a capacity of 12Ah. Some of us add a 30% safety margin to account for age and temperature effects on performance, but I suppose that's optional. First, you need to know the average current draw of the system - someone else will have to help you there as I don't have one.

We could get into discharge rate vs capacity vs temperature vs final voltage, but for now, just take the minimum "headline" battery capacity needed as being 2 x session-time x average current draw.


I have that very same box, but it's way too big for a 7Ah battery (I have a 60Ah in mine).


CTEK chargers are the bees knees, but expensive. Any (at least) 3-stage "12V lead acid" charger should do the job, but the more stages, the better the battery preservation (in general, and up to a limit, of course). Importantly, you need to match the charger's current supply rating to the Ah rating of the battery as there are limits - the charger and battery will both have information that you should match together. Some chargers have modes for AGM, Gel and Wet batteries, and these will vary the supply voltage for different charging stages - Gel and Wet are usually similar, but AGM is different. Make sure your charger is suited to charging AGM batteries (if that's what you have).

[Merlin66]

Jarrod,
IMHO I'd go for the larger 18/ 20Ah sized battery. Easily liftable and moveable....
You want a triple stage electronic charger...I used a "Battery Fighter", model BFA -012-230.
My gel cell batteries are now over seven years old and still as good as new!

[pluto]

70Ah for $70!! :eyepop:
I think I have that same pack, $75 from Dick Smith (when it was on special, normally $150) and I'm pretty sure it's 17Ah :)




I think a 7Ah battery might not be enough. Also I know my mount will draw 1amp during normal tracking rate but can draw around 2amps while slewing, not sure if a 7Ah will be happy with that kind of current draw...?

You need to get a decent battery charger. I got mine from Battery World for about $100. Jaycar will also have them but I know someone who got one for $50 from Supercheap Auto and it hasn't killed his battery yet ;)

[mental4astro]

There's an excellent thread on cheap batteries in the Equipment Forum:

http://www.iceinspace.com.au/forum/showthread.php?t=103932

These batteries are just over a year old on the shelf, so they are sold on at a greatly reduced price. I'm hoping to pick one up this week in time for this weekend.

Here's the link to the discounted batteries page:

http://www.batteryguru.com.au/25.html

Mental.

[jtm92]

105AH for $90? Sounds great. Although, I am curious; what's different about the marine batteries? Would they also be suitable?

[Larryp]

Marine batteries are also deep cycle, but they are not as robust or long-lasting as AGM or gel-cell types. As already stated, AGM is the best.:)

[Merlin66]

Guys,
seriously....if you want batteries more suited to our astronomical demands...telescope drives/ cameras/ dew heaters/ computers (with a 12v-18v convertor etc) then you really need to look at the batteries used in golf buggies or mobility scooters. These are under similar loadings and are robust to do the job.
Just my 2c

[Astro_Bot]

Those batteries usually are fine, but it's because they're deep cycle batteries, nothing more. Typically, they're large capacity and would be used in series to provide 24V, 36V or 48V, for example.

What makes a battery "deep cycle"? Thick/solid lead plates - that's basically it - OK, so there maybe alloys, etc. involved as well. High current batteries (of the type you find in your car) have thinner plates and often honeycomb construction to maximise surface area, whereas deep cycle batteries forego surface area (and thus have low maximum current supply) in order to maximise life of the plates. A hybrid battery would be somewhere in between.

A "marine" battery usually just means it's of more rugged construction. Often the same battery is labelled as a 4WD battery, and probably has a thicker casing and plates bolted in more solidly. A marine battery isn't necessarily deep cycle, but if it has heavier/thicker plates, it probably will last longer then a car battery ... probably, but not guaranteed. Marine batteries are sometimes not even sealed/maintenance free.

Also, not all AGM batteries are deep cycle, but that's where they really shine, so a lot are.

[multiweb]

http://www.allpurposebatteries.com.au/
Mine is an X-cell AGM. Don't know if it's still on the site though. Bought it many years ago. It's a 75Ah. There's a lot of different battery types on the site.

[Astro_Bot]

Thanks, Marc. Always good to know where well-made batteries are at.

[LaughingBeagles]

Some great ideas here.

I have a powertank arriving as part of a pre-Christmas deal when I bought my Celestron SLT 130. I do like the variety of connectors that comes on the unit so I think I might tweak it by taking those components (and the CB they're attached to) and build a gel deep cycle version (similar to the one I built for our campertrailer).

Great thread.