DIY: Lithium Battery Upgrade for my Astronomy Power Supply

I originally wrote this article for my astronomy club, but I think it fits for this location as well. Of course, I am modifying it a bit for this audience. For 30 minutes of my time, and admittedly using my comfort with electronics, I was able to get a brand new power supply for less than buying a new one. I think there are many such opportunities for folks out there. In this case, I think anyone could do this. The only tricky part is stripping the insulation from the charger’s wires, but more on that later.

I have been heaving into astronomy for about 8 years now. After my first year, I upgraded to put my telescope, the tube in this case was a 120mm refractor tube, on a computerized mount. This upgrade meant that I was spending most of my night looking at planets, nebulae, and galaxies, instead of looking for them. It’s rather difficult to learn the night sky. Many folks have that skill, but when my wife got pregnant, I knew I would not have the time to learn.

Getting that computerized mount, the Celestron AV-X, needed a battery, and I bought what is called the Celestron PowerTank. It’s a lead acid battery with 7 amp hours (ah) of power, and it will last several hours driving the scope. Telescopes only move to counter the motion of the earth’s rotation or when you tell it to move to a new object. The power requirements are low, so relatively small batteries can last quite a while.

After a few years, the lead acid battery stopped working so well. Most sources I found say you can get like 500 recharges on one before they lose about 50% of their capacity, but they also said there is great variation. Lithium Ion batteries can get you 2,000 to 5,000 or more before they get to 50% capacity. Dakota Lithium states that their batteries will retain 80% of their power for 2000 recharges.

I kept that old powertank, but bought their new lithium one. Fast forward to today, and that new battery is doing well, but I need more power. I now have a larger Dobsonian telescope, and it’s large mirror needs to be cooled via fans to be used right away, or I have to wait. I also added some telescope bling, some red lights to it, and I have some other ideas. The red lights are to help when I do outreach with kids, and parents, who often have not seen a telescope in person and often don’t know where to look. I can turn on these new lights to show them where the eyepiece is, then turn it off while they view the sky.

A few weeks ago, while I was cleaning out my basement, I decided that I could reuse that old powersupply rather than just buy another one for my fans and such. In fact, I felt I could give it MORE POWER. That’s a Tool Time reference; I loved that show as a kid.

The whole process was not all that difficult, nor that time consuming.  All I had to do was to unscrew the case for the Celestron Power Tank, about 10 screws.  I then took out the old lead acid battery, and put the new lithium battery in its place.  The last step was to cut off the alligator clips from the new battery charger that is tuned for the lithium ion battery, strip a bit of insulation from the wires, and then attach them to a standard 12v dc adapter.  Add a little electrical tape, and we are all set.  

A new Celestron powertank on their website goes for $70 with the lead acid battery and 7ah(amp-hours) of power.  The lithium equivalent will set you back $134.  There is a 15% off sale on their website as of this writing, so you may have to pay more if there is no sale on.  Their 17ah battery will cost you $132 for the lead acid version, and $179 for the lithium version. 

What I did is go to Dakota Lithium, although there are many other US and foreign companies you can buy from.  I did my research, and I like US based Dakota Lithium.  They offer a 12v 7ah battery and a 12v 10ah battery that both come in the same package as a standard 12v 7ah lead acid battery.  This is intentional so that you can do exactly what I did.  Their 7ah battery is $69, and their 10ah battery is $99.  You need to buy their, or someone else’s, battery charger that is designed for lithium iron phosphate batteries.  This is the exact same battery chemistry in the Celestron Lithium batteries. Lead acid battery chargers are not compatible with lithium batteries. The last part is to get that 12v dc adapter that will set you back about $0.40.  I bought a 10 pack of male and female adapters for my lighting projects on my telescope, and I had one left over.  The male form of the adapter is what you need.    

For a total cost of about $120 and about 30 minutes of my time, I got a rejuvenated, and 40% more energetic Celestron powertank.  I prefer lithium to lead acid, since they can be recharged more times and have a better discharge curve; the voltage does not drop off as quickly so devices run better longer. 

If you do a one to one comparison, the 7ah lithium upgrade would cost about $80, versus a new Celsetron for $134, thus that would represent a $50 savings over the sale price.  My option only saves $15, but you get an extra 3ah of power which is about 40% more energy stored.  This puts us fairly in the middle of the two Celestron lithium options. 

I am not getting any money from Dakota, Celestron, or anyone else from this post aside from the ads on the page. No affiliate links, this is just what I purchased. My dobsonian telescope is a Orion Astroview XX-14G. The old lead acid battery will be or course recycled at a local retailer that takes them, so no worries there.

 

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