1. Battery project for Celestron Telescope
Since nothing premade worth a crap exists for sale that I could find I decided to build my own.

2. Goal of project:
Since I was not able to find any decent portable battery + charger setup premade to run my telescope I decided to build the best one I could get. Price was not an object.
It needs to be extremely portable. I’m not lugging around a 15 lbs car battery and charger!
Long lasting battery both in terms of actual use and lifespan of the battery. The last battery I bought lasted maybe 2 years.
I do not want to do a lot of work to put it together and wanted it to be easy to use. I do this stuff for a living so I do not want to do ‘work’ for my hobbies as well.

3. Why I chose Lithium Iron Phosphate battery / Charger:
Pretty much hands down about the best battery you can get for this type of application. Battery can be recharged thousands of times fully and drained down to 0% with no memory effects and loss of voltage.
Extremely small and lightweight. Battery and charger are oly 2.3kg (5 lbs).
Lithium Iron Phosphate battery gives you the full rated Amp hours and very steady voltage output the entire discharge. In comparison lead acid batteries typically become unusable around 50% charge as their voltage drops too low as they discharge (Usually to about 9V around 50%). Even the very best deep cycle lead acid batteries usually only gives you about half it’s rated amp hours because of this.
Quick recharge time. ~3 hours for a complete recharge. Charger included with battery.

4. Entire unit is 2. 7 Kilograms (6 lbs) & fits in this 32cm (12
Entire unit is 2.7 Kilograms (6 lbs) & fits in this 32cm (12.5”) box with a handle.
Size:
32cm x 18cm x 14cm.
12.5” x 7.1” x 5.5”.
Weight:
2.7kg. 6 lbs

5. Opened up for use. Three 12 volt outlets.
Battery in middle and charger tucked in front of battery.
Includes a 30 amp fuse on the hot side of the battery.
When charging you plug in the power cord as well as clip on the red/black alligator leads.

6. Battery by itself: 12V / 15 Ah Lithium Iron Phosphate battery.
15cm x 10cm x 10cm. 1.9kg.
6” x 4” x 3.8”. 4.2 lbs.
Battery is rated at 20 AMPs continuous usage (35 AMPs peak for up to 2 seconds).
Picture is of 30 AMP version.
Battery will operate from -10 °C to 60 °C (14 °F to 140 °F)

7. Things I added to the circuit:
30 amp fuse and holder on the hot side bought at local auto parts store. About 3” of extra 10 gauge wire as well. Not really needed but being safe and makes it meet electrical code.
1 to 3 (12 volt) cigarette lighter splitter thingy. Bought at Radio Shak years ago; Soldered in.
Foam packing stuff to make it all fit in snug and tight.
Electrical tape to keep outlets from moving around inside the case.

8. Test 1:
Connected my Celestron 24cm (9.25”) telescope to it without any accessories like dew heaters and such. Just the scope and controller.
Ran the telescope continuously. Made lots of telescope movements whenever I walked past it to simulate real usage.
With battery at full charge the voltage read 13.4VDC. No drop in voltage at all even with both motors running at once.
After 2 and a half days the battery finally dropped off line all at once. Right before it died the voltage was holding strong at VDC. Then it just shut off and went to 0V.
~3 hours to recharge battery to full.

9. Test 2:
Connected my Celestron 24cm (9.25”) telescope to it with controller and Dewbuster with 1 large heater and 1 eyepiece heater (Dewbuster turned up to the maximum of 20). This is about worse electrical draw I would every have; normally the dew heaters are not cranked up that high for very long.
Ran the telescope continuously. Made lots of telescope movements whenever I walked past it to simulate real usage.
With battery at full charge the voltage read 13.5VDC. A very slight drop in voltage when both motors ran at once.
After 6 hours the battery finally dropped off line all at once. Right before it died the voltage was holding strong at VDC. Then it just shut off and went to 0V.
~3 hours to recharge battery to full.

10. Test 3:
Connected my Celestron 24cm (9.25”) telescope to it with controller and Dewbuster with 1 large heater (Dewbuster set to half way point of 10). This is about normal setting when the Dewbuster is being used.
Ran the telescope continuously. Made lots of telescope movements whenever I walked past it to simulate real usage.
With battery at full charge the voltage read 13.65VDC. A very slight drop in voltage when both motors ran at once.
After 8 hours the battery finally dropped off line all at once. Right before it died the voltage was holding strong at 12 VDC. Then it just shut off and went to 0V.
~3 hours to recharge battery to full.

11. Pros:
Extremely small and lightweight. The entire setup fits into a very small case with a handle for easy carrying. Very portable.
Extremely long lasting battery for this application. 6 hours to 2.5 days.
This battery and charger will last 10 years or more under heavy usage.
No memory issues. Use as much as you need and recharge when you need it full or partial recharges and fast ~3 hour recharge time.
The battery (Sealed) does not heat up and is completely quiet and odor free.
Charger supports 120VAC and 220VAC.
Won’t explode or catch on fire. Battery Management System prevents overcharge, over-discharge, overcurrent, temperature issues and provides cell balancing (Activated when charged to full).
No need to keep it on a (Trickle) charger when not in use. The battery will hold its charge if not used for months. Doesn’t hurt to leave it on the charger either.

12. Cons:
Expensive. Battery and charger are $177 USA. Case $ The 1 to 3 converter I already had (Most likely ~$10). A couple dollars for the fuse and fuse folder. Entire setup should be just under $200 USA. As far as telescope accessories go though this is still cheap.
No way to tell how much charge is in the battery. No indication when charger is done charging.
Cannot be connected in series or parallel with another battery. The battery management system inside won’t like it.
This case is not waterproof or extremely durable; Would add weight and bulk to do so.
Cannot charge battery when temperature is less than 0 °C = 32 °F.
Cannot use just any charger with this battery. Must be a 14.6Volts LifePo4 compatible charger but since the battery comes with one it doesn’t matter.
Cannot use battery when being charged. Doesn’t hurt the battery but the voltage may be way high.

13. Final thoughts:
If I had to buy the battery again I would get one with the terminals facing towards the inside of the battery instead of facing each other; They make all configurations. This would give more room as the terminals are very close together.
Took 3 weeks to get that case from Amazon even with prime membership. Every case I looked at locally just wouldn’t work (Too flimsy).
Fuse holder and fuse were not needed just added it for protection just in case and to make it NEC compliant.
If you go with a larger battery you will need a larger case to hold it.
If anyone needs help building one I can certainly field questions or help in person if needed. If you want to borrow it for a field test just ask.
I would of thought Test 3 would of produced much longer run times than test 2. Apparently just having that Dewbuster on at any setting drains the battery fast.

14. Where to get:
Stanley Tools and Consumer Storage STST13331 Essential Toolbox, 12.5", Black/Yellow by Stanley Tools and Consumer Storage Link:
Battery: Picture on their website is of the 30 version, not what you get. 4 AMP Charger included.
Fuse holder: 1_-1&keyword=fny30bp Available in stores.
Fuse: 1&keyword=agc30bp Available in stores.
Extra 10 gauge wire: 1&keyword=85702 only needed about 3” of it. Got mine in red as I used it for the hot side.
Did not buy the 1 to 3 splitter as I already had it. These are available all over the place though.