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Adventures in Powering the Nexstar Mount with Eneloop Rechargeables

mount equipment DIY
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#1 Justin Ducote

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Posted 16 September 2020 - 11:01 PM

Greetings everyone,

 

A while back I purchased 8 Eneloop AA rechargeable batteries to power my new Nexstar 6SE. Impressed by their value and the possibility of 2100 charge cycles, I brushed off and, for the most part, ignored the warning of Kenny at OC Telescope who cautioned me that they may not be entirely suitable to properly drive the telescope. Well, much to my disappointment, I too experienced the frustrations of the runaway mount, the grinding motors straining under insufficient voltage, and the missed gotos. This has been described by many users here*.

 

And despite coming across the occasional post or two praising their use**, I could never get them to work properly even after several repeated attempts.

 

Many simply bought an external battery pack and never looked back. Well, I discovered, to my pleasant surprise, that bundled with the Revolution Imager*** that came with the telescope was a lithium ion battery that appeared to power mount with ease. Problem solved, right? Well, sort of... For some reason, I wasn't satisfied with such an easy fix, after all I still had 8 batteries that -should have- worked.

 

After a bit more poking around, I came across a DC/DC boost converter that seemed like it would be just the right tool for the job:

 

https://www.powerstr...om/Product9.htm

 

After a few minutes of fiddling with a tiny little screwdriver to adjust the voltage pot. I think I have chanced upon telescope nirvana. I dialed in the unit to around 13 volts (I don't have a good reason why I chose this number, it just has a nice ring to it), hooked everything up and ..... Presto!!! - the unit powered up, spun freely and quickly in all directions, and life has been good ever since (at least for all of 20 minutes since I decided I should quickly hop on here and share such exciting news).

 

I will close with just a few pictures from this experiment and final observations:

 

1) Sure enough the battery back as it sits in the telescope stands ready at 10V (confirming that each individual AA cell doesn't really push more than ~ 1.2 Volts)  

 

2) Oddly enough the generic Lithium Ion Battery pack only put out 1 additional volt but the mount appeared to have no trouble running at 11 volts where it really struggled at 10 !

 

3) A picture of the step-up converter

 

4) And the final result - a nice boost of 3 volts bringing the output of the Eneloop rechargeables up to 13 volts !

 

Lastly, I have also been able to place the step-up converter in between the Lithium Ion battery and the mount bringing it too up to 13 volts, but so far it does not seem to have made any difference. 

 

justin

 

* See

https://www.cloudyni...y-aa-batteries/

https://www.cloudyni...ow-voltage-fix/

https://www.cloudyni...r-requirements/

https://www.cloudyni...upply-question/

https://www.cloudyni...star-8se-mount/

** most notably - https://www.cloudyni...-6se/?p=7889150 and https://www.cloudyni...ries/?p=9447620

*** which has turned out to be a wonderfully fun tool but that is a subject for another day.

Attached Thumbnails

  • eneloop.jpg
  • generic lithium ion.jpg
  • powerstream booster.jpg
  • boosted.jpg

Edited by Justin Ducote, 17 September 2020 - 07:09 AM.

  • mclewis1 likes this

#2 skaiser

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Posted 17 September 2020 - 08:38 AM

You might want to try  a NiZn battery.

these are available in AA batteries and put out 1.6v per cell and are fully rechargeable.

You will need a charger designed specifically for the NiZn .

you can find them sold with a custom charger 

I have used them for some robotics projects that needed “extra” power. They work very well.

take care



#3 mclewis1

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Posted 17 September 2020 - 09:43 AM

Yes, the NexStar scopes generally don't like voltages below the mid 10s. The micro controllers in either the hand controller (usually) or the motor controllers (sometimes) often start to reset when the supply voltage drops down into the low 10s. It's not a hard and fast rule however, there are scopes that will be stable down into the high 9s and others that get flaky in the high 10s.

Yes, they do really like 13 - 13.5 volts instead of a flat 12v. You'll often find that in addition to more stable operation that with the increased voltage the motors sound better and slew more smoothly under load.

 

This is the general observation of all kinds of NexStar based scopes (Alt Az or EQ) with the exception of the Evolutions. The Evo's have a built in battery and the internals report substantially different (lower) voltages via the hand controller.



#4 Justin Ducote

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Posted 21 September 2020 - 12:50 PM

For anyone who may read this in the future - I heard from Celestron Technical Support - here is what they say about the range of voltages that may be used to power the mount:

 

 

Thank you for contacting Celestron technical support; we appreciate your patience. My name is Johnny and I would be happy to assist you.

 

The range of voltage between 11.0V and 13.8 volts is reasonable for all our mounts. Mounts running at the low end of that range may notice some sluggish behavior in the motors. This might be annoying but it will not damage the mount unless you fall substantially below that range.

 

Johnny O, Celestron Technical Support




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