Aux Battery Pack for Nexstar Mount

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Aux Battery Pack for Nexstar Mount

#1

Post by chicagorandy »


Many folks advise use of an aftermarket battery pack for longer viewing sessions than just the 8 AA's onboard the mount can provide. I chose a $30 6000mah Talentcell brand I found on Amazon, they also offer one twice that capacity (and cost). For simplicity and ease of operation I chose to secure the pack to the mount's support arm, placing a double layer of that thin black expanded foam shelf liner under it as a cushion and affixing the whole shebang with a wide elastic Velcro buckle strap. The pic is worth any more words about the idea - lol I also have the OEM A/C adapter as a backup source when I'm in the yard near an outlet.

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Re: Aux Battery Pack for Nexstar Mount

#2

Post by mcolbert »


something to always keep in mind; back up battery (ies) even if we have an observatory or usually run a cable from the house. Otherwise I am amazed at the range of battery types available on the market.
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Re: Aux Battery Pack for Nexstar Mount

#3

Post by JayTee »


Very clever Randy.

Nicely done,
JT
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
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∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
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Re: Aux Battery Pack for Nexstar Mount

#4

Post by Lokifish »


I'm running 3250mah cells internally on my SLT and get around 4 long sessions a charge, so you'll get many full night's worth of viewing from a battery that size.
Russ
A.K.A "Backyard Observatory" on Facebook and Youtube

Meade SN8 w/ DIY coma corrector, Astro Modded Rubinar 1000/10 @f/5.2, 130/5 Newtonian, Pentax SMC 200/4, Canon SH 30/1.7
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Re: Aux Battery Pack for Nexstar Mount

#5

Post by chicagorandy »


Lokifish wrote: Fri Jun 14, 2019 6:18 pm I'm running 3250mah cells internally on my SLT and get around 4 long sessions a charge, so you'll get many full night's worth of viewing from a battery that size.
Is that rating at 12V? The only ones I could find on Amazon had a 3000 mwh rating at 5v.
"Don't believe everything you read on the internet." Abraham Lincoln
We may not have it all together, but together we have it all.
The older I get, the better I was.

Celestron Nexstar+ 127 SLT, several budget plossl eyepieces, Celestron 8-24mm zoom EP and a 12.5mm illuminated double reticle EP, Svbony SV205 camera w/.5 focal reducer, Celestron SkyMaster 20x80 binos on a 40 yr old QuickSet PanHead tripod, Stellarium, Sharpcap and ManyCam on my laptop, SkyView and Nightshift on my phone and a dandy little $9 red-light flashlight.
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Re: Aux Battery Pack for Nexstar Mount

#6

Post by Lokifish »


What I did was replace the AA's with three 18650 cells. That gives me the needed voltage, a flatter discharge curve, and the mount will stop working before the cells reach their max rated discharge level. It took a little rewiring and some basic soldering, but cells and a charger cost me about $30. So it paid for itself very quickly.
IMG_20190614_204547.jpg
Russ
A.K.A "Backyard Observatory" on Facebook and Youtube

Meade SN8 w/ DIY coma corrector, Astro Modded Rubinar 1000/10 @f/5.2, 130/5 Newtonian, Pentax SMC 200/4, Canon SH 30/1.7
SkyWatcher EQ6-R Pro, Modified Celestron SLT
183 OSC, 224 OSC, Canon 1100D, Sony NEX-3
Nikon 7-12 zoom, a lot of DIY/salvage eyepieces
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Re: Aux Battery Pack for Nexstar Mount

#7

Post by johnbear »


Lokifish - Nice packaging!
The 18650 Li-ion battery solution is something I have been considering for my Nextstar mounts (GT & SLT). I am considering using 4 18650s (about 16v) with a high efficiency step down Buck Converter to deliver a steady 12V output at up to 3A (< $10).
Does anyone know the minimum voltage limits for reliable SLT mount operation?
:think: Retired electronics/systems engineer, serial entrepreneur, former solo backpacker, and evolving telescope refurber.
Astro assets: 8" Collapsible SW Dob; new C8 SCT; Orion 127 Apex Mak; C5 (1980); customized OneSky; 80 & 102mm refractors, Nexstar GT, SE and SLT on sturdy BIY pier-mount tripods.
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Re: Aux Battery Pack for Nexstar Mount

#8

Post by Lady Fraktor »


12V at 1.5A is the minimum I have had my SLT operate properly at without doing strange things.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
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Re: Aux Battery Pack for Nexstar Mount

#9

Post by Lokifish »


johnbear wrote: Mon Nov 11, 2019 6:06 am Lokifish - Nice packaging!
The 18650 Li-ion battery solution is something I have been considering for my Nextstar mounts (GT & SLT). I am considering using 4 18650s (about 16v) with a high efficiency step down Buck Converter to deliver a steady 12V output at up to 3A (< $10).
Does anyone know the minimum voltage limits for reliable SLT mount operation?
Thanks!

With the 3250mah cells I'm using, I get so many nights out of it I never bothered to check.
Russ
A.K.A "Backyard Observatory" on Facebook and Youtube

Meade SN8 w/ DIY coma corrector, Astro Modded Rubinar 1000/10 @f/5.2, 130/5 Newtonian, Pentax SMC 200/4, Canon SH 30/1.7
SkyWatcher EQ6-R Pro, Modified Celestron SLT
183 OSC, 224 OSC, Canon 1100D, Sony NEX-3
Nikon 7-12 zoom, a lot of DIY/salvage eyepieces
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Re: Aux Battery Pack for Nexstar Mount

#10

Post by mariosi »


Very nice Randy.

It just happened to me . New power bank (lithium) with only two charges has swollen. I use 12v. 7.2ah (acid) for my SLT.
Power bank a.jpg
Power bank c.jpg
-Does anyone know the minimum voltage limits for reliable SLT mount operation? -
From instruction manual Nextstar
20191112_061005.jpg
Marios
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Re: Aux Battery Pack for Nexstar Mount

#11

Post by Lady Fraktor »


The mount tends to act like it is drunk at .750mA though, somewhere between 1 - 1.5A they run without hassle.
When just tracking an object the mount only pulls .750mA but needs more power when slewing or doing a goto especially if on rate 9.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
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Re: Aux Battery Pack for Nexstar Mount

#12

Post by johnbear »


Lady Fraktor wrote: Mon Nov 11, 2019 6:08 am 12V at 1.5A is the minimum I have had my SLT operate properly at without doing strange things.
Thanks for the info. I am thinking about setting the voltage at 13V and limiting the current to no more that 2.5 A for the SLT.

For my buggy (original; non-updateable; hamburger logo) GT mount) I am going to do some tests to see how well it operates at 13V and monitor the current draw. I noticed that it went wackydoodle more often when using the battery pack (or a weaker power supply). When using a beefier 12v supply it ran a whole LOT better. If I learn anything useful I'll post it here.

My 60 GT mount was my first Nexstar (from a thrift store for a few bucks and easily repaired). After using older Autostar mounts, I was impressed by how smooth, tight, and quiet it slewed. So I got a SLT mount from Wing & Sons, and now I am a convert. Also just finishing my version of Gabby's SLT tripod pier mount and looking forward to testing it with several OTAs, including my beloved customized OneSky.
:think: Retired electronics/systems engineer, serial entrepreneur, former solo backpacker, and evolving telescope refurber.
Astro assets: 8" Collapsible SW Dob; new C8 SCT; Orion 127 Apex Mak; C5 (1980); customized OneSky; 80 & 102mm refractors, Nexstar GT, SE and SLT on sturdy BIY pier-mount tripods.
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Re: Aux Battery Pack for Nexstar Mount

#13

Post by Lady Fraktor »


If you mean the internal batteries as the battery pack, these do not last very long in these mounts.
I normally use a 7Ah or 17Ah jump pack for power with mine and have no issues with operation.
I am not to sure how it will react to higher voltage going into it.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
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Re: Aux Battery Pack for Nexstar Mount

#14

Post by UlteriorModem »


Lady Fraktor wrote: Tue Nov 12, 2019 6:21 am The mount tends to act like it is drunk at .750mA though, somewhere between 1 - 1.5A they run without hassle.
When just tracking an object the mount only pulls .750mA but needs more power when slewing or doing a goto especially if on rate 9.
There is a good chance that if the current draw is 'inadequate' you are probably also getting lower voltage. Its a vicious cycle, lower voltage requires more current, while more current often results in lower voltage. Best way to ensure you dont go there is to ensure your battery can easly handle the 'peak' current draw.
Tom

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Re: Aux Battery Pack for Nexstar Mount

#15

Post by johnbear »


Lokifish wrote: Sat Jun 15, 2019 12:53 am What I did was replace the AA's with three 18650 cells. That gives me the needed voltage, a flatter discharge curve, and the mount will stop working before the cells reach their max rated discharge level. It took a little rewiring and some basic soldering, but cells and a charger cost me about $30. So it paid for itself very quickly.

IMG_20190614_204547.jpg
Lokifish - Did you have to modify your SLT mount battery chamber to fit the 18650 batteries? All of my 18650s a just a tad to long (by about 2mm) to fit in there properly, with no allowance for wire connections, etc. Are the batteries removable? if so, I'd like to know how you did that magic fitting thing you did so well. if you have a picture without the batteries could you share it with us?
:think: Retired electronics/systems engineer, serial entrepreneur, former solo backpacker, and evolving telescope refurber.
Astro assets: 8" Collapsible SW Dob; new C8 SCT; Orion 127 Apex Mak; C5 (1980); customized OneSky; 80 & 102mm refractors, Nexstar GT, SE and SLT on sturdy BIY pier-mount tripods.
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Re: Aux Battery Pack for Nexstar Mount - Some test results

#16

Post by johnbear »


Test results on my SLT and GT mounts - over the past weekend I ran sevreal voltage and current draw slewing tests using a good lab power supply as well digital meters. Note that there is an initial current surge when slewing starts, but I did not have an oscilloscope set up to measure it (probably not much more than 500ma for a fraction of a second on either mount).
:Astronomer1:
At 11.5 v (minimum voltage tested):
GT mount: Non-slewing: 190 ma; Az slews (both directions) 255 ma; Alt slews: 280 ma (both directions)

SLT mount: Non-slewing: 130 ma; Az slews (both directions) 230 ma; Alt slews: 235 ma (both directions)

At 12.5 v (nominal voltage):
GT mount: Non-slewing: 190 ma; Az slews (both directions) 260 ma; Alt slews: 290 ma (both directions)

SLT mount: Non-slewing: 130 ma; Az slews (both directions) 230 ma; Alt slews: 235 ma (both directions)

At 13.5 v (maximum voltage tested):
GT mount: Non-slewing: 190 ma; Az slews (both directions) 265 ma; Alt slews: 300 ma (both directions)

SLT mount: Non-slewing: 130 ma; Az slews (both directions) 230 ma; Alt slews: 235 ma (both directions)

The slewing current draws were much less than I expected, and the GT dew slightly more current than the SLT.
I also applied some mild hand resistance against the slews but saw no real change in the current draws.

The next evening we had a fairly clear night, so I put some fresh batteries in my SLT and took it out to check Sky Align performance. Which turned out to be AWFUL. The hand controller text had very poor light contrast, and it would go blank once in a while; then thhe scope would not stop slewing when I released the keys. So I took it back inside, expecting to have to work on it the next day. The next morning I checked the SLT batteries, and I discovered that I had put one in BACKWARDS! With the batteries in correctly, it now works as expected.

Lessons learned: 1) The SLT will noit run properly on 10.5V, and 2) ALWAYS DOUBLE CHECK how the batteries are installed.
:think: Retired electronics/systems engineer, serial entrepreneur, former solo backpacker, and evolving telescope refurber.
Astro assets: 8" Collapsible SW Dob; new C8 SCT; Orion 127 Apex Mak; C5 (1980); customized OneSky; 80 & 102mm refractors, Nexstar GT, SE and SLT on sturdy BIY pier-mount tripods.
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Re: Aux Battery Pack for Nexstar Mount

#17

Post by JayTee »


I'm surprised it ran at all with one of the batteries in backwards.

JT
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
∞ Binos: 10X50,11X70,15X70, 25X100
∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°

Searching the skies since 1966. "I never met a scope I didn't want to keep."

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