Colm
journeyman
Reged: 09/16/09
Posts: 7
Loc: SW Washington State
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Does anyone have any suggestions for making/buying a cheap rechargeable 6 volt power pack to replace the 4 D cell battery pack that runs the motors on my Orion Astroview (aka EQ3) mount?
Constantly buying batteries is a drag, and so is the battery pack itself (the mount ain't much, either, but it works OK for visual, and it's easy to carry outside).
I can do some basic wiring and soldering.
Thanks.
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--James
Orion Astroview 6 EQ Newt
Orion XT8 Classic Dob
14" Home built Dob in planning
Two Eyes
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timo4352
super member
Reged: 04/16/07
Posts: 160
Loc: Northeast Ohio
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Try: http://www.bulldogbattery.com/
I got a 6v 2.2(?)AH battery and a charger there for like $40. The battery itself was only like $8 - if you already have a charger...
Nice guys too - very helpful.
Tim
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Orion 3.6CA Reflector
and 2 homebrew scopes --
8" Hubble Bubble ballscope
8" F/8 CHief - nearing completion 
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highertheflyer
sage
Reged: 07/08/05
Posts: 325
Loc: Ft. Worth, Texas
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Here's an Emergency Light that is complete with charger and a 6 volt 4.0 AH battery.
20 Dollars....
You can remove the battery and use it with your telescope, then return it to the case and allow it to charge to become an emergency hallway light again.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38013
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grendel
sage
Reged: 04/12/09
Posts: 241
Loc: Canterbury, Kent, UK
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Maplins in the UK do 6V sealed lead acid and chargers, also look at motorcycle batteries (some of the older ones are 6V and some car battery chargers do dual voltage too.
Grendel
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1157
Loc: Gateshead.NSW Nth Coast,Austra...
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I reckon these are jumpstarters are the go, they’ll also get out of trouble if you’ve a flat battery.
I use something similar to one of these
http://www.maplin.co.uk/Module.aspx?ModuleNo=36836&C=SO&U=strat15
plugged onto the car cigarette lighter socket or one of these http://www.soldsmart.com.au/l3.aspx?goods=cb0178
Mine is a 10yo multipurpose Projecta 4x4 Jumpstarter , it has 2 x 12V lighter sockets, the jumpstarter clamps, a flashing light, a high beam torch, and a multi V socket , 1.5V, 3V , 4.5V, 6V , 9V , 12V (dials up).http://www.projecta.com.au/catalogue/cid/27/asset_id/155
Does the trick for me , my old CG5 requires 6V and it can drive it for near 48hr before requiring a recharge.
I also use it to keep my car 40L Engal car fridge / freezer running when we away from the 4x4 , or need it for picnics and BBQ (can run it for 2 hrs +/-).
I think a Projecta HD Jumpstarters and a multi V lighter socket adapter is a pretty hard combination to beat for portable DC power.
Of couse if you have a car , all you need is the adapter , a 12VDC extension cord and you are in business.
Edited by Ian Robinson (09/28/09 06:30 AM)
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magic612
professor emeritus
Reged: 09/30/08
Posts: 548
Loc: Somewhere south of Chicago, IL
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This should do it pretty easily:
6V battery options
$9 wall charger (make sure you only charge NiCd or NiMh batteries with this!)
You might need to get some compatible plugs to make it all work (Radio Shack would have some options), so you can unplug from your mount and plug into the charger. Or, here's a good option: Dean's Ultra Plugs
They'd be a bit of overkill for what you're doing, but it also ensures proper polarity (when soldered on correctly).
Hope that helps.
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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Andy Taylor
twistin' by the pool
Reged: 09/24/08
Posts: 436
Loc: t=0 UK
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Go for lead acid... plenty of grunt.
It will hold it's charge for a lot longer.
I've got a 7 amp hour in a peli case.
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Equipment list of shame:
A strange heap of assorted junk that when thrown together and dragged out into the dark shows me the wonders of the universe...
And then dews up...
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grendel
sage
Reged: 04/12/09
Posts: 241
Loc: Canterbury, Kent, UK
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I have a 2.4V 65Ah ni cad battery - wet cell, its huge
I just need a few more to make a proper pack
Grendel
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Andy Taylor
twistin' by the pool
Reged: 09/24/08
Posts: 436
Loc: t=0 UK
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NiCad batteries will self discharge very quickly. If the cell voltage drops below 1v per cell then internal reverse polarity may kill the cell...
Also, they will loose capacity at low temperatures.
The production and sale of NiCads is now banned I believe.
Nicads and similar cells may have too high a "headroom" voltage for your equipment - 7.2v+ for rechargable cells - lead acid is probably ok with 6.8v.
Don't let the smoke out!
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Equipment list of shame:
A strange heap of assorted junk that when thrown together and dragged out into the dark shows me the wonders of the universe...
And then dews up...
Edited by Andy Taylor (09/28/09 03:49 PM)
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Andy Taylor
twistin' by the pool
Reged: 09/24/08
Posts: 436
Loc: t=0 UK
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Simple and reliable...
I made a mistake - it's 10 amp hour... 
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Equipment list of shame:
A strange heap of assorted junk that when thrown together and dragged out into the dark shows me the wonders of the universe...
And then dews up...
Edited by Andy Taylor (09/28/09 04:08 PM)
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magic612
professor emeritus
Reged: 09/30/08
Posts: 548
Loc: Somewhere south of Chicago, IL
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A 5 cell NiMh battery will be, at max, about 6.75 volts when fully charged. Each cell will charge to a max of about 1.35 volts; multiplied by 5 cells, that's 6.75 volts. Under load, they'll quickly drop to their nominal 1.25V per cell.
A 5 cell 6V NiMh pack would be fine, given that brand new alkaline batteries are 1.6 volts when new, which is 6.4 volts for the 4 he's currently using. I don't think the 0.35V difference will hurt the equipment, and NiMh's don't have the "memory" or reverse polarity problems that NiCd's do.
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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grendel
sage
Reged: 04/12/09
Posts: 241
Loc: Canterbury, Kent, UK
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this was an old UPS battery - potassium hydroxide electrolyte Ni-CAD
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1157
Loc: Gateshead.NSW Nth Coast,Austra...
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NiCd batteries also have memory .... make sure you complete discharge them before recharging .
Edited by Ian Robinson (09/28/09 08:43 PM)
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Colm
journeyman
Reged: 09/16/09
Posts: 7
Loc: SW Washington State
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Thanks all. A lot to chew on here.
What kind of amp-hour rating would I want to last me most of the night? Would 6 or 10 be enough?
Would this 6V, 800mA wall charger even charge one of those 6-10 Ah SLA batteries?
Those 5 cell NiMh at Tower Hobbies seem to average between 1-2 amp-hours, though I saw a 5 Ah for about $50, which is a bit too pricey. I like the small size and weight, but need something to last at least 8 hours or so--or better yet, 12 hours, just in case.
Also, what kind of fuse would I want? It might help if I knew the amp rating for those motors.
Oh, and is it possible to put two 6V SLA or NiMh packs together and have a 12V, and possibly even wire in two ports, one for 6V, the other for 12V? That way I could use it to operate a fan or something, as well, assuming the batteries could handle it.
Sorry for all the questions, but I'm pretty clueless about these things. I a working on educating myself, but it's a slow process for me.
Thanks again.
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--James
Orion Astroview 6 EQ Newt
Orion XT8 Classic Dob
14" Home built Dob in planning
Two Eyes
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grendel
sage
Reged: 04/12/09
Posts: 241
Loc: Canterbury, Kent, UK
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yes I use 2 7Ah 6V SLA batteries, linked in series, the main reason for this was that at my local Maplin store the 6V SLA's were £3.99 each and the 12V SLA's at the same capacity were £12.99, so I bought 2 of the 6V ones and a 12V charger.
the 800mA charger will charge a 10AH battery, but will take about 14 hours to do so.
I guess you will probably be ok with a 6AH battery for one night, my 7AH battery runs my etx 80 for many sessions before needing a recharge, usually 2-3hours a session.
I'm not sure what your equivalent of Maplins is- radio shack? check their listings for SLA batteries.
Grendel
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Andy Taylor
twistin' by the pool
Reged: 09/24/08
Posts: 436
Loc: t=0 UK
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Quote:
NiCd batteries also have memory .... make sure you complete discharge them before recharging .
Thats how they go into reverse voltage internally and die.
Don't discharge below 0.9 volt per cell.
We have 300+ rechargable battery packs in our camera fleet and we have to look after them.
Recelling ain't cheap.
Memory is a bit of a myth.. I used to have a PDF file from PAG UK explaining this but can't find it...
This myth killed a lot of batteries.
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Equipment list of shame:
A strange heap of assorted junk that when thrown together and dragged out into the dark shows me the wonders of the universe...
And then dews up...
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magic612
professor emeritus
Reged: 09/30/08
Posts: 548
Loc: Somewhere south of Chicago, IL
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Quote:
Thanks all. A lot to chew on here.
What kind of amp-hour rating would I want to last me most of the night? Would 6 or 10 be enough?
I guess the first question is: How much time did you typically get from the D-cell batteries? Good alkaline D-cells, I believe, are around 8 or 10 Ah.
Quote:
Those 5 cell NiMh at Tower Hobbies seem to average between 1-2 amp-hours, though I saw a 5 Ah for about $50, which is a bit too pricey. I like the small size and weight, but need something to last at least 8 hours or so--or better yet, 12 hours, just in case.
Understood, but don't forget, the nice thing about those small ones is 1) Easy to transport 2) Quick to charge and 3) you could always have a second (or third) backup pack waiting in a warm coat pocket on a cold night, and you don't need to buy the back up right away, either. Test one, see how long it lasts, then pick up one or two more when you can. They'll only take a few hours to charge, too. So I'd think that as one "dies", you could park you scope, pull the dead pack off, and put on a fresh one and keep observing.
And don't miss the 3Ah one towards the bottom, that's not much more than some of the 1.5Ah ones. The money you'd save in D cells would add up very quickly.
--------------------
- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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grendel
sage
Reged: 04/12/09
Posts: 241
Loc: Canterbury, Kent, UK
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http://www.buchmann.ca/
this is the best site for any information about batteries, well worth the read, explains the so called memory effect and the science of battery charging
Grendel
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myersbw
member
Reged: 04/30/09
Posts: 10
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Here's one more thought...vs. piecing it together, what about using a lower priced UPS for the supply?
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3869826&CatId=233
brad
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Colm
journeyman
Reged: 09/16/09
Posts: 7
Loc: SW Washington State
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Actually, the D-cells are still going after about three 3 hour sessions. Better than I expected, really, but I still don't want to keep buying batteries.
Anyway, thanks again everyone. I think I can put something together now.
No one answered the fuse question, but I guess I can figure it out. Maybe about an amp, amp and a half...
--------------------
--James
Orion Astroview 6 EQ Newt
Orion XT8 Classic Dob
14" Home built Dob in planning
Two Eyes
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Andy Taylor
twistin' by the pool
Reged: 09/24/08
Posts: 436
Loc: t=0 UK
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To find the correct fuse rating you have to know how much current your setup draws. Connect a meter inline with the positive line (not across pos & neg)and play around. Most current will be drawn when slewing. When you have a figure add around 25% and see how it goes.
Nothing worse then popping a fuse in the dark...
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Equipment list of shame:
A strange heap of assorted junk that when thrown together and dragged out into the dark shows me the wonders of the universe...
And then dews up...
|
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