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Replacing Celestron Power Tank 17 battery

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#1 Dipole


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Posted 21 June 2008 - 11:47 AM

I've got a dead battery in my Celestron Power Tank 17 and need to replace it. I've tried to follow Celestrons instructions for battery removal but have having a hard time opening the case into two halves. I've removed ALL the screws; the ones in the instructions and all others I could find.

My problem seems to be in the handle area. It won't separate. Is there an internal catch or trick to getting this thing opened?

Reply quickly because I'm sure to get impatient and break something! (j/k)
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#2 Dipole


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Posted 21 June 2008 - 12:18 PM


The trick: there were two little tabs ahead of the push-button on top that needed to be depressed to get it to release. There was also one hidden screw (not in the instructional diagram) under the clear plastic. I had to remove ALL screws and then it separated easily.

Caution: Don't stick metal objects inside the casing to help it separate. There is still a LARGE battery inside!

#3 Fred1



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Posted 21 June 2008 - 12:28 PM

Excellent post, Dipole. I'm printing this out and attaching it to my PowerTank owner's manual. Thanks for the tips.

#4 Arctic_Eddie



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Posted 21 June 2008 - 01:06 PM

The battery in my Power Tank also died after about 6 months. It was repaired under warranty and is being returned now. I left it on the charger thinking it was smart circuitry and would not overcharge. The instructions imply differently. I think it might be better to unplug the charger when the green lights say full then maybe top it off just before use.

If you had to ship one back and pay for repairs then it's likely cheaper to replace the battery yourself as you did.

#5 bobmcc



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Posted 21 June 2008 - 01:34 PM

My Orion tank (same thing) went dead the same way, down to three volts open-circuit. I put the disconnected battery (only) on an automobile-battery charger for a while and it came back to full volts and is working well now. I also had the interesting problem of taking the tank apart and ended up removing the silly million candle-power lamp and the red light. Seventeen screws to disassemble, if I remember right. Try the auto-battery charger trick (not guaranteed).

#6 Dipole


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Posted 21 June 2008 - 01:52 PM

Yep, 17 screws. Sixteen identical and one unique one for the bright light. The red beacon lens gets a quarter turn to come off. That and the little tabs to push in front of the red push button will let it open up nicely.

I'll give the charge a try! It will be a few days before I get to a charger but I'll let you know how it goes. Mine is out of warranty so what the heck! Mailing lead acid batteries is probably expensive and this way if the battery doesn't take the charge I can take it to the recycler.

#7 Dipole


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Posted 23 June 2008 - 10:38 PM

Just a quick follow up. The original battery had developed an internal short which will not clear. So I needed a replacement. These batteries are used in computer backup systems so they aren't as rare as I'd expected.

A friend told me to check out an online site called Battery Barn (www.batterybarn.com). This guy has every battery except for cars or motorcycles. And he had an AGM1217, just what I needed! Exact spec/size as the original. So then I start thinking about shipping cost. Checking his site I noticed that he lives/works a quarter mile from my friend! I drove out after work and my PowerTank 17 is back to fully functional! Cost? US$42.

Really nice guy. So if you ever need to replace yours drop him a line.

#8 BrianRG



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Posted 20 September 2008 - 11:07 PM

I think this thread deserves a bump. The battery in my Power Tank 17 recently gave up the ghost after about two years. I just completed the transplant with the AGM-1217 from Battery Barn, and it's back from the dead! Battery Barn was great to deal with and shipped immediately. The replacement battery is actually 18 Ah, but it fits perfectly. And it's lighter than the original. Thanks to Dipole for posting this.


#9 Rich N

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Posted 20 September 2008 - 11:46 PM

I use an Optima yellow top deep cycle battery for my observing needs.


#10 Midnight Dan

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Posted 21 September 2008 - 09:04 AM


While you've got the thing open, you might want to try a small mod. The red light is fairly useless because it's way to bright for most uses. But, the light is very close to the section where the unit supplies 3V, 6V, and 9V. I rewired mine to run on 6 volts and its about the right brightness now.

There's a little circuit board connected to the light which provides the blinking capability. That circuit board has a wire coming from it that is connected to 12 volts. I just unsoldered that and connected it to one of the solder joints on the 3v/6v/9v board where it went to the 6v connector. Works great!

I wouldn't disconnect the lights completely unless you find yourself accidentally turning them on a lot. I don't use them very often, but they do come in handy every once in a while. Just my opinion.


#11 SanDiegoPaul



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Posted 21 September 2008 - 07:56 PM

Great idea Dan, to mod the power to the red light. RE: the battery, be sure you are not charging it with the OEM wall wart. Use a known good charger.

I replaced the gel battery in mine with one that cost me I think 18.95 from a local surplus store. It works great and holds charge MUCH LONGER than the orig battery ever did, even when new.

Running two dew controllers last night for instance (one on the AT80 and one on the main scope), the green light showing adequate voltage stayed on for the whole three hours I was out.

With the original battery, it would go amber showing low voltage after just one hour with a single dew controller. In fact, I never ever ran two dew strips off it until I saw the new battery acting so much better.

I've got a second 17AH unit that's just as old and the battery is weak. It won't run two dew strips at ALL and I intend to get another battery for it next time I drive by that place.

FYI what I charge them with is a Sears auto battery trickle charger. I plug it in to the cig lighter socket and turn the power switch to the forward position. I've been charging them like this for two years. The OEM wall warts only lasted a few months. So you may not need a battery, just a charger.

#12 Larry F

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Posted 22 September 2008 - 08:42 PM

...I left it on the charger thinking it was smart circuitry and would not overcharge. The instructions imply differently. I think it might be better to unplug the charger when the green lights say full then maybe top it off just before use.

Since I never was able to remember to go back to the basement the next morning and unplug the thing, I rigged up a fan timer to a power recepticle and plug the charger into that, so it will turn itself off after as many hours as I dial up, thus not overcharging the battery.

#13 Dubboy



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Posted 15 January 2009 - 06:13 PM

The red light is fairly useless because it's way to bright for most uses.

Lots of good info here. Thanks to all.
I've found that the red plastic lid from a plastic peanut jar fits over the "too" bright red light perfectly...and dims it by just the right amount.

#14 drf


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Posted 14 July 2009 - 08:24 AM

I need some help after following this old thread. I replaced my battery in the unit as described however in doing so the 2 little wires to the speaker (blue and white ) broke off the circuit board. When you open the unit the speaker is on 1 half but connected by these tiny wires to the other half. I CAN"AT SEE THE SPOTS WHERE THE WIRES GO!!! So if someone can take a photo for me of the little circuit board where the speaker wires attach I can easily resolder them. Thanks!

#15 Michael Harrison

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Posted 23 January 2010 - 02:05 PM

I've recently bought a used tank and initially had similar charging issues. I went with the suggestion of using a car charger plugged into the cig lighter socket and after a night of charging the charger thinks the battery is full. Time will tell if this works. I've got what the weather diviners think will be several days of cloud cover so I may have to test it without stars first.

#16 csa/montana


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Posted 23 January 2010 - 04:54 PM

Welcome to our two new members, drf, & Michael! Glad you joined the CN forums. This is the place to get the assistance you need, among friendly people!

#17 Skylook123



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Posted 23 January 2010 - 06:56 PM

I'll chime in and echo Carol's welcome. The more the merrier.

Specific to the Celestron Power Tank/Orion Dynamo is the alternate charging method.

Why an alternate charging method? Two reasons. The wall wart is not up to the task, and the lights that indicate status on the front face of the unit are misleading at best, flat out wrong at worst.

First, the wall wart is just not reliable. It fails early, it fails often, it fails such that its output voltage is enough to light the "charging" light but nothing else, or it fails high and boils the battery away. Bottom line, it kills the battery.

Second, if that weren't bad enough, there are a confusing pair of lights to clue you in on the status. One says "Charging", the other says "Fully Charged". Ignore the Fully Charged light. It is triggered by too low a voltage level and gives a false sense of status. In reality, it will pop on with barely over 12V available, and these batteries are not fully charged until they push well over 13V. So, it's dang near empty and tells you go ahead, use me. This kills these batteries; they are not built to run below about 50% capacity. They are built to start automobile engines: high, short duration demand. When they are pulled down with long duration use as we do, the plates start to sulfate or exfoliate. It only takes a few full use cycles to end the life of the battery. If your equipment shows input voltage dropping or shuts down completely, that's a sign you may have exceeded the battery's recovery capability if done more than once or twice. These batteries need to be kept fully charged, as soon as possible after use. So, when the light says Fully Charged and the Charging light is still on, the battery is taking the charge on its way to being ready. Don't stop until the Charging light goes off! And don't use the wall wart very long long afterwards; there is NO limiting circuitry. You get full bore all the time, which will boil away or kill the battery after the fully charged condition is reached. That is, if the wall wart hasn't already started to fail.

What to do? Best to get some sort of multi-state charger with the ability to shift modes as the battery demands. Most of us here prefer the Battery Defender or Soneil chagers which not only charge in a way that keeps the health of the battery, they have a sensing that drops the voltage and current flow to indefinitely maintain the battery at full capability without damage. Both do well. I have the Soneil charger, and it includes a mode that detects sulfation and cures it if possible. Very cheap, less than half the cost of my Orion Dymano.

How to use it? Two ways. One way is stated above. Wire the output of the charger/maintainer unit to a cigarette lighter male plug and plug it into the output of the Power Tank/Dynamo. Remember to turn on the rocker switch on the face of the unit. The charging status lights are irrelevant since they are tied to the charging input port. Just let the Defender or Soneil run the show. Don't wire the charger to a female socket and then use the plug that comes with the battery to feed the charge into the charging pin; the circuitry will slow the process way down (although the lights may be a reliable indicator of status once the Charging light goes out). The smart circuitry in the charging unit might get into a conflict with the internal charging circuit. Best to just push the juice through the output socket.

Easiest for me, though, is to just connect the charger to the jumper cables. On the Power Tank/Dynamos, they are always hot. No switches, just hook up and go. Let the charger run the show.

NOTE: I have three of these "jump start" battery units. The Dynamo works as above. The other two are in reverse regarding switches; no switch to charge through the cigarette socket, a switch needs to be activated to charger through the jumper cables. Same concept; the charger will push the current into the battery through the output source, and be happy to do so, until the internals of the charger let it shift into a maintanence mode. From charge start until next use it can be left alone. The wall wart will only charge at a slow rate, but never stop and kill the battery if left connected too long.

Hope this helps. My Orion Dynamo, identical to the Power Tank is on its fourth year and is used three or four times a month at public outreaches, two long weekends at star parties each year, and eight nights a year at the Grand Canyon Star Party. Don't use the wall wart, DO use a quality charger/maintainer, DON'T suck it down below half capacity (e.g. around 8 amps for the 17 amp-hour batteries), charge it as absolutely soon as possible after use, keep it topped off at least monthly if not used between times.

Again, welcome to the most helpful community on the internet.

#18 acadianbob


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Posted 20 July 2010 - 09:20 AM

I hook a Battery Minder to the 2 "car start" terminals and leave it on all of the time. Won't overcharge and has anti-sulfating technology. Google Battery Minder and take a look.

#19 RTLR 12



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Posted 20 July 2010 - 01:00 PM

Did any of you guys replace the 'starter' battery with a deep cycle type? They are made for repeated excessive power drains and will give a longer life cycle than the 'starter' type battery that originally comes with most of those jump packs.

I have used these poeple with good results.


#20 gmartin02



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Posted 20 July 2010 - 02:22 PM

FYI - You can get a 17 amp hour "jump start" battery (with built in charger & cig lighter outlet) from Harbor Freight for $49.99 or a 20 amp hour one from Costco (with a built in air compressor) for $64.95 (at least I have seen them in several local Costco stores in the So Cal area). Both of these also have an analog volt meter built in which the power tank does not have.

If you can find one at your local Costco the 20 amp hour one seems to be the best deal of anything on the market.

P.S. I have been using a 12 amp hour "jump start" battery I bought from Radio Shack for $39.99 for the last 5 years without problems to power my LXD55 & ASGT mounts. I have recharged it well over 100 times and it still is pushing 12 volts. My point is that you can purchase alternatives to the Power Tank from other sources for a lot less money to do the same thing.

#21 michalh


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Posted 27 September 2012 - 10:09 AM

I've had a Celestron PowerTank 7mAH and been using it with the original battery for about 10 years now. Best move I made was to purchase a Deltran Battery Tender at Sears. It trickle charges and conditions the battery to keep it in best shape. The original charger is junk. I've recently acquired 3 more 7 amp batteries that I'm building a container for as I write. I hook these up in parallel and I have plenty of power for all accessories. I like using the PowerTank as the main bus because it is fused, and has outlets for other voltage accessories. Couldn't be happier with it.

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