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Power tank died after 6 months

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#1 caernavon


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Posted 08 September 2013 - 07:00 PM

Very annoying, though I've read they can be unreliable, so perhaps not surprising. I charged it for ~20 hours the other night, and it's already saying it needs a charge.

I don't really want to spend another $60 on a replacement. What are some cheaper/better solutions? I've read about car jump starters, but those can get expensive too, though if they're more reliable that's fine.

I know 0 -- nothing, nada -- about electricity, etc., if that helps. Treat me like the proverbial 5 year old, lol. :-)

#2 hamdul



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Posted 08 September 2013 - 07:16 PM

First off a warm welcome to our Nexstar site.
I have a Schumacher XP-500. Have had it for about a year now and it has been great, no problems. Of course all I have running off of it is my 8SE. I can go for about 4 to 5 nights running it for about 2 to 3 hours per night before it needs a recharge. In short I love it. :jump: I too know little about electricity but this unit has some kind of protection so that leaving it plugged in after its fully charged will not damage the unit. :question: I got my unit at Walmart and I believe it cost around $35.00. You can check that on line.

Hope this helps


#3 ben2112


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Posted 08 September 2013 - 07:19 PM

The Powertank is a hit or miss on reliability.

Here is one that is cheaper then $60. Jump Start Battery

#4 dtripz


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Posted 08 September 2013 - 07:33 PM

Use a battery tender, the one that comes with the powertank will kill it in a year or two. Black and decker bm3b is great for this purpose and is only 20 bucks, buy it and see if it can restore your battery before buying a new pack.

#5 caernavon


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Posted 08 September 2013 - 07:50 PM

Great suggestions everyone! Thanks, I'll start looking!

#6 panhard


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Posted 08 September 2013 - 07:56 PM

Here is what I use for charging batteries. charger
Get your self a similar charger like this. A deep cycle battery is much better than a cranking battery.

#7 WarmWeatherGuy



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Posted 08 September 2013 - 08:48 PM

Very annoying, though I've read they can be unreliable, so perhaps not surprising. I charged it for ~20 hours the other night, and it's already saying it needs a charge.

Mine always says it needs a charge, yet it lasts for many hours. The circuit that makes the red and green lights work is *bleep*. I just charge it for 20 (or more) hours and assume it is charged. When it doesn't last long enough I buy a new replacement battery. It uses the same batteries as your computer UPS.

A new PowerTank might come with a battery which doesn't have much life left, because it has been on the shelf for years. I would buy a replacement battery and see how long it lasts. I write the battery install date on the thing so I can tell how long it lasts. Expect between one and two years use. Remember to keep it charged.

#8 Midnight Dan

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Posted 09 September 2013 - 08:43 AM

People tend to use the term "Powertank" generically, but I'll assume you're talking about an actual Celestron branded Powertank?

If so, the problem is usually the dumb-charger they include with the device. A dumb-charger is a simple power supply. It ALWAYS supplies power to the battery when it's plugged in, even if the battery is fully charged. Charging a fully-charged battery is bad for it and will definitely shorten its life.

In theory, with the Powertank you should be able to plug the charger in, keep an eye on the LED indicators, and unplug it when it's charged. That would keep it from overcharging. Problem is, those LEDs are notoriously bad at indicating a full charge. So people tend to leave it plugged in way too long and then the battery dies in 6 months.

The solution is a jump starter with a built in smart-charger, or use a separately purchased external smart charger. A smart charger monitors the battery voltage and shuts off when its charged. Look for an automotive jump starter that says you can leave it plugged in all the time That will indicate a smart charger.

An even better solution is to buy a separate smart charger. These devices tend to do a better job at monitoring the battery state and knowing when to shut off. But they also do other things that help the battery life like conditioning the battery before a charge, or turning on from time to time to top off or trickle charge a battery that's being stored for long periods of time. "Battery Tender" is one well known brand that makes a variety of these. Be sure to get one that's designed to work with the type of battery you have. Most automotive jump starters are SLA (sealed lead acid) batteries, of the AGM (absorbed glass mat) or Gel cell design.


#9 garyp1936


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Posted 09 September 2013 - 04:00 PM

If you have a Harbor Freight store within a reasonable distance I would second Ben's suggestion. I have been using their yellow model (in Ben's photo) for several years without any problems. It has an internal charger which seems to work well. Gary

#10 *skyguy*



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Posted 09 September 2013 - 05:20 PM

There are two features that are absolutely critical to have for longevity when buying a rechargeable battery pack. ONE: Smart Battery Charging Circuitry ... you can leave the battery charging 24/7 without overcharging the battery. TWO: Zero Memory Effect Battery ... the battery can be re-charged at any point during the discharge cycle without drastically reducing its capacity to hold a charge over time.

I bought a Duracell Powerpack 300 ($50 on sale) about 5 years ago with both these features. It still charges back up to 100% all of the time!

#11 caernavon


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Posted 09 September 2013 - 09:49 PM

Thanks for all the great suggestions! There is a Harbor Freight store about 5 miles away, so since that model isn't too expensive I think I will go there this weekend and pick one up.

#12 James74


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Posted 10 September 2013 - 12:06 AM

When you have it on the wall charger and you turn the Powertank red rocker to Charge, does the green Charging light briefly turn on and make a clicking sound?

#13 Doug Michel

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Posted 11 September 2013 - 12:28 PM

I have a similar issue with the Celestron power pack. I recently have had some time to observe in the evenings and generally look at objects south, east and west of my house from my backyard. (house behind me). I can observe close enough to the outlet to just plug in the AC cord into the unit and not rely on batteries. I was going to observe northern objects the other night and figured I should check the charge on the tank. The light is green saying it is ok, but I wanted to see since it has been nearly a year since I last used the tank. I attempted to charge it, flipped the switch to charge, and plugged it in. No lights at all. I am unsure if the plug didnt seat properly or if the lights are defective. I guess I should just replace with one of the units described above anyway but was curious if I am on the right track with my thoughts on it.

I have not attempted to use the scope with the tank hooked up yet, in the past it has been hit or miss anyway. I believe I read on another thread a long time ago that the plug to connect to the scope is a different diameter and you would have to jiggle it to get it to connect or actually bend the wires on the mount for better connection. Another reason to consider a different power tank?

#14 Greyhaven



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Posted 11 September 2013 - 05:22 PM

I purchased the celestron power tank back in 2006 it lasted for about two years and always seemed to be low on charge. When it no longer was able to hold a charge I junked it. The charger that came with it I kept. I have been using it to power my 5i directly ever since. The jack plugs into the scope and fits well. I've written here before about doing it and really seemed to upset people about the soundness in my using it that way. I can only say that it has served me well, and my scope tracks well and seems to be as dependable as any other Nexstar. The cords that are made to supply power from a separate 12 volt power source are not able to withstand the flexing and cold weather and are to unreliable. In my experience, the wall charger has worked well for over 5 years. I have no knowledge about the current power tank chargers dependability, but the one that came with my power tank has been a dependable source of power for me when AC power was available.
This is my experience with my scope and power tank charger, I don't any electronic experience, so, I am only recounting my own use of the power tank charger as a source of power for my scope.
Be Well

#15 AlBoning


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Posted 11 September 2013 - 08:29 PM

Before ordering the Orion cousin, a DynamoPro 12, to the Celestron PowerTanks, I browsed the forums (searching back two years) and came to the following conclusions which are also partly based on my experience with the DynamoPro.

The output voltage of the charger is on the high side. It could easily overcharge the battery if left connected too long. This isn't good for the battery.

The self-discharge rates on these units is a bit on the high side. If not recharged regularly they will go flat and no longer accept a charge.

The indicator lights on these units are rather imprecise and cannot be relied on to allow one to accurately judge when the unit is at full charge.

When a death has been reported it seems in all cases it could be attributed to neglect at keeping the unit charged, though it seems likely that over-charging in combination with neglect or not is also to blame.

I've had my DynamoPro now for 22 months. Within a week or two I replaced the stock charger with a Deltran Battery Tender, Jr. Since then the unit has either been connected to my Atlas (about sixty observing sessions powering a fan and slewing the mount) or to the BTJr at all times. I routinely take the voltage before and after use, then log the data into a spreadsheet. As open circuit voltage of a battery is approximately linear to the State of Charge (SOC) I can also calculate the amount of charge used, gauge the capacity of the battery, and judge if the battery's capacity has changed. The range in SOC from 100% to 0% is a mere 1.5V, roughly 12.9V to 11.4V, which will vary somewhat from one battery to the next. Discharging below 50% should be avoided, and below 20% will reduce the number of charge cycles the battery is capable of before failure.

To date the DynamoPro is charging to the same voltage as new and there is no indication of deteriorating capacity.

It is possible to replace the battery. One replacement for the battery of the DynamoPro is a Tempest TD12-12, the manufacturer claims it is deep-cycle, which is a desirable feature for batteries used in this manner. Such batteries run between 35 and 50 bux depending on vendor. It can be a bit tricky getting the case open. There's about a dozen screws and a couple can be hard to find, be sure to check around the jumper cables. Also one has to dismount the big lamp. Popping the case isn't difficult, and switching the battery is easy, as is getting it all back together. I opened the case of the DynamoPro so I could determine the brand of battery, read the specs, and get its dimensions so I'd know what to get when the time came.

I recommend visiting the Deltran website and reading their technical literature. I found it particularly interesting to read about the differing requirements of bulk charging (to 80% SOC) and absorption charging (80% to 100% SOC).


And visiting Battery University and educating oneself about batteries and the charging of them in general.


BTW charging these units with a Battery Tender is done by connecting to the jumper cables.

#16 Arctic_Eddie



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Posted 12 September 2013 - 09:23 AM

The charger that came with my Celestron Power Tank produces 15.3VDC unloaded. This and the fact that it is very light suggests that it's a regulated output switching power supply. This why some people have been successful using it as a scope line supply. However, there are some tantalum capacitors in the scope that are rated at 16VDC. This is too close for comfort for me. Also, the charger is not smart and can easily destroy the battery if left connected for too long.

I wonder if anyone has tried using 3S1P LiPo batteries. The price is coming down rapidly due to their popularity in electric RC planes. The 5V regulators in the scope will work down to 7VDC of input voltage so should be useful for the LiPo full capacity.

#17 boandpokey



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Posted 15 September 2013 - 01:42 PM

that explains why my brand new Celestron power supply tank needed charging after its first use... used it for 4 hrs and it already showed it needed charging..

#18 ben2112


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Posted 15 September 2013 - 01:49 PM

I went through 2 of them. I got one when I bought my scope as a kit. It was all messed up. I called Celestron and they sent me a brand new one. So far it's been working. But when this thing dies, I am getting a Jump Start battery or I might build my own.

#19 Peter9



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Posted 15 September 2013 - 02:04 PM

I've had my Jump Start Battery over 4 years now, first driving the 8se and now driving the CPC1100. It still does 3 to 4, two to three hour sessions between charges and is showing no signs of reduced power output.

Regards. Peter.

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#20 boandpokey



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Posted 15 September 2013 - 02:48 PM

ill be getting me one soon im sure

#21 Ski-Patroller


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Posted 02 October 2013 - 01:21 PM

When I had a Nexstar 8 GPS I bought a 72AH Gel Battery from Batteries Plus. It was about $80 IIRC and had far more capacity than the power tank. It was also a deep cycle battery.

I use a small 7.2 AH battery to run my 5i, and it will run all night. It is a deep cycle also, one designed for a UPS system.

#22 Geo.



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Posted 05 October 2013 - 01:54 PM

I recently picked up a small charger for camp {i.e., in upstate NY, a small lake cottage}. One rainy day I read the instructions. Not much new information in there, but the description of the different types of lead acid batteries was interesting, to wit:

SLI — These initials stand for Starting, Lighting and Ignition, which are the three basic functions which a battery has to perform on all normal vehicles. This battery type is usually used in cars, trucks and motorcycles. These batteries have vent caps and are often marked "Low Maintenance" or "Maintenance-free". This type of battery is designed to deliver quick bursts of energy (such as starting engines) and have a greater plate count. The plates will also be thinner and have somewhat different material composition. Most maintenance free batteries are SLI, otherwise known as Flooded, Regular or Standard Batteries. Regular batteries should not be used for deep cycle applications.

When antimony is known to be one of the materials used in the battery's construction, that battery is conventional/low maintenance type. Some low maintenance batteries have a relatively smooth top without any apparent battery filler caps. If, however, the battery manufacturer recommends periodic checking of the electrolyte level and provides access to the battery for water additions, the battery is probably a low maintenance type.

Deep-Cycle — Deep-cycle batteries are usually marked as "Deep-Cycle" or "Marine". Deep-cycle batteries are usually larger than the other types. This type of battery has less instant energy but somewhat greater long-term energy delivery than regular batteries. Deep cycle batteries have thicker plates and can survive a number of discharge cycles.

AGM — The Absorbed Glass Mat construction allows the electrolyte to be suspended in close proximity with the plate's active material. In theory, this enhances both the discharge and recharge efficiency. Actually, the AGM batteries are a variant of Sealed VRLA (valve regulated lead acid) batteries. Popular uses include high performance engine starting, power sports, deep cycle, solar and storage battery. AGM batteries are typically good deep cycle batteries, and they deliver best life performance - if recharged before the battery drops below a 50 percent charge. If these AGM batteries are completely discharged, the cycle life will be around 300 cycles. This is true of most AGM batteries rated as deep cycle batteries.

GEL — The Gel Cell is similar to the AGM style because the electrolyte is suspended, but different because technically the AGM battery is still considered to be a wet cell. The electrolyte in a GEL cell has a silica additive that causes it to set up or stiffen. The recharge voltages on this type of cell are lower than the other styles of lead acid battery. This is probably the most sensitive cell in terms of adverse reactions to over-voltage charging. Gel Batteries are best used in VERY DEEP cycle application and may last a bit longer in hot weather applications. If the incorrect battery charger is used on a Gel Cell battery, poor performance and premature failure is certain.

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