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Am I overthinking power tanks?

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#1 mkothe

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Posted 02 January 2013 - 11:05 PM

Hi,

My apologies for starting another thread about power tanks, but all these threads about how to maintain them to avoid having them lose capacity, and the various instructions on how to build better devices from marine or wheelchair batteries have made me somewhat reluctant to consider a serious goto telescope. I have a Nexstar 102 SLT which I am powering with an AC adapter for now, but if I were to get something more involved, I would like to be independent of outlets.

Unfortunately I get to observe only infrequently (less than once per month). I am looking for something that I would not have to remember to recharge every few weeks, and then remember to take off the charger after a few hours. I also would like to avoid having to become an electrical engineer and fiddle with a voltmeter to track how the battery is performing. OK, I guess I could get a voltmeter just for checking, but some of the instructions for maintaining the charge sound more involved than I would like.

Is there a solution that would allow me to plug the unit in and forget about it until needed? Maybe the battery tender devices I saw recommended, or something different than the power tank? I won't have a lot of equipment to power (I'm thinking of a Nexstar 6/8SE, maybe some dew strips and possibly a USB charger for the iPad).

I would like to avoid having to build something myself, unless it is easy and would be a substantial improvement over what is available at reasonable cost. The wheelchair battery setups sound promising in that they seem to last forever, but I don't want this to turn into a project, and also would like to avoid something that might be too unwieldy (weight, size, lots of cables etc.).

Maybe I'm getting the wrong impression and power tanks are more user-friendly than it sounds from these threads? Please keep in mind that I would use the unit fairly infrequently, so maybe that changes the situation and makes a power tank a poor choice and I should consider a different solution? Something without lead/acid batteries?

Thanks for listening and any advice,
Michael

#2 CJK

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Posted 02 January 2013 - 11:16 PM

The type of situation you're describing is pretty much the same as that faced by many boat, RV, and motorcycle owners. A good quality, deep cycle battery connected to a multi-stage charger (such as a Battery Tender) is pretty much a "set it and forget it" solution. If you don't need a huge amount of capacity, one of the jump start thingies or the power tanks is fine, but throw away the wall wart and use a Battery Tender Jr. To charge it instead.

I'm an R/C car and aircraft guy, and I've just finished building a battery power system for my astronomical endeavors -- I need to write up the details to post here, but I'm procrastinating -- and trust me, the key to a happy battery is a quality charger.

-- Chris

#3 RTLR 12

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Posted 03 January 2013 - 02:46 AM

There are some, many actually, jump packs that have 'smart charging'. You have to read the description to find the ones that do not need to be unplugged after charging and can be left plugged in all the time. I have some Vectors (Black and Decker), Schumacher's and Duracell's that all have smart charging. There are many more brands out there too and with them you don't need to buy an additional charger to maintain them.

Stan

#4 Tom and Beth

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Posted 03 January 2013 - 04:19 AM

Like Chris said; Battery Tender.

I have a wheel chair battery hooked to mine, and it's connected with a "goof resistant" plug. The battery is maintained at the proper charge, and when it's time to use it, 15 seconds max to disconnect from the charger.

All you have to do is remember to spend 15 seconds to reconnect when you get home

#5 Ira

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Posted 03 January 2013 - 07:01 AM

My AstroTec power tank is plug and play. Never had a problem with it. I do unplug it after it indicates a full charge. That's it.

/Ira

#6 Midnight Dan

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Posted 03 January 2013 - 07:27 AM

Hi Michael:

You can get automotive jump start units that have smart chargers in them so you can leave them plugged in all the time without risk of overcharging. That should be all you need.

Another option to consider is a NiMH battery pack. MUCH smaller and lighter than a lead-acid jump starter, and you can also get them with smart chargers ... but not built-in. The advantage of these is you can usually find a place to velcro them to your mount, and they add very little to overall weight of your system so you don't have another item to haul out with you.

Here's a picture of a 2-pound NiMH battery pack that I have velcroed to the base of my 8SE. I get 4-5 hours of usage per charge, powering my SE mount as well as 2 dew heaters.

Posted Image

It does take a little wiring up because you have to make a cable to fit your particular mount. Here's where I got the battery pack. http://www.onlybatte...ItemID=11075.37
The same site sells a variety of smart chargers. I just got the cheapest one, even though its a fairly slow charger:
http://www.onlybatte...ItemID=11862.12

-Dan

#7 hamdul

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Posted 03 January 2013 - 09:50 AM

Hi Michael,
I have a Schumacher XP 500 Which I got at Walmart (On Line) I think it was around $35.00. It has that feature of leaving it plugged in and not overcharging. It has worked flawlessly for me. As a former Bostonian I have to ask, Where do you observe from, certainly not the city?
Fred

#8 hamdul

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Posted 03 January 2013 - 09:53 AM

P.S. Michael
My Schumacher also has a USB port connection
Fred

#9 Al Canarelli

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Posted 03 January 2013 - 11:00 AM

I've always owned power tanks (usually 17 amp size) and enjoy their compact size, weight and the convenience they offer. I learned only recently that when they no longer accept a charge, it's not always a battery problem but rather frequently can be a wall charger problem. (I wonder how many power tanks I gave up on when the culprit was only a faulty wall charger.)

Nevertheless, the last time one of my power tanks would not take a charge from the wall charger ( Celestron 17 amp unit), I used an automotive charger instead. I connected the alligator clips of the charger directly to the alligator clips of the power tank ( red to red, black to black) and let it charge for a few hours. About 4 hours later it was fully charged. I did this months ago and the power tank is holding up as though it was brand new. Btw, the wall charger still will not charge the power tank.

#10 cliff mygatt

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Posted 03 January 2013 - 12:41 PM

Michael, I use a 12 Volt RV/Marine Deep Cycle battery in a standard plastic battery box with two 3 plug cigarette lighter adapters attached to the top. I charge it with a standard Craftsman battery charger before I take it for star parties and it lasts the 4 days of these events. I store it with my telescope accssories in the garage when not in use. It provides all the power I need with room for future use such as a laptop or CCD camera. Simple, affordable and easy to handle. Good Luck!

#11 skybsd

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Posted 03 January 2013 - 01:38 PM

Hello,
Have a look at the Kendrick Astro Power Packs.

Rather excellent quality, and helpful customer service.

Hope that helps..,

Regards,

skybsd

#12 oo_void

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Posted 03 January 2013 - 01:44 PM

Yet another one of these. Power Tanks and Jump Starters are typically designed for a short, quick burst of power, not a constant draw. The best bet is a deep cycle marine battery and a cheap battery box with 12v connector built it. Add a Battery Tender, Jr. and you're set. If I can put such a system together, anyone can ;).

#13 mkothe

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Posted 03 January 2013 - 10:39 PM

Thanks for all the input! I think I'll go with one of the power packs with built in smart charger to keep it simple for now. I like that they are one-hand portable and self-contained. The Schumacher sounds like a good option. The Amazon reviews on that one were mixed, but the price is right, and with the endorsement from Fred, I'm willing to give it a try.

Fred, I am in West Roxbury, so the skies are not great, but a bit better than right in Boston.

Michael

#14 derangedhermit

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Posted 04 January 2013 - 08:30 PM

My only suggestion (request, actually) is that you rethink leaving the charger attached to AC power all the time. Most units, e.g. the Schumacher "automatic" one referred to earlier, tell you in the User's Manual under "How to Charge" to *unplug the unit from the wall when charging is completed*. Battery chargers left plugged in and unattended have started a lot of fires in people's garages and homes.

I can promise you that having your house burn down is a life-changing event.

#15 RTLR 12

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Posted 04 January 2013 - 10:07 PM

This is what it says in my Schumacher User's manual...

The GREEN LED will light when the battery has reached full charge. This could take up to 72 hours, due to the age and condition of the battery. The charger will automatically go into maintain mode and maintain the battery at full charge without damaging it.

Stan

#16 derangedhermit

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Posted 05 January 2013 - 12:15 AM

:shrug: I went to the web site and d/l'd the XP400/XP500 pdf.
web page
Maybe it would be good to read the manual for a specific model before any purchase.

IMHO it is better to figure out some way to remember to plug the charger in for an hour or two at least once a month, and leave it unplugged the rest of the time.

#17 hamdul

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Posted 05 January 2013 - 09:34 AM

I agree, "It would be good to read the manual' And the manual CLEARLY states "The green LED will light When the battery has reached full charge. This could take up to 72 hours due to the age and condition of the Battery. The charger will automatically go into maintain mode and maintain the battery at full charge WITHOUT DAMAGING IT."
As I read it the references alluded to in the previous posts are for when the battery is being charged by the automobile battery not from house current.
Fred

#18 panhard

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Posted 05 January 2013 - 10:20 AM

Here is what I use to charge batteries. It does all my batteries. Also when storing a battery, don't put it on the ground or on concrete floor. charger.

#19 RTLR 12

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Posted 05 January 2013 - 10:36 AM

... don't put it on the ground or on concrete floor.


That is an old wives tale.

Stan

#20 EdTheEdge

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Posted 06 January 2013 - 02:08 PM

I probably shouldn't say this for fear of jinxing myself. But my Celestron 17AH powertank has been one of my most dependable pieces of equipment. It even outlasted my Battery Defender which just quit on me 2 months ago. I have replaced the Battery Defender with a Battery Tender Jr which is working OK but takes more time to recharge (all) of my batteries. I have never used the Power Tank's included charger. My Power Tank has given me flawless performance for almost 4 years now.

#21 RTLR 12

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Posted 06 January 2013 - 02:50 PM

Battery Tender JR only charges at a rate of .75 amps. Slow to charge, but easy on the battery.

Stan

#22 Smittty692k4

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Posted 07 January 2013 - 11:12 AM

Hiya Michael,

Instead of a bettery tender, I would recommend the Schumacher XP2260 power tank. ou can buy it at walart in the automotive section.

I also use the 102 SLT and a Nexstar 8SE (with dew strips)

Just wanted to throw this out there. And if you have a problem, its only Walmart, exchange it right. HAHA

Digital battery display
Non-overcharging (If you forget, it wont ruin the battery)
2 AC ports
2 Cig lighter ports
USB port

Plus extras. Been using my 2 for a year and half. No issues.

#23 zippeee

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Posted 07 January 2013 - 01:27 PM

I read somewhere that the Battery Tender Jr. gets really hot (hotter than you'd feel comfortable with leaving it plugged in and unattended), can anyone confirm this? I'd like to replace my 12v charger (a very nice, standard auto/RV one) with a low power BT of some sort.

#24 Paul G

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Posted 07 January 2013 - 02:32 PM

I read somewhere that the Battery Tender Jr. gets really hot (hotter than you'd feel comfortable with leaving it plugged in and unattended), can anyone confirm this? I'd like to replace my 12v charger (a very nice, standard auto/RV one) with a low power BT of some sort.


Mine hasn't after years of use. I use Optima blue top dual purpose marine batteries and Optima tech support recommended Battery Tender, Jr. It has worked very well for me.

#25 EdTheEdge

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Posted 08 January 2013 - 11:46 AM

I leave mine plugged in almost 24/7 charging my cars and/or my power tank. It does not get hot.






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