Am I overthinking power tanks?
Posted 02 January 2013 - 11:05 PM
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,
Posted 02 January 2013 - 11:16 PM
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.
Posted 03 January 2013 - 02:46 AM
Posted 03 January 2013 - 04:19 AM
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
Posted 03 January 2013 - 07:01 AM
Posted 03 January 2013 - 07:27 AM
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.
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:
Posted 03 January 2013 - 09:50 AM
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?
Posted 03 January 2013 - 09:53 AM
My Schumacher also has a USB port connection
Posted 03 January 2013 - 11:00 AM
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.
Posted 03 January 2013 - 12:41 PM
Posted 03 January 2013 - 01:44 PM
Posted 03 January 2013 - 10:39 PM
Fred, I am in West Roxbury, so the skies are not great, but a bit better than right in Boston.
Posted 04 January 2013 - 08:30 PM
I can promise you that having your house burn down is a life-changing event.
Posted 04 January 2013 - 10:07 PM
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.
Posted 05 January 2013 - 12:15 AM
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.
Posted 05 January 2013 - 09:34 AM
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.
Posted 05 January 2013 - 10:36 AM
... don't put it on the ground or on concrete floor.
That is an old wives tale.
Posted 06 January 2013 - 02:08 PM
Posted 06 January 2013 - 02:50 PM
Posted 07 January 2013 - 11:12 AM
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
Plus extras. Been using my 2 for a year and half. No issues.
Posted 07 January 2013 - 01:27 PM
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.
Posted 08 January 2013 - 11:46 AM