We probably get more phone calls about what battery to buy than any other call.
You want an:
80 AMP HOUR, 12 volt, DEEP CYCLE BATTERY.
NOT a Car battery.
NOT a Marine Starting Battery.
NOT a "Jump Pack" or "Power Tank".
Yes, you can get a larger unit, like a 100 amp hour and the scope will run 20% longer.
You can buy a Deep Cycle battery at Sears, Kmart, TSC....Go to the battery isle, find the Marine section, look for 80 amp hours printed on the top. They cost $60 around here. Usually you get $5 off if you trade in an old dead battery (they don't care what kind of battery, so an old car battery is fine). Don't buy a Marine Starting Battery by accident.
If you go to a real battery rebuilding store, they will have many "rebuilt" deep cycle batteries. You can save even more money by asking for any "orphan" batteries that only fit some strange brand of forklift or floor polisher. The store owner will be happy to get rid of some oddly shaped rebuilt battery. Just make sure it has built in handles!
Most Webster scopes draw an average of about 2 to 3 amps, so if you divide an 80 amp hour battery by 3 amps you get 26 hours of run time between charges.
Leave your battery on a Float Charger (never a Trickle Charger). Float chargers "top off" the battery each day, then turn off automatically. This is an inexpensive unit that is popular:
http://www.harborfreight.com/automatic-battery-float-charger-42292.html
Another popular charger is the "Battery Tender":
http://batterytender.com/
Don't charge your battery next to your scope as gasses could be created that will shorten the life of your mirror coatings.
Don't charge your battery in your house, again those corrosive gasses.
Most Deep Cycle batteries last about 10 years before needing to be "rebuilt" with new electrolyte. Because they can be rebuilt or recycled into new batteries, they are a very "green" technology.
Always store your battery upright. If you leave them on their side for long periods the electrolyte can leak out.
_________________ Eric Webster http://www.WebsterTelescopes.com
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