The care and feeding of batteries is critical for the Bedouin Astronomer, you have to bring all your electricity with you. If you run out, you may wind up not being able to observe, or even leave to go home!
Deep Cycle batteries....
Selecting the correct size battery and then charging it properly will assure long life. I strongly recommend the use of a three stage smart battery charger on your deep cycle. Here's information on a couple I have been using.
This battery charger is the best I have found for caring for a flooded acid deep cycle battery.
From the CTEK site: "The Multi US 7002 is ideal for the charging needs of your recreational vehicle, car and boat, just about any 12V vehicle. The charger is well suited for all year-round use. Thanks to the SUPPLY mode, when changing a battery you avoid losing expensive program settings. Using RECOND mode, you can correct the acid stratification that often occurs in deeply discharged batteries. The battery therby has its power restored and has a longer service life. In addition, the Multi US 7002 is recommended for Optima Yellow Top batteries."
This charger and its little brothers do exactly what the manufacturer says they will do. If you buy one get the extra pigtails for other batteries. You should get the pigtails with the little blinky light in the housing that indicates the level of charge in the battery. If you have any batteries smaller than about 25ahr you need a smaller unit. Consult their web page to select the correct model.
On a budget this is one I have used with great success. It does not have the great control over charging that the CTEK units have, but it is commonly available at Walmart and other locations.
This charger is marketed by Black & Decker and sometimes under other brands. The manufacturer (Vectron) part number is VEC1089A. I got mine at Wal-Mart.
Some good information links:
Battery University, THE BEST source of rechargable battery information!! This is essentially the "Batteries in a Portable World" in the Reader's Digest® format. I suggest buying this inexpensive book!
Deep Cycle Battery FAQ's
Deep Cycle Article
Another Deep Cycle FAQ
Maha Wizard One AA/AAA computerized charger. Few AAA/AA pencell chargers will charge the cell at a rate that prevents heating and the destruction of the cells. This charger allows you to set the charge rate (I use 800ma on AA) and will also Form or Condition the cells. See the Battery University site for information on Forming and cycling cells. You absolutely will not regret purchasing this charger. All (and I mean ALL) of my pen cell problems disappeared after purchasing this charger!
Vanson V-6988 10 bay AA & AAA battery charger. This is a not a slow charger, of 8-20 hours! For maximum battery life you want to prevent the cells from heating while they are charged or discharged. This charger will condition the cells.
Powered by an external AC adapter (850mA).
Intelligent microprocessor controlled with negative delta V (- delta V) cut-off function. Uses constant current pulse charging system. Independent charging channels for optimum charging of each cell. Ni-Mh and Ni-Cd batteries can be mixed to charge at the same time. Automatic charge and discharge function. Individual LED to indicate discharge, fast charge and trickle charge.
Charging Times (depending on level of
AAA rated capacity (180mAh-750mAh): charging time 1 to 4 hours.
AA rated capacity (500mAh-2250mAh): charging time 3 to 16 hours.
Identification of defective cells.
Over heating and short circuit protection.
Protection against wrong polarity.
Maximum charging timer control for overcharge protection.
Unique Discharge Feature---100% battery life protection.
I got mine from Green Batteries 1-800-790-7866 Ext. 1 About $50 shipped The Maha charger has essentially put this on into reserve status.