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 the one I have selected and used with great success
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:
Small Batteries
Vanson V-6988 10 bay AA & AAA battery charger. This is a slow charger, 8-20 hours! For maximum battery life you want to prevent the cells from heating while they are charged or discharged. This charger will also condition the cells.
Features
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
charge)
AAA rated capacity (180mAh-750mAh): charging time 1 to 4 hours.
AA rated capacity (500mAh-2250mAh): charging time 3 to 16 hours.
Battery Protection
Identification of defective cells.
Over heating and short circuit protection.
Protection against wrong polarity.
Maximum charging timer control for overcharge protection.
Discharge Feature
Unique Discharge Feature---100% battery life protection.
I got mine from Green Batteries 1-800-790-7866 Ext. 1 About $50 shipped