Bringing portable battery power in the field to run a telescope, mount, and other accessories is commonplace for many amateur astronomers. Many of these astronomers are content with the battery that they purchased along with their mount and telescope. Perhaps it has only powered the mount since it was purchased, and if that is likely to be the extent of its use into the future, then these astronomers may be content with an in-kind replacement of the original battery when the time comes for replacement.

As Give a Mouse a Telescope illustrates, there is always something else that most astronomers will need. A dew heater or two is added, then a camera or two (maybe one of the cameras is cooled), and maybe a focuser is added (and the list can go on and on), and soon the original battery becomes overwhelmed as it lacks the power required to get an astronomer though a full night of observing with the additional accessories.

Consider also that a battery has a limited life. As an old battery is being replaced, the astronomer replacing the battery has probably gained a greater appreciation of the range of future possibilities for his or her equipment. In this case the astronomer may want to consider a more capable power solution that can power not only the telescope and mount, but accessories that are likely to be added for future astronomical plans.

This series uses the term power solution instead of battery, as most packages that astronomers commonly refer to as “a battery” is comprised of several components that might include an enclosure for handling and protecting the battery. The enclosure may also provide panel-like surfaces for mounting other electrical components, which are likely to include some means for monitoring the battery’s voltage as it discharges, power outlets to which telescope accessories are connected, and circuit protection for the outlets. And finally, no power solution is complete without a battery charger that restores the battery’s charge after a night’s use.

Considerable attention will be paid to the battery component of the power solution because it is the most expensive component and specifying a suitable battery for a specific astronomer’s needs requires the most forethought. Most of the other components of a power solution could be the same for a given astronomer’s use case regardless of which battery that is chosen. Depending upon the battery capacity chosen and how quickly the astronomer wishes to have the battery fully recharged, the battery charger might need to scale up with the battery capacity. To be clear, a use case does not dictate the power solution; the astronomer’s power requirements and personal preferences and imagination will ultimately lead to the power solution that is chosen.

As The Astronomical Cost of a Mulligan reveals, not getting the replacement power solution (or any astronomical acquisition) right the first time can be expensive. This series of articles aims to provide some considerations to guide an astronomer’s research as replacement power solutions are explored, with the hope that the next power solution will be the right one the first time.

Safe battery depletion levels and battery charging rates are discussed in this series of articles to illuminate relationships between battery capacity, charging rates, and depletion levels.  Safe depletion levels and charging rates vary by battery type, so there is no substitute for reading the battery manufacturers literature on these subjects.

Toward this end, Part 2 of this series examines how the power requirements of the accessories that an astronomer anticipates using should be a factor in determining the right amount of battery capacity required to meet those power requirements. Once the battery is a known component of the power solution, then how the battery will be used and battery and charging considerations are addressed in Part 3. And finally, Part 4 examines some considerations that influence the selection of a commercially available power solution, or alternatively will influence a power solution design for a do-it-yourselfer.  

We hope that you find this series helpful. Please leave comments letting us and others know about your power solution and how you selected your components and the design.

© 2021 Jim Johnson and Doug Biernacki