Update (January 2016): After 3 years of use, the batteries featured in the article below started to suffer from problems associated with old batteries (such as inability to hold enough charge and leakage). I am now planning to replace the cells with fresh ones.
It is important to have a heavy-duty battery at your disposal since it provides some form of assurance, knowing that you can always bring portable power during observations. Some imaging attempts, however, do not really require that much power and it would be unwise to bring with you the whole battery pack since a couple of hours of shooting (perhaps the moon, or Jupiter, or perhaps during casual non-out-of-town observations) would only require 1 of the several batteries in the pack (not to mention that lead-acid batteries are so heavy that they could literally replace the scope’s counterweights!).
After 2 years of using my DIY field battery, I realized that some improvements must be incorporated to the original design to allow a means to separate the individual batteries and recombine them as needed, thus, minimizing the hassle of having to carry unnecessary weights.
To improve the setup, I decided to rewire the individual batteries and improve the manner the batteries are connected. I decided to devise a system that will treat the batteries as modules. This can be easily achieved by soldering a male and female connector directly to each battery, as shown below:
Attaching more batteries would mean increasing the total current rating of the whole system (i.e., longer battery life), adding 9 AH for each battery connected (since each battery has a rating of 9 AH).
This system provides flexibility in deciding how much power to bring, since one can simply attach more batteries (in parallel) as needed.
Also part of the improvement is the replacement of the switch (with one with a higher current rating), the use of a fuse as a protection for short circuit and overload, the replacement of the battery socket (from having 2 sockets to having 3 sockets to accommodate more equipment), and the use of a more powerful battery charger (from 6 ampere to 12 ampere charging current).
The field battery is the most essential component of any portable imaging setup. Since battery power is everything in the field (no power means no pictures), it must be well-built and well-designed, providing enough power without sacrificing portability.
Related article: DIY field battery
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© Anthony Urbano (Manila, Philippines)