I have a telescope with a computerized mount and some additional controlling systems. The mount requires a 5-10 minute long calibration process (to track stars accurately) every time it is powered.

I use a 12V battery to power all the things (they all use 12v), and the average battery life is around 3-4 hours. Some deep sky objects require 6+ hours of observation. I can do that only when I connect the mount to AC power due to the limited power of the battery.

Usually dark sites (far away from city lights) do not provide electricity.

How can I make my system battery hot swap-able? Is keeping a low capacity battery (enough for 1-2 minutes) on the system all the time parallel to the main battery good idea (with a diode in between to prevent backup battery charging the primary battery)?

  • \$\begingroup\$ I would make a power bank with 8 AAA batteries in series and a Zener diode at the positive end, and wire it in paralel with the current battery. the batteries will drain themselves once the current pack is done, but be aware that this will temporarily mess up any sensors that display how much battery is left, so you'll have to time it yourself. \$\endgroup\$
    – user86234
    Apr 24, 2016 at 23:50
  • \$\begingroup\$ Your idea is fine dvdmm, but I would think that changing the battery can 'decalibrate' the telescope, e.g. vibrations. If this is not an issue you can parallel how many batteries you want, just be sure to use thick enough wires. \$\endgroup\$ Apr 25, 2016 at 0:06
  • \$\begingroup\$ battery pack isolated (physically) from the power distribution with a wire. the total current is no more than 1.5 amp when all the steppers are on in the mount. So a decent wire works just fine. \$\endgroup\$
    – dvdmn
    Apr 25, 2016 at 0:26
  • \$\begingroup\$ If you're going to take two batteries anyway, would it make sense to devote one of them to the telescope mount alone, and use the other one for everything else? \$\endgroup\$
    – Dave Tweed
    Apr 25, 2016 at 0:26
  • \$\begingroup\$ Using one battery at a time is better, I can charge the other one with car's 12v output while other one runs the system. \$\endgroup\$
    – dvdmn
    Apr 25, 2016 at 0:36

1 Answer 1


Your requirements are pretty simple. You'll need a pair of connectors for the batteries and a pair of diodes. Make a connection setup like this


simulate this circuit – Schematic created using CircuitLab

Now you can connect or disconnect either connector as you wish. As long as one battery is always connected, you should have no problems.

Your diodes should be rated for at least 12 volts (20 or more is better), and at least the current required by the controller, probably at least 1 amp. Also, since the diodes will drop some voltage, Schottky diodes are preferred. Something like a 1N5820 should do you just fine. You can try sources like Jameco, Digikey or Mouser, or any number of other suppliers.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.