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I have a solar-powered LED number display whose rechargeable batteries have apparently died. I'd like to hook it up to AC power using a 3V adapter (i.e., cutting the leads from the batteries and soldering to the adapter output), but I'm unsure whether anything special needs to be done to prevent the charging circuitry from frying the adapter. Presumably a simple diode would solve any such problem, but do I need to worry about it in the first place?

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  • \$\begingroup\$ Is it one of these solar powered displays? \$\endgroup\$ – jippie Jul 14 '13 at 20:18
  • \$\begingroup\$ @jippie - not quite. More like this. \$\endgroup\$ – kurkevan Jul 14 '13 at 20:26
  • \$\begingroup\$ Why not just buy a couple of AA Nicad cells and replace the dead ones? \$\endgroup\$ – JIm Dearden Jul 14 '13 at 20:32
  • \$\begingroup\$ @JImDearden - because then I'll be repeating the task in two years, when they die again... (There isn't much sun in the spot it's mounted, so the batteries probably aren't getting fully charged.) \$\endgroup\$ – kurkevan Jul 14 '13 at 20:38
  • \$\begingroup\$ ok - then a 3V DC supply with diode should do the trick. \$\endgroup\$ – JIm Dearden Jul 14 '13 at 20:58
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Just use the adapter and cut the leads from the solar panel.

If the batteries "took over" supplying energy at night time then you needn't worry about the solar charging circuit affecting the batteries when dark and this applies if you power from an external 3V.

Cutting the leads from the solar panels stops any charging circuit causing any possible problem and emulates the night-time scenario. If you don't want to cut the leads from the solar panels, mask them off optically.

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  • \$\begingroup\$ The problem is that the numbers will then be lit 24/7. I would like to retain the switching functionality of the solar panels to cut the power during the day, while avoiding any issues that may arise from the panels' charging during the night. \$\endgroup\$ – kurkevan Jul 14 '13 at 21:36
  • \$\begingroup\$ @kurkevan Are you saying that the LEDs are dimmed during the day by the presence of light on the panel irrespective of the charge of the batteries? \$\endgroup\$ – Andy aka Jul 14 '13 at 21:58
  • \$\begingroup\$ yes; the lights only come on at night \$\endgroup\$ – kurkevan Jul 14 '13 at 22:08

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