I have an Arduino project that

  1. is powered from 12v/15A dc power source
  2. needs to switch to battery power and still get 12v (dc power may start/stop at any time)
  3. recharge the battery when dc power restored (top-off or full recharge)
  4. if battery dies, will still work from 12v main dc power (dead battery would just prevent it from powering off the battery)

I am thinking of using:

  • an 7.2v 1500mah NiMH battery-pack (weight doesn't matter, so its not worth the risk using LiIon/LiPo). 10 Cells in series.
  • BQ2002 - NiMH battery controller
  • MC34063A - boost converter to boost the 7.2v from the battery controller to 12v (I only need 12v500ma out)

Are there better battery controllers or boost converters to use?

How do I do #3 and #4?

At what rate would the battery be recharged? I want to limit this to 1amp

Will I also need a temperature sensor, at least if I only charge it at 1ah?

Do I need a voltage regulator, or is the output from the battery controller going to be stable enough for an Arduino?

I want to use existing ICs for as much as possible. I want to minimize how much I have to build, but I also can't use an Arduino shield.

  • \$\begingroup\$ Use a diode OR, you don't need the step up converter. This will result in instant power switchover when your 12v rail disappears. Read the datasheet for how to set charging current. Also you have 6 cells in series, not 10 \$\endgroup\$
    – HL-SDK
    Nov 22, 2013 at 18:20
  • \$\begingroup\$ "the risk using LiIon/LiPo" Please elaborate. \$\endgroup\$ Nov 22, 2013 at 20:04
  • \$\begingroup\$ @HL-SDK: No, he most likely does have 10 NiMH cells in series. NiMH cell voltage over most of its discharge for typical room temperatures is 1.2 V, so 10 of them makes sense. \$\endgroup\$ Nov 26, 2013 at 13:17
  • \$\begingroup\$ @OlinLathrop: He mentions using a 7.2V battery. Not sure where he got 10 from that... \$\endgroup\$ Nov 26, 2013 at 13:22

1 Answer 1


Why not use a Lead-Acid battery? Advantages include:

  • Suitable for long-term trickle charging or float charging.
  • Cheap.
  • 12 V nominal.
  • Charging is dead simple - apply ~13.4 V indefinitely.

Those guys are designed to be used for backup power supply.

  • \$\begingroup\$ Nominal, not native. Actual voltage can vary a bit. \$\endgroup\$ Nov 26, 2013 at 13:23
  • \$\begingroup\$ @IgnacioVazquez-Abrams, true. Though I get the impression that it is always above 12V, so a LDO could be sufficient for the feed-forward path. And charging is dead simple - pass to it 12 V, indeffinitely! \$\endgroup\$
    – Vorac
    Nov 26, 2013 at 13:33
  • \$\begingroup\$ Thanks a lot, @RedGrittyBrick. I hope I have not missed the point of the question entirely, in which case my answer and your edit would be useless. \$\endgroup\$
    – Vorac
    Nov 26, 2013 at 14:23
  • 2
    \$\begingroup\$ @Vorac: regardless, it's still a useful answer for future readers with relatively static applications (or some vehicle-based applications) where weight is not of paramount importance. \$\endgroup\$ Nov 26, 2013 at 14:31

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