Is it possible to use one battery pack as this one (LINK) to power one RGB LED stripe (12v) + 1 raspberry pi (via a voltage regulator like this) + 1 micro servo SG90 (THIS) ??

What would be the perfect diagram? LED straight to the battery, then step down circuit then servo and rpi in parallel? Would I need two step down circuits to ensure that peak consumption in the servo does not reboot my raspi?

Will the battery be able to provide enough mAh for the three things ?

  • \$\begingroup\$ How often are you prepared to recharge your battery? \$\endgroup\$
    – KalleMP
    Commented Sep 15, 2017 at 21:57
  • \$\begingroup\$ Once every 3h of use would be the hard limit \$\endgroup\$
    – javirs
    Commented Sep 16, 2017 at 7:43

2 Answers 2


My 12V LED strips use about 6W per meter, and the Pi will use about 2.1-3W depending onload. So expect a 9W load. It's certainly possible, but it will be more reliable with a 47uF decoupling capacitor on the input of your buck converter. Since you drive the LEDs from 3V3 transistor control (I presume), make sure the gate/base is saturated completely, or they will get too hot.

The IRLZ44N HEXFET may be a good choice. Make sure you have overdischarge protection on the battery - it can be done with a single 10V zener, or (better), a 10V zener and a NPN/PNP pair to prevent leakage when not sensing voltage. http://www.bristolwatch.com has plenty of useful schematics.

IIRC the SG90 used ~4.5V - you could get by with 4.3V I'm sure. Use the 5V rail on your Pi through a diode, and use a 2N7000 MOSFET to drive it. A catch diode may be necessary.

This "6.8Ah" battery pack can readily supply much more than the ~12-13W your hardware needs.

  • \$\begingroup\$ the LED's have their own controller pcb there is no interaction with the pi, I only need to power them. about the SG90, I readed everywhere that it is advised to NOT power them from the pi since they can suck the amperage and reboot the pi, is not the case ? \$\endgroup\$
    – javirs
    Commented Sep 14, 2017 at 14:13
  • \$\begingroup\$ Off the top of my head, the SG90 sucks 400mA at 4.6V. A catch diode and perhaps a smoothing cap will fix any problems. If you supply more than 3A to the 5V pin on the Pi, you'll have plenty to go around... and I am sure it will work fine with just a diode between 5V and input on the servo. What's the servo doing anyway? \$\endgroup\$
    – user2497
    Commented Sep 14, 2017 at 14:15
  • \$\begingroup\$ the servo only moves some stuff around the "control panel" no "torque" really needed, and only from time to time \$\endgroup\$
    – javirs
    Commented Sep 14, 2017 at 14:22
  • \$\begingroup\$ Alright, I think you're good to go then. The IRLZ44N is not fully saturated at 3V3, so if you need that, use a transistor on the 5V rail to turn it on 'more'. \$\endgroup\$
    – user2497
    Commented Sep 14, 2017 at 14:23

Input voltage: 12.6V DC

Output voltage: 12.6-10.8V DC

If the LED strips use simple resistors instead of current regulators, the battery voltage might be a bit low when partially discharged to fully light the LEDs. I suggest you wire your LED strips to a bench supply set to 10.8VDC to check if you still have enough light.


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