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mobile battery for pi and monitor help

Former Member

i been working on my own mobile pi. i got the pi side of things done but i have 2 problems left. 1st one is the poweing the monitor.

Amazon.com : 7 Inch Tft Color Lcd Car Rear View Camera Monitor Support Rotating The Screen And 2 Av Inputs : Vehicle Ove…

i been told it can runs 12V 500mA, the battery i want is Tenergy Li-Ion 18650 11.1V 7800mAh. i also like to have a solar charger for it

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  • i was trying to find a step-up to 12v at .5 amp but no luck yet. so maybe it have to be a higher voltage battery and a step down?

     

    update: how about something like this? Pololu 12V Step-Up/Step-Down Voltage Regulator S18V20F12. a step up/down 12v at 2amps. its more amps then i like but i dont know.

    for the pi its self i was thinking OKI-78SR-5/1.5-W36-C or Pololu 5V Step-Up/Step-Down Voltage Regulator S7V7F5 not sure which one is better yet

  • in reply to Former Member

    Step down is "easier" to build for the electronics engineers. That makes them cheaper.

     

    The step-up-down are even more complicated. I'd personally just chose a battery that is higher than what you need, and step down. On the other hand, I'd give you good chances that the display will work down to a reasonable cutoff voltage of 10.5V.

     

    If your battery has 7800mAh when you discharge to 3V, you'll be able to use only about 7200mAh if you discharge to 3.5V (per cel => 10.5V in your case). But you'll increase lifespan of your battery dramatically especially if you have a small leakage current in the "voltage too low, shutdown" mode. Then having the 600mAh left will give you much more time to get to a charger than when you have nothing left. And discharging below the 3V is what kills batteries......

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  • in reply to Former Member

    Step down is "easier" to build for the electronics engineers. That makes them cheaper.

     

    The step-up-down are even more complicated. I'd personally just chose a battery that is higher than what you need, and step down. On the other hand, I'd give you good chances that the display will work down to a reasonable cutoff voltage of 10.5V.

     

    If your battery has 7800mAh when you discharge to 3V, you'll be able to use only about 7200mAh if you discharge to 3.5V (per cel => 10.5V in your case). But you'll increase lifespan of your battery dramatically especially if you have a small leakage current in the "voltage too low, shutdown" mode. Then having the 600mAh left will give you much more time to get to a charger than when you have nothing left. And discharging below the 3V is what kills batteries......

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