EE question - Batteries & Multiple power sources

For my project I was planning to use 2 power sources - one for my Domino and another to drive the DC motor board sold through here.

Initially they will be based on cells that I claimed from a cordless drill batter pack for which the drill broke. It had 15 C sized 1.2v 1200 maH batteries to make up the 18v. Eventually I’ll replace them with Lipo/Life power packs for lower weight, but for now I’m using what I’ve got on had (plus I have a 2nd extra pack for even more cells ;))

My plan was to use:

  • 5 connected to the barrel plug - since they can put out up to 1.5v each, this is to be safe (and not needing an external regulator).
  • 6, to start with, for the motor controller board & the 2 brushed motors

In another thread I saw this:

My questions:

  1. So does this mean I need connect the “black” wires together from the 2 different packs?

  2. A quick sanity check - Does my power solution look ok? I realize it’s not the optimal or most efficient way to go about this, but it’s baby steps for me.

  1. Yes, tie the black wires together if they are the ground/minus/negative wires.
  2. I hope it is OK because that is what I am doing on my project.

I had this sort of configuration for RWAR, USB batteyr pack for the FEZ, RC battery for the propulsion motor.

It worked fine, and you should be too ;D

I might be misunderstanding this, but are you planning to put 5V on the barrel plug?
I’m not sure that will work. To get 5V out of the regulator the input voltage has to be higher 7-12V

Well, the batteries when charged up by my 19.2v charger, they hold about 1.5v for a while.

5 of these at 1.5v at full charge gives 6.5v - which is why I didn’t want to go to the 5v in. I may need to go 6 batteries for the FEZ for 8 (full charge) to 7.2 (running) to 6ish (mostly depleted).

I understand now :slight_smile:
not 5V but 5 x 1.5V cells. That makes sense.

I make sense … wow :o