Battery Level Monitors for 6V and 12V? How to Build

Lynxmotion Electronics & Software
1

Hardware: BasicATOM Pro on Bot Board II, 6 volt battery for CPU, 12 volt battery for Sabertooth 2X10 motor control.
I have standard rechargeable batteries, the ones in the light green shrink wrap seen in most robot stores.

The 6V only lasts about an hour. When the program starts dying/acting up, I know that the battery is low. When I switch to a charged battery and all is well, but I’d rather not wait until then.

I’d like to have a visual way (LED?) to show either “battery good” or (preferred)“battery low”.
Googleing “battery level monitor” gets me several Op-Amp (LM741) circuits that can be used to light an LED when the voltage drops to a preset level. (Sub-question - - What is the desired level for 6 and 12 volt batteries, or what voltage is used to trigger the "“voltage too low” LED??)

Is an Op-Amp circuit the way to go? …Or is there some way the Bot Board itself can be used to monitor voltage?

2

You may want to consider starting off with the built-in stuff on the BB2. That is the two analog capable pins P16 and P17 are already optionally setup to VS and VL through a 4 to 1 voltage divider using the jumpers on the board. So if you can use those pins, then your program can simply do ADIN commands to get the current analog voltage value for those two power sources. You can then convert those values to actual voltage, by:
Vin/1024 * 5v * 4

Kurt