Sabertooth Motor Controller:

I really like my Sabertooth 2x25 motor driver. I'll keep using it until it stops working. I've never had any trouble with it, and I have never exceeded it's current to the point that it got hot and shut down. I have it mounted to a 0.25 x 4.50 x 11.00 (inches) aluminum plate. That's lots of sinking for the heat.

The Sabertooth has some option switches, so that it can be used in several different configurations. I have mine set up to accept PWM R/C signals as inputs. I have a DPDT switch in the signal wires so that I can toggle the switch and drive my robot with a R/C airplane remote transmitter -or- I can reset the switch which connects my Sabertooth to a Pololu servo controller, which is driven by a Windows computer.

The board contains some LEDs to inform the user of problems or certain conditions.

Issues:

My driver board is mounted deep in my robot. I can not see these LEDs when the robot is buttoned up. It would be nice if they could just add some pins where I could attach a couple of wires and run them to an LED external to my robot's case. I am NOT going to solder to that board myself. Another issue is with the automatic LiPo low voltage cut off feature. This is a great feature! I'm using LiPos, I'll use that!

But then I found out how it works.
It does not allow you to set the cut-off voltage with dip switches. It estimates the cut-off voltage and the number of cells that you have in series when it is powered up.
IT ASSUMES THAT YOUR CELLS ARE FULLY CHARGED EVERY TIME IT IS POWERED ON. (A false assumption) and it will work until the cells are drained to the calculated voltage.
Then it shuts down, and you must recharge your batteries and start again.

Here is what happened to me.

My batteries were fully charged to 24 volts. I powered on my Sabertooth, and it read the 24v. It divided this by 4 and determined that my batteries had 6 cells in series. It uses 3v per cell as the cut-off (minimum allowable) voltage, so it multiplied 6 cells times 3 volts, and decided that it would cut me off at 18 volts. When this happened, the robot quit moving. I thought that something bad happened, and I quickly shut down the robot. I didn't see or smell any smoke, none of the fuses were blown, the computer was still running. (It can run on voltages as low as 12v).

I was down the street and had to get this heavy beast home. I could not see any warning LEDs because the board is inside the robot. So, I turned it on again. The Sabertooth saw the 18 volts from the depleted battery, it divided this by 4 and determined that I now had 4 cells in series. (I don't know if it rounds up or down) It multiplied 4 cells times 3 volts and it set my cut-off voltage to 12 volts. The Sabertooth was going to let me drain my batteries down to 12 volts now. Since I have 6 cells in series, it would allow me to suck them down to 2 volts per cell, which would destroy them.