I have a number of projects on the go, nearing completion that I plan to make use of the various Milwaukee M18 battery packs that I own for use with cordless drills etc. To be clear these project only use power from the batteries and do not charge them.
In these packs the cell terminals are directly exposed through the battery connector, without any battery protection or low voltage cutoff. The tools that connect to these cells tend to come in two varieties, low power tools that only have two contacts, and do their own low voltage cutoff (lights, radios, usb adapters), and high power tools (drills, blowers, saws) that use 4 pins, two of which are some kind of communications, which tells the controller in the tool when to shut off.
For the first part of my question, has anybody had a go at reverse engineering these comms and using them to tell their own projects to shut off.
Secondly I have been working on designing a low voltage cutoff circuit that cuts out at 17.5V, and can pass up to 20A. When having a go simulating most of the circuits around on RC car forums or stack exchange, most of them draw a fair amount of current when off and/or lack hysteresis meaning that due to source impedance the tend to oscillate due to the voltage rising again when the load is removed.
I found the ATL431 which seems to be a far superior replacement to the TLV431, plus that adding a bit of hysteresis to the voltage divider and additional gate capacitance to the mosfet greatly tidied up the result when simulating the circuit.
However li-po batteries deserve some respect, especially when they don't have proper cell protection. Can anybody see any issues with the attached circuit. The source in the schematic is set up with a 100mohm impedance.
Home
Help
Search
Login
Register
