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Use a Motor Controller Shield for intelligent control of 12V heated clothing

Hi guys / girls,

I hope you can help me to find the right product for my needs. Sorry for the long read…

I have a heated vest that is powered by a battery pack. The vest is rated at 55W at 12V. The battery packs that are normally used to power these vests are 3S li-ion packs. When fully charged output is 12.6V but that quickly goes down to 11.1V (nominal) and ends around 9V (depending on the BMS). As watt is ‘voltage ² / resistance’ the heat output is decreased significantly along the way.

  1. My goal is to create a stable 12V output from a battery pack. An option would be to build a 5S (~21V-15V) li-ion pack and use a voltage regulator to bring the voltage down to a steady 12V. As I’m also using heated gloves (36W at 12V) we are talking about 8A continuously and this might increase to max 12A in the future.

The D24V150F12 voltage regulator (Pololu 12V, 15A Step-Down Voltage Regulator D24V150F12) looks like a good candidate for this. Can anyone conform this?

  1. Now the catch… Sometimes I need to lower the heat output as the vest is simply too warm in some environments. I want to switch to a few fixed levels in terms of voltage like 11V,10V,9V and then back to 12 again. Could I use a Motor Controller Shield on top of an Arduino to convert the input voltage (~21V-15V) voltage to these preset output voltage levels (using PWM)? The Pololu Dual VNH5019 Motor Driver Shield (Pololu Dual VNH5019 Motor Driver Shield for Arduino) looks like a candidate?

I think I need to use a microprocessor for controlling it as I have no way to interact with the Arduino other than cutting the power on and off using a simple switch (between the battery pack and the Arduino. My plan would be to store the current output level in EEPROM and then retrieving that value on boot, switching to the next output level, storing that level, repeat repeat. Would this be a good way or is there a better solution?

  1. Do I need to worry about the heat generated by these boards due to inefficiencies?

Thank you very much for your time!

Leto

Hi. Leto.

Please keep in mind that we do not recommend our products be used in applications where their failure could result in injury.

  1. It seems reasonable to use a regulator to stabilize the input voltage to your heater.

  2. How well a motor driver would work for driving your heater depends on its internal circuitry. If it is just a resistive heater, the PWM output won’t get smoothed out to an effectively analog voltage like it would when driving a motor, but it might still work. You would probably have to test it to see.

2.5. If the only user input you can get is turning the unit on and off, your strategy seems reasonable. Since you will need to make changes to the Arduino code to accomplish that anyway though, a separate button for cycling through temperature settings might be nice.

  1. 12A is near the limit of what both the D24V150F12 and VNH5019 shield can handle continuously without overheating in an open room temperature environment. I expect they would be hot enough to burn. If they were close to your heater, the maximum current might be reduced by a few amps. If you only need to control one heater you could use the shield in single channel mode and get double the current capabilities.

-Claire