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Charge Monitor v1.0

Have you ever felt the need to evaluate the charging capacity (mAh) of your rechargeable batteries? If your answer is yes, then this product is for you. The inspiration behind this product comes from my experience of the power supply requirements for a vast type of robots. Mostly I have used rechargeable types of batteries in my projects, but charging them accurately had always been a problem for all of us. We all have faced situations where we want our batteries charged in the shortest possible time, but we also don't want to over-charge them. This is especially true for Li-ion type of batteries which require a very tight control of the charging profile. One more thing most people overlook but is equally important is that how the charge holding capacity of the batteries changes with usage, since it allows us to estimate the operating time of our robots. Many of the times our robots have run out of juice just before hitting the finish line just because the batteries were not fully charged when charged in a hurry! So it was a must to have the batteries charged at all times, and since I had many different kinds of batteries, it was nice to have a single charging solution for all of them.
I have searched many types of 'smart' battery chargers, but the exact functionality required by me was not found in any of them. Most of all, I wanted the charging current / voltage to be configurable for each battery chemistry type. Then, I wanted it to have the the charge (mAh) & energy (mWh) logged with charge time duration. I could not find a charger with all these features in the Indian market, so I decided to make my own and here it is: Charge Monitor v1.0 !

It is a microcontroller based smart
battery charger that also logs the mAh / mWh during the charge duration.
Ready-made chargers are available for sure, but as I said you just cannot set your own charging currents / voltages in them, and they are kind of 'dumb' as they do not provide any kind of information about the State of Charge (SoC) of the battery. Charge Monitor v1.0 is designed keeping all these points in mind. It logs many parameters about the charging process from which you can estimate the battery health. It also includes a USB port to measure and log the USB charging data! A feature specifically added for capacity estimation of Power Banks ;-)

It is having following features:
  • Input Voltage upto 30V DC
  • Output charge current setting from 50mA to 1.5 Amp in steps of 50mA
  • Battery Chemistry selection among Li-Ion, Ni-Cd/Ni-MH and Lead acid types.
  • Automatic selection of battery charge algorithm based on battery type selection.
  • 1 to 6 cells battery selection (cells in series)
  • Battery charge completion indication with blinking LED.
  • USB Connector for measuring current draw for various devices (1mA resolution, upto 2Amp)
  • Parameters are written to its non volatile memory every minute while charging (battery or USB) so that in a power fail event, charge capacity & other parameters are not lost upto previous minute.

It shows the following scrollable parameters on the 16x2 LCD:

  • Input Voltage
  • USB Current
  • Output Voltage / Output Current (with resolution of 10mV and 1mA respectively)
  • Charge out (mAh): Integration of output current over charge time duration
  • Energy out (mWh): Integration of (output current*output voltage) over charge time duration
  • Separate Charge time durations for battery charging and USB output (hh:mm:ss)

The design is based on an MSP430 microcontroller. The controller implements a buck regulator scheme to regulate the output current and voltage to charge the connected battery. The USB port is powered from LM2596 buck regulator able to supply upto 2A @ 5V.

Below is a description of the various parts of the unit:

Here are the real pics of the thing in action!

Charge Monitor v1.0 Pics

Munish_4 Kumar,
Mar 26, 2016, 12:41 AM