Battery Condition Meters (Advanced)


The BCM-5P series are a digital evolution of our popular LED battery condition meters. With an accurate voltage reference, temperature compensation, and battery protection function they are ideal for use with lithium batteries.

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The BCM-5P series are an evolution of our popular LED battery condition meters. Battery technology is improving all the time and new battery types are available with characteristics that are very different to lead acid ones. For some of these, particularly lithium based batteries, it is vital that they are not discharged below a certain voltage otherwise permanent [& expensive] damage may occur. Also lithium batteries have a much flatter discharge curve, this means that there is only a small voltage difference between 80% full and 20% which makes it tricky to measure capacity accurately.

The BCM-5Ps use an accurate reference voltage, a temperature sensor, and an Atmel microprocessor to make precise voltage measurements, compare them to known discharge curves, and then indicate the capacity accordingly.

The main features of the BCM-5P series are;

  • Very accurate [+/- 0.1V]
  • Built-in temperature compensation [depends on model]
  • Low voltage cut-off function to protect valuable batteries  [can interface to most of our controllers]
  • Will fit existing 5 LED BCM installations
  • Versions for 12V, 24V, lithium, and lead acid

For volume orders we can modify the software for different voltage curves or cut-off points for almost any battery chemistry between 11V and 30V


For 24V LiFePo4 batteries the BCM-5P2 is calibrated to the following off-load voltages:

  % capacity -10’C 0’C 20’C 50’C
Green 80% + 24.2 25.4 25.8 26.2
Green 60% 24 25.2 25.6 26
Yellow 40% 23.8 24.8 25.4 25.8
Red 20% 23.6 22.8 24.6 25.4
Red 0% + 20 20 20 20

For lead acid batteries the BCM is calibrated to the following off-load voltages:

  % capacity 24V [BCM-5P1] 12V [BCM-5P3]
Green 80% + 25.2 12.6
Green 60% 24.8 12.4
Yellow 40% 24.5 12.3
Red 20% 23.8 11.9
Red 0% + 23 11.5

Sizes of the boards are:

  • 5 LED 41 x 19mm, 10mm high

The boards mount behind a panel, with a rectangular slot for the LEDs and two fixing holes at the end of the slot. Full details are in the instruction manual.


The manual is available in PDF format:

Adobe_PDF_file_icon_32x32   Read manual

The manual is designed to be printed double-sided in A4 booklet format. To print the booklet from the PDF on a double-sided printer, select Booklet in the Page Size & Handling section of the print window, and set Orientation to Portrait.