Part 2 on Balancing Loads:    • Electrical Engineer Load Testing Ultr...  


If there are tests you'd like to see me do with these Maxwell BCAP3000 ultracaps, let me know!

This video is an overview of ultracapacitors and how to use them in an automotive environment.

Notes on balancing:
When connecting capacitors in series, the voltage drop across each capacitor is determined by the actual values not the rated values. Because ESR and capacitance vary with manufacturing tolerances, time, temperature, etc. the actual voltage drop will not be exactly equal across each capacitor. We care about this greatly when we operate our capacitor banks at or near rated voltage.
Six 2.7V caps in series are rated for 16.2 VDC. Six 2.85V caps in series are rated for 17.1 VDC. Six 2.5V caps in series are rated for 15 VDC. For each application, the user must determine what their operating voltage is and if balancing circuits are desired or needed. Balancing circuits work to maintain a consistent voltage across each capacitor, or to limit over-voltage scenarios. You can buy balancing circuits for modern ultracapacitors which allows you to use them up to rated voltage. Just follow the application notes and installation instructions for the balancing circuits.

In this video you'll notice that I am not using balancing circuits. The 2.7V cells I'm using are in a vehicle with an alternator that regulates to 12.5 VDC or 14.4 VDC depending on driving conditions. Let's work with 14.4 VDC as that is the most common regulated alternator voltage in the industry. At 14.4 VDC, each capacitor in a series string of 6 will see 2.4V. This allows for 0.3V of overage range, or 12.5%. Additionally, the K2 series of capacitors I'm using have a maximum voltage of 2.85V, which allows for additional safety. I make the decision to operate without balancing circuits because I am willing to operate with this safety factor.

You can find other references here:
https://www.maxwell.com/products/ultr...
https://hal.archives-ouvertes.fr/hal-...
https://bib.irb.hr/datoteka/942041.Su...
http://www.maxwell.com/images/documen...