Resisters AND Diodes to Balance

Resisters AND Diodes to Balance

As a survivalist, I do not use integrated circuits. I do have to use semiconductors for solar charging and balancing ultracapacitors, “CAPs”. My diode of choice is the heavy duty, high amp and high heat Schottky diode. In this post, I am addressing two concepts to hardwire a balancing circuit for a CAP bank.

For my M1 power bank, I will use LED’s, yet will still have on hand analog volt meters as a primary measurement tool. LED’s are nice to have a quick reference to any problems with my charging unit. The brighter the LED on my CAP bank means that an ultracapacitor is about to fail (too much voltage). On my Fe/Ni bank, a weak LED light indicates a cell is not charging either by a low water level or a short in one of its cells.

Figure 1


Balancing Methods

The balancer in figure (2) has both resisters and diodes, my oldest balancer. Most modern balancers, figure (1) above, sold today only contain diodes because back to back diodes actually have resistance. They resist a small amount of forward voltage. The LED diode will resist current to produce light, the Schottky diode will produce heat as it resists current. The brightest LED means there is a very high voltage on one CAP, and also this CAP has the highest resistance so to “balance” the circuit by reducing the voltage on that one CAP alone.

Figure 2

The second image, figure (2), uses a 430 ohm resisters in parallel with the diodes. This is a duel layer balancer. The bulk of the current will always take the least resistance path, the diodes. If a LED diode fails this will create an open circuit and the balancing will fail for the circuit in figure 1. But, for the circuit in figure (2), if a diode fails, the resisters will pick up the balancing load. As a survivalist, I do not depend on weak, limited life LED’s as a primary component so I will use resisters in combination with LEDs. But nice to have LEDs when they work.

Breadboarding a Balancing Circuit

Simple wiring by way of a breadboard will keep my system reparable and customizable. Though breadboards are designed for temporary, experimentation wiring, I find them useful for a final solution in small applications. Breadboards are prone to vibration and corrosion, yet reparable and easy to troubleshoot. Keep in mind, this a survival website. See Figure (3), components are not trimmed in this pic.

Figure 3

If I were manufacturing or mass producing balancers, then the components would be soldered onto circuit boards. In any case, since I am hardwiring, if an LED did fail, I could easily locate replacements to easily swap out; see Figure (4). These LED’s were recovered from a  old AC window unit control panel.  In this case, since they are soldered and trimmed, I would have to solder extender wires after extraction hoping to avoid damaging them by the thermal stress.

Figure 4

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