![]() Next, load the battery with a known resistance (560 ohms) and measure the voltage again. The method used to measure the DC resistance was to take a reading of each battery with only the input of the Fluke multimeter as a load (10M). These batteries were fresh and had never been used. It is rare to see lithium, li-poly or other cells being used so we will only test the two common compositions.Īs a baseline, I bought a new package of each type of 9v battery to test as a starting point. The "heavy duty" and alkaline batteries are the most common types used in fuzz pedals. The different construction allows alkaline cells to deliver more power for a longer period of time. The carbon rod may be alloyed with other chemcials and physically shaped to improve performance. They still have the steel shell and zinc electrode as the body but the electrolyte in the paste is potassium hydroxide instead of the chlorides used in the heavy duty batteries. A carbon rod is used as the conductive terminal for the plus side because it will not corrode, and it will be topped with a metal cap or terminal.Īlkaline batteries have a different chemical composition. Ammonium chloride or zinc chloride is mixed with manganese dioxide and carbon black paste for the positive. The body is a steel shell that is attached to a zinc electrode which serves as the negative pole. Heavy Duty batteries are sometimes called zinc-chloride cells, taken from their chemical make up. Fuzz tone changes with a depleted battery are from the lower voltage not increased resistance.Even depleted batteries have less than 200 ohms internal resistance.Battery resistance is highest at DC and decreases with frequency.Fresh batteries have low DC resistance, 5 to 25 ohms depending on construction. ![]() If you don't feel like reading the whole article and struggling through all of the technical details, I will summarize the results here. However, there is little research that has been available to provide a guideline for selecting the resistor value, so I decided to collect some used 9v batteries and subject them to a series of tests. The suggested resistors (or potentiometers) to produce the old-battery-response are usually in the 1k to 5k ohm range. There are also attempts to duplicate the aged battery characteristics with an AC power supply adapter by inserting resistance in series with the power output connection. Most claims are for a warmer, smoother distortion sound, and the effect is often attributed to the increased resistance of the battery as it ages. There have been many discussions about how a dying battery can have an impact on the sound of certain fuzz pedals, especially transistor-based circuits that have little or no power supply filtering, and that were designed to run on battery power. 9v Battery Impedance Measuring the Characteristics of Depleted Cells
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