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In this video I talk about how to measure the internal resistance of a battery, you can't just put an ohm meter on the battery and measure the resistance but you can use a volt meter and a resistor and do a little calculation. The results may surprise you, typical for a battery of 12 volts or less I'd use a 100 Ω resistor. The actual resistor value isn't critical but you do need to know it's value in order to make the calculation. You only need to have the resistor connected while the measurement is being made which could be just a second or so but you should use a resistor of adequate wattage. You can calculate the Wattage you need from
W = V ² / R
W is the wattage of the resistor you'll need
V is the anticipated 'no load' voltage of the battery
and R is the ohmic value of your load resistor you intend to use.
There are a number of ways that you can measure a batteries internal resistance but I'm just giving you a quick and easy way of making and assessment of your batteries and this will probably be the most helpful if you have a lot of rechargeable batteries and you think one or more are spoiling the whole battery bank. As I say in the video this is not an exact science but it's a very helpful indicator as to the state of a battery. As an interesting project you can calculate the resistance of say a radio or other appliance and work out how the batteries internal resistance will affect the voltage actually applied to the appliance. It gets complicated because as the voltage on to the radios terminals is reduced so is the amount of current that it draws. Nothing is ever just as straightforward is it looks at first sight.
Have fun, play safe.
Thanks for watching.
Kind Regards ... Andy
GWØJXM
