Wire-Lists #59 – Deciphering Battery Life and Voltages

Social Media WireLists59 350pxOccasionally, customers contact us because the battery reading on their  receiver (or transmitter) shows a lower voltage than when measured with a meter. Or, similarly, they report that their equipment displays low battery warnings with new batteries. There are a few explanations for this:

  1. Incorrect battery type setting
    Make sure the settings are set correctly for the battery being used: alkaline or lithium (with a time specified if using rechargeables).  If you are using lithium batteries but the setting is set at alkaline, the meter levels won’t be accurate, as the batteries discharge at different rates.
  2. Loads
    Are you measuring under load? For example:
    With lithium AA batteries, the voltage will measure 1.75 volts or higher with a new cell without a load.

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    If a load is added to the voltage meter, the voltage will be much lower as when in use. If the meter in use did not employ a resistive load to simulate an in-use current draw, the voltage would indeed measure higher. New lithium AA batteries will measure 1.75 volts or higher when tested without a resistive load. In the photograph below, a 2.4-ohm load is added to the meter, meter in resistance mode to show value.

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    If you return the meter to the voltage scale with the load attached. The noted DC voltage will show the “in use” voltage of the battery. In this case the 2.4-ohm load would draw roughly 625mA from the battery.

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    Similar results would be expected from alkaline batteries as well (though the unloaded voltage would be lower than a lithium battery).

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    If we measure a battery without load, we see 1.65 volts on the meter. Many would, at first glance, consider this a “good” battery.

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    However, if we add a load to this (same 2.4-ohm as we used prior) and measure again, the reading drops to .985 volts – under one volt and not usable in most circumstances.

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  3. Battery Door Looseness
    Is the battery door on your unit closed completely? We have found that with some of the “screw closure” battery doors, such as the ones on the SMs, loosening the screw as little as a quarter turn will result in erroneous battery readings, because the battery isn’t fully touching the contact. Check to see if this is the case. Also, for these transmitters, note that current travels through the battery door screw itself. It is a good idea to make sure the threads are clean on the screw and in the socket. The addition of silver conductive grease can also enhance conductivity and thus battery life.
  4. Battery Age
    Is the battery truly a “new” one? Sometimes, users will claim that the battery is new, but it isn’t “new out of the package.” Batteries can lose charge over time, even when merely sitting in a drawer or a bag. A new battery out of the package should show green on the unit’s LED if it has adequate charge and red if it does not. We have a video on our YouTube channel that address this issue: https://www.youtube.com/watch?v=WNq1HfNe_us

Do you have questions or concerns about battery life? Email us at our Ask The Experts box (Link to: This email address is being protected from spambots. You need JavaScript enabled to view it.) or contact our This email address is being protected from spambots. You need JavaScript enabled to view it. for details.