If it didn’t use power, it could remain on all the time.
There is pretty much no way around this. All voltmeters use power (although digital ones use their own source and draw very little from the measured voltage) but this one consumes more than most.
I think they could make one with some LCD or electrochromic display (both use a negligible amount of power) but it might be too expensive to include on each battery. Also, the voltage to state-of-charge relationship is not a simple one: discharged batteries’ voltage will rise back when not in use but the internal resistance had gone up so they no longer allow discharge at a practical current. The little heater test accounts for this, an LCD or ECD does not.
If it didn’t use power, it could remain on all the time.
There is pretty much no way around this. All voltmeters use power (although digital ones use their own source and draw very little from the measured voltage) but this one consumes more than most.
I think they could make one with some LCD or electrochromic display (both use a negligible amount of power) but it might be too expensive to include on each battery. Also, the voltage to state-of-charge relationship is not a simple one: discharged batteries’ voltage will rise back when not in use but the internal resistance had gone up so they no longer allow discharge at a practical current. The little heater test accounts for this, an LCD or ECD does not.