A lot of factors come into play. Since you say 20V they must be lithium Ion, have they always been charged soon after being used? If they are not kept charged their life gets shortened. Then again, 4 years might be not too far below the average. I think 5 or 6 might be about average.
Last edited by maple flats; 03-23-2019 at 07:06 PM.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.