I have a MOPHIE SN 123417****84 battery for more than 4 years for the use of IPhone 8 Plus (3.8 V 2420 mnAh), the problem that forces me to ask is that it is charging my cell by 25% only and not as before. I suppose there must be wear and tear on said battery due to the time of use. How can I verify this? When I load (later full load points) and I assemble it with the cel it does as I say with low load. Is there any way to measure electronically or how is this, not to rule it out? Is that the problem? . Thank you very much for the information to help me solve this problem for such a valuable element. Catalan Pellet Antonio MD