I installed what is called a "Battery Bug", thats the product name. Sounds great, plug and play, digital, constant readout, tells you the voltage and the percent left in battery and percent used last start, mount it anywhere. My system may be bad, but when I took my battery in to be replaced cause the thing said it was low, battery was fine. That was 3 years ago, bought an old fashioned lead acid and no problems since. The bug has been showing 24% battery life left just after the second time I started it up with the new battery. Yes, I inserviced the new battery exactly as stated in the manual. Thinking of going with this type of meter.