I tested a 2 yr old 65 series Napa legend flooded battery. The tester is a harbor freight resistance type tester where you input the rated CCA. The sticker on the battery shows it is an 850 CCA battery. I charged it the day before and got 718 CCA at around 50 degrees. The readout showed 3.68 ohms resistance. This got me to wondering if this is still a good battery and what is a normal percentage of loss per year as far as CCA is concerned? The CCA tested was around 84% of new.
What is normal capacity loss over time?
- Thread starter oilstudent24
- Start date
if you had tested the battery when new, using the same tester, at the same temperature, and same SOC, it likely would've been much higher than 850cca. then you could see how much its actually losing over time. once it drops to about 70% of the actual measured beginning value it's on the way out. you could keep it going for a while with judicious maintenance (charging), and some desulfation cycles, but the end is nigh. for your battery I'm guessing that 70% level will be about 630 or so. now it will probably continue to crank the engine just fine until it drops to 400ish, but the more it drops the more sulfate is coating the plates, and the greater the chances it will up and die on you at 2am when you're leaving the bar (don't ask me how I know that).
Cool. Still chasing down a possible parasitic draw. I get the start engine or radio/accessories will shut down on the F150. Put the charger on it about every week. It seems to get to the flashing green charge light in a couple hours on the Noco.
JHZR2
Staff member
If you have a parasitic draw that affects the battery time at high state of charge, it’s anybody’s guess.
Capacity loss is normal after some period of time of normal use and normal capacity. Generally, a battery at 80% of rated capacity is considered to be at the end of its useful life. But keep in mind some manufacturers brag a little with their ratings...
In this case, a test of a healthy battery at the 1 year mark would likely indicate what its real (best) capacity is as batteries can improve a touch initially. Each subsequent annual test would give an indication of capacity loss.
Your test at 50° was a bit lower in temperature than the standard of 68 deg or more. If you were to raise the temperature 20°, you would get a better result. My guess, the battery is OK.
In this case, a test of a healthy battery at the 1 year mark would likely indicate what its real (best) capacity is as batteries can improve a touch initially. Each subsequent annual test would give an indication of capacity loss.
Your test at 50° was a bit lower in temperature than the standard of 68 deg or more. If you were to raise the temperature 20°, you would get a better result. My guess, the battery is OK.
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