I had my battery tested at the store where I bought it less than two years ago. CCA was above the rating, but voltage was 12.11. According to a state of charge chart, 12.11 V is equivalent to less than 40% of the energy the battery should be capable of storing. The battery was fully charged when it was tested, so it has lost 60% of it’s capacity. The battery has a full replacement warranty if it fails within 3 years and will probably fail this winter. My mechanic has confirmed this, but isn’t willing to argue with the store. How do I get the store to honor the warranty before I get stuck somewhere with a battery that won’t start my car? thank you.
That could have taken several hour to recharge the battery, a battery can be tested without recharging it. What was the battery voltage shown on the test slip?
If the battery has a low state of charge you should recharge it, that is not a warranty issue.
The battery has not reached the point of warranty replacement so the place you bought it from is not going to do anything . If you are really concerned one option seems to be asking if they will at least give some credit towards a new one. Another option is to purchase a portable battery pack which might be handy to have anyway.
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In all the cars I have had with “Battery issues” it was always something other than the battery that was the real problem. Just my $0.02
The voltage under no load isn’t a good measure of the battery’s capability. If the battery cranks the engine robustly, which is the toughest chore a battery is asked to do, then it is ok. Beyond that you’d have to have the battery fully charged then load or conductance tested. But if the engine cranks reliably, I suspect you have no problem with your battery.
As an example, my mp3 player can be powered with alkaline or NMH batteries. The NMH fully charged will measure 1.3 volt under no load, and the partially discharged alkaline measures 1.4 volt under no load. But the NMH will easily power the mp3 player for 4-5 hours, while the alkaline won’t power it enough to even turn it on.
Thank you for taking the time to read and reply to my post, but this is stuff I already know.
Thank you for your suggestion.
A very sensible $0.02. Everything else checks out fine. It is the battery. Thanks.
Thank you for taking the time to reply. Unfortunately it wasn’t helpful, as you didn’t tell me anything I don’t already know. As you probably know, load testing and conductance testing measure two different things.
Done correctly, no load voltage does give a pretty good approximation of battery capacity to store energy. As you point out, it isn’t a good measure if it isn’t done correctly, and load testing is a more accurate way to measure battery storage capacity.
Conductance testing measures how fast a battery can deliver power, but doesn’t tell you how much power the battery can store. Many batteries with low storage capacity can pass conductance testing and crank an engine quite well, even though they won’t pass a load test.
My battery cranks well, but I’m sure that it would not pass a load test, and that it will probably fail in much less than a year.
If you have a lead acid battery with removeable caps and a hydrometer, you can measure the specific gravity in each cell. The relationship between SG and state of charge is available. If any cells are far off the norm, a new battery is called for. If they are all low, use a battery charger at a long slow setting overnight and see how it responds.
That will give you a more complete view of the battery’s condition - but if you are sure it would not pass a load test and will probably fail in under a year, you are probably already thinking about when and how and with what to proactively replace it - or what to do when it fails you.
People responding to questions have no idea how much someone knows . Therefore I say quit obsessing and just get yourself a new battery . Problem solved.
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Thank you for the thoughtful response. Yeah, I’m sure it will fail a load test, which is not how the parts store judges battery condition. So I need a new battery, but not sure I can convince the store to replace this less than two-year-old battery under their 3 year replacement warranty.
Word to the wise . . .
If you’re a costco member, start buying your batteries there. My costco carries the group 48 and 49 batteries which many european cars use
Their prices are very competitive, usually lower than autozone, and with a longer free replacement period
They don’t play games, in regards to their battery warranties
If you bring the battery in during its free replacement period . . . currently 42 months, I believe . . . they just swap out your old battery for a new one, with no questions asked. They don’t even bother to test the old one. That’s proper customer service, in my opinion 
Whereas some other vendors assume everybody is out to cheat them, and treat them accordingly 
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Thanks for the tip.