Originally Posted by bbhero
Actually I'd be rather concerned... 12.2 during the summer time temperatures is not an expected result. If anything the voltage should be higher due to the temps not being cold.
Depends on what you're testing. If testing voltage at moderate or higher load, yes cold weather can make the voltage droop during that test.
If instead measuring minimal to no load voltage, it will be lower in warmer weather because the higher the temperature, the faster the self discharge rate.
Combine self discharge rate with parasitic drain and we have the significant variable here: How long did it sit with engine off before the battery dropped to 12.2V?
You should be concerned if it hasn't sat for several days without running, unless you've been fiddling with it and reactivating the electronics by getting in and out, opening doors or hood etc several times.
If there is undue drain on the battery you could measure for excessive parasitic drain. Telling us how old they are is a start but if they are low end batteries, you might only get 2-3 years out of them. If they are higher tier batteries with a 3+ year replacement warranty, do get them checked with a load tester and replaced under warranty if they fail.