When you first turn your car off from a drive, the battery should read from 12.6 to 12.8 or maybe a little higher. If thats not the case, than you have a battery that’s not able to charge completely or the charging system isn’t charging properly. After letting it set overnight, the surface charge will be gone and a healthy battery will read 12.6 volts. Even with a parasitic draw a healthy battery will charge to 12.6 volts. After you confirm your battery is healthy and the charging system is functioning properly, then would be the time to check for parasitic draw. My first suspicion would be the air lift system pump turning on when it’s not supposed to.
I recently had a battery that tested borderline. It charged to 12.4 and worked great. But f I let it set two days the van wouldn’t turn over. I did a parasitic draw test and passed. Replaced the battery and all is well.
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