I have a 2016 vw gti I got new with original oem AGM battery. car will be 5 years old in april 2021. (not sure when battery made, havent pulled it to see date code)
-took vacation for 1 month, come home, slow start, but it works
-drive 45 miles, stop at autozone, tester says 50% charged, go home and charge to 100% then come back to test
-i drove to some stores, then home, then put digital battery charger on at 3amps set to AGM, charger said 77% when i started
-3 hours later at 100%, leave it on 3amp all nite
-next morning still reads 100%, i check voltage, 12.83 volts, i drive 45 miles and stop at autozone again
-same guy, same test machine, says BAD BATTERY and charge at 83%, hmm..only 83% after starting morning with 100% and driving 45 miles?
-guy has me start car and his tester says my starter is FINE
-guy runs test on alternator...not putting full amps to battery..says HMM.....might be alternator or battery bad and alternator is 'smart' and wont give battery more.
-guy says START WITH NEW AGM battery, then test alternator next
-go home charge to 100% again, battery voltage 12.83 volts with charger removed...NEXT MORNING check voltage and its 12.3volts and all the car did was sit all nite
scotty says????
thanks scotty!
it sounds like the battery is getting a bit tired after 5 years. If you begin to have problems starting the car then replace it.
certainly leaning towards buying new AGM soon as i dont want to be stranded during some arctic blast weather here in indiana but i find the diagnosis a bit confusing. vw says they have a HIGH END tester that would take 30 minutes and have to take battery out of care that can diagnosis it better than the quick testers but they want to charge for that.
battery dealers (actual dealers, not Walmart or Autozone) have high end testers too, and they won't charge you for a test.
or why don't you do this ...
buy a new battery now and keep it in the trunk. If your car ever fails to start, just dump the new battery in.
Thanks I finally found out it was NOT an AGM battery and there is no battery management system on the car. Had to call multiple vw dealers and talk to PARTS dept who looked up VIN and said ITS A NORMAL LEAD ACID, H5 OR H6 WILL WORK, JUST BUY ANY YOU WANT AND SLAP IT IN, NOTHING TO RESET AND WONT CAUSE THE COMPUTER ANY PROBLEMS. so i went to SAMS CLUB and they had the h6 in stock and free install. $115 and 3 year full replacement warranty. quick and easy.