I bought a brand new battery at Walmart today. Only because the old one died a block away and at 9pm. I installed the new one and nothing. I tested with my multimeter and it read only 5.79V. How is that possible? Of course by the time i figured all of this out it was dark. My headlamp batteries were dying and the store was closed. Lucky I had jumpers and a nice lady helped me. Once I got it home it died pulling into the driveway and it now tests at 6.63. The drive from there to here is about 20 minutes. Your thoughts???
Either you bought a 6V battery by mistake, or it is completely dead. The car would keep running while you were driving because the alternator would provide the correct voltage, but when the engine is idling the voltage will drop and game over. A voltage as low as 6V is marginal even to power the engine management electronics etc.– alephzeroMay 28, 2021 at 12:18
It's possible that the new battery is simply defective - like anything it's possible to buy a duff one. That said it could also just need a decent charge and I'm not sure a 20 min drive is going to be enough, the fact that it went up at all is a good indicator that the battery is ast least taking a charge. If you have a proper battery charger at home I'd suggest giving it a full charge and seeing if it holds it properly, if it doesn't charge fully or won't hold it then it's time to go back to Walmart and ask for a replacement.
Even at "0% charge" a 12V lead acid battery or a battery with some defective cells, would measure 10 to 11 volts with no load. That voltage created by the battery chemistry, not by of the amount of charge. If the OP is only measuring abut 6V, something is very wrong. May 28, 2021 at 12:24
Based on what you've posted, you have a battery from WalMart that shouldn't have gone into this car. You should remove the new battery, exchange it for another. Before you put it in the car, have it charged and professionally tested. You are doing this extra stuff because you most likely have other problems because it stalled in the driveway. You need a good fully charged battery to diagnose other problems. After the new charge and tested battery is installed the charging system needs checked. You should have both battery cables cleaned at both ends. You should see 13.8 to 14.5 volts at battery terminals with engine running.