How to fix a $4,000 hybrid battery problem with vinegar and baking soda

This is one of those ‘Don’t try this at home if you don’t know what you’re doing’ DIY tales. Two weeks after imgur user “scoodidabop” bought a used Toyota Camry Hybrid with no warranty, he got the Christmas Tree dash display with warnings like “Check VSC System,” “Check Hybrid System,” and the Check Engine light. After some Internet sleuthing he figured it could be a faulty brake actuator, assuming the hybrid system warning was a false alarm. But it wasn’t the actuator, it was the battery, a Toyota dealer telling him that his battery had “gone bad,” and he’d need $4,457 to replace it.

Then he had a brainstorm: it could be one of the cells that’s gone bad, not the whole battery. Scoodidabop has some experience as an electrician, so he figured he could test it and replace any bad cells for about $45 apiece. He removed the battery unit from the trunk and over the course of two hours tested all 68 cells four times. He found nothing wrong. So he devised another type of test and checked every cell again. He couldn’t find a problem with any of them.

Turns out the problem wasn’t in the cells, but with the dirty and corroded copper connectors at the ends of the high-voltage cables. He pulled the 34 connectors and their steel nuts, soaked them in vinegar, gave them a light steel wool scrub, soaked them in baking soda and water to counteract the vinegar, applied an anticorrosive and reinstalled them. That took an hour. When he replaced the battery, the warning lights had all gone out and the battery worked perfectly. Skill level: experience. Cost: less than $10. Perhaps it’s time for hybrids to be able to test their own cells individually. Dealers, too.