Lexus RX 400h hybrid battery

The RX 400h pack sits under the rear seat and is cooled by cabin air. Two decades on, the shops treat a battery complaint as a question about the whole pack's balance and cooling, not one module.

What owners notice

Warning lights, a charge gauge that swings from full to empty quickly, the engine running more than it used to, weaker acceleration and, on some cars, a noticeable drop in fuel economy or electric range.

What the shops check first

The battery computer's own data: the voltage of each block under load and at rest, the spread between them, internal resistance where the tools allow it, and the temperature sensors. Cooling is checked at the same time, because a blocked intake or a failed fan will make a healthy pack look sick.

What the repair usually involves

The choice is between repairing or balancing the existing pack, fitting a reconditioned pack, or fitting a new one. The shops weigh the age of the whole pack, the condition of the rest of the car and how long the owner plans to keep it, and explain that trade-off before any work starts.

What the shops' records show

The count at the top of this report is every repair order matching this problem across the EV Partners shops, recounted from their Shop-Ware records whenever they sync. Below it, each shop that has done this work shows its own share, the model years it saw and what it did, with a link to its own write-up where one exists.