What is actually inside the pack

The high-voltage battery in an electric car is not one big block. It is a pack made of modules, and each module is made of many cells. A battery management system (BMS) watches voltages and temperatures across the pack and reacts when something does not look right.

So when a warning comes on, the question is where the problem sits. It can be one module that has drifted away from the others. It can also be a sensor, a contactor, a cable or connector, or the BMS itself. Those are very different repairs.

Why a new pack is not the only answer

A quote for a complete new battery may be the right answer for your car. It may also not be. The only way to know is to measure the pack and find out what is actually wrong.

If the fault is in one or two modules, repairing or replacing just those can sometimes be possible, depending on the car. If the fault is outside the cells, the pack itself may be fine.

What to ask for before you agree to a repair

• What exactly failed. A fault code, a module number, a part. Not only "the battery".
• The measurements. Ask to see the readings for each module, so you can see whether the problem is in one place or across the whole pack.
• The options. Module repair, part replacement or a full pack, and what each one costs.
• A second opinion if the quote is for a full pack and nobody can show you why.

How we handle it

We start with a diagnosis. You get the numbers for every module and a quote, and nothing is repaired until you say yes. How a diagnosis works.