HV battery & power electronics
Tesla & EV HV battery and power electronics repair
When a car will not charge, will not go into drive or shows a high-voltage warning, the fault can be in the parts around the battery rather than in the cells. We replace contactors, the PCS and the pyro fuse, with the programming the car needs afterwards.
Common on Model 3 · Model Y · Model S · Model X
Symptom checker
What is your car doing?
Pick what you notice. We’ll show the system it is often related to and what to send us. Only a check at the workshop can confirm the cause.
- The car won’t charge Often related to HV battery & power electronics
The work
What the check covers
- Contactor operation
- Pyro fuse condition
- PCS output to the low-voltage system
- Stored high-voltage alerts and fault history
- Insulation resistance of the high-voltage parts
What we repair
- High-voltage contactor replacement
- PCS (power conversion system) replacement
- Pyro fuse replacement
- Programming and configuration after replacement
- Battery health (state-of-health) report
In detail
More than cells
The high-voltage battery is a sealed pack of cells, but around it sit the parts that switch, protect and convert its power. Contactors are heavy-duty switches that connect the pack to the car when you drive or charge. The pyro fuse cuts the circuit in a crash or a serious fault. On the Tesla Model 3 and Model Y, the PCS charges the battery from AC chargers and keeps the low-voltage battery topped up.
When one of these parts fails, the car can refuse to charge or drive, or show a high-voltage warning, even if the cells themselves are healthy. Replacing the failed part, and programming the car to accept it, can bring the car back without replacing the whole pack.
High voltage is not a DIY job
A Tesla battery works at several hundred volts. The orange cables and the parts inside the pack can hold a dangerous charge even when the car is switched off. Do not open, unplug or cut any high-voltage part yourself. If the car has been in a flood or a crash, keep away from the battery area and call for help.
Heat and the battery
Battery cells age faster when they are kept hot. Parking in the shade in summer, not leaving the battery full for long periods, and keeping the cooling system clean all help. Our cooling system service covers the radiator and coolant that keep the pack cool.
A car that keeps flattening its 12V or 16V battery can also have a PCS fault; see 12V and 16V battery.
System map
Other systems we work on
Illustration: a generic electric-car chassis seen from above, not any particular make or model.
FAQ
Questions owners ask
Does my Tesla need a new battery pack?
Not always. Many faults that look like a failed battery, such as the car not charging or not going into drive, come from the parts around the pack: the contactors, the PCS or the pyro fuse. These are replaced on their own, without a battery replacement. Recall repairs are free at Tesla, so check your VIN with Tesla first.
What is the PCS on a Tesla?
On the Model 3 and Model Y, the PCS (power conversion system) combines the on-board charger, which charges the battery from AC chargers, and the DC-DC converter, which keeps the low-voltage battery charged. When it fails, the car may stop charging or show low-voltage warnings.
What does a pyro fuse do?
It is a fuse with a small charge that cuts the high-voltage circuit in a crash or a serious fault. Once it has fired it must be replaced, and the car may need programming afterwards.
Is a contactor recall covered for my car?
Check your VIN with Tesla first. If your car is part of a recall, Tesla does the repair free of charge.
Do you replace complete battery packs?
Send the car's model and year, the warning and the battery's history on WhatsApp. We check the pack first and explain whether a repair or a replacement makes sense.
Car not charging, or a high-voltage warning?
Send a photo of the warning with the car's model and year on WhatsApp.