The move to 800 V platforms
High-voltage fast charging has become a main direction in electromobility. Porsche’s Taycan introduced the first 800 V architecture in 2019, with an 800 V DC fast-charge system supporting up to 350 kW, and from 2021 the approach spread — Hyundai and Kia announced 800 V platforms and a number of Chinese OEMs (BYD, Great Wall, GAC, XPeng among them) launched or announced their own. Fast-charge performance at higher bus voltage has become a product differentiator, and it raises the voltage the monitoring electronics have to stand off.
Why every EV monitors its own HV system
An EV or hybrid is built from many electrical modules that all have to stay healthy for the vehicle to move, and functional-safety standards require a network that continuously checks the insulation of the high-voltage system. That monitoring network has to connect to and disconnect from the HV bus repeatedly and reliably, which calls for a switch with high isolation and consistent behavior. Sealed reed relays are well matched to the role.
What the relay contributes to insulation monitoring
For insulation-resistance measurement, a reed relay’s capacitance is comparatively linear with temperature and its sealed contacts do not wear the way mechanical contacts do. In service it reads isolation voltage while adding leakage only in the picoampere range, and it switches within roughly 1 ms, supporting millions of operations (the exact figure is load-dependent). When pack insulation begins to degrade, the monitoring channel can raise an alarm early enough to turn a potential safety event into a scheduled service visit.
HVR series: 4 kV to 20 kV withstand
For high-voltage platforms the HVR series spans 4 kV, 5 kV, 6 kV, 10 kV, 15 kV and 20 kV withstand ratings:
- Switching voltage to 10 kVDC
- Switching current 3 A; pulse current options of 5 A, 10 A or 20 A
- Insulation resistance above 10 TΩ
- Multiple outline sizes for different board layouts
SIP-HV series: instrumentation grade in a smaller body
For space-constrained designs, the molded single-in-line SIP-HV is an instrumentation-grade HV relay:
- Switching to 1 kVDC, with breakdown to 4 kVDC
- Insulation resistance above 5 × 1012 Ω
- Roughly half the PCB footprint of a traditional DIP package
- Coil resistance 140–2000 Ω
- 1A (SPST), normally open contact form
- Maximum rating 100 W / 1000 VDC / 1 A
Selection against a rising bus voltage
As architectures move from 400 V toward 800 V and higher, the isolation-monitoring front end sees proportionally higher voltage and needs wider isolation margins with less leakage. Two separate numbers should drive the choice: the continuous switching voltage the channel actually carries, and the breakdown or withstand headroom required by the safety rating. HVR supplies the high-headroom end (to 20 kV withstand, 10 kVDC switching) while SIP-HV covers compact boards at 1 kVDC switching and 4 kVDC breakdown; selecting between them is a question of where the monitoring circuit sits on that voltage and space trade-off rather than a single default.
About SHR AUTOSENSOR
SHR AUTOSENSOR TECH LIMITED (SHR AUTOSENSOR) manufactures high-voltage reed relays, mercury wetted relays and high-voltage DC contactors. Contact: [email protected] | +86 13761571029 | www.reed-relay.com