Parts / High-Voltage / HV Contactor Box

BuckWired HV Contactor Box, isometric view of the assembled box

BWDHVPDU

HV Contactor Box

Plug-and-play high-voltage distribution: main contactors, precharge, traction fuse, current sensing, charger and DC/DC circuits and fused accessory outputs sized for what actually hangs off them, in one sealed enclosure. The most dangerous part of the build, already solved.

$3,300 Built to order · ships in 1–2 weeks
System voltage96–500V
Current250A cont / 1000A pk
Main fuse180V / 700A
Current sensorCANbus
PrechargeIncluded
SealingGasketed

180V / 700A suits 144V nominal packs — they can sit as high as 180V before any load goes on the pack, so the fuse is 300V-rated to stay clear of that. The main fuse protects the DC input to the inverter only. High-voltage accessories — charger, DC-DC, coolant heater — carry their own fusing.

The CANbus sensor reports live pack current to your BMS or VCU. Leave it out if your setup already measures current elsewhere.

Selected: 180V / 700A, with CANbus current sensor.

Lead time 1–2 weeks. Every box is built to order and configured to your pack, so nothing ships from a shelf. If you are working to a deadline, tell us before you order and we will be straight with you about whether we can hit it.

Request a quote

Built in Oceanside, CA — by the person who answers your email
Tested before it ships — every unit, no exceptions
Connector kits included — Deutsch 19-pin LV, Jonhon HV
Warranty: 90 days from delivery, box and internal parts
Shipping: UPS, $50 per order, insured for full value
International: by quote — email us

What it does

One box between your pack and everything else

In a conversion, the contactor box is the gate. It connects the pack to the drivetrain when the car is on, disconnects it when the car is off, limits inrush at startup, and blows before your motor does. Doing that on a bench with loose relays is how projects stall — or worse.

Switching

HV (+) and HV (−) main contactors on nickel-plated copper bus bars, with hi or lo coil control so it drops into whichever way your system drives its relays.

Precharge

Internal precharge relay, included as standard. Brings the DC bus up gently instead of slamming your inverter capacitors on every key-on.

Protection

Internal traction fuse sized to your pack voltage, protecting the DC input to the inverter. HV accessories carry their own fusing.

HVIL

A high-voltage interlock loop runs through the LV circular plug, so the system knows whether the HV connections are actually mated before anything goes live.

Charging

Two charger inputs at 25A each, so a second charger doesn't mean a second box or a spliced cable.

DC/DC

One 15A DC/DC output to run your 12V system, fused and terminated inside the enclosure.

HV accessories

Two accessory outputs on their own mini contactors, one for a heater element and one for an AC compressor, each fused 20A or 30A to suit your pack voltage. The contactors are 50A parts — sized well above what either circuit draws, because the cost of headroom is low and the cost of a marginal contactor is not.

What you are paying for

Configured, assembled, and shipped in one to two weeks

Most people who buy this could build one, and some of them have. What this buys is the time back — the sourcing, the sizing decisions and the bench hours that sit between a pile of parts and a component you can bolt in. For a shop with a car on the lift, or a builder who would rather be driving by spring, that trade tends to make sense.

Configured, not generic

Built to your pack voltage and your accessory loads. The traction fuse is sized to your system, not to a catalog average, and the accessory outputs are fused for what you are actually running.

The decisions are made

Contactor selection, precharge resistor value, fuse ratings, bus bar sizing, coil polarity. All of it worked out already, against packs and drivetrains we have wired before.

Assembled and terminated

Bus bars, internal wiring and connector kits done to a consistent standard, in a gasketed enclosure with an aluminum base plate. It arrives as a component, ready to go in.

Time on the calendar

One to two weeks and it is on your bench, ready to mount. Gathering the same parts from four suppliers usually takes longer than that on its own.

Someone to ask

A printed schematic in the box, and the person who built it answering the email. There is no support queue between you and the answer.

Built to be worked on

Labeled, documented and laid out so that the next person in there — probably you, three years from now — can read it instead of reverse-engineering it.

Specifications

Spec sheet

If something you need isn't here, ask — it means we haven't written it down yet, not that we don't know it.

Electrical

System voltage96–500V DC
Continuous current250A
Peak current1000A
Main contactorsHV (+) and HV (−)
Bus barsNickel-plated copper
PrechargeIncluded
Precharge relayInternal, included
Precharge resistorTE TH350 50Rj2319
Main fuse — option180V / 700A · 300V-rated fuse
Main fuse — option500V / 400A · 500V-rated fuse
Pack range — 180V option144V nominal, 180V top
Pack range — 500V option360V nominal, 450V typical top
Main fuse protectsInverter DC input only
HV accessory fusingSeparate, per accessory
Current sensorCANbus 500A or 1,000A, or none
External sensor optionHall effect on the 2/0 cable
Coil controlHi or Lo selectable
Charger inputs2 × 25A
DC/DC output1 × 15A
HV accessory outputs2, each 20A or 30A fused
Accessory contactors50A
Output 1Heater element
Output 2AC compressor
HVIL loopIncluded, via LV circular plug

Connections

HV battery & inverter plugsJonhon, 70mm² / 2/0
Main HV cable70mm² (2/0)
Charger, DC/DC & accessoryUp to 10 AWG
Internal wire runsUnder 12″
LV connectorDeutsch 19-pin circular
Cable orientation180° straight approach
Plug & pin kitsIncluded, HV and LV

Enclosure

BaseAluminum plate
BodyPA66-GF30
SealingGasketed
Ingress protectionNot formally tested
Design targetIP65
Water exposureDirect spray not advised
Enclosure400 × 386 × 150 mm
Enclosure (imperial)15.74 × 15.19 × 5.91 in
Install envelope605 mm / 23.82 in deep
Cable bend radiusAllow for 2/0 minimum
MountingMetal surface, for heat dissipation
OrientationAny

Order & support

180V / 700A$3,100 · $3,300 w/ sensor
500V / 400A$3,300 · $3,500 w/ sensor
Lead time1–2 weeks
CarrierUPS
ShippingUPS, $50 per order
InsuranceFull value, included
InternationalBy quote only
Built inOceanside, CA
TestingEvery unit before shipping
Warranty90 days from delivery
DocumentationSchematic & manual included

Compatibility

What it works with

The box doesn't care what drives the car — it cares about voltage and current. That means it drops into most of what people are building right now.

Controllers / VCUs

  • EV-Controls T2-C
  • AEM EV VCU275
  • Dynam Labs VCU+
  • Netgain X1
  • Curtis 1238 / 1239(e)
  • Controller collection

Motor setups

  • Tesla S/X LDU & SDU
  • Cascadia IM225 / IM375
  • Netgain Hyper9 / Hyper9HV
  • HPEVS AC-34, AC-50 (96V)
  • HPEVS AC-35, AC-51 (144V)

Battery management

  • Orion 2
  • Thunderstruck MCU
  • Vero BMS V2
  • AEM EV BMSM

Pack voltage

  • 96–500V nominal
  • 250A continuous
  • 1000A peak

Before you buy

Documentation

Nobody should commit to a part this size without knowing whether it fits. Dimensional drawings are free to download in both imperial and metric. Full wiring directions and pinouts ship printed in the box.

PDF

Dimensional drawing — imperial

Overall dimensions in inches, including the cable approach envelope, so you can plan packaging before you order.

 PDF

Dimensional drawing — metric

Overall dimensions in millimeters, including the cable approach envelope, so you can plan packaging before you order.
Isometric render of the contactor box outer envelope
STEP

3D model

Outer envelope only, internals stripped. Drop it into your CAD and check packaging before you commit.

Sizing

Will your accessories fit these outputs?

Compressors and heater elements are constant-power loads, so the current they pull depends on your pack voltage — the same part draws nearly four times the current on a 96V system as it does on 360V. Rather than publish a list of approved brands that goes stale, here is the limit. Check your part’s continuous current against it.

AC compressor

Maximum compressor power the 30A output supports, by pack voltage:

96V pack~2,400W
144V pack~3,600W
360V pack~9,000W

A 27cc compressor draws about 15A continuous at 144V, which fits comfortably. A 33cc unit is roughly a third more. The combination to watch is a large compressor on a low-voltage pack — a 33cc on 96V is beyond this output, while the same compressor on 360V is barely a load at all.

Heater element

A 1500W element, the common single-element kit, by pack voltage:

72V pack~21A — 30A fuse
96V pack~16A — 30A fuse
144V pack~10A — 20A fuse
380V pack~4A — 20A fuse

Double the element and you double the current. A 3000W setup fits on 144V and above; on 96V or below it belongs on its own circuit, not this output. PTC elements also draw hardest when cold, which is why the fusing is sized above steady-state draw rather than to it.

Fuse ratings assume continuous load at 80% of rating. Current rises as the pack drops toward its low-voltage cutoff, so these figures are worked from the bottom of each range, not from nominal.

⚡

This is high-voltage equipment

A 400V DC pack can kill you, and it does not care how careful you usually are. This box is built to be installed by someone who understands high-voltage safety practice — insulated tools, a service disconnect, proper PPE, and never working on a live system alone.

Plan the space before you order. The box is 400 × 386 × 150 mm, but allow roughly 605 mm of depth once the 2/0 cables are on it — that cable has a minimum bend radius and it does not negotiate. Mocking the envelope up in cardboard first has saved more than one builder from finding out half an inch too late.

One install detail worth knowing before you start: the 2/0 plug latches are trimmed to clear the neighboring connectors, so the latch alone will not pull a plug home. Push firmly on the cable toward the box as you mate it, and confirm it is seated and locked before you energize anything. Full pinouts and the rest of the detail are in the wiring directions.

The enclosure is gasketed and built to an IP65 target, but it has not been formally tested to that standard — treat it as sealed against dust and incidental moisture, not against direct water. Mount it somewhere a pressure washer will never reach.

Every box ships with a wiring schematic and a manual covering correct installation and the ways it can be used improperly. Read both before you terminate anything — they exist because the mistakes they prevent are expensive and, in a few cases, permanent.

Questions

About this box

Why does it cost what it does?

It arrives configured to your build and ready to install. Contactors, fusing and connectors at this rating are not cheap to begin with, but the parts are the smaller half of it. The rest is the sizing work — contactor selection, precharge resistor value, fuse ratings matched to your pack voltage and accessory loads — along with the assembly, the labeling and the testing. Think of it as a preconfigured time saver for an experienced shop or a DIY builder who would rather spend their weekends on the car than on sourcing and spec sheets. If you would rather build your own, that is a perfectly reasonable call, and we are happy to answer questions either way.

What does the warranty cover?

The box and its internal parts, 90 days from delivery. Not covered: exterior connectors and terminations crimped and installed by the customer, and anything powered through the box.

Can I build this myself for less?

On parts alone, often yes — and if you enjoy that side of a build, it is a good project. What this saves you is the sourcing and the sizing work, and the troubleshooting that tends to follow a precharge or contactor choice that turns out to be slightly off. It is a known-good starting point, so the rest of the conversion is where your time goes.

Does it come pre-wired to my drive unit?

No — the box handles pack-side switching and protection. The connection from your controller to your drive unit is a separate harness. If you're running an EV-Controls T2-C with Tesla drive units, we make those too.

What do I need to tell you when I order?

Two things. Your pack voltage — nominal, and a description of the pack if you have one, since that tells us where it tops out and which fuse variant suits it. And which HV accessories you are running off the box: a heater element, an AC compressor, both, or neither, along with their power ratings if you know them. That is what sets the accessory fusing. Anything else you want to tell us about the build is welcome, but those two answers are what we actually need.

Can it be configured differently?

Most of what we build is one-off in some way. If your build needs different fusing, a different cable entry, or a different footprint, send the details through and we'll quote it.

What does shipping cost?

Everything goes UPS. Shipping is a flat $50 per order, and that includes insurance for the full value of what is in the carton — not a carrier default that would leave you arguing over a fraction of it if a box arrives crushed. Ordering a box alongside a harness or a panel costs less than ordering them separately, so it is worth putting the build on one order where you can. International orders are quoted individually — VAT and import handling vary too much by country to price in advance. Email will@buckwired.com with your destination and we will quote it.

How long until it ships?

One to two weeks from the time your configuration is confirmed. Nothing sits on a shelf — every box is built to order. If you're working to a deadline, say so up front and we'll be straight with you about whether we can hit it.

Goes with

Finish the system

Chassis tie-in panel

FRP-T2COR2

Chassis Tie-In Panel

40 fuse, 10 relay, dual bussed. The main 12V panel for the rest of the car.

$850
T2-C drive unit harness

T2C-LDU / SDU / LDU+SDU / SDU+SDU

T2-C Drive Unit Harness

Plug and play between an EV-Controls T2-C and Tesla drive units.

from $620