A patrol vehicle that carries its own license-plate-recognition network: UniFi AI LPR cameras on the roof, a compact Protect console in the trunk, cellular backhaul — all powered by the car's own 12V electrical system, no generator, no auxiliary battery bank. This page is the component research, the power math, and the chassis shortlist.
Research compiled October 2026. Power figures are measured or manufacturer-specified; assumptions are stated inline.
Fixed LPR poles cover intersections. A mobile ALPR car covers everything between them: every parked car on every street, every pass through the neighborhood, matched against the stolen-plate and watchlist feeds in near real time. The patrol already drives nightly 7 PM–3 AM; the car just records plates while it drives.
The fixed poles already run UniFi AI LPR cameras. The car uses the same stack so detections land in the same Protect pipeline.
| Spec | Value |
|---|---|
| Sensor | 1/1.8" 8MP, 3840×2160 @ 30fps |
| Lens | 3× optical zoom, f/4.1–12.3mm |
| Plate capture | Vehicles up to 90 km/h, ~2 lanes |
| Night | IR 15m + dedicated LPR night-mode filter |
| OCR | On-camera plate recognition (edge AI); Protect aggregates searchable plate events |
| Power | PoE+ (802.3at), 25.5W max, 42.5–57V input |
| Edge storage | microSD slot (64GB+) — failover if console link drops |
| Environment | IP66, IK04, −20 to 50°C |
| Mount | Pole mount included (38–50mm); 130×151×303mm, 1.5kg |
| Price | ~$499 (launch; verify current store price) |
Key implication: it's a PoE+ camera, not plain PoE. Every power design below must deliver 802.3at. Typical draw with IR on is ~18–22W per camera (25.5W is the max).
UniFi cameras must be adopted to a Protect console — there is no console-free mode (UniFi Express runs Network only, no Protect). For a vehicle, the Cloud Gateway Max ($199, or $279 with 512GB) is the pick: handles 5× 4K cameras, takes an NVMe SSD up to 2TB, and draws only ~10W typical (16.1W max) from USB-C 5V/5A — easy to feed from 12V with a buck converter. Add a 2TB NVMe (~$130) for roughly 5 days of continuous 4-camera 4K recording; event-only recording stretches much further.
Open item: verify the UCG-Max's operating-temperature spec before trunk-mounting it in a hot car. The CloudKey+ G2 was ruled out specifically because its 0–35°C rating won't survive a parked car in summer.
UniFi now makes its own cellular modem — the U5G-Max ($399, PoE-powered, dual SIM + eSIM, AT&T/T-Mobile certified) plugs into the gateway as a WAN and shows up in the UniFi dashboard. It handles plate-event uploads and remote live view. Budget ~8W for it (power draw not published). A $99 UniFi 5G Backup dongle is the cheaper failover-only path.
The critical part. The Tycon TP-DCDC-1248GD-HP ($115) takes 10–15VDC in and puts out 56V 35W 802.3at PoE — proper negotiation, not passive, with 35W of headroom over the camera's 25.5W max. One injector per camera keeps failure domains isolated. Do not substitute the cheaper 24V passive-PoE injectors; the AI LPR requires 48V-class 802.3at.
Direct DC-DC conversion runs ~92–95% efficient. The alternative — a 12V inverter feeding AC PoE bricks — stacks two conversions (~72–79% combined) and costs ~25–30% more 12V current for the same camera load, plus fan noise and 120V in the trunk. DC-DC wins on every axis.
The whole question. Two builds, measured against what a stock SUV alternator and battery can actually deliver.
| Build | Typical | Max | Current @ 13.8V |
|---|---|---|---|
| 2-camera (2× AI LPR + UCG-Max + 5G modem + 2× Tycon) | ~65W | ~85W | ~4.7A typ / ~6.2A max |
| 4-camera (4× AI LPR + UCG-Max + 5G modem + 4× Tycon) | ~110W | ~135W | ~8.0A typ / ~9.8A max |
Per camera: ~22W typical at the lens, ~1.5W lost in the DC-DC injector, so ~23.5W pulled from 12V. Console ~10W via a 12V→USB-C buck (~92% efficient). Modem ~8W estimated. These are planning figures with headroom; the max column assumes IR illuminators on, full processing, hot night.
A typical Group 65/H6 SUV battery holds ~70Ah; about half is safely usable before crank voltage sags. That gives roughly 6 hours engine-off for the 2-camera rig and ~3.5 hours for the 4-camera rig. A low-voltage disconnect at ~12.1V is mandatory so the gear can never strand the car.
FEASIBLE No added power works. A 60–120W gear load pulls 5–12A from the 12V bus. Against a 200–250A alternator — which still makes 30–50% of rated output at idle — that's a rounding error, even with headlights and HVAC running.
| Scenario | Verdict |
|---|---|
| Engine-on driving | Yes Trivially feasible on every candidate chassis. |
| Engine-on idling for hours | Yes on PIU, Tahoe PPV, F-150, Sequoia. GM engineered the Tahoe PPV to run a 100A idle load for 4 hours; Ford/GM police packages auto-raise idle RPM if voltage sags. The 4Runner's 130A alternator is thin at idle (~7A spare with HVAC on) — HVAC discipline or a ~$600 high-output alternator fixes it. |
| Engine-off 30–60 min | Yes 90W of gear ≈ 9A → one hour is 9Ah, about 22% of a PIU battery's usable capacity, 11% of the Tahoe PPV's dual-battery 165Ah. Fine occasionally; repeated engine-off cycling without drive time to recharge will walk the battery down over days. |
Worked example: 90W of PoE load through Tycon injectors at 85% planning efficiency → 106W bus draw → 7.7A @ 13.8V, ~16W of waste heat (negligible), ~0.19 hp mechanical — unmeasurable fuel impact. Night-patrol baseline at idle runs ~30–65A depending on HVAC; spare idle capacity on a PIU/Tahoe is ~55A (760W) after that baseline.
Two mandatory electrical items: a low-voltage disconnect (e.g., Victron BatteryProtect, disconnect ~12.1V, reconnect ~13.2V) so the gear can never strand the car, and fused distribution (25–30A MIDI fuse on an 8 AWG home run, fused block, 3–5A per camera leg).
Ranked for a community night-patrol ALPR car: alternator headroom, idle durability, roof-mount friendliness, cargo space for gear, and used-market value.
For a Menlo Oaks neighborhood patrol (not law enforcement), the PIU Hybrid is the sweet spot: police-grade idle durability and wiring, hybrid efficiency for 8-hour shifts, and auction prices that leave budget for the electronics. Price ranges are 2026 auction/retail guides — verify against the specific VIN's build sheet and hour meter.
| Item | 2-camera build | 4-camera build |
|---|---|---|
| UniFi AI LPR cameras | 2 × $499 = $998 | 4 × $499 = $1,996 |
| Cloud Gateway Max | $199 | $199 |
| 2TB NVMe SSD | ~$130 | ~$130 |
| UniFi 5G Max modem | $399 | $399 |
| Tycon TP-DCDC-1248GD-HP injectors | 2 × $115 = $230 | 4 × $115 = $460 |
| 12V→USB-C PD buck + fuses/wiring/LVD | ~$80 | ~$80 |
| Roof crossbar clamps + isolation mounts | ~$100–200 | ~$150–250 |
| Total | ~$2,150–2,250 | ~$3,400–3,500 |
Cellular data plan not included (~$20–50/mo for a tablet/IoT line depending on carrier). Prices are October 2026 street/store figures; verify the AI LPR's current US store price before budgeting.
Compiled October 2026 for the Menlo Oaks community security project. Specs from manufacturer datasheets and store listings; vehicle electrical figures are typical values — verify against the specific VIN's alternator rating before buying hardware. This is a planning document, not an installation manual.