Solar surveillance trailer battery runtime cannot be read from a battery label alone. It depends on five connected inputs: the total electrical load, system voltage, usable—not nominal—battery energy, conversion losses, and the amount of reserve required when solar charging is weak or unavailable.
For a useful estimate, calculate the trailer as an energy system:
- add every continuous and scheduled load;
- convert the battery bank into watt-hours;
- apply a documented usable-energy allowance and system-loss allowance;
- divide usable energy by daily consumption to estimate no-sun autonomy; and
- check whether the solar array can replace that daily consumption in the site's difficult season.
This guide shows the method. It does not promise a universal runtime for any trailer. Final sizing should use the exact camera, recorder, router, battery, controller and solar configuration offered for the project.
Why amp-hours do not answer the runtime question
An amp-hour figure is incomplete without voltage. A 200 Ah battery at 12 V contains one quarter of the nominal energy of a 200 Ah battery at 48 V:
Nominal battery energy (Wh) = voltage (V) × capacity (Ah)
Bank wiring matters too. Batteries connected in series increase voltage; batteries connected in parallel increase amp-hour capacity. Before calculating anything, ask the supplier for the battery-bank voltage, total bank capacity, battery chemistry and wiring arrangement.
Even the resulting watt-hour figure is nominal energy, not a runtime promise. The planned usable share may be lower because of the permitted depth of discharge, battery-management settings, temperature, battery age and the need to retain a reserve. Power conversion, cabling, controllers and auxiliary equipment also consume energy.
That is why two trailers carrying batteries with similar Ah labels can deliver very different autonomy.
Start with the complete surveillance load
The base load normally runs 24 hours a day. It may include cameras, infrared illumination, a network video recorder or edge recorder, a 4G/5G router, radio links, a PoE switch, controller electronics and environmental equipment. Floodlights, speakers or warning devices may be scheduled or event-driven.
Build the load list from measured average power or manufacturer data for the intended operating mode. Do not size from maximum device wattage alone if a verified duty-cycle value is available, but do not ignore night-mode infrared, heater, fan, analytics or transmission peaks either.
| Load | Quantity | Power per unit | Hours per day | Daily energy |
|---|---|---|---|---|
| Cameras | 4 | 8 W | 24 h | 768 Wh |
| Router | 1 | 12 W | 24 h | 288 Wh |
| Recorder and PoE switch | 1 set | 25 W | 24 h | 600 Wh |
| Controller and other continuous loads | 1 set | 15 W | 24 h | 360 Wh |
| Illustrative total | 85 W average | 2,040 Wh/day |
These numbers are a worked example, not a LUMTA product specification. Replace every value with the proposed equipment data. If lighting is included, calculate it separately as wattage multiplied by scheduled hours and then add it to the daily total.
Convert nominal battery capacity into planning energy
Use this sequence:
Nominal energy (kWh) = bank voltage × bank amp-hours ÷ 1,000
Planning usable energy = nominal energy × usable-energy factor × delivery-efficiency factor
The usable-energy factor must come from the proposed battery and warranty conditions. The delivery-efficiency factor represents the agreed allowance for power-path losses. Do not copy either factor from a generic article into a purchase specification.
For an illustration only, consider a 24 V, 400 Ah bank:
- nominal energy: 24 × 400 ÷ 1,000 = 9.6 kWh;
- if the project deliberately models 80% usable energy: 9.6 × 0.80 = 7.68 kWh;
- if it then applies a 90% delivery allowance: 7.68 × 0.90 = 6.91 kWh available to the loads.
With the illustrative 2.04 kWh/day load above, the first-pass no-sun autonomy is:
6.91 kWh ÷ 2.04 kWh/day = about 3.4 days
This is a planning result under stated assumptions—not guaranteed field runtime. Lower temperatures, battery ageing, a changed camera package or more frequent lighting can reduce it.
The inputs that change runtime most
| Input | What to request | Why it matters |
|---|---|---|
| Camera package | Quantity, model, day/night draw, IR or heater use | Cameras can change power by mode and time of day. |
| Recording | NVR, edge recorder or cloud-only; storage hardware | Recording hardware is often a continuous auxiliary load. |
| Connectivity | Router, modem, radio, antenna and transmission schedule | Communications equipment operates even when nobody is viewing the feed. |
| Lighting and deterrence | Lamp wattage, daily schedule, event frequency | A short high-power lighting period can materially raise daily energy use. |
| Battery bank | Chemistry, voltage, Ah, usable-energy limit, low-voltage cutoff | These define how much stored energy is actually available. |
| Site climate | Location, operating months, temperature, shade and panel orientation | Solar harvest and battery performance vary by site and season. |
| Required reserve | Consecutive low-sun days and acceptable recovery time | Reserve is a project risk decision, not a universal product number. |
| Backup strategy | Grid, generator, swappable battery or service response | Backup changes the consequence of an extended energy deficit. |
Battery autonomy and solar recovery are different tests
Battery autonomy asks: how long can the system support the load without useful charging? Solar recovery asks: can the array replace the energy used each day and recover the reserve after poor weather? A large battery can pass the first test and still lose charge over time if the array is undersized.
For a screening calculation:
Required array power (kW) = daily load (kWh) ÷ (planning sun hours × solar-system factor)
Using the illustrative 2.04 kWh/day load, three planning sun-hours and a 0.70 combined system factor gives:
2.04 ÷ (3 × 0.70) = about 0.97 kW of array power
This is not a final design. The planning sun-hours must represent the site and operating season—not an annual national average. The system factor must reflect the proposed module orientation, temperature, controller, wiring, soiling and shading assumptions. Tools such as NREL PVWatts can support an initial location-based solar estimate; an Australian project should also use suitable local solar-resource data and the actual installation geometry.
If the array only replaces the average daily load, it may maintain charge in normal conditions but recover too slowly after several poor days. A complete proposal should therefore show both the normal daily energy balance and the recovery case.
A seven-step sizing workflow
- Define the monitoring duty.
- Build a 24-hour energy budget.
- Confirm the complete battery bank.
- Choose the required no-sun reserve.
- Size solar for the difficult operating period.
- Run sensitivity cases.
- Validate the assumptions after deployment.
1. Define the monitoring duty
List what must operate continuously, what runs only at night and what is event-driven. Include the required recording, remote access and lighting behaviour.
2. Build a 24-hour energy budget
For each device, multiply watts by hours per day. Use separate day and night lines where power changes. Add a justified design allowance rather than hiding uncertainty inside one arbitrary number.
3. Confirm the battery bank—not just individual batteries
Record bank voltage, total Ah, battery chemistry, series/parallel arrangement, permissible depth of discharge, low-voltage cutoff, warranty conditions and temperature range.
4. Choose the no-sun reserve requirement
Decide how many low-sun days the site must tolerate and what happens if that reserve is exhausted. A critical remote asset and a temporary low-risk site should not automatically use the same assumption.
5. Size solar for the difficult operating period
Use the destination, operating months, panel orientation and shading. Test daily replacement and post-weather recovery rather than relying on annual-average sunshine.
6. Run sensitivity cases
At minimum, test higher night consumption, a larger camera package, reduced solar harvest, lower usable battery energy and battery ageing. The point is to find which assumption can break the design.
7. Validate after deployment
Record daily energy production, battery state of charge, low-voltage events and actual device consumption. Compare the measurements with the design assumptions, then adjust schedules or hardware before the difficult season.
What a supplier's runtime statement should include
A usable runtime statement should identify:
- the exact powered equipment and its assumed duty cycle;
- battery chemistry, bank voltage, nominal energy and assumed usable energy;
- conversion and auxiliary-loss assumptions;
- the definition of autonomy, such as hours or days without useful solar input;
- location, operating season, shade and panel orientation;
- the recovery assumption after low-sun weather; and
- the conditions that would require backup power or a larger system.
Treat an unqualified statement such as “five days of runtime” as incomplete until those conditions are supplied. Current industry pages also frame autonomy around load and system configuration rather than battery capacity alone; see the runtime discussions from Critical Technology Solutions and Sharpvue. Supplier examples are useful for identifying questions, but the purchase decision should use the proposed configuration and site-specific calculation.
Frequently asked questions
How long will a 200 Ah battery run a surveillance trailer?
There is no reliable answer without the bank voltage, battery chemistry, usable-energy limit, system losses and total load. Convert the complete bank to watt-hours first, then divide planning usable energy by daily consumption.
Should the camera load be calculated at rated or average power?
Use measured or manufacturer-supported consumption for each relevant operating mode, then test a conservative case. Night infrared, heating, analytics, recording and communications can change the load.
How many days of battery reserve should an Australian remote site use?
There is no universal number. Choose the reserve from the site's seasonal solar resource, shade, criticality, access time, backup method and acceptable outage risk. Document the reason so competing quotes use the same condition.
Does a larger solar array always solve a runtime problem?
Not by itself. The array must have suitable exposure and controller capacity, while the battery still needs enough usable energy to bridge nights and low-sun periods. Excess array power also cannot correct an unidentified continuous load or heavy shading.
What should I send for a configuration review?
Send the project location, operating months, camera and recorder models, communications hardware, lighting schedule, required no-sun reserve, shading information, backup strategy, quantity and destination. If device models are undecided, send the monitoring objective and ask for the power assumptions to be itemised in the quotation.
Compare a configuration against your site's energy budget
Review LUMTA's solar surveillance trailer range and remote security planning guide. For a project-specific review, provide the load list, location, operating season and required reserve so the power package can be discussed in writing.