Solar surveillance trailer runtime explained

Runtime, in its simplest form:

hours = usable watt-hours ÷ average watts

Getting the two inputs right is where the work is.

Converting amp-hours to watt-hours

Vendors publish batteries in either unit. Multiply amp-hours by nominal system voltage: a 200 Ah bank at 48V is 9,600 Wh; a 100 Ah bank at 12V is only 1,200 Wh. This is why quoting amp-hours without voltage is meaningless, and why a '200 Ah' trailer can be eight times the battery of another '100 Ah' trailer.

Usable is less than nameplate

Lithium systems are typically managed to 80–90% depth of discharge to preserve cycle life, and the battery management system will cut off before zero. Assume roughly 85% of nameplate is actually available, so 9,600 Wh becomes around 8,200 Wh usable.

Average load, not idle load

Cameras are the smallest part of the budget on a modern unit — a documented figure like 14 W total camera draw is realistic for low-power cameras. The bigger consumers are the cellular radio while transmitting, edge analytics, the recorder or gateway, PTZ motors, and any heating. Ask for total system draw while streaming, not camera draw alone.

Temperature derating

Lithium capacity falls in cold weather and charging is restricted below freezing. A runtime figure measured at 20°C will overstate what you get in a northern January — exactly when nights are longest and solar harvest is lowest. Ask whether the figure is derated and whether the battery is heated.

Worked example: 9,600 Wh nameplate at 85% usable is about 8,200 Wh. At a 45 W average system draw that is roughly 180 hours, or about 7.5 days. At 150 W it is about 55 hours — just over two days. Same trailer, same battery. The load is the whole story.

Buyers usually ask “how long does it run with no sun?” That is the reserve question, and it matters for a bad stretch of weather. But day to day, the question that determines whether a unit stays up indefinitely is different: does average daily harvest exceed average daily consumption?

If harvest exceeds consumption across the worst month at your latitude, the battery is a buffer and the unit runs indefinitely. If it does not, the battery is a countdown and the unit will eventually brown out no matter how large the bank is. Both numbers matter, and the array-to-battery ratio tells you which design philosophy a vendor has chosen.

A large battery with a modest array is a reserve-led design: long endurance, slow recovery, and often paired with a generator input for exactly that reason. A larger array relative to storage is a harvest-led design: it recovers within a day and tends to stay ahead of load, at the cost of less absolute reserve. Neither is wrong — they suit different sites. A heavily shaded urban lot cannot harvest, so reserve and generator support win. An open rural site with good exposure favours harvest.

Of the six providers whose public materials we reviewed as of September 2026, three publish battery capacity, three publish solar wattage, and one publishes runtime and recharge time. None publish the load their figures assume.

Read that table as a disclosure map rather than a quality ranking. Several of these providers sell a managed service where they carry responsibility for the unit performing, which is a legitimate reason not to publish component specifications. But if you are buying the equipment, the performance risk transfers to you, and you need the numbers.

Note also that the two largest batteries pair with quite different arrays. Verkada's 13.2 kWh option behind 1600 W is a strong combination on both axes. Mobile Pro Systems' 12,500 Wh behind 800 W is clearly reserve-led, which is consistent with offering a generator. Sharpvue's ~9.6 kWh behind 1,170 W is harvest-led, with a generator input available where a site needs it.

What is total system draw while streaming, in watts?

Not camera draw. If a vendor cannot answer this, they have not measured it, and every runtime claim they make is an estimate.

What runtime do you guarantee at that draw, with no solar input?

Ask for it in writing, with the depth of discharge and temperature stated.

What is the array wattage, and what daily harvest does it produce in December at my latitude?

A vendor experienced in your region will have a real answer. Harvest in December can be a third of June at northern latitudes.

Is the battery heated, and what happens below freezing?

Lithium charging is restricted or blocked when cold. An unheated bank in a northern winter may not accept charge on the coldest mornings.

What is the recharge time from empty to full, in hours of usable sun?

This is the recovery figure. A unit that takes two days of sun to recover from a drawdown is chasing its own load.

Is there a generator or AC input, and what connector?

Not a failure of the solar design — a sensible hedge for shaded or high-load sites. Ask whether it is standard or an option.

“Unlimited runtime.” No solar system has unlimited runtime; energy in must exceed energy out, and on a sufficiently dark or heavily-loaded site it will not. A vendor using that phrase is either describing energy-positive operation imprecisely or has not thought about your site. Ask them to restate it as a reserve figure at a stated load and see what comes back.

The same applies to any unqualified single number, including favourable ones. A published figure like “8–10 days” is useful only with its qualifiers attached — configuration, camera count, load, temperature, battery condition and available solar all move it, and a vendor that states those is giving you something you can actually verify against your own site.