Guide
Everything a buyer needs to understand about mobile battery energy storage — what it is, what it replaces, what it can run and how to specify one properly.
A BESS is a battery energy storage system: a rechargeable battery unit that stores electrical energy and delivers it on demand. A mobile BESS is that system built onto a trailer or into a container so it can be moved between sites rather than installed permanently.
Three components matter. The cells store the energy — in commercial systems these are usually lithium iron phosphate (LFP), chosen for thermal stability and long cycle life. The inverter converts stored DC energy back to AC at the voltage and frequency your equipment expects. The battery management system controls charging, discharging and cell balancing so the pack stays safe and reaches its rated life.
Everything else — the enclosure, the trailer, the transfer switch, the receptacles, the HMI — exists to make those three things usable on a working site.
A generator creates electricity by burning fuel. A BESS stores electricity created elsewhere. That single difference explains every practical consequence: no fuel deliveries, no exhaust, no carbon monoxide, no noise, no oil or filters — but also a finite amount of energy between recharges.
The second difference is efficiency at part load. A diesel engine is at its worst when lightly loaded, and running one that way for weeks causes wet stacking. A battery is indifferent — it is as efficient delivering 10% of its rating as 90%. Since most temporary power installations are sized for a peak that rarely happens, this is where the real-world difference shows up.
A mobile BESS is not a universal answer. Very large continuous loads over weeks with no recharge window will exhaust any practical pack — that is what generators are good at. Large plant with sustained high draw, heavy welding operations and industrial process loads generally sit outside a single trailer's range.
The usual answer in those cases is not 'use a generator instead' but a hybrid: the battery carries the load and a right-sized generator starts only to recharge it, then drops to standby. Generator runtime falls sharply and the engine runs in its efficient band while it does run.
| Site type | Typical draw | Sensible starting point |
|---|---|---|
| Single trade, small crew | Tools, lighting, one cabin | 15 kWh trailer |
| Medium compound or unit | Several cabins, security, tools | 30 kWh trailer |
| Stage, production or heavier draw | 8 kW continuous, high peaks | 30 kWh at 8 kW continuous |
| Whole compound or facility | Sustained multi-load | Containerised, to 8.3 MWh |
Two numbers decide everything. Power (kW) must exceed your largest simultaneous load including starting currents — get this wrong and the system trips. Energy (kWh) must cover total use between recharges — get this wrong and you run out early.
Then three constraints: the voltage and phase your equipment needs, the recharge window your site can actually offer, and how long the system will be deployed, which decides whether to rent or buy.
If you do not have kW and kWh figures, a list of equipment with ratings and daily operating hours gets you there. We do this sizing routinely — send the list and we will return a configuration and a runtime figure.
Questions answered
A mobile BESS is a battery energy storage system built onto a trailer or into a container so it can be moved between sites. It stores electrical energy and delivers it on demand without fuel, noise or emissions.
It depends entirely on the load. A 30 kWh system runs a typical construction site for 4 to 8 hours, or emergency lighting and communications for up to 7 days at low load. Solar recharging extends runtime indefinitely where daily use fits within the array's output.
For most temporary and standby applications, yes. Where the load is genuinely continuous and high, a hybrid arrangement is used instead: the battery carries the load and a right-sized generator runs only to recharge it.
Get in touch
Tell us the site, the load and the runtime you need. Our Austin engineering team comes back with a configuration, a runtime estimate and a price.
+1 512-316-7347
info@pulsar.industries
WhatsApp +1 512-585-8293
