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What Should My Trailer Builder Build In for Off-Grid Solar and Battery Power?

by Lucie
(London)

Olive green single-axle catering trailer with roof solar panels serving lunch to a queue at a London market

Olive green single-axle catering trailer with roof solar panels serving lunch to a queue at a London market

Inquiry: Off-Grid Solar Setup & Approved Equipment Suppliers for 3m Catering Trailer

Dear Support Team,

I am currently finalizing the specifications for a custom-built 3m mobile catering trailer for our business, Veg & Virtue ELAN Ltd. We intend to operate off-grid using a hybrid setup (Solar PV + LiFePO4 Battery + Backup Power / Shore Hookup) for serving hot lunches, gelato, specialty coffee, and refreshments.

Before we lock in the final manufacturing CAD drawings with our trailer builder, we want to ensure full compliance with UK regulations, EHO food safety standards, and IET BS 7671 (Section 717) requirements.

Basic Trailer Specifications:

Dimensions: 3.0 m (L) x 2.0 m (W) x 2.0 m (H)

Chassis / Towing: Single axle with AL-KO / VIN-compliant towing assembly

Factory Readiness Planned: Structural roof reinforcement (min. 40kg static/dynamic load capacity), IP68 waterproof roof cable entry gland with conduit, and an 18mm plywood backing board in the tech compartment.

Could you please assist or advise us on the following:

Compliance & Structural Guidance: Are there any specific NCASS or BS 7671 standards regarding roof-mounted solar PV systems, battery safety compartment ventilation, or cabling pathways that we must ensure the factory incorporates at the shell stage?

Approved Partner Recommendations: Could you refer us to NCASS-approved suppliers, auto-electricians, or mobile power system integrators in the London / South East area who specialize in installing and certifying off-grid solar/battery systems for catering trailers?

Electrical Safety Certification: What specific electrical safety sign-offs (e.g., BS 7671 / PAT testing) will be required by local authorities and market operators for this type of hybrid off-grid setup before we begin trading?

Thank you for your guidance. We look forward to your advice and to utilizing NCASS support as we launch our venture.

Kind regards,

Lucie

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by: MobCater

Hi Lucie, just so you know, we are not NCASS, we are an independent site run by me, but I am glad you got in touch, because asking these things before the CAD drawings are signed off is exactly the right time. Changing a shell later costs far more than drawing it right now.

On standards, the wiring in any catering trailer falls under Section 717 of BS 7671, the part covering mobile and transportable units. Your solar array also brings in Section 712 for PV systems, and the battery bank should follow the battery manufacturer's installation instructions and the newer battery guidance in the regulations. I am not aware of an NCASS standard specific to roof solar, so BS 7671 is the one your electrician will design and test to. Lithium iron phosphate is a sensible choice because it does not give off gas the way lead acid batteries do, but it still needs a ventilated, fire resistant compartment that stays cool, with the battery and inverter fixed down so nothing moves on the road.

The point I would push hardest with your builder is separation from your gas, if you are running any. Batteries, inverters and charge controllers are all ignition sources, so they must never share a space with LPG cylinders. The gas locker should be sealed from the inside of the trailer and vented at low level to the outside. Ask the factory to fit a proper cable route from that roof gland down to the tech compartment, with fused protection close to the battery and a clearly labelled isolator you can reach quickly.

I would also be honest with yourself about the load. A few LED lights and a fridge sit happily on solar, but a two group espresso machine can pull close to 3kW, and a gelato display freezer runs all day. A 3m roof will not carry enough panel to replace that, so expect your shore hookup or a quiet generator to do the heavy lifting on busy days, with the solar topping up the battery.

For certification, a newly built installation should come with an Electrical Installation Certificate, not just a condition report, covering the whole system including the inverter and the changeover between solar, battery and shore power. Any gas appliances need a Gas Safe registered engineer and their certificate, and your portable appliances should be PAT tested. Markets and events will usually ask for those alongside your insurance and food business registration. To find installers in London and the South East, search the NICEIC and NAPIT registers and ask straight out whether they have certified Section 717 units with batteries before. Electricians who fit out motorhomes and boats are often the ones who know this work best.

Good luck with it

David

Disclaimer: Electrical installation and testing on a catering unit must be carried out by a qualified electrician registered with a competent person scheme such as NICEIC or NAPIT, and any gas work by a Gas Safe registered engineer. Never attempt either yourself. Standards and local requirements can change, so always confirm what your council, market operators and insurer need before you trade.

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