Frequently Asked Questions

Answers before you buy, not after

What workshops, distributors and van converters ask us most — mounting, sizing, panel types, batteries and shipping. Search it, or pick a category.

Questions we get asked most often by workshops, distributors and van converters. If yours is not here, ask us directly — we answer technical questions before you buy, not after.

Mounting and installation

Do I have to drill holes in the roof?

No — our ABS bracket sets are designed to be bonded, not drilled. The brackets are adhered to the roof with structural tape or adhesive and the panel is fixed to the brackets, so the roof skin is never penetrated. This is the single most common reason customers choose them: a drilled hole in a vehicle roof is a leak waiting to happen, and it is very difficult to undo. Aluminium sets can be bonded or bolted, depending on the roof.

Why use brackets at all if flexible panels can be glued straight down?

Airflow. A panel bonded flat to a roof has nowhere to lose heat, and a hot panel produces less power — the loss is real and it happens every sunny day, which is exactly when you wanted the power. Brackets lift the panel a few millimetres and let air move underneath. They also route the cabling below the panel rather than across the roof, and they make the panel removable later without destroying it.

How many brackets do I need?

It depends on the panel’s dimensions rather than its wattage. As a rough guide, smaller panels are supported by a 4-piece set, mid-size panels by 5 or 6 pieces, and long panels by a 7-piece set. Send us the panel dimensions and we will tell you which set fits — including for panels you did not buy from us.

Can I install the system myself?

Mechanically, yes — bonding brackets and a panel is within reach of a competent DIY installer. The electrical side deserves more respect. Two rules that catch people out: connect the battery to the charge controller before you connect the panel (many controllers need to see battery voltage first to identify the system voltage), and never mount a controller in a sealed compartment — they need airflow or they throttle back and eventually shut down.

Choosing a system

How much solar do I actually need?

Work backwards from your daily consumption, not from the roof space. The arithmetic is simple enough to do on a napkin:

1. Add up what you use in a day, in watt-hours (a 40 W fridge running 12 hours = 480 Wh).
2. Battery capacity: daily Wh ÷ 12 V ÷ 0.8 (you should not routinely flatten a battery) = the amp-hours you need.
3. Panel wattage: battery Ah × 12 V ÷ 5 useful sun hours = the watts to recharge it in a day.

Five sun hours is a fair year-round working figure for much of Europe; northern latitudes in winter are considerably less, and if you camp off-grid in December you should size up. Send us your load list and we will do this properly for your case.

Flexible, rigid or folding — which panel type?

Flexible if the roof is curved or weight matters; rigid if you want the longest service life; folding if you would rather not attach anything to the vehicle at all. Flexible panels are thin, light and follow a contoured roof, which is why most van conversions use them. Rigid panels are heavier and need a flat mounting area, but they run cooler and carry a far longer warranty — 5 years full and 25 years output, against 1 and 5. Folding panels attach to nothing and can be aimed at the sun. We sell all three and we will not push you toward the one with the better margin — the full comparison is here.

How long do flexible panels last?

Not 25 years, whatever anyone tells you. The 25-year figure belongs to framed glass panels on buildings. Flexible laminates on a hot vehicle roof degrade considerably faster — the industry reality is a service life in the region of five to seven years, with output declining over that period. We would rather you heard that from us before you buy than discover it in year six. Warranty terms are stated on each product page.

MPPT or PWM controller?

MPPT for anything above roughly 200 W, PWM only for small, budget installations. A PWM controller drags the panel down to battery voltage and wastes the difference; an MPPT controller converts it, recovering meaningful extra energy — the gain is largest in cold, bright conditions and when the battery is low, which is precisely when you need it. On a 100 W trickle-charge setup the extra cost is hard to justify. On a 400 W system, PWM is a false economy.

Lithium or AGM battery?

LiFePO4 unless the budget will not stretch, or the vehicle overwinters somewhere that freezes. The usable capacity is what decides it: you should not routinely take a lead-acid battery below 50%, while LiFePO4 is comfortable to 80% or more — so the same nominal rating gives you roughly 1.6 times the usable energy, at about half the weight. The one real limitation is cold: charging lithium below 0 °C damages it, so an unheated winter storage yard is a genuine argument for AGM. More on the trade-off here.

What is a back-contact panel?

Back-contact cells move the electrical contacts to the rear of the cell instead of running busbars across the front. Nothing shades the front face, and the panel reads as a clean black rectangle rather than a grid of silver lines — which matters if the roof is visible. It is a newer cell technology than standard monocrystalline; we are still assembling the full technical data on this range, so ask us and we will send the factory’s data sheet rather than paraphrase it.

Can I use these on a boat?

Customers do, and the mounting principle is the same. But we will be straight with you: our brackets have not been salt-spray tested, so we do not describe them as marine-grade. Marine installations also fall under electrical standards that do not apply to road vehicles, and fasteners in a salt environment raise galvanic corrosion issues that a campervan never faces. If the boat is your primary use case, tell us and we will advise honestly on what is and is not suitable.

Wiring and accessories

Should I wire two panels in series or in parallel?

Series on a clean roof with an MPPT controller; parallel where shading is likely. In series the voltages add and the current stays the same, so thinner cable does the job and an MPPT controller has useful headroom to work with. But a series string runs at the current of its worst panel — shade one and it throttles the rest. A motorhome roof full of air conditioners and roof lights is usually a parallel job. Full explanation, and the two mistakes that damage equipment.

What size cable do I need?

It depends on the current and the length of the run, not on the connector. Losses rise with the square of the current, so a long run from a large array wants a bigger cross-section — 4 mm² is fine for a short run on a single panel, while a long run from a 400 W array wants 6 or 10 mm². Undersized cable does not fail dramatically; it just quietly wastes output as heat, permanently. Tell us the run length and the array and we will specify it — see our extension cable range.

My power station has a different socket. Do you have an adapter?

Probably. Portable power stations, battery boxes and controllers use a range of DC inlets — XT60, DC5521, DC7909, Anderson, GX16 aviation — and we stock over twenty ready-made leads covering the common ones, from 20 cm to 10 m. Tell us the make and model of your device rather than the connector name and we will tell you which lead fits. See adapter cables.

Do I need fuses in a solar array?

With two panels in parallel, usually tolerated. From three panels upwards, fusing stops being optional — if one panel develops a fault, the combined current of all the others can flow back into it. We supply in-line fuse connectors and combiners rated for the array size.

Buying from us

Why is there no price on the site?

We sell to workshops, converters and distributors, and prices depend on configuration, quantity and destination. A published single-unit price would be wrong for almost everyone. Send us what you need and you will get a real quotation.

Can you supply under our own brand?

Yes, on the bracket sets — the tooling is ours, so private label and packaging changes are straightforward. For sourced components we will tell you what the partner factory can and cannot do rather than promising on their behalf.

Do you ship to Europe? What about WEEE registration?

Europe is our main market. Topenergy holds German WEEE registration DE 69775827 in our own company name — see the certifications page. For other EU member states, tell us where the goods are landing and we will confirm what is in place before you commit.

Do you sell to individuals?

Our brackets are available to end customers through online marketplaces. This site is aimed at trade buyers — workshops, converters, retailers and distributors — where we can quote properly and support the sale afterwards.