Solar Panel Compatibility: A Plain Guide to Adding Solar to a Zeliox System

The Short Answer

Yes, every Zeliox system sold in Australia can charge from solar panels. How it happens differs by model. The ECO line (ECO SLIM, ECO II) connects panels through an optional MPPT charge controller called the Solar Mate. The NEO 4000 has an MPPT controller built in, so you wire a panel array straight to its solar input.

The part that trips people up is sizing. A panel's wattage is a laboratory rating, not a promise of what it delivers on the roof of a parked van in winter. This guide covers what the solar input on each model actually accepts, how to work out how much panel you need for your loads, and where the wiring decisions stop being a DIY job.

What Solar Input Actually Means

A portable power system's solar input is a DC connection that feeds the battery through a charge controller. The controller matters more than the panels. It does two jobs: it converts the panel's output to the voltage the battery wants, and it stops the battery overcharging. On a Zeliox system, that controller uses MPPT, which stands for Maximum Power Point Tracking.

The simplest way to think about MPPT: a solar panel has one operating point where it produces the most power for the current conditions, and that point moves constantly with light and temperature. An MPPT controller keeps finding it. Zeliox's Solar Mate documentation claims this can lift output by as much as 30% compared with cheaper PWM controllers. Take that as the manufacturer's number, not a guarantee for your installation. The direction is right, though, and it's why MPPT is worth having on a vehicle where light conditions change all day.

A solar input rating is a limit, not a yield. “Up to 1,440 W” on the NEO 4000 means the charge circuit accepts up to that much power. What your panels actually deliver depends on where you park, the season, the weather, shading, and how clean the glass is.

Solar on Each Zeliox model

Three models are sold in Australia. Here is how each one takes solar.

ECO SLIM — 0.64 kWh (50 Ah, 12.8 V) battery.
Solar charging works through the optional Solar Mate MPPT controller; the official charge table quotes about 2 h 10 m to full from a 300 W array.

ECO II — 1.3 kWh (100 Ah, 12.8 V) battery.
Same Solar Mate route; about 4 h 20 m to full from a 300 W array.

NEO 4000 — 2.4 kWh (48 V) battery, expandable to 9.6 kWh.
MPPT built in. Accepts up to 1,800 W of panels; the charge circuit tops out at 1,440 W.

Charge times come from the Zeliox product datasheet (03/2025) and assume a discharged battery charged with no loads running. The panel array's voltage and current limits come from the Solar Mate controller fitted, not from the ECO unit itself, which is why the wiring section below matters.

ECO SLIM and ECO II: the Solar Mate route

The ECO manual is direct about this: “To harvest sun energy, optional solar panels and a MPPT-converter needs to be installed. Ask your installer for Zeliox approved products.” The approved product is the Solar Mate, an MPPT charge controller that connects to the ECO through an RJ45 communication port. Two sizes are listed for the ECO range:

• Solar Mate SF100-30 (article number ZEL-07-016) and
• Solar Mate SF100-50 (article number ZEL-07-017).

The SF100-50 is the one to spec if you want the ECO II's full 30 A DC-DC input available for solar. The controller supports 12 V and 24 V systems, so it covers both models.

NEO 4000: solar input built in

The NEO 4000 needs no extra controller. Its MPPT charger accepts PV input between 15 and 60 V DC (at 25 °C), up to 1,800 W of panels, and charges at up to 30 A at 48 V, which equals 1,440 W of charge power.

Note the gap between those last two numbers. You can hang up to 1,800 W of panels off the NEO 4000, but the charge circuit tops out at 1,440 W. Oversizing the array isn't wasted: it pushes the charge toward that cap earlier and later in the day. But don't expect 1,800 W to reach the battery. The same 1,440 W cap applies to charging from a 12 V vehicle alternator. On a 24 V vehicle, the input can reach 2,400 W.

How to size panels for your loads

Work through this in order. You need three numbers: your daily energy use, the solar yield where the vehicle works, and a derate factor for real-world mounting.

Step 1: add up your daily load in watt-hours

List what runs off the system in a typical day and multiply each item's wattage by the hours it runs. A mobile service van might look like this:

That example is a worked illustration, not a fleet benchmark. Your numbers come from your own load audit: the ratings on the gear, plus some margin for compressor startup and inefficiencies.

Step 2: find your local solar yield

The Australian Government's energy.gov.au publishes typical daily generation per kilowatt of panels, averaged across a year: 5.0 kWh in Alice Springs, 4.4 kWh in Darwin, Perth, 4.3 kWh in Canberra, 4.2 kWh in Adelaide, Brisbane and Cairns, 4.0 kWh in Sydney, 3.6 kWh in Melbourne and 3.5 kWh in Hobart.

Two things that table is telling you. Panels produce more than the yearly average in summer and less in winter, and a flat-mounted van roof produces less than the optimally tilted array these figures assume. Which brings us to the derate.

Step 3: apply a derate factor

A flat roof array on a vehicle, with partial shading and a charge controller in the path, delivers somewhere around 70–80% of the headline yield in practice. Use 75% for a first pass and treat the result as an estimate to verify with your installer, not a figure to promise a fleet manager.

The worked example

A vehicle working around Sydney, with the 2.1 kWh daily load from Step 1: 2,100 Wh ÷ (4.0 kWh/kW/day × 0.75) = 700 W of panels. Same vehicle in Hobart: 2,100 ÷ (3.5 × 0.75) = 800 W. In Darwin: 2,100 ÷ (4.4 × 0.75) = 636 W, so 700 W of panel covers it.

A 700 W array on a van roof is a real footprint: roughly seven 100 W panels, or a pair of 350 W panels and change. If your load audit comes out at that level, solar is supplementing your driving and shore charging, not replacing them. Which is fine. A vehicle that drives daily charges faster from the alternator than any roof array will. Solar earns its keep on vehicles that sit, or that work far from a power point.

One more check before you order panels: charge time. Dividing panel wattage by system voltage gives you the rough charge current. On a 12.8 V system, a 300 W panel delivers around 19 A at realistic output, which is what the charge times above assume. If the array exceeds the Solar Mate's charge current rating, the surplus is clipped. That's the number to match, and your installer will check it against the controller's spec sheet, not the panel brochure.

Voltage and wiring: where it stops being a DIY job

Two numbers on a panel datasheet matter more than the wattage sticker when you're connecting to a charge controller: Voc (open-circuit voltage) and Isc (short-circuit current). Voc is the highest voltage the panel puts out with no load attached, and it rises in cold weather, which is exactly when a battery system with a heat pack is most likely to be working.

Here's a worked example of why this bites. The Solar Mate SF100 series accepts up to 100 V of open-circuit voltage. Two common 150 W panels, each with a Voc of 49.5 V, wired in series give 99 V, just inside the limit on a mild day. At 0 °C that same series pair can present around 107 V. Over the limit. The controller protects itself, but it protects itself by not working.

This is not a problem to solve in a guide. It's a problem for the person running the cables, and the rule is simple: the array's cold-weather Voc, the controller's input rating, and the cable sizes all get checked together by the installer, against the manuals for the actual hardware being fitted. Zeliox's own installation documentation puts solar wiring squarely in the installer's scope, and wiring that ignores the controller's limits can void warranties on both the controller and the ECO.

What the guide can say is the shape of the decision. Series wiring (positive to negative) adds voltage, keeps current low, allows thinner cable; watch the cold-weather Voc limit. Parallel wiring (positive to positive) adds current, keeps voltage at the single-panel level; it needs thicker cable and a combiner done properly. On the NEO 4000 the same logic applies with its 15–60 V PV window: a single large-format 48 V-panel string is fine; series strings must stay under 60 V even on a frost morning.

What solar will and won't do on a work vehicle

Be clear-eyed about what a roof array buys you.

It will top up the battery on parked vehicles, stretch off-grid work between drives, and shave shore-power charging for vehicles that mostly sit at a depot. Through the middle of the day, a well-sized array on the NEO 4000 can genuinely run light loads and charge simultaneously.

It won't make a vehicle fully energy-independent. Panel ratings assume standard test conditions: 25 °C cell temperature, 1,000 W/m² of light, optimal angle, no shading, clean glass. A flat van roof under a Hobart overcast in July meets none of those. Solar on a vehicle is a range extender for your battery, not a replacement for charging while driving or from the grid.

The honest sizing question isn't “how many watts can I fit on the roof” but “how many watt-hours does my work need each day, and what mix of driving, shore power and solar covers it cheapest.” Panels are the most expensive watt of the three. They're also the only one that works where the other two don't.

Choosing panels

Zeliox doesn't publish a list of approved panel brands, and this guide won't invent one. What the documentation does say: ask your installer for Zeliox-approved products, because the panels, the Solar Mate controller and the ECO unit are tested as a system. Panels and controller from the same supplier means one party is responsible when something doesn't play nice.

When you're comparing panels, check in this order:

1. Voc and Isc at your coldest expected operating temperature. These determine whether the controller can accept the array at all.

2. Physical size and mounting. Van roof space is the binding constraint, not budget.

3. Cell type and temperature coefficient. On a dark roof in summer, a panel's output drops as it heats; a gentler temperature coefficient loses less.

4. Warranty and availability in Australia. A 25-year performance warranty is only worth what's behind it locally.

Skip the wattage race. A 200 W panel that fits the roof and matches the controller beats a 400 W panel that does neither.