Cyclone Koji Solar Battery Damage: Why “Drying It Out” is Dangerous

The rain has finally stopped in Cairns, leaving behind that familiar, steamy silence that follows a tropical deluge. As the waters of Ex-Tropical Cyclone Koji recede from the Barron River catchment and the streets of Townsville begin to dry, the immediate instinct is to return to normal. We hose down the driveways, drag the soggy carpets to the curb, and reach for the switchboard to turn the lights back on.

But for thousands of Queensland homes equipped with the latest solar and battery technology, this moment of “recovery” is actually the moment of highest risk.

For a decade, we treated solar systems as passive glass on the roof—rugged, simple, and largely waterproof. But the energy landscape of 2026 is different. We are no longer just storing panels on our roofs; we are storing volatile chemistry in our garages. As the sun comes out today, it is not just drying the mud; it is heating up a potential crisis that the industry—and insurers—have been warning us about for months.

I spoke this morning with Brenton Hielscher, Managing Director of Hielscher Electrical, who has been on the ground in Cairns coordinating safety inspections since dawn. His assessment was blunt: “The storm didn’t blow the systems off the walls. It just drowned them. And that is far more dangerous.”

The “Delayed Fuse” of Water Ingress

The primary danger in the wake of Koji isn’t the wind damage we can see; it’s the water damage we can’t.

Sure Insurance reported yesterday that the majority of early claims are for “water entry through roofs and windows”¹. This is the critical detail that experts like Hielscher are fixated on. Cyclonic rain—even from a decaying Category 2 system—doesn’t fall down; it drives sideways. It finds entry points that standard vertical rain never touches.

According to extreme weather protocols from Global Sustainable Energy Solutions (GSES), this specific type of ingress creates a “delayed fuse” for solar systems.

When water breaches a DC isolator or, more critically, a lithium-ion battery unit, it doesn’t always cause an immediate bang. It sits there. As the sun comes out today, residual moisture and salt deposits begin to corrode internal circuitry. This creates tracking paths for electricity—bridges that shouldn’t exist.

“A submerged or dampened battery doesn’t always fail immediately,”

Hielscher warns. “It waits. When the system is re-energized, or even if it sits idle with charge remaining, these shorts can trigger thermal runaway.”

The Queensland Fire Department has been explicit on this: a battery that has been submerged, especially in saltwater or brackish floodwater, is no longer a power source. It is hazardous waste.

The Chemistry of Catastrophe: Why 2026 is Different

To understand why local experts are sounding the alarm so loudly this week, you have to look inside the box.

Ten years ago, a flooded solar system was a nuisance. The old string inverters were essentially simple power electronics. If they got wet, they shorted out, popped a breaker, and died. It was an expensive replacement, but it wasn’t a catastrophe.

Solar batteries have changed the equation entirely.

We are no longer just dealing with electricity; we are dealing with high-energy density chemistry. Most legacy batteries installed across Cairns and the Cassowary Coast in the last boom (2020–2024) rely on lithium-ion architectures that, while efficient, are chemically volatile when compromised.

When floodwater containing silt, salt, and contaminants breaches the casing of a battery pack, it doesn’t just “short out” the unit. It creates conductive bridges between cells. In a 400V battery stack, this internal tracking can bypass the Battery Management System (BMS). Once that BMS is bypassed, you lose the brain that stops the battery from overheating.

This is where the nightmare scenario of Thermal Runaway begins.

“We aren’t talking about a candle flame,” Hielscher explains.

“We are talking about a chemical reaction that generates its own oxygen and burns at over 1000°C. You cannot put it out with a garden hose. You basically have to let it burn until the fuel is gone.”

This is why SA TS 5398—the new battery safety standard that became mandatory on January 1st—is so critical. It forces manufacturers to prove their enclosures can withstand not just “rain,” but the kind of environmental assault we just saw from Koji. It demands better propagation checks and tougher ingress protection.

But here is the hard truth for Far North Queensland: Thousands of batteries on our walls right now are pre-2026 stock. They don’t meet these new standards. They were the “budget option” sold by door-knockers who have long since left town. And right now, those budget batteries are sitting in damp garages from Tully to Townsville, ticking.

The Financial Shockwave: Insurance is Watching

If the physical safety risk isn’t enough to give you pause, the financial reality should.

Just days before the rain started, on January 6, IAG (Insurance Australia Group) released a landmark safety report that flagged a massive “safety gap” in the Australian market⁴. Developed in collaboration with EV FireSafe, the research highlights a direct correlation between “low-quality, untested products” and catastrophic failure events—specifically when exposed to saltwater flooding.

The timing of this report is not a coincidence. Insurers are signaling a shift in tolerance.

For homeowners, the fine print is brutal. Most product warranties for inverters and batteries are instantly voided if the unit is submerged. If you attempt to turn your system back on without a certified inspection and it causes a fire, you may find yourself navigating a claims process that is far less sympathetic than it was five years ago.

“The days of ‘she’ll be right’ are over,” say’s Hielscher.

“In 2026, ‘she’ll be right’ will likely lead to your claim being denied. If you re-energize a drowned system without a solar battery safety check, you are effectively taking ownership of that liability. Don’t quote me though. Be sure to seek your own professional advise from your insurer or financial expert.”

From Yasi to Koji: The Evolution of Risk

It is worth pausing to look at how much the landscape has shifted. Hielscher, who has been servicing the region for decades, draws a sharp parallel to Cyclone Yasi in 2011.

“I remember walking through the wreckage of Cardwell and Mission Beach after Yasi. Back then, the solar industry was in its infancy. A 5kW system cost $20,000, and you only saw them on the roofs of early adopters. A bit like the yachts at Hinchinbrook at the time.”

During Yasi, the biggest fear was mechanical. Did the rail hold? Did the panels turn into frisbees?

Fifteen years later, the risk profile has flipped. Mechanical engineering has improved drastically; we rarely see panels flying off roofs anymore because the racking standards (AS/NZS 1170.2) are robust, and most local installers know how to bolt down for Region C.

But while the mechanical risk has dropped, the electrical risk has skyrocketed.

In 2011, we didn’t have 10kWh of lithium storage bolted to the side of the house. We didn’t have rapid shutdown requirements or complex hybrid inverters managing export limits. We had simple systems for simple times.

“Cyclone Koji represents the first true test of the ‘Modern Solar Home’ in a severe weather event,” Hielscher notes.

“We now have homes in Cairns that are essentially micro-power stations. When the Ergon grid goes down—as it did for 30,000 customers this week—these homes are designed to keep running.”

That is a miracle of engineering, but it demands a higher tier of responsibility. In 2011, if the grid went down, the solar went off. Safe. Simple. In 2026, a house can be blacked out from the street but live with 240V power inside, fueled by a battery that might be sitting in a puddle.

This shift from “Passive Generation” to “Active Storage” means that electrical contractors aren’t just tradies anymore; they are asset managers. And for the homeowners of North Queensland, it means the “set and forget” mentality is dead.

A Strategic Pivot: From “Installers” to “Resilience Partners”

This event offers a stark choice for the North Queensland solar industry. We can hide from the warranty calls, or we can step up.

The weeks following Ex-Tropical Cyclone Koji should not be about selling new systems; they must be about securing the existing ones. There is an immediate, moral, and commercial imperative for local electrical businesses to pivot their operations from “sales” to “safety audits.”

Hielscher Electrical has already begun this pivot, deploying teams to conduct “Post-Flood Storm Checks” across the region. Their approach is a blueprint for the industry: stop waiting for the phone to ring with a complaint, and start dialing with a solution.

Call to Arms: The Post-Flood Protocol

For Homeowners:

1. The “Red Zone” Rule: If floodwaters reached your inverter or battery, consider the system dead. Do not attempt to dry it out. Do not attempt to turn it on.
2. Assume it’s Live: Solar panels generate voltage as long as there is daylight. Even if the grid is down and your main switch is off, the DC cables running through your roof and walls are live. Treat them with extreme caution.
3. Hazmat, Not Hard Rubbish: If your battery is damaged, do not throw it on the pile with the ruined carpet. A crushed or punctured battery in a garbage truck is a fire waiting to happen. Contact your local council for specific hazardous disposal instructions.

For Industry Leaders:

1. Launch “Amnesty” Inspections: Offer a fixed-price safety check. Use thermal imaging cameras to detect internal hotspots in DC isolators and inverters that might look dry on the outside but are arcing on the inside.
2. Educate on “Void” vs. “Safe”: Be the honest broker. Tell your clients clearly: “This inverter might turn on today, but it is corroded. Your warranty is gone. Let’s replace it before it becomes a fire risk.”
3. Upgrade the Standard: If you are replacing gear this month, do not put IP54 equipment back on a wall that just saw horizontal rain. Upgrade to IP66. Move the gear higher. Sell the resilience, not just the kilowatt-hours.

The storm has passed, but the test of our industry’s maturity is just beginning. Let’s make sure that when the lights come back on in North Queensland, they stay on safely.

Don’t Guess When It Comes to Safety.

The storm has passed, but the risk to your home may be just beginning. If your solar or battery system was exposed to wind-driven rain or floodwaters during Ex-Tropical Cyclone Koji, do not attempt to restart it yourself. Invisible corrosion and water ingress can turn a working system into a fire hazard in seconds.

Hielscher Electrical is Cairns’ dedicated energy safety expert. Our local, experienced team is currently deploying across the region to conduct Post-Storm Safety Audits. We use advanced thermal imaging and testing protocols to ensure your system is safe, compliant, and ready to run.

Secure your peace of mind today!

📞 Call the Hielscher Emergency Response Team: 07 4033 0521

🌐 Book Your Safety Inspection Online: https://hielscherelectrical.com.au/contact/

⚠️ For emergencies, dial 000

We keep the lights on—safely.