A Fire Next to My Home Battery: What We Learnt

At 12:15 pm on a Monday, my wife Sue rang and told me our home battery was on fire.

When it was clear that Sue and our family dog were safely out of our home, and the firies were on their way. One of my first thoughts was:

“Oh, great. The Murdoch media and my mate Jamie are going to have a field day with this.”

Because when you’ve spent years talking about solar and batteries, having your own battery burst into flames would be just a little embarrassing.

Fortunately, it hadn’t. The short version is that the battery didn’t cause the fire and, as far as we can tell, wasn’t caused by the inverter either. While that was certainly a relief, there was still a fire right next to our solar and battery equipment, and some important lessons to learn from it.

In the beginning, we had a 12.8kWh battery and a very neat installation with all cables concealed behind the industry-standard Formply mounting board.

No, It Probably Wasn’t Arson

After the fire was out and the immediate danger had passed, we started trying to work out what the hell had happened. Our resident fact checker, Ronald Brakels, suggested that, because I’d recently appeared on television criticising a solar retailer, perhaps it was arson. I think he was joking, although with Ronald, you can never be entirely sure.

But no, I don’t seriously think an angry solar installer crept into my garage and set fire to the isolator. The evidence points to an electrical fault. Exactly what failed, we may never know, as it all burst into flames.

Once the flames were extinguished, the fire service rang for their on-call solar electrician to make safe and restore mains power. The remains were plonked upside down against the wall.

Getting Someone Competent To Look At It

Once I’d finished making insurance calls, I invited our resident installer, Anthony Bennett, to inspect the damage.

In considerably more colourful language, Anthony was quick to point out that he’s more of a farmer than a fire investigator, but he does know solar installations and has set many things on fire as a professional primary producer.

Looking at where the fire began, how it spread and which components survived, it seemed reasonably obvious that the inverter itself wasn’t the source. Despite the heat and flames around it, the inverter was still largely intact.

The AC isolator and breaker at the apparent point of ignition were not. They had been burnt to smithereens, which makes identifying the exact failure rather more difficult.

That blue circle used to be a few circuit breakers in an enclosure. This seems to have been the seat of the fire, from where the flames licked up the Formply board and fried the inverter.

As Anthony goes on to detail :

Looking at the remains of Trev’s system was both eye-opening and a bit frustrating. Everything was so thoroughly burnt that there was no telltale, no single point of failure. Often, a bad connection overheats; sometimes it arcs, fizzes, or burns, but it usually fails as an open circuit, so when the lights go out, things cool and the flames self-extinguish.

This isn’t Trev’s circuit breaker, but the screwdriver points to the failure, a connection simply left loose. I’ve highlighted the vacant terminal. When you tighten the screw (red), it draws the loop (blue) toward the tinned copper seat, which clamps the cable or bussbar tight.

When the electrician arrived, there was an obvious cause. In this instance, I could see the various cables going in and out of the inverter; the terminations in what remained of the circuit breakers appeared solid. There were ferrules on the flexible cables, and none of them was burnt open. I expect a poor connection would be blown apart, melted, and rounded off like an arc-welding electrode.

When I spoke to the Office of the Technical Regulator, they explained that electrical fires aren’t uncommon, but just don’t make the news much.  They pointed out that compliant electrical products are flame-retardant, whereas cheap plastic is basically just fuel.

The best approach to prevent this sort of conflagration is to use quality equipment and to be doubly sure, get a thermographic report from a maintenance electrician every spring. It’s the law for places like nursing homes to do this, but the cost for a homeowner is probably a bit much.

This is a thermal image of a hard-working single-phase solar-powered switchboard. The 63 A main switch on the left is warm, but the 40 A-rated inverter circuit breaker is carrying a continuous 8 kW or 35 A load.

You could buy yourself a thermal camera and have endless fun around the house for a week, but a homeowner can’t legally open the switchboard to get a meaningful image.

There Was A Serious Amount Of Power Going Through It

The fire happened on a sunny early-spring day. The battery was charged, the solar was generating strongly, and the system was exporting close to 10 kW to the grid.

It did that day after day through the previous spring and summer without a problem. But 10 kW is still a serious amount of power moving through cables and electrical equipment. Endless spring sunshine can also mean there’s no diversity. Unlike a simmering stove that cycles on and off, solar goes full steam, soaking everything with heat for hours on end.

The current working theory is that repeated heating and cooling may have caused a terminal to loosen or a contact to deteriorate, eventually resulting in a poor connection, which overheated. That’s my layperson’s understanding, not a confirmed technical finding.

Compliant Doesn’t Mean Nothing Can Go Wrong

To my knowledge, the installation was fully compliant with all the standards and best practices.

It wasn’t in a habitable part of the house. It wasn’t next to a window. It was mounted on a suitable backing board. There was nothing obviously dodgy about the installation.

But Anthony made one observation that has stuck with me; cement sheeting behind the equipment may have prevented the fire from spreading, or at least slowed it down significantly. The coating on the Formply is really tough, but it’s not fireproof, so once it got going, the plywood was fuel for the fire.

That’s one of the biggest lessons I’ve taken from this. Compliance matters, but it doesn’t eliminate every risk. A good installation should also consider what might happen if something fails anyway.

What’s behind the equipment? What’s beside it? Where could a fire spread? How close is the inverter to the battery? Is there anything practical that could contain a fire or buy people more time?

The day before, my system was cracking along. By 10 am, it peaked at 10.7 kW, the battery was charged, and it began exporting 9 kW to the grid for the next 3 hours. The EV harvested 7 kW from 1 to 2:30 pm, then the production tailed off.

We Were Lucky Sue Was Home

This is the part that I just don’t want to think about: what if Sue hadn’t been home?

She realised something was wrong when the power went out and acted very quickly. If the house had been empty, who knows how long the fire might have continued before somebody noticed?

It was close to the batteries and our EV. From there, it could potentially have spread further into the house. I don’t particularly enjoy imagining what that might have looked like. And could you imagine the news stories!

It also made me wonder whether we should have had a smoke alarm in the garage, connected to the alarms inside the house. If Sue had been elsewhere in the house, an alarm might have alerted her before the power failure did. If nobody had been home, perhaps it would have attracted a neighbour’s attention sooner.

The next day was similarly great for solar. By 10 am, it peaked at 10.4 kW. The battery was charged, and it began exporting 9 kW to the grid for the next 2 hours before a fire caused an abrupt stop.

So, What Should Homeowners Do?

I’m still confident we chose good equipment and used an extremely competent installer. And yet, something still caught fire.

That doesn’t mean solar and battery installations are inherently unsafe. But it is a reminder that solar and battery installations handle serious amounts of energy, and no electrical system is entirely without risk.

Choose your installer carefully. Choose reputable equipment. Have the system inspected and maintained.

But also think about what happens if something goes wrong:

• Where are the inverter, battery and isolators installed?
• Are they accessible, and do you know how to shut them down if needed?
• What materials are behind and around them?
• How easily could a fire spread?
• How quickly would somebody inside the house know?
• Is there an appropriate way to detect a fire earlier?
• Could fire-resistant backing or better separation reduce the consequences?

We were lucky. Sue was home. Everyone got out safely. The fire brigade arrived¹, and the flames didn’t reach the batteries, our EV or the house.

The point isn’t to frighten people away from solar or batteries. It’s to learn from a near miss instead of shrugging our shoulders and pretending that compliance means nothing can ever go wrong.

While we might change a few things on the new installation, this event hasn’t changed my opinion of home electrification. I’d have to hand in my resignation letter if it did.

The future is undoubtedly electric, but holy shit, things can still be dangerous.