Beware The Best Laid Plans Of Mice And Batteries

Is your battery warm and cosy this winter? Yes, it probably is.

This means it could be a very attractive house for a mouse, so be warned – rodents are terrible for electrical installations, and a mouse plague is currently chewing its way through Australia.

As a farmer, I’ve always despised rats & mice, but this was a difficult thing to express to my brother’s former girlfriend and the pet rat she kept for a couple of years, mainly on her person.

In younger days our family had a menagerie of rabbits, chooks, pigeons and a duck, so there was always a battle to keep them fed without creating a welcoming home for rodents. A wine bottle laid over a bucket was a good trap for mice, but we found the most reliable way to end a big fat rat was actually using a rabbit trap.

Do Rats Damage Home Batteries?

All kinds of life will seek out a warm spot in winter, and rodents are famous for nesting in roof spaces, car engine bays, and anywhere else they can chew their way into.

Where this matters for solar and battery systems is wiring, because PCV insulation is no match for sharp teeth, and the critters have no respect for electricity.

Here we see the rats have helpfully rounded off the edges of the timber, but probably got an uncomfortable tingle from chewing through the red wire.

When modern battery solar hybrids are wired for “whole home” backup, the mains cables that power your entire house can be fed through the inverter in some instances. The ordinary loads of household consumption will warm this wiring up and additional energy for things like EV charging, solar generation or “free hours” battery charging only adds to the temperature.

Here we see behind the switchboard, a hard-working solar inverter heating the supply wire & breaker on the RHS, while the main switch on the LHS is also sweating a little under the load.

Check Your Enclosures

A well-executed switchboard will have pretty neatly fitted wiring, so if there are any gaps bigger than the diameter of a pencil, legally, they should be caulked with intumescent sealant.

Out in the real world, many switchboards have gaping holes through which mice will waltz on their way to a nice warm abode. Some of them will even piss into the safety switches and randomly trip your circuits.

Shaded in pink, we see the shutter you slide across to accommodate large bunches of cables. It should be behind the “live parts” label. However, the vandal who wired this board simply punched the entire assembly out of the enclosure, leaving a gaping hole for mice and sharp edges for the cables to pass through.

It can be difficult for a homeowner to check inside a switchboard, as (for good reason) you’re not legally allowed to remove the escutcheon or open the meter panel. However, mouse droppings or smell are a warning that should be heeded.

Where solar and battery installations sometimes fall victim is nicely fitted ducts for wiring are also nice secure homes for mice, with access holes to the wall cavity or ceiling space; and an electric blanket to nest with.

Issues arise when the mice decide to do some renovations, and they chew up the wiring inside the enclosure to create some extra space.

These lovely cable ducts can hide furry little surprises.

Keep Rodents Out Of Switchboards

Well-executed wiring is the only way to really combat rodents. Making sure the buggers can’t get into switchboards and enclosures is essential.

Nice warm switchboard full of mouse s#it. Yuck.

Many don’t realise that unless it’s shiny smooth metal, almost any surface will give a mouse enough purchase to climb walls with tiny sharp claws. I’ve watched them go straight up a brick chimney or timber doorframe, so electrical cable tray is a funpark and soft PVC insulation isn’t much different to a rope ladder.

From the off-grid system above, you have to work with what you’ve got. Luckily, this half-arsed electrician was typically averse to cleaning up, so I found scraps of switchboard material left over to screw back over the gaping holes and caulked the rest to exclude the mice.

Bait Is Bad

Please be aware that while poisons can be an essential tool for controlling pests, mice are at the bottom of the food chain. When they’re eaten by owls & raptors, these birds can fall prey to the same anticoagulant rodenticides building up in their system.

Look at the label.

First generation anticoagulants include warfarin, coumatetralyl, and diphacinone. They typically require multiple feeds to deliver a lethal dose and pose a lower risk to wildlife.

Second-generation anticoagulants include brodifacoum, bromadiolone, difenacoum, difethialone, and flocoumafen. Often lethal after a single dose, these poisons persist longer in the environment, which increases the risk of secondary poisoning to wildlife.

For more on how to protect your home energy gear from unwelcome visitors, read about how to stop solar inverters from becoming a bird nest.