Its always better to plug in if you can, but for remote pastures away from the yard site, a battery-powered fencer charged via a solar panel is the only option.
Remember, though, that deep-cycle batteries need to stay as close to 100 per cent charged as possible. Repeated heavy cycling – running them down below 50 per cent of a full charge – will kill a battery in less than a year. They need to be fed electricity every day, and many people unwittingly starve their batteries to death by using a solar panel that is too small.
“You’ve got to match the right size solar panel to the fencer,” said Rex. “If you’ve got a fencer that is taking five amps out of the battery every day, and your solar panel is only putting three back in, it’s going to be a dead battery, isn’t it?”
It’s always better to use a charge controller and figure on overfeeding a battery, because cloudy days happen, and they may leave the battery in an undercharged state. Leaving a battery drained too low for too long ruins it by allowing sulphate deposits to build up on the lead plates. If kept charged and topped up with de-ionized water twice a year, deep cycle batteries should last five years or more.
A “dirty” fence – one with lots of faults – won’t drain the battery any faster than a clean fence, but extremely low temperatures severely limit the storage capacity of lead-acid batteries, said Rex.