[PK]

The instructions (now mislaid) for the two batteries that came with the electric fence kit I bought this summer mentioned something about not letting them run right down but to re-charge before that point. I think it said that the normal re-charger wouldn’t  work? Does that make sense to anyone? I won’t be needing them until next year so do I need to keep re-charging them over winter?

[SallyintNorth]

As a rule of thumb, no battery does well if it’s allowed to run right down, and all batteries leak a bit so need a little top up if being not used for months.

Maybe give them a little top up after a month. Or every six weeks the next time if they didn’t seem to have lost any charge after a month.

We do not take this advice, either bit of it, and our batteries do not last very long

[shep53]

Buy a 12v battery tester, cheap compared to new battery

[mab]

If, as I'm assuming, they're 12v 'lead-acid'  (i.e. car / leisure / gel / agm) batteries then yes, they should be fully re-charged for  storage, the top wiped clean of any residue and stored in a cool dry place if possible. they would benefit from a brief top-up charge periodically - over winter I'd say 3-4 months is okay between top-ups but if stored at room temp then maybe 1-2 months between top-ups.
In use they ought to be re-charged before they go flat - I try to recharge mine before they drop below 12.0v; if you let them get down to 9v they won't last as long; <9v and you'll be replacing them very soon.
Not sure what they mean about a normal charger not working - a modern 'intelligent' charger may not work if the battery is flat as they need something typically >9v to detect that the battery is there and connected the right way before they turn on. Unless the batteries are sealed types - i.e. gel or AGM which ought to be charged with a charger that has a 'gel' setting. Were they supplied with a specific charger?

[clanger]

Have a look at CTEK battery chargers. With this, you can connect it up, plug it in and then forget about it until you require it again in the spring. They monitor the charge in the battery and top up when it starts to get a little low.  I'm not sure about the smaller models, but I know that their larger models can also restore/recover batteries that have been over-discharged.

I use one on my caravan over winter to keep the battery tip-top for the next season.

HTH,

Chris