This video may interest some of us Where is the True North Pole?

I have played with a powerful magnet next to my compass for 10 minutes and it seems to have put it back right. No idea if it is going to last though.

I haven't come across batteries being a possible cause which doesn't surprise me since I don't believe batteries generate EM fields. It's amazing though you have had 3 reverse themselves. There must be a common cause I guess

No success, so far. Could this problem come from the fact that I store my compass in the same pocket as the replacement batteries for my GPS?

Hi Nic - thanks for your post and the link to the article you gave. I had not seen that particular one. It does emphasise the potential problem that we all need to be aware of. Did you manage to re- magnetise your compasses yourself?

This is my third compass that reverses polarity i.e. North points South.
Reverse polarity a risk to climbers, mountain body warns

On a recent trip to Scotland I was amazed to find that my Silva compass was failing to point north. The needle just seemed to wander around not really settling in any particular direction. I hasten to say this was not due to the proximity of other metallic items or magnetic rocks - as later checks against the compasses of other walkers showed. The problem was potentially quite serious since I was attempting to navigate from a featureless summit in heavy mist.
I had never heard of a magnetic compass failing to point north but on my return a google search revealed that my experience was not unique and I thought the results of my investigations may be of interest/benefit to others.
It appears the most common source of the problem is storing your compass in the presence of electro-magnetic fields. These can lead to a reversal in polarity i.e. the compass points south rather than north. Such fields are all around us but those generated by mobile phone or car speakers are thought to be of particular relevance. Reporters advise not keeping your compass in the same pocket as your mobile phone nor leaving it in the car door compartment next to the speaker.
It is also worth noting that all magnets (which of course includes compass needles) will, over time, degrade. (Older members might recall using 'keepers' to slow this process down). Physical impacts can also have a negative effect on magnets resulting in a reverse polarity or a degradation in the magnetic strength of the needle, the problem it seems I had experienced.
Should your compass ever suffer from this problem then it needs re-magnetising. This, fortunately, is something you can easily do your yourself. Just get a small bar magnet eg a fridge magnet and 'stroke' the compass needle from fulcrum to the needle's north tip a few times.
But the overall advice is - check your compass is working before you go out.
It would be interesting to know if other members have experienced this problem.