An Observation on batteries and magnetism

[e2matrix]

If this is already well understood I apologize but in doing a Google search I couldn't find anything about this.  This was observed when I had a container with 12 AA batteries of various types (Eneloop NiMh, Tenergy NiMh and some PowerGenix NiZn) that I sat down near a good quality compass.  I noticed the needle moved a bit.  So I pulled out the 3 different types of batteries and found all 3 attracted the North end of the compass needle when the positive pole of the battery was held over it.  When the negative pole of the battery was held over the needle it deflected the North end.  The slightly higher voltage NiZn's had a somewhat stronger push and pull.  I also tried some Lithium 3 volt batteries with the same results. 
   Are batteries weak magnets?  I've never noticed them picking up fine particles of metal.  I used one of the strongest batteries to see if it would pick up some very tiny metal flakes left over from drilling.  I couldn't get even a tiny fleck to stick on either end of the battery. 

   What is the cause of this effect?  Is the compass detecting a small leakage of electrons from one battery pole to the other?  A Google search seemed to find nothing but the effect of magnets ON batteries. 

  In the process of trying to find out about this effect I found that a magnet like a horseshoe type will give a voltage with a piece of paper between it and a metal plate or it's keeper.  I got 30 to 45 millivolts with a strong U shaped Neo magnet and it's keeper.  So now I've got that magnets are batteries and batteries are magnets     LOL

[IotaYodi]

What is the cause of this effect?

There is an electric charge within the battery. Put a compass close enough and it will pick it up. The field in the battery becomes stronger than the external Earths magnetic field when in close proximity to it.

[mscoffman]

Experimental assumption caution is warranted here: Those metal end plates
are probably stamped steel to protect the battery. There may be a residual
mag field.

:S:MarkSCoffman

[e2matrix]

   I was later showing someone this effect in the evening when I pulled a battery out of the container and the exact opposite was happening from earlier.  Now the positive pole was deflecting the North pointer of the compass and the negative end was attracting it!  My first thought was probably silly as I thought it had something to do with the time of day.  But as it turns out all the other batteries were still doing the same as earlier and only this one battery was doing the opposite.  This seems very odd as most of these are new and from the same package.  The odd battery is reading correct voltage and polarity on a voltmeter.  Perhaps what Mark said is right in that the metal itself may be retaining some magnetism but after trying 4 different battery types and 12 total batteries all were the same except the one.  And in every case if one polarity of the battery was North attracting then the opposite polarity end of the battery was North repelling.  Seems odd although I can think of some explanations that might cover it.