Canon A40 Never use batteries that look like this.

20
¡Never mix unused and partially used batteries. Always
load four fresh (or fully recharged) batteries at the same
time.
¡Never mix batteries of different types or from different
manufacturers. All four batteries should be identical.
¡Before inserting the batteries, wipe the battery terminals well
with a dry cloth. Oil from one’s skin or other dirt may cause a
considerable reduction in the number of recordable images or
reduced usage time.
¡Battery performance deteriorates at low temperatures
(especially with alkaline batteries). If you are using the camera
in cold areas and batteries are running down faster than they
should, you may be able to restore performance by placing
batteries in an inner pocket to warm them up prior to use. But
be careful that you don’t put the batteries into a pocket
together with a metal key chain or other metallic objects, as
these objects may cause batteries to short-circuit.
¡If you do not plan to use the camera for a long time, remove
the batteries from the camera and store them in a safe place.
Batteries may leak and damage the camera if left installed
during prolonged periods of non-use.
WARNING
Never use damaged batteries or batteries whose outer seal is
completely or partially missing or peeled off, as there is risk
that such batteries may leak, overheat, or burst. Always check
the seals on store-bought batteries before loading them, as
some batteries may come with defective seals. Do not use
batteries with defective seals.
Never use batteries that look like this.
Batteries with all or part of the seal (electrical
insulation sheath) peeled off.