The process of particle collision in the vicinity of black holes is known to
generate unbounded energies in the center-of-mass frame (the Banados-Silk-West
(BSW) effect) under specific conditions. We consider this process in the
charged black hole metrics, namely, the Reissner-Nordstrom (RN) and
Majumdar-Papapetrou (MP) metrics. We consider the energy extraction from
Bardeen regular black hole due to BSW effect. Like in RN case, we show that
there is no restriction on energy extraction, but for real charged particles
this effect is negligible. We derive necessary and sufficient conditions for
this process. The conditions for the BSW effect in RN and MP metrics are shown
to be identical, which is explained by the asymptotic equivalence of the two
metrics near the horizons. Energy extraction in the RN metric is discussed. It
is shown that if two real particles collide while falling onto a black hole,
they are extremely unlikely to generate an ultra-massive particle. For the case
of head-on collisions, we derive an upper bound on extracted mass, which
depends on the lapse function of the metric at the point of collision.Comment: 10 pages, accepted to Gravitation and Cosmolog