Liberator had at least seven energy banks, since Dayna mentioned bank seven in Terminal.
Some information was given in The Web. Once caught in the Web, Liberator had enough power for 100 hours of thrust (presumably sublight flight at full power?). Each shot fired by the neutron blasters reduced this time by three hours. Power banks 1 and 2 were drained after two shots, but the prior state of the ship's energy reserves was not stated and they may have been almost drained or full before these shots were fired.
Further information on the energy banks (or power banks, as they were sometimes called) was given in Duel. At the start of the episode, four banks were exhausted and required 48 hours to recharge (implicitly, 12 hours per bank, but this could be a gross oversimplification). Low power reserves restricted ship speed, since Standard by 2 was stated to be the best manageable speed, and even then not for long with reserves so low. When the ship came under attack, banks 5, 6 and 7 were on full power, the rest on zero (confirming the presence of no more than seven banks on Liberator). The ship was then subjected to a number of hits by plasma bolts, the force wall activated only for the period of impact. Bank 5 was reduced to 70% power after one hit, to 40% after 3 hits and to 0% after 6 hits. If nothing else, this implies that a hit is never simply a hit.
In Hostage the Liberator was hit by at least 12 plasma bolts, after which the energy banks were reduced to 45% capacity.
Also in Duel, it was noted that a pursuit ship had insufficient power to keep firing after loosing seven plasma bolts. This was the only reference to power reserves and consumption in such a vessel.