  Quantitative analyses of low-mass hydrogen-deficient (super-)giant stars -
so-called extreme helium stars - to date face two major difficulties. First,
theory fails to reproduce the observed helium lines in their entirety, wings
and line cores. Second, a general mismatch exists for effective temperatures
derived from ionization equilibria and from spectral energy distributions.
Here, we demonstrate how the issue can be resolved using state-of-the-art
non-LTE line-formation for these chemically peculiar objects. Two unique
high-gravity B-type objects are discussed in detail, the pulsating variable
V652 Her and the metal-poor star HD144941. In the first case atmospheric
parameters from published LTE analyses are largely recovered, in the other a
systematic offset is found. Hydrogen abundances are systematically smaller than
previously reported, by up to a factor ~2. Extreme helium stars turn out to be
important testbeds for non-LTE model atoms for helium. Improved non-LTE
computations show that analyses assuming LTE or based on older non-LTE model
atoms can predict equivalent widths, for the HeI 10830A transition in
particular, in error by up to a factor ~3.
