I've used NiMH cells to make my glfider battery for over 5 years now.
I always charge them with an RC Hobby charger, they have given
excellent performance.

The reason I went to 11 cells is to get 14 volts so as to insure that
my aircraft radio did not drop off due to low voltage at the end of
the day (10.5 v is the cutoff for most radios).

The reason for not using Li chemestry cells is concern for possible
overheating, bursting of cells, and resultant "Very Energetic" fire
from the release of the Lithium inside the cells. The RC hobby has
burned down well over 100 houses, apartments, cars, trucks, model
planes and garages during the learning phases of using LiPoly
chemistry cells. They require extreme care in all phases of use to
avoid catching fire when overcharged, over-discharged, or compromising
the plastic cases. Currentlfy the biggest issue is "Balancing " them
so that one or more cells don't reach full charge prematurely. This
requires a tap on each cell led out to a balancing set of circuitry.
All this information, advice and hardware information is freely
available on the RC Forums.

The Li-ion and LiFe (A123) chemistries are also suseptable to these
events, but because of the steel cases, like NiCad & NiMh, will resist
abuse better than LiPoly. In actual practice they still use
specialized charging and balancing circuits, and usually over-
discharging circuits, esp. in consumer devices such as Laptops and
Cameras.

IMHO the NiMH is the most reasonable replacement for the SLA
batteries, unless you really want to be on the cutting edge (Bleeding
Edge) of the Li technology.
I was also unaware that many others had equiped their gliders with
NiMh batteries and and had uniformly good results with their use.


BTW, I take issue with; "Both LiFePO4 series (of batteries) are
claimed to be able to be charged on most standard lead
acid chargers (set for AGM/GEL cells)", unless a complete set of
charging and balancing circuity is included in the package. And at the
prices quoted, they really should be!!

Happy thermals,

Wayne