I have two NiMh packs in my Nimbus.

One replaces a 7.5 Ah SLA, its 2/3 the size of the SLA, half the weight
and its capacity is nominally 9 Ah but it delivers more like 10.5 given
my discharge curve. The other is a replacement for the lead brick of an
18 AH SLA in the nose, weighs 1/2 the 18 AH, nominally rated at 13 Ah
and delivers about 16.

Yes I have a switchable diode to ensure I don't over volatage the panel
when the cells are topped right off. I did have a small problem with a
Colibri logger that went haywire on 17 volts ( in spite of what the ,
now corrected, manual said )

Charging also requires a microprocessor controlled specialised charger.

The batteries perform extremely well over a wide temperatire range.
I have saved about 5 kg of weight right in the nose of the ship.
The extra voltage is good for the radio range.
The current capacity and voltage of the system spins up my 14v Horizon
in about 90 seconds ( 3 turns before going into cloud if left late )