Theo wrote:
You could probably use an MPPT in CC-CV mode, like this one:

By which I mean, you set the constant voltage (CV) to be the fully-charged
voltage of your battery (about 1.55V for a single NiMH), and the
constant current (CC) to your desired charge current. The battery charges
in constant-current mode until it reaches the set voltage, when the current
tails off:
http://www.ti.com/lit/an/slyt468/slyt468.pdf

The modules have potentiometers to set these values - you'd have to
calibrate them with resistors as a dummy load.

Theo