[Yaesu] FNB-38 battery pack (for FT-51)?

[Avi - Modi'im Orchards]

Howdy all,

I need some new battery packs for my FT-51.

I am looking for suggestions of suppliers,

or alternatively would like to crack open my existing packs and replace the 
cells with NiMH cells. The OEM packs were only 600 mAh, and are now probably 
about a quarter of that.

Has anyone done this? Will either a standard Yaesu charger or a W&W 
MasterCharger Ia properly charge a pack constructed in this manner?  I could 
easily construct a timer circuit to stop the charger at some preset time 
interval, or the W&W has a detection circuit (Vmax?) that switches it to 
trickle mode.

vy 73,

-avi 4X6UA