If the current is kept low enough, it's very easy.
The cheapest way to charge a nickel metal hydride battery is to charge at C/10 or below (10% of the rated capacity per hour). So a 100 mAH battery would be charged at 10 mA for 15 hours. This method does not require an end-of-charge sensor and ensures a full charge. Modern cells have an oxygen recycling catalyst which prevents damage to the battery on overcharge, but this recycling cannot keep up if the charge rate is over C/10.
The datasheet assumes that the batteries are going to be left permanently connected to the mains 24/7, with no break.
In this case they are being charged from solar cells so they will have a break for at least 8 hours (in summer) so it doesn't matter, they'll be fine at 0.1C, if not even slightly higher.
Charge stability shouldn't be a problem if they're charged every day.
You can buy hybrid NiMH batteries which hold the charge more and come ready charged but their capacity is slightly lower than that of a normal cell of the same size.
You can buy hybrid NiMH batteries which hold the charge more and come ready charged but their capacity is slightly lower than that of a normal cell of the same size.
All the Energizer Ni-MH cells are the new type. They are made in Japan maybe by Sanyo who also make the new ones.
Energizer's 9V Ni-MH battery is not the new type and is made in Germany.