Damon,
Don't bother with a resistor.
Inside the house will drop the PV output like a rock. In perfect onditions, the PV will make maybe 30ma. In the house, maybe 10ma? And that 10ma will not be many hours (minutes) per day.
It takes "X" ma to hold nimh at float voltage.
A 30ma PV is NOT going to hold 2000ma of fully charged nimh at float voltage. I would be very surprised if 30ma of solar (outside, in perfect conditions) could get them up to 1.3V/cell. And the PV will not be making anywhere near 30ma in the house.
Might try a quick test.
Charge the nimh up completely, so they are at 1.4 ~ 1.44 V/cell for a while.
At noon on a good solar day, take the 1.4V/cell batteries out of the grid charger, put them in the 30ma solar charger outside, and watch the V/cell drop because there is not enough ma to hold the voltage up.
Remove the batteries, and check the Isc of the PV in the house. The reduction in ma will make the overcharging worry even less of an issue.
There just will not be enough ma to overcharge/overvoltage the 2000mah nimh pack.
Been a long time, but seems like my ~100ma PVs into 1200 to 1850mah nimh would reach about 1.37V/cell then just sit there until the sun started drifting down. Seems like even 3 x 100ma PVs would act about the same, and those PVs are 12V into battery packs from 3V to 12V.
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http://fieldlines.com/board/index.php/topic,127848.0.html )
The good thing about charging slow like that is (I believe) the charging efficiency is much better.
G-