Has anyone here used NIMH batteries for solar storage?
I am thinking of trying to use them, instead of Lead acid or Lithium.
If someone has used them, any info as pro and con or setup would be appreciated.
I have 3 100 watt panels and will have approx 1.6KwH of NIMH.
25p10s at 5.5Ah per 10s at 12v nominal. 5.5 x 25 x 12 = 1650 if my math is right.
I am planning on using an arduino to make my own solar controller.

Crikey, you waited 9 years to make your first post :)
No reason NiMh shouldn't work fine once you use the correct charging algorithm, the only downside might be the self discharge but I don't think that will be a major obstacle for you.

Sorry if posted already, I only skimmed the three pages. Niall of Raglan Electric Bikes here in NZ has done exactly what you want to do :) https://www.youtube.com/watch?v=FRW5PdDkhP0 and https://www.facebook.com/RaglanElectric/

Back to the actual charge controller though. I have one and used a 24v wall wart plug to the input to top off a 48v Chevy Volt lithium module with it. I love the fact that you can set charge points and it will limit the current flow once reached.