Paul, look at the specs - they only put out up to 1,000 mah, which would not power a keyboard for very long - a few minutes at most.

Gary cool
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

K+E=W (Knowledge Plus Experience = Wisdom.)