Mark_Nguyen said:
Early concept art from Rick Sternbach showed a bed for Data which recharged him sorta like a huge D-cell battery charger, with teminals for his head and feet. No physical connections - he'd just lie in the bed and it'd light up. This was obviously not used as a concept, since we later see him sleeping ins a regular bed.
While TNG's heydey was really before the real-life wireless revolution, I see no reason he couldn't recharge without having to plug himself to something. He's always sitting at that workstaion of his, which is unique among props - perhaps that had a recharging function.
There's no real way to recharge by walking around, since he has to expend energy to walk (shaking a wristwatch to charge it is really just transferring energy from your body too). You could theorhetically absorb potential energy from gravity by walking down stairs, but how often does THAT happen in Trek?
Mark