Currently, there is only one tier of battery chargers, and it does not allow modules, leaving no other option for scaling rather than linear growth (you need ~220 of them to satisfy 1 blue belt of small batteries). For modules producivity or green modules this is correct because otherwise this will create a net positive energy loop.

However, the speed modules are different. Math says that as long as speed bonus is smaller than power usage penalty, you will have to spend more energy to charge the battery that can be extracted from it, which should be totally OK. (I don't speak about dischargers here, ofc.)

Math:

E₀  = P₀  * t₀ 
E' = P' * t' = (P₀ * (1+p)) * (t₀ / (1+s))
E' = E₀ * (1+p)/(1+s) = E₀ * [ 1 + (p-s)/(1+s) ]
E' > E₀  <=> p > s > 0