Nickel battery balancer
Active balancing is simply not necessary with NiCd and NiMH battery chemistries. It doesn't harm a fully charged cell to be somewhat over-charged in order to bring a slower-charging cell up to full charge.

You can't do that with rechargeable Lithium cells &mdash; they tend to do bad things with the slightest amount of overcharge, which is why active balancers were developed.