I find it a little anoying that we not only have to wait for the illusive commercial cell balancers. As Leo pointed out, they are here already. Apart from that, this holds back innovation as there are a lot of roboteers who are capable of implementing this themselves on a professional level.
What realy rattles my cage is that not only do we have to wait until they are available, we then have to wait until they are approved in the rules, which can take quite a while.
What id like to see is that we make rules based on what is acutally needed, not on what people are screaming on the forum. Most of the time this involves stating that there are no cell balancers for more then 7 cells, or that a certain speed controller has a cutoff voltage set to X which means that Y number of cells should be obligatory.

I propose the following, a lot of which is already in the rules as they are:

Rule:
- On lithium batteries, cell balancing is obligatory.
- On lithium battery packs, fuses rated at their peak maxiumum discharge current are obligatory.
- Using lithium batteries, All power electronics (motor drives, etc.) are obliged to have a cut-off voltage to prevent over-discharging of the batterypack.

For approval of the tech-check, the roboteer has to be able to produce the following:
- A datasheet of the cells in the batterypack
- A datasheet of the cell-balancer used
- The configuration settings used on the cell balancer and a wireing diagram.
- A datasheet of the charger used.
- The configuration of the charger and a wireing diagram.
- Datasheets of the powerelectronics used (motor drives, etc.)
- The configuration settings, specifically the cut-off voltage, and a wireing diagram.

If you are unsure that your system will be allowed on an event, gather the information you need for tech-checking and consult the event organizer.

Because battery technology changes very quickly there is no use for stating specific number of cells or voltages. In the end its up to the tech check to determine if its safe.

As there is always an issue with the maximum voltage 36V, it is up to the FRA to recommend a maximum number of cells for a specific technology, but only based on the maximum allowed voltage. That is the only limit that makes any sense to me.

This would translate in the following way, for maximum cells in series (based on nominal voltage): Pb: 18 cells, NiCd/NiMh: 30 cells, LiFePo: 11 cells.

Just my 2 Eurocents