Charger / balancer co-design

[icysubdweller]

This might be a common topic or something that's been discussed to death in the past, and if so, I apologize... please direct me what to look for in the archives.  But I didn't find anything via a quick search.

In the process of upgrading one EV (lead acid-based) and planning a second (LiFePO4-based), I've spent a lot of time pondering the questions of charging and balancing the cells.  I've come to the conclusion that these are not separate tasks.  So I find it unusual in the EV community that the two topics are treated so separately.  You buy your charger from company X, and then your balancers from company Y, and you pray they play nice together.

Your charger comes pre-configured with a charge profile from the factory, and the balancer boards have the unsavory job of trying to fight against that charge profile to get all the batteries charged before the charger shuts off.  What's going on here?  I seem to be missing something.

Another possibility I've explored... and which I am using on the lead acid EV I'm upgrading... is to install separate chargers on every battery.  Seems quite practical if you only have 10 batteries to charge.  But when you get into LiFePO4 territory, now you're talking about 45, 50, 90, 100 cells to charge individually?  It seems like there must be some economies of scale that would be missed by installing separate chargers on every cell.

Yet, in many ways, having each cell charge individually is the ideal.

How can that ideal be accomplished with a series charger and balancer boards?  Wouldn't the answer be that the individual cell balancers know the charge profile of the individual cells, and they direct charging at a local level?  The charger would become a cooperative partner that provides the total voltage needed by the pack right now, with the current limited by (the smallest current any single cell needs + the maximum current a balancer board can shunt).

Are there any chargers out there right now that match this design philosophy?  I have heard suggestions that perhaps the Manzanita chargers do this, but their website is very "least common denominator" in this respect.  About their chargers, the Manzanita website says (and I quote), "The actual power delivered is a function of input and output voltage."  Whereas I'd like to see something that says, "The actual power delivered is a function of input and output voltage, the needs of the individual cells as they charge, and the capabilities of the balancer boards."

Thanks for any thoughts on the subject,
Rodney