Why is there no individual Cell Charging BMS?

[zedconnor]

Why isn't there a system where lets say a charger (inverter/charge controller/or anything) delivers the required voltage to a lets say 48V battery pack.
The BMS of the pack takes this whole voltage, but it then charges the individual cells with 3.55V(or 3.65V) max with individual charging cables running to each cell, if one cell reached the max voltage, it will stop charging that particular cell, but it will continue to charge all other cells that have not reached max yet.
Why isn't there any such charging solution for battery packs?
Why do we need to do the tiresome balancing thing all the time?

 

[upnorthandpersonal]

Complexity mostly, and because cells shouldn't drift by much. A BMS with active balancer solves things without much added complexity. I don't balance manually anymore: just make a pack, put it in use, and let the active balacer take care of it.

 

[400bird]

Why do we need to do the tiresome balancing thing all the time?

What do you mean, "all the time?"
Is your pack massively out of balance and needs constant work?

 

[zedconnor]

What do you mean, "all the time?"
Is your pack massively out of balance and needs constant work?

I am a new firsttime battery seller so I need to balance hundreds of cells. :')

 

[DIYrich]

if one cell reached the max voltage, it will stop charging that particular cell, but it will continue to charge all other cells that have not reached max yet.

Why do we need to do the tiresome balancing thing all the time?

You sort of described "tiresome balancing". With active balance, it will take from the high voltage cell, and give it to the low voltage cell.

The problem is: The cells are already wired in parallel. The BMS can't break the busbars and give each cell 3.65v. What it can do is drop the voltage on a little wire to draw current from going to that cell, and boost the voltage on a different wire to feed in a little more current to that cell.

Now if you want to spend a lot more money on a BMS, it can have a high current wire to each battery, and internally switch between serial mode when discharging, and switch to parallel mode when charging. Or, it could keep all batteries in parallel mode with huge buck converters to step down the incoming 48v when charging, and step-up the 3.65v to 48v when discharging.

 

[copec]

Why isn't there a system where lets say a charger (inverter/charge controller/or anything) delivers the required voltage to a lets say 48V battery pack.
The BMS of the pack takes this whole voltage, but it then charges the individual cells with 3.55V(or 3.65V) max with individual charging cables running to each cell, if one cell reached the max voltage, it will stop charging that particular cell, but it will continue to charge all other cells that have not reached max yet.
Why isn't there any such charging solution for battery packs?
Why do we need to do the tiresome balancing thing all the time?

Are you talking about just the cells that are in series? There BMS's with "active balancers" that can do this now by shifting charge around. They can be set to also only do it when it is charging and/or discharging. I like active balancers because I've never found even all new from the same batch cells stay exactly in balance, and I would rather move charge around rather then burn it off with passive balance, in reality though that is an OCD thing, and the savings probably aren't even quantifiable other than piece of mind because I feel like my pack is always in balance.

 

[DIYrich]

You sort of described "tiresome balancing". With active balance, it will take from the high voltage cell, and give it to the low voltage cell.

The problem is: The cells are already wired in parallel series. The BMS can't break the busbars and give each cell 3.65v. What it can do is drop the voltage on a little wire to draw current from going to that cell, and boost the voltage on a different wire to feed in a little more current to that cell.

Now if you want to spend a lot more money on a BMS, it can have a high current wire to each battery, and internally switch between serial mode when discharging, and switch to parallel mode when charging. Or, it could keep all batteries in parallel mode with huge buck converters to step down the incoming 48v when charging, and step-up the 3.65v to 48v when discharging.

 

[toms]

You could use a few imax Lipro’s to do what you are asking.

I know a few people that have large LiFePO4 banks that use individual cell charging.