What BMS uses inductive balancing?

[curiouscarbon]

HV batteries (>90v) are gaining traction.

i see what you did there ?

 

[Warpspeed]

To maximize balancing current, it seems necessary to have a boost-buck architecture (for cell-to-cell).

Extract energy from all cells in series (maximizing voltage input) and then buck to a single cell seems like quite a powerful approach, which sidesteps the need for a boost component.

Capacitors seem to degrade over time from drying out and such, which highlights an appeal of inductive type.

However, there has yet to be any "active balancer" (induction or capacitance type) that has proved to be reliable and effective.

I am excited for a future where active cell balancing is considered a well addressed engineering topic

Its certainly possible, I have developed a practical very low impedance inductive balancer circuit that works really well, but like many of my ideas its never going to be a commercial success. Far too expensive to build to compete with cheap Chinese rubbish.

Even as a DIY project, most people will say, that looks like far too much work to build that. Cannot be bothered, not interested.
I just want to sit here on my couch and order something over the internet and have it delivered.

Everybody expects to receive a miracle, but are only prepared to pay fifty cents for it.

 

[curiouscarbon]

So tired of cheap junk that doesn't even do what's on the tin... the problem space feels clearly defined.

Even if a minority view, I'd rather pay 50 usd for an active balancer that WORKS than 16 usd for one that "technically functions" and destroys itself from ripple current 7 months into operating continuously.

 

[Warpspeed]

That is the problem CC.
Just the large single ferrite toroid used in my own balancer cost me just under 50 usd all by itself.

It fascinates me that people readily spend multiple thousands of dollars on a large battery, but are only prepared to spend peanuts on battery life support equipment.

 

[curiouscarbon]

Well said.

It's much more than just the cost of the cells.

Properly engineering a robust long term solution will demand a cost in research and hardware.

 

[Sean Very North]

It fascinates me that people readily spend multiple thousands of dollars on a large battery, often comprising multiple cells of differing capacity, and are seemingly content to spend peanuts on a BMS that can't cope with the obviously predictable imbalance issues that quickly arise ... buy quality, well matched cells and the cheap, ineffective balancing device "issue" goes away.

 

[curiouscarbon]

All cells age with time, temperature, cycles, .... (change of internal resistance, etc.)

Including the hardware to gracefully adapt to this aging, from the beginning, makes me one of "those weirdos"

 

[octal_ip]

Hello, can you develop more on this. Im looking to use them in 4S16P 40Ah LFP Pack, studying connecting it Permanently. Would love your input.

Other than what's already been mentioned, the problem with the ETA3000 based balancers is that they only activate when there's more than 100mV difference between adjacent cells. This is far too high for my liking, as by this point the balancer has too much catching up to do.

I have one of these balancers on a small battery and it does provide reasonably high balancing currents, however by the time it kicks in the BMS is often close to having to cut charging due to high individual cell voltages. I'm guessing the manufacturer didn't elect to use a lower delta voltage because the voltage sensing just isn't accurate enough in these ICs.