transformer isolated cell balancing?

[Farfle]

Hello all, another hair brained scheme here, but if you had a bunch of isolating transformers attached thru a rectifier to the cells at a cell level, and then fed a frequency to all of them, could you achieve anything useful? Kind of like attaching an isolated dcdc converter to all the cells, but without all the extra parts and features.

Or is there something I am missing?

 

[Fuzzy Head]

I thought up a similar idea not too long ago. Theoretically it would be a far superior method of charging as all the cells are charged individually and it is possible to build. However each cell would still have to be current and voltage limited by circuitry, like each cell having its own single isolated power supply.

My guess as to why we do not hear about them is because the charger would be very complex to build, require huge numbers of parts, take up a lot of space and cost a fortune compared to what is commonly avalable.

It will be interesting to hear what others have to say about the idea.

 

[amberwolf]

Theoretically possible, but unless you used a high frequency, then to get larger currents you need larger heavier transformers, if using regular 60hz AC from the wall.

Then as said above you still need current limiting and voltage cutoffs, per-cell.

Might end up less complex than multiple DC-DC units as far as total component count inside the DC-DC's goes, or it might not, but overall it's a lot more stuff to deal with designing, and probably larger and heavier, especially if you use DC-DC units that have CL and HVC already.

 

[fechter]

This has been considered several times in the past. With a separate transformer for each cell and a crude diode rectifier, the voltage difference between cells could be significant, and each cell would probably need some kind of regulator.

If you use a large single transformer with separate secondary windings for each cell, things will tend to stay much more closely balanced between cells and a simple rectifier may actually work pretty well.

Separate dc-dc converters for each cell works quite well if you can find the right converters.

 

[Kin]

I was under the impression hyena's 6s balance-lead charger was like this.

 

[amberwolf]

Do you mean this one?
http://endless-sphere.com/forums/viewtopic.php?f=31&t=41107

 

[Kin]

Yeah! I just skimmed the thread and couldn't find any pictures of the internals or discussion of how it worked...but I guess it seems like it's a relevant addition to this thread nontheless, as its in the same frame of mind.