For the trolls

Doesn't matter if you clicked the link I sent. Given that you embedded the same video (with your suggestion that other people "will learn something or maybe not"!), it's fair to presume you've watched the video you chose to embed.

Whether to have a single BMS unit or a distributed one is a simple choice in the packaging design.

It's not the number of sense wires that dictates your choice of a single or distributed BMS. It's the other way around: the choice determines how many wires you need.

Toyota likes a single BMS, and Toyota understands what that choice means: when they are building an NiMH battery, they can get away with one sense wire for every twelfth cell, and when they're not, they need per-individual-cell sense wires. That's why their non-NiMH BMS needs so many more sense wires.

Had they wanted their non-NiMH version not to have so many wires all running to a single BMS, they could have gone distributed, and moved some of the BMS functionality into each module. One way or another, the BMS needs to respond to every single cell's condition, and it doesn't matter which way they do it. What matters is Toyota knows they need to do it, and they do it.

Nexcell's lithium pack chose a module packaging of ten Li cells (5s2p) per module and fourteen modules. That would be ok if there were also five sense wires coming out of each module and there was a replacement BMS with 70 sense inputs to go in place of Toyota's NiMH one.

If that seemed like too many wires, there was the alternative of moving some BMS functionality into each module to use fewer wires. One way or another, the BMS needs to respond to every single cell's condition, and it doesn't matter which way that's done. What matters is needing to do it and not doing it.

The V3 (non-GT) seems to be two big modules of 35 cells each. 35 sense wires out of each module would do the trick, again replacing Toyota's NiMH BMS with a 70-input sodium one. Or, again, five sense wires out of each V3 GT module (if those are 5s, I haven't seen one's insides).

Or, again as an alternative, move some of the BMS logic into each module to avoid all those wires out. The choice of how to do it doesn't matter. What matters is needing to do it and not doing it.

 

What ChapmanF describes in post number 22 on this thread really is key.

And he summed it up quite well.

As far as Azusa Price's idea about coming up with a pack that works better...

I don't imagine anyone is going to come up with their own cells for a replacement.

It's more likely it would use some sort of off the shelf automotive cell.

Once the cell has been chosen then if required by the chemistry, some sort of hardware software battery management system would also need to be created.

(This is the part ChapmanF and others have noted)

For the Honda Insight world there is a n aftermarket drop in lithium replacement packs that use OEM Honda modules repurposed from other vehicle's modules.

In conjunction with those modules is a separate hardware / software packages that does the battery monitoring and management.

The battery monitoring and management package is open source. And likely could be adapted in some way to be used for the prius.

Heck, nextcell battery designers could take a look at that and use it to add the additional battery monitoring and management function to any or all of their products.

 

So, whom shall we learn from here? Toyota, for having designed and built cars, and knowing when a battery chemistry calls for per-cell monitoring, and doing it?

Or Azusa, for having "worked on the Prius system for 10 years and knowing its limits and needs."? (And for so adroitly changing the subject once shown that Toyota knows to do per-cell monitoring with framedrops from the exact video he pretends to school others with?)

 

Is it legal to completely change the batteries without going through government safety approvals? Maybe even crash testing? Not sure. If it doesn’t meet standards it shouldn’t get a license plate.