ironhydroxide @ ironhydroxide @sh.itjust.works

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6

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778

Joined

2 yr. ago

They eat cake? /s

It's always been a Wendy's. Can I get my frosty now?

What is that thing?

Honestly, if food was as much as mortgage, that's not too bad. It's bad when those combined are more than 3/4 the average income.

The real problem is pay is extremely low for the productivity.

But, now hear me out, what if there was also a rabbit?

That would be terrible? What are some prompts so I can be sure not to use them?

Soon as those hurdles are surmounted, armies will train then freeze conscripts. Only thawing when they need meat for the grinder, or when better weapons come out that need more training.

That's the only way they get brought back en masse.

Ah, I got the Abfalleimer. Didn't get the other. My German isn't very good.

Gallon of prop wash, that's a new one for me.

I'd have probably been caught by that one for at least a few paces.

A tensioned trash can?

It is, especially when the choice that leads to that extra weight is less reliable, less efficient, and more costly. All things you don't particularly want in a car

So let's get back to the real discussion on how the packs actually work. Can you explain how a microcontroller is supposed to put cells in and out of the circuit?

It's a very good motivator for critical thinking though.

Not sure where you're getting "one total massive cell" from anything I wrote.

Every pack is made of a bunch of smaller batteries. You can't get 400v without batteries in series, from batteries that only make ~3v.

Just saw your last paragraph edit. It's a car pack, every ounce matters, and doubly so when it only adds complexity, reduces efficiency, and reduces reliability.

And an estimate of weight of the extra interconnect.... let's say it's 8' from back to front of the pack, a 350v pack and a 250kw motor. This means minimum of 715 A. Busbar that is rated for 700-800A @30c rise has cross section of 1/4"x2". For the 8' length that means we have 48in^3 of copper. That is ~16lbs of copper alone. Not counting the contactors, insulation, etc.

Most packs have only 2 contactors. Not 2 per cell. The only way to have spare cells that are not in active use all the time is to physically disconnect the cells from the rest of the pack. The only way to do that is to have contactors at each "end" of the cell, or cell pack, that you want to switch in and out.

Car packs are _{360-800v nominal depending on the car/pack. To get to those voltages with the normal cells (}3.2-3.7v nominal)you need between 95 and 250 cells in series (wired one to another directly, all the power goes through all the cells).

Let's do an example. The simplest pack possible. A 95s1p meaning 95 cells wired negative to positive in a single line. A contactor at each end to cut power to the car for safety.

This is the simplest pack. Also the lowest range and worst for cell wear.

So say you want to "double" the range? You "simply" build an entire separate pack, and drop it next to the first with it's own set of contactors, right?

But in that case you have doubled the amount of interconnect bus in the pack(the wires to get the high current out of the battery), as well as contactors.

You could get to the same power storage (range and longevity) by making a 95s2p pack with one set of contactors.

So instead of 2 lines of cells, you connect each cell to it's partner with a small piece of wire then connect that to the next cell in the pack.

This means you don't need the extra long wire from the back to the front of the pack for the second set. The tradeoff is you can't physically disconnect the second cells, but you don't need the weight and complexity of extra contactors, and the long wire for second cell set.

So what's the actual benefit of physically disconnecting the second set of cells?

When one battery dies in the 95s1p pack, the whole pack is useless, as all the power from the remaining 94 cells must travel through the one high resistance cell.

In a 95s2p pack each cell only has to take half the current of the entire pack (improving as you go up in parallel cell count).

You would be able to run one 95s1p dead, then switch to the other and keep driving till that is dead. But the efficiency of that is actually less than you get if you just had one 95s2p you ran from full till dead.

So again, being able to physically disconnect some cells in the pack only adds weight, complexity, and risk.

The Tesla car with "less range" that can be "unlocked" is literally just a software setting that limits the charge/discharge voltage of the entire pack, not switching in and out battery cells physically.

So... As you said

It's okay to be wrong.

Tbf, the feds should probably just investigate everything Boeing does.

Fixed that for you.

No. Handwaving a microcontroller doesn't fix it unless you have two high current contactors per cell, and multiple intermediate busses and contactors, it's not going to work.

That's going to add a ton in transmission complexity, and weight, that doesn't really benefit the battery at all. Along with the fact that cells should be balanced in wear and cycles. It just doesn't make sense.

No. The packs aren't like flash storage where they have spare blocks to use when one block wears out. Essentially switching in something that wasn't used at all before.

The cells are all connected physically, being charged and drained. They do not connect and disconnect cells when wear occurs. They have software limitations on how far to charge and discharge (at what voltage and c rating). Yes, a larger pack will last longer if the charge/discharge cycles aren't as "deep". But no, they don't have spare cells just to cover wear.

That's...... not how battery packs work

Plate.

Just salad wraps, bowls, and more. The more could be plates, or any other random vessel in or on which to place a salad.

If they were it wouldn't be Windows