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Finer grained battery discharge boosts range:
Nissan Leafs, which go about 107 miles on a charge, sometimes end up relegated to commuter cars due to battery-life worries. The mass-market, standard Tesla Model 3 can go double that, but even that distance can be disconcerting on long road trips.
Both batteries could work about 50 percent longer with a device provisionally patented by Vanderbilt University's Ken Pence, professor of the practice of engineering management, and Tim Potteiger, a Ph.D. student in electrical engineering. It reconfigures modules in electric car battery packs to be online or offline—depending on whether they're going to pull down the other modules.
The two used Tesla's open-source, high-density, lithium-ion battery to model their method of improving durability, adding a controller to each of the battery's cells.
"We know there are some battery cells that run out of juice earlier than others, and when they do, the others run less efficiently," Potteiger said. "We make sure they all run out of energy at the same time, and there's none left over."
Is a 50% boost in range worth the expense of the extra controllers?
(Score: 5, Insightful) by jmorris on Wednesday November 22 2017, @01:24AM (2 children)
As usual with mandatory "battery life problems solved" articles, the snake oil content is high. Doesn't look like you actually get improved range, what you DO get is improved battery service life and that is a good thing. You get the "up to" 50% better range on aged batteries so since a battery is usually declared defunct at the 50% of original life point, at what would normally be the end of service life you could still be getting 75% of rated range. That is nice and almost certainly justifies the additional electronics. Whether it will justify licensing the patent is something we will need to see.
(Score: 3, Funny) by bob_super on Wednesday November 22 2017, @01:42AM (1 child)
Just put a DC/DC converter on each cell to go around any patent. If you really gain 50%, you can sacrifice 5%.
(Score: 4, Informative) by anubi on Wednesday November 22 2017, @03:43AM
"Charge balancers" are a pretty mature technology.
I just gave you the Google keyword. Do your own research from there if you are so inclined.
While I could see a *particular* design being covered with a design patent for that specific implementation, its hard for me to imagine anyone getting nailed for building their own custom device.
There are many off-the-shelf IC's just for this.
Or you can "roll your own" if you want.
One of the designs I did with Solar was a flyback design, knowing full good and well a multi-secondary flyback transformer ( identical turns count secondaries ) will try to set equal voltages on all secondary windings. So, drive the primary off the full stack, and use lots of secondary windings to equalize the voltage at all levels of the stack.
BTW, nothing said I have to use ONE magnetic core.... I can use many.... with the primaries of all in series so as to force equal excitation current so variances in core material and construction would drop out. That way I could make devices with hundreds of taps for hundreds of cells in series.
Mine were in groups of six. For mechanical layout convenience. Fourteen of 'em. About a 300V stack of 3.6V Lithium. Your designs may vary by your own needs. Nothing says you have to use magnetic energy transfer. Some people use capacitors to do it.
It was easy for me to monitor cell health with little current transformers that saw the charge pulse. Cheap and accurate. They did not measure DC; just the charge pulse.
We monitored cell voltages for safety purposes, but the physics of the magnetic design would pretty much guarantee that the lowest voltages got the lion's share of the energy from the transformer, while the higher-voltage cells kept their flyback charge diode reversed "off" - so that battery voltage / Ncells was a pretty accurate representation of the voltage across each cell unless we were showing significant pulse strength imbalances among the secondary windings.
Being the balancer was microprocessor controlled, it was quite easy to optimize the primary drive for the amount of energy we needed to transfer based on the imbalances we were reading, along with keeping a C++ struct array filled with the strength of the pulse from each current transformer.
The weakest cells got help. The strongest cells subsidized them, until the whole stack was depleted.
I have also seen a lot of capacitive charge-pump based balancers.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]