Tesla's "Secret" Battery

All around the US, electric grids are already strained. A heat wave brings about exploding transformers as ACs increase peak usage well beyond their rather conservative ratings.

I can imagine a spike in EV usage and charging bringing the grid to its knees.

Oh, and I just love the idea of using EVs as local batteries to supplement the grid. Put that many more cycles on the EVs’ batteries… No thanks.

We get this question all the time, nearly every week somebody (usually not an EV driver) comes up with this “range extender” idea on the EV forums. The problem is that you can’t charge a battery while it is being used to drive the car—the duty cycle of driving an EV with both motoring and regen modes, results in varying voltage and currents in and out of the pack.

Imagine the complexity of a Charger that would be required to compensate in real time for these currents; as it is now no chargers exist that will sink current, they expect to provide either a constant current or a constant voltage for a lithium ion battery pack. (CC/CV)

The conversion losses would be huge: convert fuel to run an IC engine and turn a loaded generator, then to extract electrical power from generator, rectify the generator output (AC) to create a high voltage DC buss with PFC, chop this DC thru boost transformers and rectify to create the DC voltage and current to recharge the pack. Now add some non-existent protection control stage to account for the acceleration and deceleration of the driver’s foot.

That is why the hybrids have both electric and IC engines, it is an easier cat to skin.

Most commutes are 50 miles or less, the newer EVs have 100 miles or more of range. You don’t need a range extender for commuting, but for the several times a year when you need to make a long trip, then go rent a car. Keeps it all simple.

It’s true that power is lost through mechanical drivetrains. This is why electric motors are so efficient-direct drive, no transmission, clutch, torque converters or solenoids and valves to actuate. Also no drive shaft. Not to mention the power delivery of an electric motor (100% power available immediately). As far as a hybrid drive train, the best ones are a diesel electric configuration. For those to be most efficient, they need to be run at a constant speed.

I think understand your logic and it sounds right.
Could the car not have 2 separate packs though?
One to power the car now while it is in motion and another that is powered by the IC when range or excessive current demands are obvious (heat, AC, Mountains) so the reserve pack is always topped up, the packs would alternate usage as needed. Then you do not need fancy charging logic?
Still have the home charging deal, just talking about in motion charging usage with the dual pack.
Just a thought from a dummy.

The only EV with unlimited driving range is Tesla, due to (1) their network of fast supercharging stations and (2) the thermal control system of their packs. Nobody else even comes close. Look up their 0-60 times compared with exotic supercars.

The Prius Prime does Toyota’s complex, but also kind of simple Power Split Device transaxle. And the latest Prius engine is over 40% efficient.
I think one of the issues with the steady-state-genset methodology is on-demand power and charge/discharge efficiency. Yes the generator/motor is efficient either way, but charging energy into a battery pack and getting it back out has a bunch of loss. The next issue is hard driving - If the genset is designed only to run at optimal efficiency, you’re probably looking at something like 20 horsepower (a guess based on optimal Prius engine range). If your driver is on the freeway driving a bit aggressive, or doing other not-recommended activities like towing (you should see what has been towed by a Prius…), that could be continually exceeded until the pack was depleted. With Prius Prime, when in Hybrid mode, the engine responds to demand and then takes a % off the top for charging - generally, depending on battery state of charge and current power demand level. If the pack’s low enough it won’t add any electric boost, it will only take take take… a bit higher and it will allow net 0 charging for the highest power demands, but still not give any charge up… and higher yet it will allow some electric boost to the drivetrain.

There’s been some other very interesting points about the viability of home charging for EVs/plug-in hybrids. Super valid! Not everywhere is suburbs. Yes, this model works very well for traditional American suburban living, but fails most elsewhere. Rural electricity grids may not be up to handling a fast charger at every location - and the same goes for stressed, dense urban grids. Even more for urban locations, is Space and Charger Access (as has been mentioned already in this thread). Almost everyone in a condo or apartment will not have charger access. The last time I went to some EV company’s website (I’m not even sure if it was Tesla or another), they had a survey that included questions about if you owned your home and if you had a garage (and detached/attached) to try to determine if EVs were “right” for you, in addition to other questions about daily miles driven.

A last point: I see a lot of arguments online about cost of ownership and cost of entry for EVs, but I rarely actually see “home charger installation” mentioned. If I fully drain the range on my hypothetical Tesla, how do I charge that overnight if I don’t have some kind of fast charger installed? A standard outlet/circuit in US residential is 120VAC*/15A, so 1800W. Wouldn’t the “base” of ~65kWh for a model S take 36 hours to charge that way? Okay, so you install a second Dryer outlet… pay the electrician… you get 240/30. That’s still a nine hour charge, and I’m assuming there’s no charging losses here. Or let’s say the 54kWh pack, current lowest for a model 3 (at least that I saw on Wikipedia). Still 30 hours for 120/15 and a work-night possible 7.5 for 240/30.

I don’t have time to fully respond at the moment but a few half baked thoughts here. First off, I don’t think I agree with the “you can’t charge while pulling a variable load from a battery” statement. I’ve worked in battery research and development for many years now and definitely have different experience. Next, I get a sense that there are Tesla fans among us. While it’s fine, the bias in this discussion won’t get us far. In terms of the complexity to convert an AC generator to DC… I say why are we not using a DC generator in the first place? I think an AC generator example creates a more complicated than necessary image of the system. I don’t agree either that renting a car every weekend is the most cost effective, practical, nor simple solution to having car that meets all of our needs.

Regarding the Prius system and IC efficiency, realize that the 40% thermal efficiency is a peak value under ideal load/rpm. To the wheels and in a real world driving cycle, low 30s is a more accurate figure. Toyota’s hybrid integration is definitely top notch and I respect it highly.

As for people misusing and overtaxing their car and potentially becoming depleted of pack power, I ask what would happen in a pure EV in that scenario? Also, if you were forced to pull over after such an event and allow the on-board system to recharge for a while, how is this different/worse than running out of gas or needing to plug-in?

Range extended HEVs aren’t the answer for everything, but I do believe they’d dominate a market share if effort was put in to creating one that functioned well.

PS: When bringing up charge/discharge round trip efficiency as a draw-back of a RE-EV, is this not also happening in every other EV/Hybrid that uses batteries?

Also, a split-pack design would be one way to get around any variable load situation. Also can be a way to do thermal management. Dual chemistry opportunities could also come into play here…

Sorry folks,
I’ll see myself out :beer:

Old-timey cars used to use generators, in fact. Simply a motor run backwards. The problem is that generated (haha) voltage was a function of rpm. Run the engine too slowly for too long, and the battery would discharge. Run it too fast for too long, and the battery would overcharge.

Also, the brushes would have to handle the full current being supplied. Sparking, electrically noisy, wearing very quickly, lots of drawbacks.

In contrast, alternators have the stators handling the bulk current. The rotor, connected via slip-rings, would handle much less current, and would be used to control the output (separate or integrated regulator).

So even at low rpm, you could overtickle the rotor so that maximum current/voltage could be supplied (within reason). And at high rpm, instead of frying the battery, you would scale back the tickle-current and still maintain a constant voltage.

“Converting AC to DC” was as simple as a diode-pack. 3 phases would have lot of overlap to appear as almost-DC (lots of ripple, though).

Last advantage is that the heavy-current windings of an alternator were on the outside, and could be press-fit to the case for good heat-transfer, and even have open vents to help cool the windings. A generator would have the windings buried inside, far from any good heat-path.

Nope, I’ll stick with alternators any day.

Don’t leave us hangin bro, you can’t throw out juicy tidbits like that and not follow up with some basic non-proprietary details.

I once conversed with a couple who had a Tesla and were towing a small, molded-fiberglass travel trailer. Besides planning their route to hit charging stations, they were staying in campgrounds with 50A service and using that to recharge overnight.

Exactly. And also cities will be so much quieter and with far less air pollution. But we also need a battery technology that is not toxic and limited.

Plus, there needs to be a way to cleanly recycle degraded cells.

Selling them to flashlight nuts on ebay is not a viable solution.

:+1:

There’s money to be made in recycling lithium batteries if done right, you know. It’s not really environmentally friendly and pretty expensive at the moment.

The best thing for battery packs that have dropped to 80% capacity is to use them in the home, slap a solar array on the roof and charge it during the day, come home and use that to recharge your ev, leaving only 20% for the mains :money_mouth_face:

A 50kwh battery would mean only 10kw, easily done on home power.

Cheers David who would love to have the money to go off grid totally

Absolutely.

There is also the question weather cutting down forests just to place inefficient solar panels is anything but continuing the problems that planet has anyway.
Maybe some would like to see tons of hills filled with solar panels, apparently some people say they are ok with that and I have already seen some place almost becoming entirely like that, instead of the lush vegetation there are tons of solar panels on small hills.

Considering that even housing in certain areas lack any nature around I can understand why the majority living in large concrete or no nature cities are in favor of just plastering the country side with solar panels.

The surface area needed to even generate all the earth’s electricity is surprisingly limited so the entire countryside needs not plastered with solar panels at all. But to choose the nicest spots for solar panels sounds like a bad idea, people have created enough ugly places for that.

When they’re gasping for air because O2 production starts declining, maybe they’ll think otherwise.

Well said. Tesla Model X looks great, but it’s a joke for reliability—too many manufacturing issues are the cause. One gripe I have with Tesla—TOO MUCH TOUCH SCREEN RELIANCE! You need tactile controls. Electric cars ARE making progress, though. VW/Audi will be featuring some in the next few years.

My 2007 Audi A3 has been a phenomenally reliable car, with tons of torque, sports car handling, & good looks. Just mediocre gas mileage. I’ve decided to continue with it, instead of going to yet another internal combustion engine vehicle. I will hang onto it a bit longer then go electric and very much looking forward to it. I’ll miss my loyal steed, the A3… but will have fond memories.

Rooftops are the best place for solar panels— look at Hawaii. They have given proper credit for individuals to install them (and MOST have), so no new power plants needed. The “grid” is charged by thousands of independant roof-top installs in any given town around Maui where my friend lives (the last 30 years). It works and no nature impact as the roofs are already there and look as good with panels as with out.

Putting solar on a rooftop increases R factor in hot places like Kansas too (where I am one of 750 grid tied installs out of 450,000 customers, sadly). It makes sense in so many ways and there are no transmission losses when we power MOST of our own home’s needs in summer from 50 ft away (when the sun is shining of course). We also chose an East/West array for our PV system to better “fit” the needs of the grid WHEN we are producing electricity (with 1/2 our production coming from the west array to off-set “peak demand” times for AC use- the #1 use of electricity in summer here).

But Wall Street HATES solar when it cut’s into coal and nuke plant profits and so most power companies the last decade have fought to screw us on the credits. Kansas finally got a decent governor who stopped our dumb* electric company from charging “demand” charges (and other penalty actions they tried to use) against we FEW solar users. But damage is done sadly, and little solar is happening around these parts.

So for the most part, the big energy companies DID effectively shut down solar here in the Midwest. They’ll take their energy credits (and they do get MANY millions a year) to build thousands of windmills and charge customers a premium for “wind energy”. Meanwhile, my PV system has been in service four years this August and it’s paid about 1/2 of its cost to date (after tax credits were figured in). With a 10 year warranty on my inverters and 25 years on the panels, we hope to break even in the next 3-4 years then it’s all gravy money wise (*until we upgrade gear— but the panels have a great lifespan and inverter cost isn’t much compared to the initial install cost so I think we’re good for the long-term).

If 100k roof tops in our market were online today (as was the plan 10 years back), we really would be making a positive impact. But it always goes back to the problem of scale and if you don’t hit a tipping point, you aren’t doing a LOT of good— but at least we are doing a “little” good :innocent:

And, I OF COURSE am waiting for Tesla (and co.) to get batteries cheap enough to build a power-wall. Today, with my soldering iron, ranch engineering skills, and available building to house batteries… going off grid would STILL cost me about $12k (or more if I want MORE than 3-4 days of back-up for dark, stormy times). I’d have to update my inverters, buy batteries AND add 10 more panels (in a south array). My largest electric bill is December as I have no panels facing south, so to go year-round I’d have to spend about what I did on my initial install (approx $15k, and all DYI here so I didn’t pay a contractor the extra $6-8K for a typical system my size at 8500kw).

But if we get to $1 Panny Bs, I probably would upgrade and install DIY batteries and new “hybrid” inverters as I’d save another $600 - $800k a year off the electric bill. But needing about 5000 batteries, at $2 each today… it’s not worth doing (yet).

Anyone have an idea of how “cell to pack” packaging of cells differs from “bundling cells” ?