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Author Topic: Batteries: Today's Energy Solution  (Read 209391 times)

Bruce Steele

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Re: Batteries: Today's Energy Solution
« Reply #1200 on: October 09, 2019, 10:01:17 PM »
Sig, One of the requirements for a powerwall install is a WiFi connection because the powerwall actively communicates with ( tesla? PG&E ? ) It tracks your use of the powerwall because that is a condition of the rebate . It can take over your powerwall and use it’s energy if you sign an agreement for Tesla to use your power. I must be nuts because I agreed and the installer said “ nobody else ever agreed “ that he installed.
 Bottom line is powerwall kinda runs with assistance from Tesla?  Do you know if it can be programmed to charge 45-85% like Archimid suggested ? Do you think it would help save battery life?

Sigmetnow

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Re: Batteries: Today's Energy Solution
« Reply #1201 on: October 10, 2019, 02:12:38 AM »
Sig, One of the requirements for a powerwall install is a WiFi connection because the powerwall actively communicates with ( tesla? PG&E ? ) It tracks your use of the powerwall because that is a condition of the rebate . It can take over your powerwall and use it’s energy if you sign an agreement for Tesla to use your power. I must be nuts because I agreed and the installer said “ nobody else ever agreed “ that he installed.
 Bottom line is powerwall kinda runs with assistance from Tesla?  Do you know if it can be programmed to charge 45-85% like Archimid suggested ? Do you think it would help save battery life?

I would think Tesla’s programming would be designed to give the best results.  Remember, Powerwall battery chemistry is different than that for the cars — because the daily cycling and use is different — so don’t base your decision on what you’ve read about car battery packs.  But if you find a feature you really think would be helpful, give Elon a tweet.  If he thinks it’s a good idea, he’ll do it.  :)
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Archimid

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Re: Batteries: Today's Energy Solution
« Reply #1202 on: October 10, 2019, 03:50:57 AM »
Each battery chemistry has its own sweet spot for battery degradation, typically around the middle of the SOC at a cell level. As I understand it, close to 100% SOC is usually harmful to the battery. But then again Bruce is charging to 99%, not 100%. That may be the difference of hundreds of cycles,

Also as Sigmetnow points out, the battery chemistry in Powerwalls might be completely different from automotive batteries. It makes all the sense in the world. The specific chemistry of these batteries was chosen with Powerwall use in mind, not driving. It may be that the sweet spot of Bruce's batteries is right at 99%.
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Sigmetnow

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Re: Batteries: Today's Energy Solution
« Reply #1203 on: October 10, 2019, 04:06:49 AM »
...
Also as Sigmetnow points out, the battery chemistry in Powerwalls might be completely different from automotive batteries. It makes all the sense in the world. The specific chemistry of these batteries was chosen with Powerwall use in mind, not driving. It may be that the sweet spot of Bruce's batteries is right at 99%.

Powerwall 2 uses different chemistry from even Powerwall 1 (remember those original curved cabinets?).  It now also incorporates inverters inside the cabinet.
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Hefaistos

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Re: Batteries: Today's Energy Solution
« Reply #1204 on: October 10, 2019, 10:16:09 AM »
Each battery chemistry has its own sweet spot for battery degradation, typically around the middle of the SOC at a cell level. As I understand it, close to 100% SOC is usually harmful to the battery. But then again Bruce is charging to 99%, not 100%. That may be the difference of hundreds of cycles,

Also as Sigmetnow points out, the battery chemistry in Powerwalls might be completely different from automotive batteries. It makes all the sense in the world. The specific chemistry of these batteries was chosen with Powerwall use in mind, not driving. It may be that the sweet spot of Bruce's batteries is right at 99%.

Or it may be that what is displayed as 100% is actually only 90% or so of the physical capacity. Why should consumers even know about things that the producer anyway has decided is out of bounds?

NeilT

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Re: Batteries: Today's Energy Solution
« Reply #1205 on: October 10, 2019, 01:37:01 PM »
Regardless of the chemistry, the determination of cycle number, for Li batteries is the depth of discharge.  As Archimid says and I have posted limks to more than once, that cycle barrier is around 50% SOC.  The gateway to deep cycle is around 40%.

The lower you go, the closer you come to a full cycle.

The other determination is heat.  The largest amount of heat generated is in the last 10% of charge, or over 90%.  This is because, over 50%, the battery resists charge and starts to generate heat. You need a very good cooling system to take that last 10% without impact plus a charger which is highly sensitive to charge amps and heat effect.

Current chemistry Li batteries vary from one type to another, but they all suffer from deep discharge cycling.  The number of cycles varies depending on the chemistry, but the range is known.  It is 500 to 2000.

Until the new Tesla formula, with many more cycles, arrives, that is the barrier.

However, the good news is that charging from 40% to 90% only incurs a part cycle.  Which can change the charging from hundreds to tens of thousands.

The information is out there, no point in linking it again.
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Tor Bejnar

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Re: Batteries: Today's Energy Solution
« Reply #1206 on: October 10, 2019, 05:31:03 PM »
Are there phone chargers that will 'unplug' the phone (or phones that will 'unplug' from the charger) when the charge reaches 90% (when set for this 'option')?  And a 'special' alarm on the phone when it reaches 40%?
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NeilT

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Re: Batteries: Today's Energy Solution
« Reply #1207 on: October 10, 2019, 06:12:39 PM »
Not in the OS, but I did find two apps. One charge limiter and one notifier.

These were Android.  There is a simple rule of thumb.  If you want battery life and longevity, don't buy apple.  Unless you use your phone for 5 minutes of calls a day and don't browse on it.

No idea how they work.

I buy very large phones which have massive batteries and usually end the day over 50%.  The least used is usually 70% or more.  I charge to full every night.

It is 5pm and I'm looking at my second phone, it has 92% battery left.

My batteries tend to last 4 years or so.  Or, quite often, longer than the phone.
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TerryM

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Re: Batteries: Today's Energy Solution
« Reply #1208 on: October 10, 2019, 10:56:49 PM »
Neil
Perhaps a more honest metric might be the usable Wh available in a particular rechargeable battery?
ie A 100 KWh battery that's designed to operate between a 40% charge and a 90% charge might be designated as having a usable range of 50 KWh, where another battery designed to operate between a 50% charge and an 80% charge could be marketed as having a usable charge of 30 KWh.


It would certainly make comparative shopping much easier. :)


Another metric that would be useful would be the percentage of energy required to charge a particular battery.
ie. If it requires 55KWh to charge a Usable Range 50KWh, then the battery could be said to have a 90% efficiency rating.
I believe something similar to my "efficiency rating" is available, but it's usually well hidden in the small print.


Terry

Archimid

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Re: Batteries: Today's Energy Solution
« Reply #1209 on: October 11, 2019, 04:53:56 AM »
The Powerwall 2 has 14 kWh batteries with 13.5 kWh usable*. I'll assume .25 kWh is the top reserve and .25 kWh the bottom reserve. This means that when the Powerwall 2 app says it is charged to 100%, in reality, it is charged to 98%. When the app says 99% charged the actual charge is 97%.

Please see the following chart for a generic li+ battery:



If the batteries are not charged to their maximum capacity they last much longer. From the image it can be inferred that if the max voltage is limited to lower voltages, the line straightens asymptotically to the horizontal but for fewer gains than the initial voltage limits. This analysis excludes all other failure modes.

Tesla already took the big savings away by limiting the usable max voltage, but there may be significant cycles to gain by using a lower maximum charge.

However, the behavior of the batteries at lower charge must also be accounted for before overriding installation settings.  Although I'm sure that, in general, a lower max charge is better, these batteries are highly customized for their task. The additives for these batteries, the BMS and the hardware surrounding the batteries have been highly optimized.

*Powerwall 2 spec sheet: https://www.tesla.com/sites/default/files/pdfs/powerwall/Powerwall%202_AC_Datasheet_en_northamerica.pdf
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NeilT

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Re: Batteries: Today's Energy Solution
« Reply #1210 on: October 11, 2019, 04:02:00 PM »
The top 10% is a killer due to heat.  Dropping to the first 10% is a killer due to chemistry of the cells under low SOC and high drain.

The top 10% can be alleviated by very aggressive BMS cooling systems.

The low SOC is far more tricky as the damage doesn't just occur when charging, it is an inherent part of discharging the battery to that level.

Take your mobile and run it out of power, put it in a drawer and leave it for a year or two. You will find that the RTC on the phone has totally discharged the battery.

Open your phone and you will find a swollen battery which can never be charged again.

Chemistry.  No charge required.

Active BMS is a learning process.  Charging warm at low levels, cooling at high levels, aggressive voltage and ampage regulation; all help.

But the physics and the chemistry of the underelying cells does not change, no matter how smart your system is.

This is why the new chemistry postulated by Tesla could be a game changer.  But we have to remember this is a moderate power solution, not a high power solution. Driving experience more akin to trying to crank your reluctant cat in the depths of winter using a leisure battery.
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sidd

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Re: Batteries: Today's Energy Solution
« Reply #1211 on: October 11, 2019, 10:50:54 PM »
Re:  crank your reluctant cat in the depths of winter

This typo made me laugh out loud enuf that the neighbour's cat woke up and leapt back over the fence from a snoozing start on my lap.

The scratches she left are ugly, but not particularly painful. Luckily she missed my crotch.

sidd

Sigmetnow

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Re: Batteries: Today's Energy Solution
« Reply #1212 on: October 12, 2019, 02:58:45 AM »
cyberGRID software connects Tesla large-scale battery to Slovenian energy markets
Quote
cyberGRID’s award-winning cyberNOC software* met an important milestone today with its integration with Ngen’s Tesla 12MW/24MWh battery storage system located in Jesenice, Slovenia. This represents the largest battery system installed in Slovenia and one of the largest operational energy storage systems in Europe.
...
With regards to the integration of renewable energy, cyberGRID’s platform thus plays a pivotal role in EU-wide efforts towards decarbonisation. cyberNOC also reduces the risk of investment in large-scale battery storage systems by enabling the participation in various energy markets, not just the primary reserve. More specifically, cyberNOC can provide battery operators at C&I locations the opportunity to participate in markets such as the primary, secondary (aFRR) and tertiary (mFRR) control markets, offer grid stability, peak shaving services, frequency and voltage control, and community-level storage.
https://www.cyber-grid.com/cybergrid-software-connects-tesla-large-scale-battery-to-slovenian-energy-markets/
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Archimid

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Re: Batteries: Today's Energy Solution
« Reply #1213 on: October 12, 2019, 11:45:39 AM »
They created a rechargeable world

https://www.nobelprize.org/prizes/chemistry/

Quote
The 2019 Nobel Prize in Chemistry are awarded to John Goodenough, M. Stanley Whittingham and Akira Yoshino “for the development of lithium-ion batteries”. Through their work, they have created the right conditions for a wireless and fossil fuel-free society, and so brought the greatest benefit to humankind..



I am an energy reservoir seemingly intent on lowering entropy for self preservation.

NeilT

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Re: Batteries: Today's Energy Solution
« Reply #1214 on: October 12, 2019, 08:14:36 PM »
Re:  crank your reluctant cat in the depths of winter

This typo made me laugh out loud enuf that the neighbour's cat woke up and leapt back over the fence from a snoozing start on my lap.

Glad I could provide some levity... My keyboard on my phone makes arbitrary decisions on what key I pressed....

In this case the UK QWERTY keyboard does actually have r and t side by side.....
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Robert A. Heinlein

Tor Bejnar

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Re: Batteries: Today's Energy Solution
« Reply #1215 on: October 12, 2019, 10:00:48 PM »
...
In this case the UK QWERTY keyboard does actually have r and t side by side.....
And you expect us to take your word for it that you actually use a keyboard with the UK QWERTY set up‽   :o ::) :P :)
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NeilT

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Re: Batteries: Today's Energy Solution
« Reply #1216 on: October 13, 2019, 12:31:34 PM »
No, I expect you to be Skeptical and check....

Sadly, on my stock Android browser, the smilies above don't work.....
Being right too soon is socially unacceptable.

Robert A. Heinlein