Electric cars get power from a strained grid?

[brianl703]

Originally Posted By: bob_ninja
Thus when a heat wave hits and ACs are pulling too much power form the grid, then the grid may send a signal to thermostats to increase temp setting a few degrees to reduce AC usage. That way they could avert overloading the grid.


The local electric company here uses load management switches (and has since 1979--they were one of the first in the country to start using them). The deal they offer is that if you allow them to install one (free of charge) on your electric water heater or central air conditioner, they will troubleshoot problems with that unit and fix them if they are minor.

The load management switches they use are radio controlled, I believe they operate on a VHF frequency in the paging band (somewhere around 140-160Mhz). They are configurable to one of 65,535 addresses. When they recieve a signal they disconnect the attached load from it's power supply for 15 minutes. In typical use the power company turns off 1/4 of the load management switches at a time, so if they need to control load for an hour all switches will have cycled for 15 minutes during that hour.

The load management switches also delay power-on for several minutes if the power is interrupted, which probably helps in a power outage.

 

[ShiningArcanine]

Originally Posted By: bob_ninja
SA,
Advances in rechargable batteries have been very slow and full of problems. NiMH cells have a higher energy density than NiCd, but are more fragile. LiIon are yet more dense, but explode. While you may read about new advances from time to time, they never actually tell you about drawbacks or even financial viability. So I wouldn't expect a huge jump in battery capacity to happen in a near future.

The other major problem is cost. Sure new battery technology has increased the capacity and performance, but also the costs. So even if a higher capacity is available in the future there is no guarantee that it will also be affordable.


It is not possible for a Lithium Ion battery to explode unless either someone tampers with it or it is defective. Both cases are extremely rare among the billions of batteries that have been made.

 

[brianl703]

A malfunctioning charger sure as [censored] can make a lithium-ion battery explode!

 

[ShiningArcanine]

Lithium-ion batteries have safety circuitry to prevent that. If the charger malfunctions and provides and excessively high voltage or current, I believe that fuses in the safety circuitry will burn out before the battery has the opportunity to explode.

 

[bob_ninja]

SA is correct that so long as a protection circuit is present and operates properly then it will regulate the load/charging to prevent dangerous levels. That is fine.

The problem occurs when vibrations cause internal defects which safety circuits cannot detect. The exploding laptop batteries had breaches of anode/cathode separator membranes that cause short circuits and thermal runaway - fires and explosions. Clearly this is even higher risk for cars that may encounter far stronger shocks, like in accidents. The concern is that LiIon battery with a compromised internal structure due to a sudden deceleration (accident) could cause dangerous thermal runaway reasction.

Thus hese new safer lithium batteries are designed for the worst case scenario, meaning total failure of any protection circuits as well as compromised structure (broken cells). The chemicals used are different and cannot react such that an explosion or fire results. That is the primary advance enabling Lithium battery use in cars. According to the interviews I heard, even without the coolong system at most batteries get hot, but cannot start a flame.

 

[benjamming]

Originally Posted By: bob_ninja
The chemicals used are different...


elaborate please

 

[ShiningArcanine]

Originally Posted By: benjamming
Originally Posted By: bob_ninja
The chemicals used are different...


elaborate please


That does sound somewhat humorous, but in Lithium Ion batteries, although the principle chemical component is Lithium, there are other chemicals, that compose the anode and cathode, without which, the function of the battery would be impossible. For instance, Graphite anodes are presently used in most, if not all, Lithium Ion batteries. A recent advance in Lithium Ion battery technology that we will see in the market in about 5 years involves the usage of a Silicon anode, which allows an increase in the energy density of Lithium Ion batteries by a factor of 10. Historically, Titanium Sulfide anodes have been used. Cathodes used in Lithium Ion batteries are quite diverse and it is on the cathode chemistry that the majority of Lithium Ion battery research is focused. Commercial cathodes typically use Cobalt Oxide, Manganese Spinel or Iron Phosphate. Electrolytes used in lithium ion batteries are more diverse still and are far too numerous to list. Beyond that are differences in the structures of the anodes and cathodes and the structure of the batteries as a whole. Many times, research aimed at improving Lithium Ion batteries involves using new structures. The new Silicon Anode that enables a ten-fold increase in energy density uses silicon nanowires to form small forests that allows silicon to be used as an anode material, whereas in the past, silicon anodes disintegrated because the structure of the silicon was not able to expand and contract gracefully with discharge/recharge cycles.

Lithium Ion batteries are chemically quite diverse. The fact that they use the same ions does not make them all identical. If you care for more detailed information, I am sure that Google, Wikipedia and batteryuniversity.com will be more than able to accommodate you. Being a biochemistry/computer science double major, lithium ion battery chemistries are neither my field nor my concern and I find the prospect of the lithium/lithium ion cells (it is more proper to call them electrochemical cells than batteries) in my cell phone, laptop or calculator exploding to be so unlikely that I do not concern myself with it, much like how I do not concern myself with the prospect of being struck by positive lightning, as if I did, I would never leave my home.

 

[Papa Bear]

On-peak, mid-peak, off-peak hours .. strained electric grid .. high possibility of brown out and black out conditions ....
...sounds ominous and expensive.
.
.
. I think I would just wheel out the 5000 watt 16hp generator and recharge the batteries in my EV in the driveway. Question is..
...how many Jerry cans of gas would I need to keep the generator running all night in the driveway ???

 

[brianl703]

Originally Posted By: ShiningArcanine
I find the prospect of the lithium/lithium ion cells (it is more proper to call them electrochemical cells than batteries) in my cell phone, laptop or calculator exploding to be so unlikely that I do not concern myself with it


I bet you hook up jumper cables without wearing safety glasses, too.

 

[XS650]

Originally Posted By: Papa Bear
On-peak, mid-peak, off-peak hours .. strained electric grid .. high possibility of brown out and black out conditions ....
...sounds ominous and expensive.
.
.
. I think I would just wheel out the 5000 watt 16hp generator and recharge the batteries in my EV in the driveway. Question is..
...how many Jerry cans of gas would I need to keep the generator running all night in the driveway ???

Mount the generator and gas can in your EV...Instant hybrid.