powerwall2 behavior when paired with solar

[Mike90250]

But for some it is not as comfortable as a battery backup, which does not require you to think about buying fuel (if even available in an outage), does not emit any toxic fumes, does not require maintenance, can be relied upon to start and stop smoothly if you are away from home …

So no question that a gas powered generator is cheaper as a backup solution, but it does not offer the same level of comfort as a lithium battery does (especially if connected to solar).
And yes comfort is a relative thing that will vary based on each person and their specific situation

Just because you don't know of the issues & problems of Li batteries, does not mean they are "maintenance free" or inherently safe.

https://www.kcra.com/article/15-exposed-to-toxic-fumes-after-responding-to-fairfield-house-fire/27933317

FAIRFIELD, Calif. (KCRA) —
Fifteen first responders were treated for exposure to toxic fumes after helping battle a house fire over the weekend in Fairfield, officials said Tuesday.
The Fairfield Fire Department said 11 firefighters and four officers reported feeling sick after being exposed to the fumes.


Crews responded to a fire at a home on Ash Court around 5 p.m. Saturday. There, crews found 200 pounds of lithium-ion batteries in the garage, the Fairfield Police Department said. According to officials, the batteries emitted fluoride gas after being exposed to the fire. < mod note - actually Hydrofluoric acid fumes. >

That's when the 15 people were exposed to the toxic fumes.

The fire department also said the incident was so toxic that crews had to throw away all the hoses and boots that were exposed while battling the blaze.

[Ampster]

@SunEagle, you are correct, there is no right or wrong. These are just two different opinions. As I said earlier, it is nice we have choices.

[Ampster]

Just because you don't know of the issues & problems of Li batteries, does not mean they are "maintenance free" or inherently safe.
..............

I agree it is important to know the issues and problems of LI batteries. Since there are a number of different Li chemistries it would have been more informative if the reporter had actually been more specific so we could all know which ones to avoid. The puzzling thing was the last paragraph which said, "Investigators are now trying to determine what kind of business the homeowner was running."
I do know Lipo batteries which are often used in RC helicopters are extremely volatile. I don't know if they are the ones that release hydroflouric acid fumes. Hydroflouric acid is nasty stuff. Some refineries use it in their process. A refinery explosion in Torrance almost released 25,000 pounds of that stuff near my former home.

EDIT: I followed up on the Fairfield battery fire and it turns out the guy was running an electric bicycle repair business out of his garage. He was charging a lot of batteries. I can only presume he did not have the right controls over temperature and/or voltage. The important issue to understand about Lithium batteries is they do not tolerate overcharging or charging at multiple C rates because they will overheat and combust. I would not recommend them to anyone who does not understand the different chemistries and the specifics of charging each of those chemistries.

Earlier I mentioned Lipo batteries because when they are used in RC helicopters or other RC hobbies the participants are often in a hurry to charge their toy fast and that is when the problems often occur. In fact, hobby stores sell fireproof bags that can be used to safely contain the fireworks when one of those Lipos go off.

[Ampster]

I am sure there are some Californian households that have atypical electricity usage patterns that can justify the economics of a home battery system but I am talking about mainstream households. .......

I guess it depends on what you call mainstream. I think you are correct that the majority of Californians are not a market for battery backed solar systems.

I do think a market size of one million probably exists in California based on a back of the envelope calculation.
PG & E and SCE have a customer base of 30 million.
The median household income in California is $71,000
The CEC has a policy to have the IOUs adopt TOU rates in the next few years.
A market size of one million is clearly not mainstream but if I were selling battery backed hybrid inverter systems I would think it was a market worth looking at.

[Ampster]

Part of the problem is and always will be getting and using assumptions about future conditions and things like utility rates, inflation, alternate investments, etc., as well as how long to make the analysis run.

That reminds me of the saying, "Don't let perfect be the enemy of good." I have no problem using assumptions for modeling. No doubt it is important to test the assumptions along the way and sometimes they don't turn out to be exactly as predicted. Indecision is actually a decision to do nothing.

It seems to me that at this time, batteries aren't cost effective for most users as a means to avoid peak rates.
.

Probably correct for the majority of people out there. It is clearly a niche market at this time. As a tool to leverage solar by load shifting batteries are more than just a means to avoid peak rates. With big differentials between peak and off peak there are also arbitrage opportunities.

[J.P.M.]

That reminds me of the saying, "Don't let perfect be the enemy of good." I have no problem using assumptions for modeling. No doubt it is important to test the assumptions along the way and sometimes they don't turn out to be exactly as predicted. Indecision is actually a decision to do nothing.

Don't know why you'd think that. Perfection is an unattainable goal. Modeling may get you a less imperfect design if done well. Perfection is the goal of a fool. Constant improvement is attainable.

It's good you have no problem with assumptions because aside from death and taxes, everything about the future and particularly when dealing with engineering models including solar modeling and the economic analysis that is usually not done in any serious way is all based on assumptions of future conditions. No way to avoid assumptions.

The trick is to know which assumptions may be a better fit with reality as it unfolds. I've found some experience and a lot of luck seem to help.

On indecision: Indecision is the inability, for whatever reason(s), to make a decision. It implies awareness of a condition but the inability to decide what to do about it. Doing nothing is often the result. That's a passive action.

A conscious, reasoned decision to do nothing is indeed a positive action and may be a viable choice depending on the opinions and conclusions of the decision maker.

The two are not the same.

And, of course, hypothesis (assumption) testing is important. But starting with realistic assumptions that reflect reality and the real world, and knowing why those choices may be more realistic than other assumptions saves a lot of waste at the front end of the design process.

Choose to act, educate, design, implement, observe, modify, iterate.

Take what you want of the above. Scrap the rest.

[Ampster]

Don't know why you'd think that.
...

Sometimes on this forum I see paralysis of decision making by too much analysis. I thought I would offer another viewpoint. That is the benefit of forums like this.

[bcroe]

Brainstorming is good, but then a solution must be chosen.

I look for elegant solutions. That is one that has no negatives compared to the earlier
design. Like disc brakes. A lot of stuff here did not reach elegant status until until a
very long design consideration process. Am so glad I did not rush to a quick fix.

I see a huge amount of un elegant stuff these days. Bandaid a quick fix together, ever
adding complexity and negatives to the solution. Bruce Roe

[Ampster]

Brainstorming is good, but then a solution must be chosen.

I have enjoyed the brainstorming processes you have shared. Architects sometmes refer to a design Charette as a similar brainstorming process. I think in many cases the final decision is often optimum when reached in a collaborative process.

[J.P.M.]

Sometimes on this forum I see paralysis of decision making by too much analysis. I thought I would offer another viewpoint. That is the benefit of forums like this.

I respect your viewpoint and share the idea that over analysis can lead to confusion.
But that's not what I often see around here and elsewhere.
What I often see looks to me like red herring criticism of ideas that take more than one sentence to explain from folks that have short attention spans and lack critical thinking skills.
One of the consequences of the great dumbing of America.
There's a lot of middle ground between simplistic answers that don't explain anything and endless analysis for its own sake.
Rant mode off.

[scrambler]

I respect your viewpoint and share the idea that over analysis can lead to confusion.
But that's not what I often see around here and elsewhere.
What I often see looks to me like red herring criticism of ideas that take more than one sentence to explain from folks that have short attention spans and lack critical thinking skills.
One of the consequences of the great dumbing of America.
There's a lot of middle ground between simplistic answers that don't explain anything and endless analysis for its own sake.
Rant mode off.

+10

[solardreamer]

Judging by the last few posts I still see a battery for backup power mindset. I have friends being told by home battery vendors that they don't anything else for backup power which I believe is very misleading. For backup power usage (i.e. not load shifting/grid avoidance), I would like home battery vendors to be more honest and tell consumers they still need a generator for reliable on-demand backup power and home battery is a nice add-on for additional convenience (e.g. emissions, noise, etc.). So, it should be a generator vs generator+home battery consideration for the consumers.

[J.P.M.]

I think in many cases the final decision is often optimum when reached in a collaborative process.

Sort of like the idea that a camel is a horse designed by committee ?

When I was still working and if a meeting was seen as a necessary evil, I usually tried to hold it in a room with no chairs. Not popular, but the meetings were a lot more productive, shorter and a lot less frequent. My bosses usually thought I was a prick, but they were also engineers and usually left me alone.

Collaboration too, has limits. Someone must lead and channel it.

[scrambler]

So, it should be a generator vs generator+home battery consideration for the consumers.

I agree people should be made clearly aware of all the pros and cons of the various solutions.
That said, the final choice depends on every customer needs, circumstances and preferences.

In my case nothing is Critical to the point that I would even consider a generator. I used to have a generator and I have lived with two electric cars for 6 years now, and I would definitely prefer a Lithium Battery backup solution (combined with solar).
Battery backup would offers me all I need with much more comfort.
But yes, it will cost me extra for that comfort

[RichardCullip]

Sort of like the idea that a camel is a horse designed by committee ?

When I was still working and if a meeting was seen as a necessary evil, I usually tried to hold it in a room with no chairs. Not popular, but the meetings were a lot more productive, shorter and a lot less frequent. My bosses usually thought I was a prick, but they were also engineers and usually left me alone.

Collaboration too, has limits. Someone must lead and channel it.

When I was working in the oil industry up in Bakersfield, we had plenty of meetings. They grew more numerous towards the end of my career. Quite often I had the thought that "None of us is as dumb as all of us" running thru my head whenever we struggled to reach consensus.