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Words of wisdom from the joint SCA and Pagan community. First attributed to Isaac Bonewits.Never meddle in the affairs of Wizards, as it makes them soggy and hard to light.
Popular Filk song.Don't ever set the cat on fire,
you only will annoy it....SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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I'm an electrical engineer this is enough to allow me to read a battery datasheet and make an informed decision.
There are many relevant parameter when you want to compare batteries.
A good battery datasheet must provide you with enough informations to be able to take a good decision even if you are not an engineer.
Then if you read enough datasheets about one battery chemistry you start to see the common parameters the advantages and limitations of that battery technology for your particular application.
As an engineer in general you have the basic skills to understand anything as long as you get involved enough. And I did extensive research in the last two or three years regarding energy storage mostly LiFePO4 batteries and Supercapacitors also renewable energy including thermal electric, wind and solar there are also youtube videos on a lot of this subjects on my channel.
What I presented was a table with a simplified calculation based on values taken from manufacturer datasheet. How will be this something else than a fact.Thinking something is fine such as I think about a lot of politicians but that doesn't make it fact.
Now you can dispute the formula used if you think I made a mistake.
One of the most important factors as long as a battery meets the specific requirements for your application is the amortisation cost that last line in my table.
Like I mentioned just the very basic parameters are taken in to account in that table so most people will (I was thinking) easily understand even if that price/kWh stored is not accurate because of the oversimplification.
I also mentioned that if you where to take more parameters in to account and make that number more closer to reality then Lead Acid will look even worse.
Now this last phrase you can take as my opinion as long as I do not present a table that takes in consideration all this additional parameters and shows that I was right.
I think you read the document listed in my original post paid by the US department of energy and the conclusion of that tests. There are plenty of those studies with the same overall results. And the study was ordered to investigate the use of those battery for stationary energy storage not for transportation.
As solar panels are almost free and all coal power plants will be phased out there will be a need for large scale grid connected batteries and those need to be cost effective.Comment
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Sometimes it's the very technical people who have to be the most careful when stepping outside their area of expertise. I know some people who are very smart in their field, and think that makes them smart in some other field, too. Random guys on Internet message boards (like me) seem to be especially prone.
Like this.16x TenK 410W modules + 14x TenK 500W invertersComment
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I agree but I'm not afraid to be proven wrong. Besides I'm an electrical engineering what other speciality will give me a better inside in to energy storage?
Maybe as a chemist I will have a different insight in to batteries but is not necessary probably for the argument I made here, that LiFePO4 is a better alternative to Lead Acid form an economic perspective.Comment
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Here are some links of energy storage solutions from large manufacturers Like Bosh, Sony and SMA all of them using Lithium for energy storage.
Sony even mention the use of Lithium Iron Phosphate but I guess the others use the same.
They claim 10 to 20 years of life with daily cycling as high as 90% DOD one of them mentioned 6000 full cycles and Bosh mentions 7000 cycles or over 20 years.
Here are the links
http://bosch-solar-storage.com/techn...thium-battery/ Bosh about the battery.
I'm sure there are way more out there usually selling in Europe for now probably because they can get the best profit there.Comment
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I love LifePo4 like you do.
However, in the real world, specs don't mean anything to the common man unless you can get products *easily* and at an affordable price. That means sitting on the shelf at an auto parts store with competetive pricing to prove that they've made it to the rest of the world.
Of course I know different and how to get this stuff from EV parts dealers and whatnot.
The key issue is the up-front price. What if Lifepo4 had a cycle life of 100 years? It wouldn't matter if that little 10ah / 100 year lifepo4 cost $10k to start with, nobody can afford it. If you botch your capacity need calculations, it is hard to recover. In fact, if you need more, you have to start over.
Sadly, Lifepo4 will remain in a niche market - either unavailable to the common man (aside from powersports batteries or battery geeks like you and I), or contained inside proprietary oem gear. That's how it looks now at least.
No amount of cheering from the peanut gallery will sway corporate. In fact, I think they have dawdled around so much, that I have actually replaced one of my failed lifepo4's (my fault) with an AGM. Right now it's a rich-man's game due to the up-front pricing.Comment
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I have to disagree and agree at the same time
with the availability of LiFePO4.
In Europe most renewable energy store have ready to use complete storage systems as you seen in the links above from Sony or Bosh they contain the battery and battery management system. They are a bit expensive but competitive with Lead Acid since Lithium can be discharged 90% where Lead Acid is recommended around 30% so you can get away with at least half the capacity those reducing the initial investment.
Now is true that I don't see something like this on the North American renewable store there my be a few reasons for that. One has to do with manufacturers like the ones i mentioned that want to get a large profit and prefer to start selling in Europe where electricity price is higher and they sell to on grid people.
The offgrid market is unbelievably small so they will never be a target.
Life of the battery is similar about 10 to 20 years for LiFePO4 and Lead Acid difference is for this to be the case you need premium Lead Acid batteries discharged only about 20% in average or LiFePO4 discharged 80%.
The charge efficiency on Lead Acid is quite bad in the top 20% not much higher than 20% and the charge current must be limited by PWM or and MPPT controller. Where LiFePO4 will be way over 95% efficient so with the same solar PV panel array you get at least double the energy in the battery during the day.
I have just a 2.5kWh battery on my offgrid house (No problem with discharge rate they can do 1C with no problem or loss of efficiency). I will have needed at least 10kWh if I will have went with Lead Acid. My battery was 1200$ and should last for at least 10 years with absolutely no maintenance.
As I mentioned before in my climate will have been impossible to use Lead Acid way to cold and they need venting no way you can heat a vented box with -40C (-40F) outside. Where my LiFePO4 sits nicely inside the house where is warm and need no venting.
Yes it was the problem with no Solar BMS charger and needed to put the effort to build my own. Is about 75% financed on Kickstarter and there is one more week. If it is successful I can have that Solar BMS working on my battery and finally be able to know the SOC and not always count manually the kWh used. It will be open source so almost any one with enough knowledge can build one a bit expensive since is only one (prototype pricing) but much easier that it was for me.Comment
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I understand your enthusiasm, and would fill my garage with a bank of CALB cells in a heartbeat - I just can't afford it in the capacity I need.
Despite the great specs, we are still dealing with up-front costs, which most corporate bean-counters will laugh at, and homebrewers will question. They may be just as comfortable doing a few replacements of AGM instead.
In fact, I just accidentally killed one of my test lifepo4's by taking it down to zero volts. Game over. With Pb, I can restore them with my bench supply, although they will have taken a major hit. Still, they can be placed back in service in the meantime until replacements arrive.
And I know why your are keeping your lifepo4's in the house. Nice and warm. Lifepo4's don't like extreme cold, although if you run some current through them to warm them up internally, they will come up to speed. BUT not ideal if your application needs immediate full capacity in extreme cold.
I hope your project is successful, but know that some may want to blame your bms if their battery bank dies. How are you going to deal with that?Comment
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Usually you need about 2x to 4x less capacity with LiFePO4 (If I where to replace my 2.5kWh LiFePO4 with Lead Acid I will look for around 8 to 10kWh) so upfront cost is the same or smaller.
Yes it will be game over if you over discharge the LiFePO4 to zero but That is why a BMS is needed and with a good BMS you will never have this problem.In fact, I just accidentally killed one of my test lifepo4's by taking it down to zero volts. Game over. With Pb, I can restore them with my bench supply, although they will have taken a major hit. Still, they can be placed back in service in the meantime until replacements arrive.
Lead Acid will dislike cold even more and drop in available capacity much more than LiFePO4. The advantage is that LiFePO4 do not release Hydrogen or anything else and they can easily stay inside and they only take a fraction of the Lead Acid 3x smaller for the same capacity and 3x smaller capacity is about 9x less space than Lead Acid.And I know why your are keeping your lifepo4's in the house. Nice and warm. Lifepo4's don't like extreme cold, although if you run some current through them to warm them up internally, they will come up to speed. BUT not ideal if your application needs immediate full capacity in extreme cold.
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I hope your project is successful, but know that some may want to blame your bms if their battery bank dies. How are you going to deal with that?[/QUOTE]
There are still over 5 days on Kickstarter and project is 85% funded so it is a good chance it will be funded (even if I was hoping for more)
There is almost no chance for the battery bank to die with my BMS unless user sets improper thresholds for the battery since the main IC taking care of the battery is made by a large company with huge experience in this and I only use a microcontroller to program this IC and monitor the battery (all sorts of parameters) and to calculate SOC extremely important.
If they use my predefined parameter there is no chance and if they set improper parameters like min 0.8V for LiFePO4 it will still survive but take a hit in cycle life.
I will only have around 50 bakers and discussed with almost every one individually they are all quite capable of understanding how to work with LiFePO4 most even have already the battery but no proper BMS.
They all understand what they are getting and that is a fully programmable BMS (If I will have put restrictions then it will not be so flexible but will have been impossible to kill a battery) I can reprogram one unit just for LiFePO4 with no possibility to change that but I will not like such a BMS.Comment
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Hog wash and everyone here knows it. With Lead acid you need 5 day reserve capacity which nets you 2.5 days to CYA for cloudy days. So if a person needs 1 Kwh per day on a 12 volt system using lead acid needs a 400 AH battery. If using LFP needs 300 AH to yeild the same autonomy. That is a fact jack so quit your BS make believe numbers. You keep using the same bogus data to support your view. You have to compare APPLES TO APPLES. All you got is rootie tootie fruit salad mumbo jumbo trying to baffle laymen. Pros know better and you are not getting away with it here.MSEE, PEComment
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However (switching to oranges warning) if you are looking only at the daily cyclic use of energy and are willing and able to use a generator more often when needed instead of having multi-day autonomy in the battery bank, then you can use a 2-4X smaller LFP bank.
Even if you do include autonomy, the ability to run LFP down to nominal 0% SOC without damage while not taking the comparable FLA bank below 50% SOC to get autonomy will still count for at least a factor of two. (That assumes, of course, that you are willing to cycle your LFP all the way up to 100% SOC routinely, which is yet another fruit question.)
It certainly helps all around if each person making large and unpopular claims explicitly states all his assumptions and conditions and that later commenters on that claim either respect those assumptions or refute individually the assumptions that they think are wrong. (either unwise or contrary to physical laws, that is.)
So far I see this discussion as one where both sides (assumption: there are only two sides. That may not be correct.) are arguing a particular result while explicitly or implicitly using different assumptions.
Continue to keep it civil and we may end up with a very useful discussion.
Here are some proposed common assumptions for your evauluation:
1. For FLA, daily cycling between 80% SOC and 100% SOC is optimal and autonomy cycling as low as 50% SOC is acceptable. I inow that Chris Olson does not agree with the first part of this and he has a lot of practical experience to back this up.
2. For LFP, cycling between 40% and 60% (or some other slightly shifted range) is optimal and autonomy cycling down to 0% SOC is acceptable with a generator available.
3. Recognize that the design (engineering) goals for a commercial solar backup system with a minimum load which must always be supported may be different from the design goals of a system for an actively managed off-grid life. This can lead to a whole range of differing assumptions.
Now, on that basis, shake hands and come out fighting.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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