LiFeYPo4 questions

[DyslexicDancer]

I had a question for those of you in the know.

I want to experiment a little with LiFeYPo4 batteries for a solar off grid setup. Currently I use regular FLA batteries for a small back-up system, but I'm contemplating a much larger system for an off grid cabin and I want to do some research on LYP batteries because they seem like a much better option than FLA. If I can truly get 8000 Cycles at 50% DOD with a LYP battery, they would probably be cheaper in the long run then FLA

My plan is to get 4 100ah LiFeYPo4 batteries. The ones I’m looking at are these >http://www.alliancerenewableenergy.c...-LFP100AHA.htm

Next I plan on using a Morningstar TS-MPPT-60 charge controller with two 230 watt 24v panels. I don't expect much MPPT benefit other than the fact that the TS-MPPT-60 can be set to a custom charge setting and will down convert my panel's 24 volts to the battery bank's 12 volts, but what charge settings would I program into the TS-MPPT-60 for a LiFeYPo4 battery bank?

Next I have read that a BMS is not absolutely necessary if you Bottom Balance and only charge to 3.5 volts per cell, however none of the threads I have read actually cover how to bottom balance the battery bank. I assume I need a specific charger set up to charge one cell at a time (to a certain voltage?) and then a way to discharge each cell individually so that all the cells are at the same bottom voltage???? Any help on the proper way to bottom balance and what Items I will need to do it would be greatly appreciated.

Lastly I was planning on using a Celllog8s http://www.hobbyking.com/hobbyking/s...2_8S_Lipo.html to monitor the battery and a few Turnigy Watt meters http://www.hobbyking.com/hobbyking/s...dproduct=10080 to provide data on solar panel output (amps/volts), charge controller output (amps/volts) and one to act as battery out Amp meter. I have read that you cannot use battery voltage to measure SOC on a LYP battery and that you basically have to use an Amp counter to determine SOC

[Sunking]

Not going to work. LFP batteries are not compatible with charge controllers made for lead acid.

[DyslexicDancer]

Not going to work. LFP batteries are not compatible with charge controllers made for lead acid.

Well that's bad news, I thought I had read that it was possible with a MPPT charge controller that allowed you to set a custom charge profile, But to be honest I don't remember the Blog I was reading that talked about it.
Is it the lack of a BMS or just an incompatibility issue?

[Mike90250]

.....Is it the lack of a BMS or just an incompatibility issue?

yes & partly

If you want the Li cells to last, each needs a BMS.

The charge controller will willingly pump out power and they regulate themselves by the voltage they sense. They have no way to interpret what the BMS system is trying to tell them.

I can use a custom programed controller to charge my NiFe bank, because the batteries are very forgiving. Li is not forgiving.

[SunEagle]

yes & partly

If you want the Li cells to last, each needs a BMS.

The charge controller will willingly pump out power and they regulate themselves by the voltage they sense. They have no way to interpret what the BMS system is trying to tell them.

I can use a custom programed controller to charge my NiFe bank, because the batteries are very forgiving. Li is not forgiving.

Not only is lithium not forgiving it can be down right hostile when abused.

[bonaire]

I don't trust a LiFEPO4 battery that says max voltage is 4.2V. It should be more like 3.6V. Li-Ion Poly blends can run up to 4.2V each. I guess it is the 'Y' componentry that gives it the higher voltage range.

If you design a BMS for cell balancing and install and utilize proper taps you might have something. This is what I would say is the future of solar PV storage. The cost of Lithium packs and BMS systems is a little higher than what people are used to for Lead Acid. One company, A123 Systems (rip), built 2MW trailers for energy storage using their small cylindrical LiFEPO4 cells. Of course, heavy with the BMS and monitoring circuits. 80,000 cells per trailer.

Also, when charging, there is no float charge. You just need to stop charging lithium altogether once you hit your set maximum voltage. And you cannot let cells go beyond the cell's maximum or risk serious problems. One of them is "venting with flame".

Certain LiFEPO4 blends have been known to be fine if overcharged and abused (such as A123 Systems cells) but since the ones you're looking at are not exactly the samething, be very careful. Also, you can alter where such cells are stored. Lithium cells do like 70*F environments but can be stored and used in lower temperatures, such as 50*F or 40*F. They do lose their efficacy down there, though. I wouldn't do this experiment in a home. Do it in a shed or outdoor sealed construction.

HobbyKing, and a few others sell battery balancers which can be wired up. However, I don't know if they work at the wattage ratings you are talking about. I would also suggest a 24V system rather than a 12V system. More cells means less amps drawn out when you pull power from the system.

What I think you are doing is great and worth a try. It's possible we will see such systems a lot more commonplace in the future. One partnership between Panasonic and PowerOne is doing this to create PV Renewable energy storage systems.

Found this, not bad: http://gwl-power.tumblr.com/

I did a little reading on LiFEYPo4 v. LiFePO4. Interesting idea to help with colder temperatures. A good 100Ah LiFEPO4 would work fine and have a lower nominal voltage and tying four together in series would still be just about 13.2V nominally. Four LiFeYPo4 would be higher. So, determine if that is ok for you. A lot of the DIY Electric Vehicle converters have been using LiFEPO4.

[Sunking]

DyslexicDancer, what you are running into is there is no demand yet for charging LFP batteries with solar or wind. Well they do but for RC models or very small batteries.

It is real easy to charge LFP batteries, in fact the charging algorithm is less complicated then any of the lead acid technologies. A lithium charger is a voltage regulated device. The difference between Lead and Litium is with lithium needs a higher voltage for each cell, tighter voltage tolerance, and terminate the charge as soon the current tapers down to 3 to 5% of initial charge. That is a very simple charger to make. All it is just a simple float voltage, and current monitor.

Now the hard part is the BMS to keep the cells balanced.

[DyslexicDancer]

I don't trust a LiFEPO4 battery that says max voltage is 4.2V. It should be more like 3.6V. Li-Ion Poly blends can run up to 4.2V each. I guess it is the 'Y' componentry that gives it the higher voltage range.

If you design a BMS for cell balancing and install and utilize proper taps you might have something. This is what I would say is the future of solar PV storage. The cost of Lithium packs and BMS systems is a little higher than what people are used to for Lead Acid. One company, A123 Systems (rip), built 2MW trailers for energy storage using their small cylindrical LiFEPO4 cells. Of course, heavy with the BMS and monitoring circuits. 80,000 cells per trailer.

Also, when charging, there is no float charge. You just need to stop charging lithium altogether once you hit your set maximum voltage. And you cannot let cells go beyond the cell's maximum or risk serious problems. One of them is "venting with flame".

Certain LiFEPO4 blends have been known to be fine if overcharged and abused (such as A123 Systems cells) but since the ones you're looking at are not exactly the samething, be very careful. Also, you can alter where such cells are stored. Lithium cells do like 70*F environments but can be stored and used in lower temperatures, such as 50*F or 40*F. They do lose their efficacy down there, though. I wouldn't do this experiment in a home. Do it in a shed or outdoor sealed construction.

HobbyKing, and a few others sell battery balancers which can be wired up. However, I don't know if they work at the wattage ratings you are talking about. I would also suggest a 24V system rather than a 12V system. More cells means less amps drawn out when you pull power from the system.

What I think you are doing is great and worth a try. It's possible we will see such systems a lot more commonplace in the future. One partnership between Panasonic and PowerOne is doing this to create PV Renewable energy storage systems.

Found this, not bad: http://gwl-power.tumblr.com/

I did a little reading on LiFEYPo4 v. LiFePO4. Interesting idea to help with colder temperatures. A good 100Ah LiFEPO4 would work fine and have a lower nominal voltage and tying four together in series would still be just about 13.2V nominally. Four LiFeYPo4 would be higher. So, determine if that is ok for you. A lot of the DIY Electric Vehicle converters have been using LiFEPO4.

I couldn't find the Blog site I was talking about, But I did find another, much more informative blog site http://solarbodge.blogspot.com/2012_07_01_archive.html he even includes information on bottom balancing and MPPT charge controller settings.

The only reason I was interested in LiFeYPo4 over the more common LiFePo4 is that it is suppose to have a higher cycle life, at least that is what the author of the blog was claiming 8000 cycles at 70% D.O.D. for the LiFeYPo4 vs 5000 Cycles at 70% D.O.D. for the LiFePo4. I have no idea if this is true or not, but if true I would rather have the batteries that give an extra 3000 cycles.

About the voltage difference, I have no Idea, the Author of the blog states that he only charges to 3.97 volts once during the initial cell balancing, and then after bottom balancing at 2.75 volts he only charges to 3.5 volts per cell and then has a low voltage cut off when the cells reach 3 volts per cell. His claim is that by living between 3.0 and 3.5 volts per cell that he looses battery bank capacity (approximately 20%), but that no BMS is needed and his battery pack stays in balance.

If he is correct I could live with a Lithium battery de-rated to 80% of it's normal Ah rating without the expense and hassle of a complicated BMS. Now the real question is will it work long term. The author of the Blog states he has 188 daily Charge/Discharge cycle using his method with no BMS and so far he is reporting zero issues, so only time will tell if it will work long term.

I was thinking I could use a charger/balancer like this http://www.hobbyking.com/hobbyking/s...y_Charger.html with a PSU like this http://www.hobbyking.com/hobbyking/s...Chargers_.html for the initial cell balancing. It may take a while as the charger only has 20A of output, but it's not too expensive.

[inetdog]

If he is correct I could live with a Lithium battery de-rated to 80% of it's normal Ah rating without the expense and hassle of a complicated BMS. Now the real question is will it work long term. The author of the Blog states he has 188 daily Charge/Discharge cycle using his method with no BMS and so far he is reporting zero issues, so only time will tell if it will work long term.

From the released data, it looks like Boeing thought that they could get a long life from their LiCo0₂ battery by staying within the middle 80% of its range too. And they even had a full (although possibly brain dead) BMS with balancing.

I see no reason to expect that staying within the middle 80% would eliminate the need for balancing. Reduce it, yes, but there is no such thing as equalization for Li-Ion batteries, so cell imbalances will arise eventually. Only there will be no BMS to detect it, so he will need to keep watching it carefully. Keeping the whole bank below an average voltage of 3.5 volts is no guarantee that one cell will not exceed that voltage, or even 4+ volts.

Ask Elon Mosk (Tesla) whether balancing is necessary.

Quick digression: SolarCity is offering a battery based solar option using a Tesla-designed battery (probably a lot of 18650 size cells, if they use the same technology as the cars.) Does anyone have any feedback on the current state of that SolarCity offering?

[russ]

I saw Elon Musk say Boeing should have gone to him for a fix - that would have been something - not like he is all that great an engineer.

[inetdog]

I saw Elon Musk say Boeing should have gone to him for a fix - that would have been something - not like he is all that great an engineer.

No, but he is good on concepts and hires good engineers!

[SolarEU]

LiFeYPo4 questions - where to find installations

I want to experiment a little with LiFeYPo4 batteries for a solar off grid setup.

I was checking the internet to see some installations for off-grid or half off-grid with Lithium (LiFeYPo4) packs. No much found. Are there any users on the forum who have working setup and wish to share details with others? Or some links to working installations? Thanks in advance.

[Sunking]

I was checking the internet to see some installations for off-grid or half off-grid with Lithium (LiFeYPo4) packs. No much found. Are there any users on the forum who have working setup and wish to share details with others? Or some links to working installations? Thanks in advance.

While it can be done I doubt you will find many who actually employ Lithium. This is due to 2 main reasons.

1. Expensive. LiPo or any of the lithium chemistry cost as low as 4 to 5 times more than Lead Acid, and up to 10 times more per Kwh. To compound the problem less expensive Lithium (4 to 5 X) only can get around 300 to 500 cycles. It is just prohibitively expensive and no real price breaks in the near future.

2 Second problem is easily solved, but to date no Charge Controller manufactures offer controllers for Lithium. This is due to the very high cost of lithium batteries and there is no demand for such controllers so manufactures do not make them. One exception is for th every small lithium batteries used in cell phones and RC models. But those are of no use due to very low power.

So until Lithium battery prices can compete and last as long as Lead Acid, don't hold your breath because it is not in the future any time soon. When it does happen will come from the Electric Vehicle market. Solar or RE will just be a secondary beneficiary of the EV market.

[SolarEU]

While it can be done I doubt you will find many who actually employ Lithium. This is due to 2 main reasons.

I found one interesting photo-set here: http://gwl-power.tumblr.com/post/717...-microinverter
but I do not see how is this to work in reality. I also do not like the installation on the wooden pallet.

My idea is store the energy during the day, when I am not at home, to use it later in the evening when I come home.

[PNjunction]

My plan is to get 4 100ah LiFeYPo4 batteries.

Ok, a 4S pack for a nominal 12v system in a relatively low-current house-bank application. This is far different from an EV / racing setup so that simplifies things.

The 4S string in a house-bank application that starts with quality cells to begin with, and used from about 80% to 10% DOD is not a major concern for balance, but one would want to keep an eye on it of course over time. It is about the easiest string to keep in balance from a nominal 12v point of view in a low-current app. We are not talking about balancing 50 or 100's of individual EV cells. However with only 4 cells to deal with, it would be extremely easy to use something like a

Revolectrix FMA Cellpro Powerlab balance charger. You may not even need it all the time, just once in awhile.

Solar charging is a simple CV scenario. Set your charge controller to the appropriate cutoff voltage, and disable any temp compensation. That's your HVC. For an LVC, you'll want some sort of monitoring / cutoff to prevent you from totally discharging the cells. Design your setup for no more than 80% DOD.

If you want a specific Lifepo4 (or perhaps lifeypo4) solar charge controller, take a look at Genasun's offerings although I am doing just fine with my little morningstar pwm cc's set to 14.1v although I *could* take it to 14.4v if I wanted to.

My own investigation into Lifepo4 with solar on a small scale has revealed that there is waaaay too much confusion between lithium-cobalt accidents and abuse, and not enough hands on and research on the vastly improved safety from those who have actually done it with lifepo4. Despite the outrageous cost of my own powersports lifepo4 battery experiments (should have gone CALB or Balqon or others to begin with), I am totally pleased with the performance and differing characteristics than my beloved agm setups. Of course I'd like to see prices come down like everyone else, but I'm not waiting - life is too short.

The tendency unfortunately is that lifepo4 gets a bad rap from those who buy and use counterfeit / gray market / abused cells that are also not sized appropriately for the job and have insufficient wiring infrastructures to properly support their application. Winging-it with junk basically, and having to compensate by overcomplicating things. Of course there are always the over-hyped videos of people purposely abusing lifepo4's just for the thrill of it. Nobody looks at the old acid-spewing overcharging of fla or agm's in a similar manner because that doesn't make a good news-bite anymore.

I think you'll do just FINE with your proposed setup, as long as 100ah is sufficient for your needs and your dealer is providing quality and not new-old stock and the like.