LiFePO4 - The future for off-grid battery banks?

[PNjunction]

That, and the whole Fiskar / A123 thing. Old history, and times and manufacturing procedures has moved onwards towards the better. A123 is still around, whereas the average consumer thinks of bankruptcy as out for the count. Not true, but makes great fodder for the WSJ.

Tell ya, what - If I were in charge of Volkswagen, I'd have no hesitation going LFP with A123 and doing it right and inexpensively. Who knows ...

[Sunking]

That's the thing - I don't care what Tesla is doing for the following reasons:

Calm down al I am pointing out wheen it comes to charge rates there is no real difference between an EV and Solar Application. If anything with solar you will charge at a faster rate than an EV.

On the discharge side my comment was to point out even discharge rates are similar in Fractional C-Rate. With a Tesla cruising you are talking about C/6 discharge rates, unless you expect to go 300 mph for an hour.

What I think we agree upon overall Solar is less forgiving, not in charge or discharge rates, but rather environmental conditions. We do not need the level of Automation an EV needs. You do not need any active BMS or really even a BMS if you know what you are doing. All you really need to do is run PSOC and set your LVD correctly so it is impossible to ever have an over discharge.

One thing we can do is use some of the same ideas, the biggie is not allowing yourself to use full capacity. You never fully charge, and leave plenty in the tank. No EV will alow a customer full access. Tesla did open most of the capacity in Roadsters. Unknown to the public Tesla upgraded everyone capacity by 15 Kwh on their older Roadsters. It was done while their customers were sleeping. All Telsa did was upgrade the Firmware while you were sleeping. It is by limiting access that allows then such long battery life. Chevy and Nissan also do the same, they just do not have as much to play with.

[dax]

Just found this site by mistake and found it interesting so joined. We've been using lifepo4 energy packs for almost 6 years and was surprised to see the claims of them only having lives of 2-3 years. That's not our experience and we have a number of installations with life times of 4-5 years and our first pack, is nearly 6 years old and is used every day on job sites. None have suffered any loss of capacity and have changed the lives of those we have installed for. Now our customers cook using them, heat hot water and use almost whatever they want.

We only install lifepo4 now, gave up agm and gel almost 2 years ago when we'd proved the concept of lifepo4 in off grid installs. We also use lifepo4 on job sites instead of taking a genny with us because they work so well, providing much more energy and extremely rapid charging.

We carry 120ah packs and with one 250w solar panel, have power all day. We designed our own charge systems and are in the process of designing and building a real dedicated liffepo4 charge system that has no need for BMS or active cell balancing. Presently the solar charge controllers we are using, remove the need for a BMS and if our customers were intelligent enough, we wouldn't use BMS at all. However many customers have no idea how to use energy system properly, so we are making a charger which will control the system without any intervention. Currently we use active cell balancers and a BMS for customer installs, our own work pack have no BMS or balancing and they work fine on our solar charge controllers.

You could look at it this way, our first pack, has been used for at least 300 days a year for over 5 years working and on non work day, we use it for leisure and camping. In fact I use the dam thing for just about everything I need for power and carry it in the tractors on our farm. So it could be classed as cycling at least 1500 times. We don't see it that way, because of the charge/discharge parameters we use.

We also have lifepo4 as starter batteries in all our vehicle, work and personal. The two (24v) in the tip truck have been in use for over 4 years and they are amazing for staring engines, so much power they for instantly, except in very cold weather.

One thing we learnt early, is not to use big capacity cells. Our first commercial packs were 100ah cells, big mistake. When one cell collapsed, the entire system went down and we lost a lot of money using big brand cells and almost made us give up on lifepo4. So we went for 40-50ah military/industrial prismatic cells, which is what our first two packs consisted of and have not had a problem since.

[PNjunction]

Hi Dax and welcome!

Your experience sounds typical, although I'd like to know what those big-brand 100ah cells were, and if they were new, or perhaps new-old-stock that had previous owners? Also interested in your current cell manufacturer. Here, we are mostly familiar with Winston, GBS, and CALB, and on the smaller scale, A123.

If you read through all the threads, you'll see we've covered the whole bottom-balance vs top-balance scene, individual cell-bleeder boards, which I and others eschew, and even shoehorning solar CC's designed primarily for lead into LFP use by careful selection of voltages, disabling temp-comp and so forth. Or just bite the bullet and grab a Mastervolt, or Genasun LFP controller for the smaller stuff.

It isn't hard, but it isn't ready for the guy next door. Much like a Rolls-Surrette isn't for the guy next door who doesn't know what a hydrometer is...

Again, welcome, but like with all LFP threads across the globe, keep your flamesuit on.

[SunEagle]

Just found this site by mistake and found it interesting so joined. We've been using lifepo4 energy packs for almost 6 years and was surprised to see the claims of them only having lives of 2-3 years. That's not our experience and we have a number of installations with life times of 4-5 years and our first pack, is nearly 6 years old and is used every day on job sites. None have suffered any loss of capacity and have changed the lives of those we have installed for. Now our customers cook using them, heat hot water and use almost whatever they want.

We only install lifepo4 now, gave up agm and gel almost 2 years ago when we'd proved the concept of lifepo4 in off grid installs. We also use lifepo4 on job sites instead of taking a genny with us because they work so well, providing much more energy and extremely rapid charging.

We carry 120ah packs and with one 250w solar panel, have power all day. We designed our own charge systems and are in the process of designing and building a real dedicated liffepo4 charge system that has no need for BMS or active cell balancing. Presently the solar charge controllers we are using, remove the need for a BMS and if our customers were intelligent enough, we wouldn't use BMS at all. However many customers have no idea how to use energy system properly, so we are making a charger which will control the system without any intervention. Currently we use active cell balancers and a BMS for customer installs, our own work pack have no BMS or balancing and they work fine on our solar charge controllers.

You could look at it this way, our first pack, has been used for at least 300 days a year for over 5 years working and on non work day, we use it for leisure and camping. In fact I use the dam thing for just about everything I need for power and carry it in the tractors on our farm. So it could be classed as cycling at least 1500 times. We don't see it that way, because of the charge/discharge parameters we use.

We also have lifepo4 as starter batteries in all our vehicle, work and personal. The two (24v) in the tip truck have been in use for over 4 years and they are amazing for staring engines, so much power they for instantly, except in very cold weather.

One thing we learnt early, is not to use big capacity cells. Our first commercial packs were 100ah cells, big mistake. When one cell collapsed, the entire system went down and we lost a lot of money using big brand cells and almost made us give up on lifepo4. So we went for 40-50ah military/industrial prismatic cells, which is what our first two packs consisted of and have not had a problem since.

Sounds interesting. I would like to know a little more about your energy packs. Although they seem a little small at 120Ah & 250watts to be be able to generate enough power for most off grid users or what most electric hand tools need to run which would be closer to 1000 watts.

[Sunking]

We carry 120ah packs and with one 250w solar panel, have power all day. We designed our own charge systems and are in the process of designing and building a real dedicated liffepo4 charge system that has no need for BMS or active cell balancing. Presently the solar charge controllers we are using, remove the need for a BMS and if our customers were intelligent enough, we wouldn't use BMS at all. However many customers have no idea how to use energy system properly, so we are making a charger which will control the system without any intervention. Currently we use active cell balancers and a BMS for customer installs, our own work pack have no BMS or balancing and they work fine on our solar charge controllers.

Careful when you say that there are two schills here who will castrate you for even thinking of NOT USING A BMS. Fortunately I think they have left and given up.

[PNjunction]

Presently the solar charge controllers we are using, remove the need for a BMS and if our customers were intelligent enough, we wouldn't use BMS at all. However many customers have no idea how to use energy system properly, so we are making a charger which will control the system without any intervention. Currently we use active cell balancers and a BMS for customer installs, our own work pack have no BMS or balancing and they work fine on our solar charge controllers.

Many of the problems stem from applying lead-acid methadology to LFP's differing chemistry. That is, thinking in terms of 100% SOC to XX% SOC, rather than being conservative at the top end, and of course using an LVD at the bottom.

One temptation left over from lead-acid is to become swayed by the "take them down to 20% SOC", and design a system once again around 100-20% SOC. That leaves you with no autonomy, and unnecessarily spending too much *time* at full charge when looked at from a calendrical total timescale which is harmful. Personally, I derate the stated cell capacity by 20% to start with just to give myself a bit of a hedge for daily-cycling calculated needs.

Top balance as we know is a total misnomer, as each cell has it's own capacity and internal resistance. Thus, spending time with bleed-off boards, especially if they are puny little bleeders, and don't present yet another failure point down the road, is a mind-game to slowly match voltages, which only means you are spending more time overall at a relatively high SOC, which LFP doesn't like sitting around in all day. It becomes self-defeating to become TOO anal about it - especially for our relatively comfy low-current conservative application.

Still, I use top-balance *for convenience*, but after an initial sanity check on the first few cycles, they spend their time without any bleeder board balancing at a much lower voltage, like 3.5v per cell under charge. Rested, they are all about 3.45v, but again, voltage is not the best indicator of cell health. Therefore, I try not to buy trash from e-bike / hacker retailers, but reputable dealerships - just like I do with lead-acid.

In the end, the discussion here is for relatively knowledgeable battery guys, and not necessarily taking into account trying to protect the guy next door like a manufacturer would. We aren't manufacturer's, but end-users. It is kind of like not worrying too much about the guy next door who buys a bank of Rolls-Surrette Pb batteries, and puts an automotive little battery tender on them and walks away for a few years, although we might have some advice upon seeing that.

One thing we learnt early, is not to use big capacity cells. Our first commercial packs were 100ah cells, big mistake. When one cell collapsed, the entire system went down and we lost a lot of money using big brand cells and almost made us give up on lifepo4.

I'd still like to know more details about that - such as manufacturer, model, age and so forth. Other things crop up like were the terminals which have dissimilar metals as contacts cleaned, tight, and perhaps a little coating of NoAlox / Penetrox and the like applied so there are no rogue high-resistance contacts?

[dax]

Sounds interesting. I would like to know a little more about your energy packs. Although they seem a little small at 120Ah & 250watts to be be able to generate enough power for most off grid users or what most electric hand tools need to run which would be closer to 1000 watts.

Don't use the 120amp packs for off grid homes and this is the 21st century, so the majority of our tools are all cordless and the packs mostly sit on the panel all day connected to the chargers with a 2000w PSW inverter. As 90% of our work is off grid, these packs save us a lot of money in time and infrastructure set ups.

[Sunking]

One thing we learnt early, is not to use big capacity cells. Our first commercial packs were 100ah cells, big mistake. When one cell collapsed, the entire system went down and we lost a lot of money using big brand cells and almost made us give up on lifepo4. So we went for 40-50ah military/industrial prismatic cells, which is what our first two packs consisted of and have not had a problem since.

You still have a problem and did not learn what the mistake was. You over discharged your battery, or you over charged them take your pick. The problem surfaced because you did not monitor the batteries an dvoltages. Cell size and format does not matter. Size only matters if you are a .......

[dax]

The brand of the 100amp cells, we tried were winston, none lasted more than 3 years, whilst our no brand chinese industrial grade cells, are still going after nearly 6 years and none of our installs using these 40-50amp cells have had a problem, other than wiring and small electronic failures. There have been a few bad cells, most get discovered before installing as we always run a pack for a week before it goes in.

Picked up my first 120amp pack at an overseas trade fair as they used them for demo's, so they were reasonable cheap for the time and we continue to use them for all our installs and at a much cheaper price compared to any of the brand names. There are also some safety reasons we don't use winston or other plastic encased cells, we learnt early on after a bush fire went through an area we had some installs. The plastic winston cells melted in the heat, whilst our metal cells didn't, but some of the cells buckled, yet still held full charge,

Our cell packs are connected via 3mm copper bar, balance our cells before installation, charge and take energy from 4 points of the pack, which makes a huge difference to keeping them in balance. Read here about bottom cell balancing, but it makes absolutely no sense to me and can't see how it would work with large lifepo4 packs. It may work on aa or aaa cells. To the best of my knowledge, our systems rarely ever get down to load cut off and if there is a load on the pack during charging, then they balance extremely well.

Our off grid systems range from 3kw solar, 1000amp lifepo4 up. The biggest we've installed was for hotel and that was 5000amp lifepo4 and 10kw of solar, backed by a 3kw wind generator and 6kva vegetable oil powered generator. They use the cooking oil from their kitchen to run the genny, saving a heap.

[Living Large]

Cell size and format does not matter. Size only matters if you are a .......

Whoa, daddy.

[SolarBen]

Hi!

I have an off-grid home with LiFePO4 cells and did this for the *exact* reasoning above - I use it for cooking and all power for my home. I designed the system around the cells, and used a Morningstar MPPT regulator in 'custom' mode.

My pack was US$7000 and came with BMS it is 300Ah 51.2V (nominal 48V)

Any questions?

Hello Steve, I would be curious to know how your LiFePO4 batteries have performed since you posted this message?

[SolarBen]

JOSCO yes standard adjustable output voltage PWM CHARGER..
Here is a repeat of that post explaining all..

IF anyone is interested this is how I have set up 3 x100ahr LiFePo4 batteries for charging by solar and for use with MSW inverter..
Im not claiming this is the correct way or even the best way to do it,, But dont tell me it wont work as all 3 systems been in use over 2 years now almost 3 years with NO PROBLEMS
Charger a 30a PWP 12v charger set to output 14.8v with no equalization..
Battery cell over charging 1x 3.9V 1watt zenner diode and 1x10ohm resistor across each cell
One low voltage sensor set to disconnect the inverter and anything else connected to the battery pack at 10v
Facts as found out the expensive way by me are if you discharge a cell below about 2.2 v it will be destroyed even if done just one time only.
If you over charge above about 4.4v they have a very short life.
If you look at charts from the manufacturesr you find there is little power above 3.8v and it stays fairly constant until about 2.5v then hits a brick wall.
So use between those 2 voltages and all is well with the world.
I have never found a MSW inverter that has problems with operating between 15.5v and 10.5 v and that is the usual specs given by most MSW invereter manufacturers..

Hello John, I would be curious to know how your LiFePO4 batteries have performed since you posted this message?

[dax]

You still have a problem and did not learn what the mistake was. You over discharged your battery, or you over charged them take your pick. The problem surfaced because you did not monitor the batteries an dvoltages. Cell size and format does not matter. Size only matters if you are a .......

Let me point out a few facts you probably won't understand, after reading just a few of your posts. Been a master builder for almost 40 years, did my first off grid solar install in 1982, using exide 2 volt 500amp batteries in rural NSW and since have done many over the years

Five years ago my company began installing lifepo4 instead of lead acid, after a year of experimentation and testing, to work out from all the garbage about them by so called experts, as to how they operated and the best voltage parameters for long service life. We installed our 2000th lifepo4 unit in August this year.

Currently we are doing 2-3 installs a week, which consist of new systems and replacing lead acid with lifepo4 and are in negotiations to take an entire town off grid next year. Once the logistics and permissions are in place and the economics are worked out, it should go ahead. It will be a pretty easy thing to do as the town happens to be at the end of the grid. There are a couple of logistical sticking points, but we are confident they can be overcome easily.

I'm not going to address your attempt at insulting me, or your silly claims of us over charging or discharging our cells as the problem with winston cells. Having not read many of your posts, will leave it to others to determine your veracity, but you have made some claims which I find rather insulting and shows your lack of working knowledge and experience of this chemistry.

You have claimed there are no dedicated lifepo4 solar charge controllers, except one very expensive low capacity piece of junk. For the last 3 years, we have been having manufactured dedicated lifepo4 solar charge controllers, of 40 and 60 amp and this year have begun offering them to the general public. Our 40ah charger retails for around $500, 60amp, $700, they are used in parallel up to 10 units and any number of banks. If you know how to use them properly, there is no need for bms or cell balancers. However our customer installs all have active balancers and bms, early next year we will have a dedicated solar charger which will have no need for any form of balancers or bms, as it will charge individual cell lines to their set capacity. They are single stage bulk chargers, which are designed to reduce cycling as much as possible so and extend life, without losing capacity.

Our experience has allowed us to work out the best approach for off grid systems and with 5 years actual working experience, we have it under control and are able to install economically sensible system for people. We have spent years getting to what we feel is a safe reliable and economic system, way different to others and it works properly.

I'm not an qualified electrician, but have 5 in my employ and a number of apprentices, all have qualifications in AC and DC, plus two electronics. This is because we no longer put in low voltage lifepo4 systems, they are all AC 240v, driven by 12v PSW inverters, using 24v panels. That enables us to walk in to AC established premises and change it over quickly and cheaply, utilising existing wiring. All that needs to be done basically is change the light globes to LED and teach the customer how to use their system.

[Living Large]

Hello John, I would be curious to know how your LiFePO4 batteries have performed since you posted this message?

You can PM these people to ask them questions. Both of them said they use BMS, which has been discussed here extensively in the past year. Wikipedia has an article on BMS that you may find useful:

https://en.wikipedia.org/wiki/Battery_management_system