LiFePO4 - The future for off-grid battery banks?

[lkruper]

couldnt get reply with quote to work, but the info I posted is a direct cut and paste from the online brochure.

Quote did not work for me either. So, how did they come up with 27 years?

[Bala]

<<< WHY USE LITHIUM
It’s simple it lasts much longer the SFK 1000AHA
battery can charge and discharge up to 1100 times
at 50% depth of discharge at one cycle a day that’s
a 27 Year life span
That’s more than twice that of a top quality gel-cell
and up to FIVE times that of a cheap wet cell or AGM
battery >>>

What planet has a year made up of only 40 days?

1100 cycles / 365 days = 3 years life expectancy at 50% DOD

Are you sure this is not a 2.7 year life span here on planet earth?

couldnt get reply with quote to work, but the info I posted is a direct cut and paste from the online brochure.

[lkruper]

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.

Are you saying that your company has 1000s of LIFEPO systems that have been working for 5 years and have undergone 1825 cycles and are still going strong? Can you give more specifics about where these batteries came from and how much they cost? Can you identify your company? Do they advertise these batteries and your success rate, because what you report sounds quite sensational.

[lkruper]

<<< WHY USE LITHIUM
It’s simple it lasts much longer the SFK 1000AHA
battery can charge and discharge up to 1100 times
at 50% depth of discharge at one cycle a day that’s
a 27 Year life span
That’s more than twice that of a top quality gel-cell
and up to FIVE times that of a cheap wet cell or AGM
battery >>>

What planet has a year made up of only 40 days?

1100 cycles / 365 days = 3 years life expectancy at 50% DOD

Are you sure this is not a 2.7 year life span here on planet earth?

[Bala]

I was browsing last night to see what warrantys are offered on the units supplied complete.

if they come with bms Lvd etc etc then there really should be nothing a customer can do to them to damaged them unless they leave them flat for a very long time. So suppliers should be able to give a good warranty, trouble is there would be no service dealer near where i live. So they would likely charge to travel.

I didnt spend a lot of time on it but did find this gem.


WHY USE LITHIUM
It’s simple it lasts much longer the SFK 1000AHA
battery can charge and discharge up to 1100 times
at 50% depth of discharge at one cycle a day that’s
a 27 Year life span
That’s more than twice that of a top quality gel-cell
and up to FIVE times that of a cheap wet cell or AGM
battery

[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

[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.

[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?

[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?

[Living Large]

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

Whoa, daddy.

[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.

[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]

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.

[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?

[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.