battery information

[machinemaker]

I am starting to design and build an off-grid system for our homestead. Any references on types of batteries: books, web pages, articles? I find a lot of information from distributors, but it would be nice to get some unbiased, not a sales pitch.
Kent

[bigrockcandymountain]

https://www.fieldlines.com/index.php?action=profile;area=showposts;u=75786

Here is a long thread by scruff with lots of battery testing type stuff.  His conclusion is pretty much don't buy lithium. They are overpriced, overhyped, under delivering compared to lead.  I'll let him explain why.

I have a very basic flooded lead acid bank.  8 pcs 6 volt surrette rolls s550 in one string for 48v.  I think forklift batteries may be a better value from what i have read, but I am happy with what I have.  We are at 5 years and so far so good. 

Lead is very old technology and it almost seems impossible that it would still compete.

[Scruff]

"There are liars, cheats...and then there are battery salesmen"
- Rupert Murray Smith

Flooded 2V cells are the best battery you will get for a static application imo.
Old = proven.

LFP here
Lead....er...not too sure I've figured them out from here, here, and a decade of scrutiny.

Most sources on either don't really stand up.

Then there's 10s of other battery types.

[JW]

I have found AGM battery's suck and have a fault design that is too ready. 6v deep cycle battery always have twice the capacity over 12v.

[Scruff]

They do suck.

They're a 600 cycle finite electrolyte lump compared to a 1200 cycle water-cooled lump. Lauded as the dogs danglies because of the higher mark-up to resellers.
2 to 3 times more expensive than the ones that are better than twice as good.

Has anyone ever noticed that when vested interests compare Li-ion to lead they usually choose AGM in the lead corner? Not Flooded and definitely never flooded OPzS?...

AGM kool-aid producers moved to more expensive pastures.

[SparWeb]

I also support using lead batteries.

If you read my recent posts about my batteries, and maybe some of the stuff I will be writing soon about pulling them apart, then you might get the mistaken impression that I'm frustrated, or they're giving me a headache.  That's not really the case.  I just happen to be at the end of a very long lifecycle (~20 years!) which really is a gift, looking back on it.

I might also try getting old lead-acid batteries from recyclers, like the ones I have now, just in case I can be lucky again.

2021: https://www.fieldlines.com/index.php/topic,150357.0.html

2013: https://www.fieldlines.com/index.php/topic,148036.0.html

2009: https://www.fieldlines.com/index.php/topic,130251.0.html

2007: https://www.fieldlines.com/index.php/topic,136157.0.html

These batteries were old when I got them... 14 years ago!

[Bruce S]

I too am all for using Pb based batteries.
The recycling of them is already very matured and what better way to keep the Pb from just sitting around leaching into the ground?

If interstate batteries was still around here where they used to sell DIY batteries , I'd be all over that!
Our local recycler know me by sight from the amount of little 12V7A cells I keep bringing :-). I'm oe of the few he's still paying in cash!
 

SparWeb;
I don't know your location, but if you are anywhere near a marina. You might go ask them about the trolling batteries.
My Niece works for one, I bought 3 @25USD/ea of them from the reseller each weighing in at 30Kg/ea  and they are still kicking even on my lowly system that recently just expanded up a 200w 12V system.
I  use them mainly in the summer for my Alky system and aux power for the LED grow lights during the deep winter.

I can get you a pic of the battery if you'd like.
Will you be looking into re-configuring that pack with a failing cell into a different sized setup?
 
Cheers
Bruce S

[Scruff]

Indeed. I would not consider cell problems to be battery problems in a 2V cell built system SparWeb.

Something, something, baby, bathwater, moles & mountain hills...

[Scruff]

This data blows my mind..





~1000 days using the system
6 years.

0.14MWh used.
140Wh per day average (plus solar direct to load + butane + diesel + solid fuel)

You know what every camper needs?
3000 cycle batteries that don't work in the cold, or like alternators that are set up to deliver rated output.....for 5 weekends every year...

Less is more.

[Scruff]

...and another thing...the battery is overrated.

You're doing off-grid right when you're not using the battery. If you could power all your loads on demand like the national utilities have been doing since electrification it'd be more efficient and less expensive. The battery has many benefits but we ought to bare in mind that the systems are optimised in "direct drive" generator to load.

Hence we don't need better batteries, we need better generation injection.
Solar panels last 30years+ and are resellable.
Batteries last 2 >20 years and there's an efficiency tax on the hardware associated with using them.

The main reason how I could live on an average of 140Wh a day is every appliance I ran was DC. No inverter quiescent, no double conversion losses.
It's not scalable unless you have shares in a copper mine.

[machinemaker]

Thanks for all the feedback, still a bit confused. So, what do you suggest for volume of storage? I have reviewed our current grid usage and have an estimate of what we can harvest from a wind turbine and the micro-hydro potential here on the homestead. How many days reserve would you advise for backup? I figure that most of the year, except late summer we have nearly the same wind and creek flow, but there are times when the wind does not blow. I think solar is bit of a wild card with our days/weeks of grey skies.
It looks like most replies are for lead-acid batteries or am I reading the comments wrong?
kent

[bigrockcandymountain]

What is your grid usage now and how willing are you to conserve power when you are short?
I have 2 days storage in the batteries(10 kwh) and I'm quite happy with that. (428ah 48v fla) That is to 50% discharge.  Once or twice a year we might go lower.  We don't do laundry or cook with electricity unless we have lots though.  I also live in a very sunny, windy place so we have lots of power most days.  Your hydro should be similar i would think. 

You are correct most of us here like lead acid batteries.  Maybe there will be a discussion on type of lead.  Forklift vs L16 vs industrial vs agm etc.  There are quite a few choices for different price and capacity ranges.

I have L16s and i like them. They live in the basement so need to be small enough to haul by hand.  Otherwise a forklift battry might have been slightly better value. 

[Scruff]

Thanks for all the feedback, still a bit confused. So, what do you suggest for volume of storage?

A battery. Appreciating that 2:1 generation: battery is better than 2:1 Battery to generation.
ie oversizing the generation capability is money better spent than a big reserve.
Diesel to fill the gaps is expensive power.
If you do have a backup diesel, design it to run @ 80% duty.

How many days reserve would you advise for backup?

For a liveaboard 1 week moderate use. 3 weeks frugal use. Nominal daily generation 150% usage.
For a static application 10% per day.

I think solar is bit of a wild card with our days/weeks of grey skies.

I think you'll be surprised it's the cheapest power source on the market.

It looks like most replies are for lead-acid batteries or am I reading the comments wrong?

I got no loyalty to a battery.
I go for best cost per kWh lifetime with considerations to climate operating parameters, practical usefulness, system integration considerations and the usual safety concerns.
Flooded batterys are hard to beat but sometimes the weight and spill risk bias one to a more expensive less performance based battery. Eg. LFP / AGMs on racing sailboats.

I have 2 days storage in the batteries(10 kwh) and I'm quite happy with that. (428ah 48v fla) That is to 50% discharge.

  I have half a day's storage in the batteries (10kWh)and I'll probably at least 3x that. (800-ish Ah 24v mixed AGM + GEL) That is to 50% discharge.
All of them are freecycled bar 80Ah that's from a linked system.

[Scruff]

I am starting to design and build an off-grid system for our homestead.

I have reviewed our current grid usage...

As in the existing homestead or a new build?
In terms of efficiency off-grid isn't anywhere as green as grid-tied.
It does not make sense to take a grid-tied installation off-grid.

In certain cases there's exceptions like we waste less when we have less or have to make it.
In most circumstances, successful off-grid isn't about sustainability as much as it is "the only alternative."

It's pretty easy to design an off-grid-tied system.
If you filter all your DIY off-grid hardware with a single tickey box hybrid inverter (legality depending on regional rules) you'll do better by the world and your pocket.

Off-grid-tied does not require a substantial battery, the generators never have to be curtailed, oversizing is optional, utility power is cheaper and cleaner than diesel and petrol gensets, the rest of the network can use your excess power instead of dumping it or throttling it, your green power exported to your neighbours is offsetting fossil fuel burning at the utility power plants.
It's super reliable and lower maintenence.

[bigrockcandymountain]

I thought about doing an off grid tied here after i knew a bit more about this stuff.  The grid is only 300m away.  A 20a line at 240v would be plenty to both import and export power.  If it wasn't for red tape, a $30/month charge for the base rate, and a crappy price for power sold back to the grid i might consider it.

 The way it is now we use almost 100% of our generated power, the excess going to water heating.  We also only used diesel a total of 3 hours this year, so that's not really a problem either. 

I'd suggest you do some solar if you are off grid too.  Even in moderate cloud they make some power and with prices right now, it's pretty easy to oversize.  Solar is also incredibly, almost boringly reliable.  Wind and hydro not so much. 

[JimOK]

I just switched from lead acid to LiFePO4 Lithium. Unlike their predecessors (Lithium Ion), the LiFePO4 are much safer. The RV industry is starting to switch over due to weight and life expectancy. Price has come WAY down. More expensive than lead acid up front. Average in the life expectancy, they are less expensive. Expected life is 5000 cycles. They do not sulfate. You can leave them at a partial charge for weeks with no worries. No more depth of discharge concerns. You can use 90% of the rated capacity with no concerns. I am replacing two banks of T105 6 volt lead acid batteries. These were rated at 225 Ahs. Two banks gave me a rating of 450 Ahs. We are limited to a 50% depth of discharge on lead acid. So we are back to 225 Ahs usable. They really need to be full charged every day or two to prevent sulfation. I paid $110 per battery seven years ago. They are $125 each now. Sixteen batteries would have cost $2000. I bought thirty two 272 Ah cells (3.2 volts each) from China for $4233 delivered. It takes sixteen cells to make a 48 volt nominal bank. Two banks gives me 544 Ahs, of which 90% is available. That's 490 Ahs, compared to 225 originally. I don't have to worry about long periods of discharge. At 5000 cycles, I should get 15 to 20 years of service. Don't have to add water. They do not need ventilated.
They are not without issues. These are not the heavy duty lead acid cells we are used to. They are about half the weight. They come in smaller rectangular 3.2 volt cells, with small 6mm studs. They need a battery management system (BMS) ($150) to keep the from being over charged or over discharged. Draining them below 2.5 volts per cell will kill them. Charging them above 3.65 volts per cell will kill them. Charging them when the cells are below 32 degree F will kill them. They need to be installed in a confinement rack, and preferably under compression. Like any battery, they like to be kept at 70 degrees F. They need to be kept above 32 degrees.
If I bought the T105s for $2000, the life expectancy would be 7 years or $286 per year, or $1.27/Ah/year. LiFePO4 at $4233 for 15 years is $282 per year, or $0.52/Ah/year. If they go 20 years, I am ahead ever further. More capacity, no adding water, no sulfation.
Just my two cents worth. Trying something new. It may be a bust.

[clockmanFRA]

Please find below a little document i have put together from 2 long time users of Li-Ion and LifePO4.

Both these guys have actual experiences, you may find their comments useful.

NEW BATTERY TECHNOLGIES FOR OFF GRID, 2021.

This is the present situation from Off Grid folk and installers from around the World.  The 2 responses are from folk that actually have working systems of many years duration.

QUESTION asked ……

Hi all,
I am trying to get a better understanding of energy storage system design with lithium ion batteries. I work in developing countries where lithium ion batteries are still very uncommon outside of plug-and-play PV systems, but are likely to become more prevalent in the coming years. I only have experience with BMZ and Sonnen from years ago in the states. A few questions that I hope might lead to an interesting discussion:
1. It seems like LiFePo is the preferred chemistry for off-grid applications. It seems like Discover and SimpliPhi are popular and produce a good product. Are there other recommended brands? Any thoughts for what would be the most appropriate for smaller, very remote installations in the developing world?
2. Is anyone using NMC batteries here? If so, what brand?
3. Are there any other lithium-based chemistries that are currently commonly used for off-grid applications or will be in the future? Any that might be particularly interesting for developing country applications?
4. Is it possible to develop design general guidelines for energy storage system sizing with lithium ion batteries like has been done with lead acid batteries? Lead acid batteries definitely vary in their parameters by manufacturer, but there are some guidelines (DoD/cycles and charging/discharging current) that seem to hold reasonably consistent for AGM/Gel/FLA that can be used for design purposes.
Could this be done with the major lithium chemistries or do you see them as varying too much between manufacturer? For example:
LiFePo:

•   SimpliPhi recommends a maximum C/2 charge and discharge rate. Claims a useable DoD of 100%. Recommend an 80% DoD for best cycle life. Claims around 98% roundtrip efficiency.
•   Discover recommends a maximum C/1 charge and discharge rate. Claims a useable DoD of 90%. Claims around 98% roundtrip efficiency.
•   Blue Planet Energy recommends a maximum C/2 discharge rate. Claims a useable DoD of 100%. Claims around 98% roundtrip efficiency.
Would it work to use general sizing parameters for LiFePo like:
•   Maximum charge/discharge of C/2. (Is this reasonably consistent?)
•   Recommended DoD 80% (Would provide a storage buffer. Does this tend to provide best LCOE?)
•   Roundtrip efficiency 98% (Should this be more conservative?)
•   Minimum charging temperature 0C.
Any/all thoughts welcome!

RESPONSE  No1,,,,,,,,,

1) Lead acid batteries are forgiving, and generally "die" gracefully

2) Li batteries are unforgiving.   1 overcharge or 1 deep discharge, and they are toast.   Might get a few more cycles out of them before they die, but either condition damages the battery.

3) LFP / LiFePo / LP4 (all the same battery, just different abbreviations) are the "safer" batteries that tend to just fail, or swell up and stink.   Any of the other Li chemistry mixes, involve failure with fire or going bang.

4) Some Mfg's include the top and bottom 10% safety margins internal their BMS systems.
 Some don't and you have to program that into your loads and chargers.  Your Mileage May Vary. Some rate the full capacity, but only deliver 70% of capacity.
 Lead acid batteries like 50% -100%, so same protocols will NOT work for each.

RESPONSE No 2………….

Each lithium type has its advantages and disadvantages, mostly related to energy density, specific power, life expectancy, performance, cost and safety. LiFePo4 is more of a compromise, it isn't the lightest nor can it deliver the current some others can however they are one of the safest, which is why they are a popular choice. The pre-assembled batteries or battery systems are roughly double the price of building a bank using prysmatic cells, some system can be integrated with other equipment, inverters etcetera, able to communicate information from the BMS regarding state of charge.

2. There are some I believe who are using NMC in the form of Nissan leaf batteries

3. Generally, a battery is chosen for a specific application, LIPO for example is extremely light with high performance capabilities, which is why they are the choice for drones, they are however dangerous, since weight is not as important but safety is makes LiFePo4 an ideal choice for off grid. There are variations even within that LFP made to enhance certain aspects of performance, according to some articles I've read. Not sure there is anything specifically available for developing countries but one thing is known, lithium batteries do not perform in temperatures below 0°C.

4. There are some manufacturers of drop in replacement type LFP who advertise that their battery can be discharged to 100% of the listed capacity, but in fact the actual capacity is greater, the BMS cuts the load when ~20% to protect against damage. Simpliphi has different warranty periods for differing charge /discharge levels, it is good practice when building a DIY bank to keep within certain parameters, commonly 90% and 20% of capacity. This extends the cycle count expectancy, programmable BMS's are available which can be set to whatever value is desired, but manufacturers will be cautious to preserve their reputation, one would hope.

My grateful thanks to these 2 contributors who have kindly allowed me to use their responses.

Note,  I believe there is merit in these new technologies, but getting actual empirical evidence from working systems for long-term reliability is another matter.

[JimOK]

1) Lead acid batteries are forgiving, and generally "die" gracefully.

Unless you accidentally run them dead one time, then they lose capacity and start dying pretty quick.

2) Li batteries are unforgiving.   1 overcharge or 1 deep discharge, and they are toast.   Might get a few more cycles out of them before they die, but either condition damages the battery.

Same as lead acid. Many expensive L16s have been run dead by accident. Their 15 year expectancy dropped to 1 or 2 years. That's why I stuck with the 6 volt golf cart batteries. Just in case I screwed up. Been known to happen.

3) LFP / LiFePo / LP4  are the "safer" batteries that tend to just fail, or swell up and stink.

Swell up and fail is a 'true' statement. Most LiFePO4s are made in China. They do not advertise that the battery needs to be caged and compressed. But, when push come to shove, they will admit this. All of their test data on prismatic cells are in a test cage with 12 psi applied the sides of the cell. Without a cage and compression, the cell will swell. The swelling causes internal cell damage and drastically shortens cell life. The cage and compression is a 'pain in the neck'. Once you assemble a bank, you don't move them easily.

 4) Some Mfg's include the top and bottom 10% safety margins internal their BMS systems.
 Some don't and you have to program that into your loads and chargers.  Your Mileage May Vary. Some rate the full capacity, but only deliver 70% of capacity.
 Lead acid batteries like 50% -100%, so same protocols will NOT work for each.

LiFePO4 batteries operate from 2.5 volts to 3.65 volts. Lead acid battery protocols will not work for LIFePO4 batteries. Totally different chemistry. Totally different characteristics. These cells have proven to deliver 100%+ of their rated capacity between these two voltages. My research and experience shows that they have a very flat charge/discharge curve at 3.2 volts over most of there capacity. When you approach the end of discharge, the voltage drops off quickly from 3.2 volts to 2.5 volts. The same on the charge side. The voltage slowly rises from 3.2 volts to 3.4 volts. Then the last 5% of the charge cycle, the voltage rapidly rises to 3.65 volts. If you limit the operating voltage zone of the battery from 3.0 volts to 3.4 volts, you will get 90% of the rated capacity every cycle AND you will avoid the over charging and over discharging associated with early cell death. These are programmed into the LiFePO4 chargers and BMS. The BMS is the safety device to protect the battery and ensure long life. I also program these charge parameters into my solar charger and inverter.
I am still fairly new to LiFePO4 batteries (9 months). I have done a lot of research. So far they are performing well.
I will keep you posted as time goes by. I am not afraid to admit I was wrong, if and when they fail. Keeping my fingers crossed.
Hopes this helps to understand the LiFePO4 prismatic batteries better. Just a note. The cage and compression does not apply to the round cylinder cells. Only the rectangular prismatic cells.

[clockmanFRA]

Hi JimOK,

And welcome to this forum.

Yes please, always good to get feedback from real users about the long term work and use of LiFePO4 batteries.

[machinemaker]

Thank you for the information!! I am still reading and working through the material. I had to come in to work today, just to have someone onsite, so I have spent the morning reading and pulling some ideas to together. If any of you are within a half a days drive of western PA and have an existing system or want some help installing, message me and I would be glad to make a visit.
Thanks, kent