The Electric Revolution

[Jack by the hedge]

... LFP (also known as LiFePO4) are far more stable and extremely unlikely to go into thermal runaway (ie catching fire), and LYP (LiFeYPO4) are practically impossible to get go into thermal runaway at all...

<new to all this> Ah. So "LiFePO4" is "LFP". Our newly installed battery says its type is "LifePO4 Prismatic Cell".

I'm just finding my way with stuff like its recommended minimum SoC. Manufacturer says 10% but I don't know if it's a case of "that's what they would say" or if that's good advice for a long, reliable life.

 

[Ivor the Engineer]

<new to all this> Ah. So "LiFePO4" is "LFP". Our newly installed battery says its type is "LifePO4 Prismatic Cell".

I'm just finding my way with stuff like its recommended minimum SoC. Manufacturer says 10% but I don't know if it's a case of "that's what they would say" or if that's good advice for a long, reliable life.

It's a trade-off. What's the period of the warranty on the battery?

 

[Jack by the hedge]

It's a trade-off. What's the period of the warranty on the battery?

10 years.

 

[Ivor the Engineer]

10 years.

If it's been provided by a reputable company such as Octopus Energy then expect it to last at least that long under normal use. The battery management system will prevent you from significantly affecting the lifetime below the warranty period.

 

[acbytesla]

If it's been provided by a reputable company such as Octopus Energy then expect it to last at least that long under normal use. The battery management system will prevent you from significantly affecting the lifetime below the warranty period.

They likely will last much longer. But hold slightly less electricity. The same is true for the panels. Supposedly 1.5 percent each year. I haven't seen it though on my install.

 

[acbytesla]

Something is happening in the development of batteries that is increasing their development exponentially faster. That is the ability to test new battery chemistries much faster than ever before. The combination of cheaper faster computers and sheaper better electron microscopes allows scientists today to see what happens in real time at an atomic level.

I don't believe it's just my naturally over-optimistic view that 10 years from now, some batteries will have 5 times plus the energy density and other batteries will be a 10th the cost. Just not necessarily the same battery chemistry.

 

[Rolfe]

Newsflash: Other countries don't all have the same mix of renewable sources. For example, some countries such as the UK have lots of wind power, which still provides plenty of energy even when the sun goes down. Thus it makes sense to encourage people to store this energy during off-peak hours to keep the wind farms economical and reduce the peak loading on the national grid, as consumers can use energy they have stored locally at non-peak time to meet their energy needs during peak time.

This is exactly what Rolfe is doing and what the energy companies and the grid want people to do, which is why they still offer the electricity cheap.

I suspect it would probably be advantageous to the grid if I exported a bit earlier than 10 pm to 11.30 pm which is what suits me best. But without an incentive, or even actual confirmation that this is the case, I'll just go on with what I'm doing. If Octopus repeats its (cunningly disguised) offer from last year to get people to export for an hour during the evening peak, I will certaily do it.

 

[Rolfe]

If it's been provided by a reputable company such as Octopus Energy then expect it to last at least that long under normal use. The battery management system will prevent you from significantly affecting the lifetime below the warranty period.

Mine is a GivEnergy product. I don't expect to run into problems. As @acbytesla said, and I remarked earlier, the effect if it happens is just somewhat reduced capacity, and since I have way more capacity than I actually need, it's not an issue. This battery is going to last well into the time in the future when replacements will be maybe a couple of hundred pounds.

I molly-coddle my e-bike battery (NMC, I think) a bit (to the point of taking a bike ride yesterday I didn't really want because I'd inadvertently charged it to 100% and it ain't good to leave it sitting at 100% for a week). I have a bit of a care for my LFP car battery even though it's pretty robust. I think my home battery can take what it's being asked to do.

 

[Jack by the hedge]

... I don't believe it's just my naturally over-optimistic view that 10 years from now, some batteries will have 5 times plus the energy density and other batteries will be a 10th the cost. Just not necessarily the same battery chemistry.

Yeah, I rather assume by the time we're thinking of replacing any components in our system it'll be because something significantly better is irresistibly cheap. The panels themselves have a decent chance of outlasting me.

 

[Ivor the Engineer]

I suspect it would probably be advantageous to the grid if I exported a bit earlier than 10 pm to 11.30 pm which is what suits me best. But without an incentive, or even actual confirmation that this is the case, I'll just go on with what I'm doing. If Octopus repeats its (cunningly disguised) offer from last year to get people to export for an hour during the evening peak, I will certaily do it.

Yep! ETA: https://www.cse.org.uk/advice/getting-smarter-with-energy/

 

[acbytesla]

Mine is a GivEnergy product. I don't expect to run into problems. As @acbytesla said, and I remarked earlier, the effect if it happens is just somewhat reduced capacity, and since I have way more capacity than I actually need, it's not an issue. This battery is going to last well into the time in the future when replacements will be maybe a couple of hundred pounds.

And with my recent reading, I'm not convinced that it actually negatively affects the battery. The common belief has always been that it reduces the longevity of the battery. But recent data suggests extreme cycling can repair batteries. But I'm also not sure I would embrace this finding just yet.

 

[Rolfe]

Yep! ETA: https://www.cse.org.uk/advice/getting-smarter-with-energy/
View attachment 65050

The offer was a perk if you used less than you usually did during a peak evening hour. I thought it didn't apply to me because I don't use any mains electricity at that time anyway. The house is running on the battery. It was only later that someone explained to me that if I  exported say 4 kwh during that hour I'd get credited with using 4 kwh less than usual, and I'd get the 60p export payment as well.

 

[Dabop]

<new to all this> Ah. So "LiFePO4" is "LFP". Our newly installed battery says its type is "LifePO4 Prismatic Cell".

I'm just finding my way with stuff like its recommended minimum SoC. Manufacturer says 10% but I don't know if it's a case of "that's what they would say" or if that's good advice for a long, reliable life.

Prismatic cells are what mine are too (except LYP/LiFeYPO4- doped with Yttrium to give better extreme temperature handling ability and even longer service life- but costs a bit more than LFP and not quite as energy dense ie bigger/slightly heavier than LFP for the same energy storage)

Running down to 10% is a heavy discharge- and will have a notably shorter service life/number of charge cycles- most cell manufacturers (which is NOT the 'battery' manufacturer in most cases btw) recommend 20% as the minimum, and 30% for better service life- this actually applies to ALL types of batteries- the deeper the discharge the shorter the service life.... (some claim 100% discharge is possible on LFP- if they say this- walk away.... what else are they lying about...)

Discharging to 10% is a common tactic in the cheaper end of the market- it makes the apparent capacity of the battery pack look bigger- and thats always a good sales tactic to people who don't know any better...'WE got a 22kwh battery pack, the 'other' lots is only 19.9kWh' what they don't say is that they are both using identical cells internally, and by driving them that much harder- you are losing 1000-2000 extra charge cycles and the entire pack will need to be replaced that much earlier!!!


Using my own banks datasheets as an example- look at the difference in cycle life between discharging to 80% every time (5000 charge cycles) and instead only going down to 30% left or 70% DOD (depth of discharge) which takes them out to 7000 charge cycles minimum!!!! (cycled daily, 7000 cycles is 19.6 years lol)

Remember that LFP has slightly less charge cycles (3000-5000) but heat can kill them faster (which is why i went the LYP route- it gets bloody hot here in summer- 40-45C for weeks/months on end...and sometimes hotter- that can take literally a thousand or more charge cycles off the service life of a LFP bank!!!


Deep cycling is always bad for service life- 'some' think that extreme discharge RATES are the same as deep discharging- nope- deep discharge (down to 10% DOD left) is ALWAYS bad- occasional high current discharge rates on the other hand do have SOME theory to support them at least- it can break down dendrite growth and surface contamination/doping of the plate surface- which can indeed extend the service life- this however does come with a 'Buuut...' caution- the discharge rate has to be high- but not 'too' high that it damages the cell itself- its a 'juggling act'

 

[Jack by the hedge]

Thanks. The battery spec says >4,000 cycles at 10% min SoC. I think I might nudge that up to 20%. Heat will not be a problem. Cold might be, for a few days a year, but the battery has an integrated heater for that.

 

[acbytesla]

Deep cycling is always bad for service life- 'some' think that extreme discharge RATES are the same as deep discharging- nope- deep discharge (down to 10% DOD left) is ALWAYS bad- occasional high current discharge rates on the other hand do have SOME theory to support them at least- it can break down dendrite growth and surface contamination/doping of the plate surface- which can indeed extend the service life- this however does come with a 'Buuut...' caution- the discharge rate has to be high- but not 'too' high that it damages the cell itself- its a 'juggling act'

I have always babied my batteries. A habit I developed with my old deep cycle 6 volt lead acid batteries that I used on my RV before I switched to Lifepo. I tried to keep them always charged above 70%. I try and keep my Lifepo batteries above 50% which is hard to do here during the winter months. Seeing it drop to 25% SOC happened a few times last winter. And once two years ago it dropped so low that everything shut down. So I think I'm doing it right.

That said, I think the scientists are developing a better understanding not just how to maintain batteries better but what happens under during different charging cycles. Things like ability to hold a charge and dendrite formation. And that we might see new recommendations on how to best maintain our batteries

Here's a video on the subject.
.

 

[Ivor the Engineer]

Thanks. The battery spec says >4,000 cycles at 10% min SoC. I think I might nudge that up to 20%. Heat will not be a problem. Cold might be, for a few days a year, but the battery has an integrated heater for that.

...or just over 10 years given 1 cycle per day. What was that warranty period again?

 

[Jack by the hedge]

...or just over 10 years given 1 cycle per day. What was that warranty period again?

What's the point of a 10 year warranty if it lasts 10 years and 1 day then drops dead?

Let me rephrase that: what's the point to me of etc etc. I'd be happier if the battery lasted 15 or 20 years. But if the cost of achieving that is that my 5kWh battery only has 3.5kWh useable, then maybe it's not really worth babying it. Especially if a replacement in 10 years is going to be half the price.

 

[Ivor the Engineer]

What's the point of a 10 year warranty if it lasts 10 years and 1 day then drops dead?

Let me rephrase that: what's the point to me of etc etc. I'd be happier if the battery lasted 15 or 20 years. But if the cost of achieving that is that my 5kWh battery only has 3.5kWh useable, then maybe it's not really worth babying it. Especially if a replacement in 10 years is going to be half the price.

It's not going to drop dead. It will lose capacity. Batteries in the future will be better and less expensive. The optimum is very difficult to determine, since babying it will also cost you money in lost revenue or increased purchase of electricity from the grid. There's also the intangible cost of losing the time you could have spent doing something rewarding rather than stressing over whether your home battery is at 15.1% or 17.95% SoC.

 

[acbytesla]

What's the point of a 10 year warranty if it lasts 10 years and 1 day then drops dead?

Let me rephrase that: what's the point to me of etc etc. I'd be happier if the battery lasted 15 or 20 years. But if the cost of achieving that is that my 5kWh battery only has 3.5kWh useable, then maybe it's not really worth babying it. Especially if a replacement in 10 years is going to be half the price.

My attitude was different 6 years ago when a 100ah 12 volt battery was $800. And now I can buy a 400ah battery for less than $500. And 2 years from now, likely around $250.

 

[acbytesla]

My panels are giving me close to zero the last couple of days and it might be a week before they generate anything more than 1 kilowatt a day. Gray and overcast, forecast shows atmospheric river overhead and non-stop rain for a week. Time to go into super conservation mode. And maybe fire up the generator.