Nickel Iron vs. Lead Acid - Off Grid battery debate

[Mike90250]

Let's stay civil gents. NiFe only goes 10 years, then you have to refresh the electrolyte That cost me a couple grand for lab grade chemicals (lab grade needed if you want a long life.)

There is also the convenience factor, of I really never worry about the batteries, I just run the genset enough in winter (90 minutes, 3 pints of diesel)) to get one more day.

[johnpearcey]

And NiFe are a factor of ~7... So you'd buy lead-acid if they were 1/5th the cost but they're 1/7th the cost? So why did you buy NiFe?



Energy is energy. You can use 100kWh in the winter to make up for the worse round-trip efficiency of NiFe or ~50kWh keeping lead acid in absorption for the prescribed time.... numbers.

It's silly to think that NiFe is going to save fuel. They don't make energy. If your panels aren't producing enough energy to keep lead-acid batteries topped up then they're not going to make enough energy to keep the lights on with NiFe. You're either going to burn fuel charging lead-acid or burn even more fuel keeping the lights on.

I gave you an example of how NiFe saves fuel. Go back and read it.

[nwdiver]

Told you. Factor of 5. See my last post. You either get it or you don't. I'll say no more on the matter.

And NiFe are a factor of ~7... So you'd buy lead-acid if they were 1/5th the cost but they're 1/7th the cost? So why did you buy NiFe?

In miserable cloudy parts of the world, NiFe wins hands down.

Energy is energy. You can use 100kWh in the winter to make up for the worse round-trip efficiency of NiFe or ~50kWh keeping lead acid in absorption for the prescribed time.... numbers.

It's silly to think that NiFe is going to save fuel. They don't make energy. If your panels aren't producing enough energy to keep lead-acid batteries topped up then they're not going to make enough energy to keep the lights on with NiFe. You're either going to burn fuel charging lead-acid or burn even more fuel keeping the lights on.

[johnpearcey]

.... yeah.... all that adds up to a longer life. NiFe is an invincible battery that lasts forever. I'd pay ~3x more per Ah for that... not 7x more.

I've probably gone a couple weeks without a complete absorption cycle but I don't make a habit of it and the batteries are still working. It's not like doing this once, twice or 3 times immediately destroys the battery. It just gradually reduces the life. If the reduction from 'improper' use is less than the calendar life then it really doesn't matter and the battery will still last ~8 years. I really only needs to last ~6 or so.

Lets run a simulation; My choices where 200Ah of NiFe for $9200 or 400Ah of Lead-Acid for $3000

I start with $9200 and replace the lead acid every 8 years. Historically I earn on average ~7% in index funds.

Year	NiFe	PbSO4
2019	0	$6200
2021	0	$7098
2023	0	$8126
2025	0	$9304
2027 Replace	0	10652 - 3000 = $7652
2035 Replace	0	13161 - 3000 = $10161
2043 Replace	0	17477 - 3000 = $14477
2051 Replace	0	24901 - 3000 = $21901
2059 Replace	0	37670 - 3000 = $34670

Compound interest is the 8th wonder of the world. So given this situation you'd still choose NiFe? What if 400Ah of Lead-Acid was $2k? $1k? At what price would it win in your mind? Economics matters.

As far as fuel burn for battery maintenance... let's think about this. With NiFe you get ~0.6w for every 1w that goes in. With Lead-Acid it's ~0.8w including the energy used for absorption cycles. NiFe is invincible but even NiFe can't create energy. So whatever extra fuel you'd be using to properly charge lead-acid you'd be using anyway to keep the lights on with NiFe.

Told you. Factor of 5. See my last post. You either get it or you don't. I'll say no more on the matter.

[johnpearcey]

.... no.... with any quality lead-acid you'd need ~2x the capacity to get 8 years.

And the charging is an energy issue which IS efficiency. If 10kWh only gets your to 95% with NiFe then 7kWh would get you to 100%. You'd need less energy to get to 100%.

So if a lead acid battery was 80% cheaper per Ah you'd buy lead acid? 'Cause that's about what I faced. I paid $6/Ah for the L16s because NiFe was $46/Ah. >7x more expensive.

Absorption charging issues are lead-acids best kept secrets! For example: I use about 30Ah over night from my NiFe bank. If there is no sunshine the next day I can put back the charged used by running the generator. With NiFe you charge at constant current usually at C/5. For me I would charge at 16Amps. The charge efficiency is 80% which means I'd run the generator for 2.34hrs. That would cost me 1.64EUR. If I were using lead-acid I'd need to charge for 10hrs and the diesel cost would be 7EUR. That's over 4x the cost to recharge. I could of course decide not to charge at all that day and wait another day - then I have to double my lead-acid bank size to ensure that the usage does not go further than say 30% DOD. Then I can charge the next day, again for 10hrs. If I go 5 days like this then I'd need 5x the lead-acid bank size. On the 5th day, running the generator for 10hrs to fully charge the lead-acid bank would be about the same as 5 daily charges for NiFe. And it is very common where I live to get 5 straight days of zero sunshine. This is why I use a 5x factor with lead-acid. I paid 2.2k EUR for 80Ah NiFe which would equate to 400Ah lead-acid at a cost of over 3kEUR. And I don't have to change my batteries in 5 years time (because they wouldn't last 8yrs with that kind of usage). In miserable cloudy parts of the world, NiFe wins hands down.

[nwdiver]

Nope. There is absolutely no worry about damaging them (unless you boil them dry)
Partial charge for 2 weeks (clouds/rain) No worry
Cold no worry (as long as you planned ahead for the capacity reduction EVERY battery experiences when cold) They can't freeze where most humans live.
Heat - affects all batteries negatively.
over charge If you don't melt them, just add more water

I add about 15 gallons every 3 months. The batteries have large water freeboard above the plates. The ^automatic^ watering system took a lot of effort out of pulling caps, using a funnel, cleaning caps and on to the next. I was spending 2 hours every month. Now I spend about 4 hours every 3 months.

I too, am located in a winter gloom zone, storms come in for 6-12 days at a time, and not needing to burn fuel to complete Absorb is a godsend.

.... yeah.... all that adds up to a longer life. NiFe is an invincible battery that lasts forever. I'd pay ~3x more per Ah for that... not 7x more.

I've probably gone a couple weeks without a complete absorption cycle but I don't make a habit of it and the batteries are still working. It's not like doing this once, twice or 3 times immediately destroys the battery. It just gradually reduces the life. If the reduction from 'improper' use is less than the calendar life then it really doesn't matter and the battery will still last ~8 years. I really only needs to last ~6 or so.

Lets run a simulation; My choices where 200Ah of NiFe for $9200 or 400Ah of Lead-Acid for $3000

I start with $9200 and replace the lead acid every 8 years. Historically I earn on average ~7% in index funds.

Year	NiFe	PbSO4
2019	0	$6200
2021	0	$7098
2023	0	$8126
2025	0	$9304
2027 Replace	0	10652 - 3000 = $7652
2035 Replace	0	13161 - 3000 = $10161
2043 Replace	0	17477 - 3000 = $14477
2051 Replace	0	24901 - 3000 = $21901
2059 Replace	0	37670 - 3000 = $34670

Compound interest is the 8th wonder of the world. So given this situation you'd still choose NiFe? What if 400Ah of Lead-Acid was $2k? $1k? At what price would it win in your mind? Economics matters.

As far as fuel burn for battery maintenance... let's think about this. With NiFe you get ~0.6w for every 1w that goes in. With Lead-Acid it's ~0.8w including the energy used for absorption cycles. NiFe is invincible but even NiFe can't create energy. So whatever extra fuel you'd be using to properly charge lead-acid you'd be using anyway to keep the lights on with NiFe.

[Mike90250]

...........Here's the point I realized. The only real benefit to NiFe is lifespan. .........

Nope. There is absolutely no worry about damaging them (unless you boil them dry)
Partial charge for 2 weeks (clouds/rain) No worry
Cold no worry (as long as you planned ahead for the capacity reduction EVERY battery experiences when cold) They can't freeze where most humans live.
Heat - affects all batteries negatively.
over charge If you don't melt them, just add more water

I add about 15 gallons every 3 months. The batteries have large water freeboard above the plates. The ^automatic^ watering system took a lot of effort out of pulling caps, using a funnel, cleaning caps and on to the next. I was spending 2 hours every month. Now I spend about 4 hours every 3 months.

I too, am located in a winter gloom zone, storms come in for 6-12 days at a time, and not needing to burn fuel to complete Absorb is a godsend.

[johnpearcey]

.... no.... with any quality lead-acid you'd need ~2x the capacity to get 8 years.

And the charging is an energy issue which IS efficiency. If 10kWh only gets your to 95% with NiFe then 7kWh would get you to 100%. You'd need less energy to get to 100%.

So if a lead acid battery was 80% cheaper per Ah you'd buy lead acid? 'Cause that's about what I faced. I paid $6/Ah for the L16s because NiFe was $46/Ah. >7x more expensive.

As I said, it's a charging profile issue not efficiency. You've continually missed this point. It's the extended length of time a lead-acid needs to top up. That's where the cost of running a generator is prohibitive. And 2x capacity would not protect you against this, you'd need a lot more, more like 5x.

[nwdiver]

I'd probably need around 5x the capacity of lead-acid to stand even a chance to reach 8yrs.

.... no.... with any quality lead-acid you'd need ~2x the capacity to get 8 years.

And the charging is an energy issue which IS efficiency. If 10kWh only gets your to 95% with NiFe then 7kWh would get you to 100%. You'd need less energy to get to 100%.

So if a lead acid battery was 80% cheaper per Ah you'd buy lead acid? 'Cause that's about what I faced. I paid $6/Ah for the L16s because NiFe was $46/Ah. >7x more expensive.

[johnpearcey]

...... point being that the 'problem' you mentioned previously of only getting to 95% and being unable to fully charge as lead-acid batteries require would not occur with lead-acid batteries in your case....

The 60% round-trip efficiency alone is almost a deal killer BEFORE the cost is considered. That's terrible, I thought NiFe was closer to 70%. Looking at my monitor I've put 1754kWh into my batteries and gotten 1463kWh out for an efficiency of 83% but that includes a lot of unnecessary absorption time.

It's already happening... the battery in my Tesla is 8 years old, I've cycled ~60MWh through it and it still retains >90% of its original capacity. I had considered lithium but reducing the burden on the supply chain, cost and recyclability put lead-acid over the top.

Here's a question I pose to nuclear advocates. How much cheaper would a 8 year battery have to be compared to NiFe for it to be the winner over NiFe for you? If I could get a NiFe for <3x the cost per Ah (total not 'usable') vs lead-acid I would choose NiFe. So if a 200Ah NiFe battery was available for <$4500 I agree that might be a better deal... but not >$9k. So how cheap would a lead-acid with a 8yr life have to be for you to chose lead acid over NiFe?

This is the trap people fall into... they choose one quality they think is critical and ignore all the others. A generator that emits no carbon and can operate 24/7 for 18 months without re-fueling is awesome.... how much does it cost? A battery that's invincible and lasts ~forever is great... how much does it cost? Economics matters.

The charging problem is a charging profile issue, not an efficiency issue. With the last 5% for a lead acid, the generator has to run on and on and on until the current finally drops to an amp or so. With NiFe, you just stop it when you like, no harm done and plenty of diesel saved. I'd probably need around 5x the capacity of lead-acid to stand even a chance to reach 8yrs. My 3rd experiment was last year - I bought 4 cheap (Banner) 100Ah for about 500EUR. They lasted 12 months at 20% DOD. I've attached a graph of the charge capacity (green) for the year so you can see what the usage was. Voltage is black and amps is blue. You can see it dropping 5Ah every month. (The dip in Feb is not to be believed, an effect of the initial forming charge I think). You can see a S.G. adjustment in Oct and Dec. By Feb, completely unusable. Screenshot from 2020-07-14 22-02-03.png

[nwdiver]

Yes, the efficiency of my NiFe is currently running at 59% which is not great at all. But to be honest I really haven't noticed it because when the sun shines it's free ...... But if it happens, I'll be trying some out for sure. Keep me posted!

...... point being that the 'problem' you mentioned previously of only getting to 95% and being unable to fully charge as lead-acid batteries require would not occur with lead-acid batteries in your case....

The 60% round-trip efficiency alone is almost a deal killer BEFORE the cost is considered. That's terrible, I thought NiFe was closer to 70%. Looking at my monitor I've put 1754kWh into my batteries and gotten 1463kWh out for an efficiency of 83% but that includes a lot of unnecessary absorption time.

It's already happening... the battery in my Tesla is 8 years old, I've cycled ~60MWh through it and it still retains >90% of its original capacity. I had considered lithium but reducing the burden on the supply chain, cost and recyclability put lead-acid over the top.

Here's a question I pose to nuclear advocates. How much cheaper would a 8 year battery have to be compared to NiFe for it to be the winner over NiFe for you? If I could get a NiFe for <3x the cost per Ah (total not 'usable') vs lead-acid I would choose NiFe. So if a 200Ah NiFe battery was available for <$4500 I agree that might be a better deal... but not >$9k. So how cheap would a lead-acid with a 8yr life have to be for you to chose lead acid over NiFe?

This is the trap people fall into... they choose one quality they think is critical and ignore all the others. A generator that emits no carbon and can operate 24/7 for 18 months without re-fueling is awesome.... how much does it cost? A battery that's invincible and lasts ~forever is great... how much does it cost? Economics matters.

[johnpearcey]

You'd get lead-acid to 100% for the same energy that it takes to get your NiFe to 90% because the coulombic efficiency of lead-acid is ~15% higher than NiFe. After cost that's the other big compromise with NiFe; I didn't want the potential head-ache of importing direct from China so I bought from an American Company. But for an apples-apples comparison the ~same lead-acid battery I bought for ~$2500 here I could import from China for <$1k so the cost difference really doesn't change.

Hopefully this debate will be a moot point by the time my L16s need replacing in ~8 years. We need a battery with ~90% round-trip efficiency that cost <$100/kWh, doesn't require maintenance and lasts ~20 years. Good chance something like that is coming soon, we're already getting close.

Yes, the efficiency of my NiFe is currently running at 59% which is not great at all. But to be honest I really haven't noticed it because when the sun shines it's free. So if you drop 40%, you kinda don't care. It just means it takes 2 days to fully charge rather than 1. And the cost of running a generator is (oddly) roughly the same per hour no matter how hard you run it. Better efficiency would of course be welcome since it would translate into savings in fuel and solar arrays. But the other compromise which you haven't mentioned which I've noticed more with NiFe is that you can't pull as much power from them as you can lead-acid. Frankly, for raw power, lead-acid rock, no question. But in my environment, lead-acid are way too fragile whereas NiFe are far more robust. If I could get a wind turbine up then I'd probably comfortably use lead-acid but that would cost over 12k.

I'm not sure I share your optimism though in battery development. Corporates don't like products that last 20yrs, they like a faster buck and quicker turn-around. But if it happens, I'll be trying some out for sure. Keep me posted!

[nwdiver]

I imported direct from China. That price included transport costs and all import duties. I agree that reducing the spend on a depreciating asset is a good idea and especially if you can put that money to use elsewhere. But that's not really the main issue here. In your situation, a lead-acid might indeed last 8yrs but in certain use-cases, as I keep repeating, the lead-acids will die a very early death. They will absolutely not last 8yrs. During the winter here, I could never top them up to more than about 95%. And if you can't do that, then you loose that top 5%. If you keep that up regularly, the capacity will drop very quickly indeed. This is one of the downsides with lead-acid. You have to spend hours at tiny currents topping up that last 5%. Fine when the suns shines all day and not good when you go weeks without sunshine. NiFe just don't have that problem. You can run them all their life at whatever charge capacity you wish. That's a real cost saver when running generators. I could have spent the money on extra solar panels instead of NiFe but then I'd still have to replace the lead-acids every 8 years. I also don't have the room for more panels just at this moment.

You'd get lead-acid to 100% for the same energy that it takes to get your NiFe to 90% because the coulombic efficiency of lead-acid is ~15% higher than NiFe. After cost that's the other big compromise with NiFe; I didn't want the potential head-ache of importing direct from China so I bought from an American Company. But for an apples-apples comparison the ~same lead-acid battery I bought for ~$2500 here I could import from China for <$1k so the cost difference really doesn't change.

Hopefully this debate will be a moot point by the time my L16s need replacing in ~8 years. We need a battery with ~90% round-trip efficiency that cost <$100/kWh, doesn't require maintenance and lasts ~20 years. Good chance something like that is coming soon, we're already getting close.

[johnpearcey]

I use my GC2s ~everyday. Lead-Acid batteries last if you cycle them gently.

I paid $2500 for a battery that suited by needs of <200Ah of storage ~180 days/yr and ~250Ah 15 days/yr. Where are you finding 120Ah NiFe for $3500? The only dealer in the US that sells NiFe (Iron Edison) sells 100Ah for $4200. If I wanted a NiFe battery with 200Ah of usable capacity I would need to spend ~$9200. If I wanted to cover the other few days that I wanted a bit more ~$12600. How would spending $9200 in an infinite 200Ah battery have worked out better than $3k on a 8yr and investing the difference? The $6k I didn't spend is already $7500 (been a good year). I have little doubt it will be $12k in 8 years with all the ups and downs of the market. What is an investment in NiFe getting me aside from saving a little work once a decade?

I imported direct from China. That price included transport costs and all import duties. I agree that reducing the spend on a depreciating asset is a good idea and especially if you can put that money to use elsewhere. But that's not really the main issue here. In your situation, a lead-acid might indeed last 8yrs but in certain use-cases, as I keep repeating, the lead-acids will die a very early death. They will absolutely not last 8yrs. During the winter here, I could never top them up to more than about 95%. And if you can't do that, then you loose that top 5%. If you keep that up regularly, the capacity will drop very quickly indeed. This is one of the downsides with lead-acid. You have to spend hours at tiny currents topping up that last 5%. Fine when the suns shines all day and not good when you go weeks without sunshine. NiFe just don't have that problem. You can run them all their life at whatever charge capacity you wish. That's a real cost saver when running generators. I could have spent the money on extra solar panels instead of NiFe but then I'd still have to replace the lead-acids every 8 years. I also don't have the room for more panels just at this moment.

[nwdiver]

And my cheap car battery is still going for 7 years which proves that lead-acids only last if you don't use them. So you have paid around 2.5k for the ability to actually use 120Ah regularly. The price for 120Ah set of NiFe is about 3.5k. That will last you 20 years which is 175pa. You will need to replace your lead-acids at least twice in that time by your own admission costing you 2.5k + 3.2k +4.2k = 10k over 24 years = 416pa. How could NiFe not make sense?

I use my GC2s ~everyday. Lead-Acid batteries last if you cycle them gently.

I paid $2500 for a battery that suited my needs of <200Ah of storage ~180 days/yr and ~250Ah 15 days/yr. Where are you finding 120Ah NiFe for $3500? The only dealer in the US that sells NiFe (Iron Edison) sells 100Ah for $4200. If I wanted a NiFe battery with 200Ah of usable capacity I would need to spend ~$9200. If I wanted to cover the other few days that I wanted a bit more ~$12600. How would spending $9200 in an infinite 200Ah battery have worked out better than $3k on a 8yr and investing the difference? The $6k I didn't spend is already $7500 (been a good year). I have little doubt it will be $12k in 8 years with all the ups and downs of the market. What is an investment in NiFe getting me aside from saving a little work once a decade?