Nickel Iron vs. Lead Acid - Off Grid battery debate

[johnpearcey]

2 years? Did you buy used? I have GC2s that are still going after 6 years...

Agreed; You need to get quality lead-acids and ~2x the Ah that you usually need so DOD rarely exceeds 50%. That would last ~8-10 years (not 2) and save just as much diesel for 1/3rd the cost of NiFe. Take that savings... put it in a S&P index... then buy another lead-acid bank in 8-10 years and figure out what you're gonna spend the other ~$9k on. But this is 200Ah of NiFe for $9k vs 400Ah of lead-acid for $3k. What size battery do you have?

Here's the point I realized. The only real benefit to NiFe is lifespan. The faster charging doesn't benefit me because my lead-acid bank can already charge faster than my CC can charge them. If your PV array and battery bank are sized correctly this should be true. So the only benefit is the battery bank lasts forever but at ~3x the cost even after doubling the Ah of the lead-acid bank to limit DOD >50% the math doesn't even come close to working. In most situations why would someone spend $9k once instead of $3k every 8 years? What benefit would be realized?

I would argue that the lead acid carries the additional benefit of having a 'reserve'. Yeah... it will damage the battery a bit more to discharged it to 70% but if you're only doing that once a month it's won't be that bad so you can get ~300Ah out ~occasionally while with a 200Ah NiFe you get >200Ah ~never. So between 400Ah of PbSO4 for $3k or 200Ah of NiFe for $9k I don't see how NiFe makes sense. Maybe $6k but not $9k.

In my specific example it actually came out to <$3k. I bought 8 Trojan SPRE 415s for $305ea. I regularly cycle them to ~30% and occasionally to 50% (maybe once every ~45 days to 60%). They should last >8 years with the type of use (we'll see). How would NiFe have made more sense?

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?

[nwdiver]

Here in Ireland, 400Ah lead-acids would be dead in 2yrs or the diesel cost would be higher than the battery cost.

2 years? Did you buy used? I have GC2s that are still going after 6 years...

Agreed; You need to get quality lead-acids and ~2x the Ah that you usually need so DOD rarely exceeds 50%. That would last ~8-10 years (not 2) and save just as much diesel for 1/3rd the cost of NiFe. Take that savings... put it in a S&P index... then buy another lead-acid bank in 8-10 years and figure out what you're gonna spend the other ~$9k on. But this is 200Ah of NiFe for $9k vs 400Ah of lead-acid for $3k. What size battery do you have?

Here's the point I realized. The only real benefit to NiFe is lifespan. The faster charging doesn't benefit me because my lead-acid bank can already charge faster than my CC can charge them. If your PV array and battery bank are sized correctly this should be true. So the only benefit is the battery bank lasts forever but at ~3x the cost even after doubling the Ah of the lead-acid bank to limit DOD >50% the math doesn't even come close to working. In most situations why would someone spend $9k once instead of $3k every 8 years? What benefit would be realized?

I would argue that the lead acid carries the additional benefit of having a 'reserve'. Yeah... it will damage the battery a bit more to discharged it to 70% but if you're only doing that once a month it's won't be that bad so you can get ~300Ah out ~occasionally while with a 200Ah NiFe you get >200Ah ~never. So between 400Ah of PbSO4 for $3k or 200Ah of NiFe for $9k I don't see how NiFe makes sense. Maybe $6k but not $9k.

In my specific example it actually came out to <$3k. I bought 8 Trojan SPRE 415s for $305ea. I regularly cycle them to ~30% and occasionally to 50% (maybe once every ~45 days to 60%). They should last >8 years with the type of use (we'll see). How would NiFe have made more sense?

[johnpearcey]

I said I had seriously considered it until I looked at the numbers in terms of the time value of money. Spending $3k every 8-10 years makes A LOT more sense than spending even $6k once. $9k is a non-starter. If 400Ah wasn't enough I can always go with 600Ah and still come out ahead. Economics matters. This isn't on-grid vs off-grid this is off-grid vs off-grid. Why needlessly spend money to achieve the ~same result? The best solution is found in the middle. GC2s are too cheap and super-batteries are too expensive. Something like a L16 makes the most sense because math. If you don't trust banks and keep gold bars buried in the backyard NiFe may make the most sense... I make my $$$ work for me.

As I said, NiFe have saved me loads on diesel (about 20ltrs/w). Not to mention the wear and tear on the generator. And my NiFe cost me 2k, so in 2yrs time, these NiFe pay for themselves whereas lead-acids are dead. Time-value of money is irrelevant here. And I'm not sure where I'd get 3k in 8 years time anyway, I'll be too old to work. And I don't need any help with my maths thanks, I have a BSc in Mathematics and Physics and plenty of spreadsheets and data to analyse this problem. The maths only works if you get your original assumptions right. We live in different environments and you have to consider the system as a whole. Here in Ireland, 400Ah lead-acids would be dead in 2yrs or the diesel cost would be higher than the battery cost. And this set of NiFe batteries should last me 15-20 years. And yes, I do have some gold bars and just take a look at the spot price recently. It's going to go a lot higher.
Update: We've had 2 straight weeks of dark cloud cover here where I live. How large would a bank of lead-acids need to be to get through this and stand any chance of lasting 8 years??

[nwdiver]

Is there anything paying usable dividends now ?

Figure of speech for growth in general. My investments are up ~25% y/y. Mostly thanks to TSLA. It's an outlier but $6k invested in TSLA 8 years ago would definitely be enough for a new bank of L16s..... And a house to power with them

[Mike90250]

Is there anything paying usable dividends now ?

[nwdiver]

You talk like you actually used 80Ah of NiFe. But you previously said you didn't buy them. So which is it?

I said I had seriously considered it until I looked at the numbers in terms of the time value of money. Spending $3k every 8-10 years makes A LOT more sense than spending even $6k once. $9k is a non-starter. If 400Ah wasn't enough I can always go with 600Ah and still come out ahead. Economics matters. This isn't on-grid vs off-grid this is off-grid vs off-grid. Why needlessly spend money to achieve the ~same result? The best solution is found in the middle. GC2s are too cheap and super-batteries are too expensive. Something like a L16 makes the most sense because math. If you don't trust banks and keep gold bars buried in the backyard NiFe may make the most sense... I make my $$$ work for me.

[johnpearcey]

I guess you can think that way but for some (me included) I don't want to live through a time where we all have to fend for ourselves. I guess I am just getting too old for that stuff.

Well I don't want to either. But it's not necessarily a case of needing to fend for ourselves, more like whether we want to sign up to the 'new normal'. I don't and I won't. Personally I think that the elites will ensure that the power grids and the internet will be kept running at all costs otherwise their 'new normal' won't work. I don't want to be earning crypto-currency browny points in order to pay my electricity bill. I'll be off-grid with my chickens and vege-plots living the 'old' normal. At least until my NiFe's pack up - lol.

[SunEagle]

You talk like you actually used 80Ah of NiFe. But you previously said you didn't buy them. So which is it? You can cycle the NiFe to zero which you can't do with the lead-acid types. I've had various types of deep cycle lead-acid for the previous 3 years and they all degraded by about 0.8% of each Ah used no matter how shallow they were used. The other thing with NiFe is that you can charge them in a few hours which you can't do with lead-acid. This is a big money saver when you're located in a country where you can go many weeks without sunshine and have to use a generator. NiFe will save you a fortune on diesel, way more than your 'value of money'. I do agree though that spending large capital up front is not the best way if it can be delayed obviously. But remember also that people who are off-grid do not do so to save money. Connecting to your local grid is way cheaper. So why do we do it? Because we don't trust the economics of our society and want something which will soldier on for many years, long after the grid has packed up and long after fiat currency has crashed. We've been called crazy until Coronavirus popped up and cause havoc and we don't look so stupid now. If things get worse, which is very likely, we could see things like hyper-inflation and even fiat money crash. Then you're going to wish you'd spent the 9k when it was so cheap!!

I guess you can think that way but for some (me included) I don't want to live through a time where we all have to fend for ourselves. I guess I am just getting too old for that stuff.

[johnpearcey]

No; 80Ah wouldn't get me through some nights. 200Ah would. Even cycling the L16s to ~50% DOD sometimes they should last ~8 years. I've been running mostly off-grid since March using L16s to get a feel for the challenges. Maybe half of my cycles are to ~50% and ~30% are only to ~20%. With that kind of use I should get >8 years out of the batteries. Makes more sense to spend $3k every 8 years than spend $9k once due to the time value of money.

You talk like you actually used 80Ah of NiFe. But you previously said you didn't buy them. So which is it? You can cycle the NiFe to zero which you can't do with the lead-acid types. I've had various types of deep cycle lead-acid for the previous 3 years and they all degraded by about 0.8% of each Ah used no matter how shallow they were used. The other thing with NiFe is that you can charge them in a few hours which you can't do with lead-acid. This is a big money saver when you're located in a country where you can go many weeks without sunshine and have to use a generator. NiFe will save you a fortune on diesel, way more than your 'value of money'. I do agree though that spending large capital up front is not the best way if it can be delayed obviously. But remember also that people who are off-grid do not do so to save money. Connecting to your local grid is way cheaper. So why do we do it? Because we don't trust the economics of our society and want something which will soldier on for many years, long after the grid has packed up and long after fiat currency has crashed. We've been called crazy until Coronavirus popped up and cause havoc and we don't look so stupid now. If things get worse, which is very likely, we could see things like hyper-inflation and even fiat money crash. Then you're going to wish you'd spent the 9k when it was so cheap!!

[SunEagle]

Yep; There could be a magic perfect battery that will last 1M years, smells like roses when it charges and spits out a grill cheese sandwich when it ends it's absorption cycle but if it costs $1,000/kWh I'm not going to be interested. I'll buy the one that costs <$200/kWh, lasts ~8 years, invest the difference and use the dividends to replace the battery every 8 years and still have plenty left over for a panini press.

+1. Works for me.

[nwdiver]

As I have always stated you have to do the math. Basically how many kWh will a battery system provide each cycle and how many cycles it provides over it's life. That gets you a value that you divide into the cost. That produces a $/kWh which is easy to compare to all battery systems or a POCO.

Yep; There could be a magic perfect battery that will last 1M years, smells like roses when it charges and spits out a grill cheese sandwich when it ends it's absorption cycle but if it costs $1,000/kWh I'm not going to be interested. I'll buy the one that costs <$200/kWh, lasts ~8 years, invest the difference and use the dividends to replace the battery every 8 years and still have plenty left over for a panini press.

[SunEagle]

As I have always stated you have to do the math. Basically how many kWh will a battery system provide each cycle and how many cycles it provides over it's life. That gets you a value that you divide into the cost. That produces a $/kWh which is easy to compare to all battery systems or a POCO.

[nwdiver]

Surely a fairer comparison of 415Ah of L16 would be more like 80Ah of NiFe?

No; 80Ah wouldn't get me through some nights. 200Ah would. Even cycling the L16s to ~50% DOD sometimes they should last ~8 years. I've been running mostly off-grid since March using L16s to get a feel for the challenges. Maybe half of my cycles are to ~50% and ~30% are only to ~20%. With that kind of use I should get >8 years out of the batteries. Makes more sense to spend $3k every 8 years than spend $9k once due to the time value of money.

[johnpearcey]

I had considered either industrial or NiFe batteries due to their longevity until I remembered the time value of money. I bought 415Ah of L16 batteries for $3k. 200Ah of NiFe would have cost me $9k. The ~$6k I saved will be ~$12k by the time the L16s die and I can just spend $3k on more L16s (or hopefully something even better in 10 years) and send the old ones to be recycled. And on and on and on.

Surely a fairer comparison of 415Ah of L16 would be more like 80Ah of NiFe?

[nwdiver]

I'm currently using NiFe off-grid. Just changed over from lead-acid. Lead-acid are not actually cheaper despite what people keep saying. The capital outlay is more for equivalent *quoted* Ah. The problem with lead-acid is that you can't effectively use more than 20% of the quoted capacity. But with NiFe you can use all of it.

I had considered either industrial or NiFe batteries due to their longevity until I remembered the time value of money. I bought 415Ah of L16 batteries for $3k. 200Ah of NiFe would have cost me $9k. The ~$6k I saved will be ~$12k by the time the L16s die and I can just spend $3k on more L16s (or hopefully something even better in 10 years) and send the old ones to be recycled. And on and on and on.