50% discharge on AGM batteries - old wife's tail

[wattmatters]

Thank you, the days of lead acid on a PV system are gone. It makes no sense really.

Agreed, other than for existing storage banks and niche applications.

An example being mine where the lead acid battery has one job - to act as cheap reserve capacity when cycle count isn't a consideration. My reserve capacity costs less than 1/4 of what it would cost to keep LiFePO₄ on reserve.

 

[sunsurfer]

Agreed, other than for existing storage banks and niche applications.

An example being mine where the lead acid battery has one job - to act as cheap reserve capacity when cycle count isn't a consideration. My reserve capacity costs less than 1/4 of what it would cost to keep LiFePO₄ on reserve.

sometimes a lead bank can come for free. I have aprx. 20kw in a lead bank thats made up of 31 series truck batteries. They where all pretty much new and I use them for covering when clouds roll through. I paid nothing for them. They work great as a buffer but I really can't cycle them. They will get replaced by LFP in the future.

 

[SamDeleted]

Thank you, the days of lead acid on a PV system are gone. It makes no sense really.

Out of interest then , what does you LiFePo4 bank work out at price per lifetime usable kWh?



Here's the maths on a gel bank, (trying to keep it simple I'm going to use manufacturer cycle rating)



16 x GF06240V SONNENSCHEIN dry fit gel , 270ah c20 1,620wh / 25920wh total

Rated for 700 full 100% cycles

700 X 25920wh = 18,144,000 lifetime watt/h (18,144kwh)

Paid £1,350 gbp delivered


£1,350 ÷ 18,144kwh = £0.0744 GBP per lifetime kWh ($0.094 USD)





So I understand about all the disadvantages of lead acid, but I think that figure is going to be hard to beat ....

It gets even better if you do 50% soc cycles:

£1,350 ÷ 20,684 kWh = £0.065 GBP per Lifetime kWh ($0.082 USD)

 

[littleharbor2]

Looking at Oz's figures , lead acid Vs LiFePo4 per lifetime energy unit:

Lead acid $0.089

LiFiPo4 $0.071

So yea like you said better bang for buck , but not as bigger gap as some might believe....

the real problem with lithium is the huge up front costs, literally double

Lead acid battery prices have jumped pretty high in this part of the world. If you build your own LFP battery from individual cells you are literally getting LFP cheaper, amp hour vs. amp hour. Plus you get nearly double the usable amp hours of capacity.

 

[Zwy]

54Kwh bank, cost was $11K USD for the complete battery before 30% tax credit, 6000 cycles expected lifespan. If you look in the archives (search is currently not working) you will find a breakdown per Kwh. In my signature below, there is a link to my house battery build. I could shave off 15% if I used something like a JK BMs.

$11,000 divided by 6000 cycles= $1.83 per cycle

$1.83 divided by 54=$0.0339 per Kwh

For usable capacity of 48.6Kwh = $0.0377 per Kwh

With 30% tax credit:

$7,700 divided by 6000 cycles= $1.28 per cycle

$1.28 divided by 54= $0.238 per Kwh

$1.28 divided by 48.6Kwh= $0.264 per Kwh

Cheaper BMS- Cost would be $9,350

$9,350 divided by 6000 cycles= $1.55 per cycle

$1.55 divided by 54= $0.29 per Kwh

$1.55 divided by 48.6= $0.319 per Kwh

With tax credit- $6545

$6545 divided by 6000 cycles = $1.09 per cycle

$1.09 divided by 54= $0.020 per Kwh

$1.09 divided by 48.6=$0.0224 per Kwh

 

[SamDeleted]

54Kwh bank, cost was $11K USD for the complete battery before 30% tax credit, 6000 cycles expected lifespan. If you look in the archives (search is currently not working) you will find a breakdown per Kwh. In my signature below, there is a link to my house battery build. I could shave off 15% if I used something like a JK BMs.

$11,000 divided by 6000 cycles= $1.83 per cycle

$1.83 divided by 54=$0.0339 per Kwh

For usable capacity of 48.6Kwh = $0.0377 per Kwh

With 30% tax credit:

$7,700 divided by 6000 cycles= $1.28 per cycle

$1.28 divided by 54= $0.238 per Kwh

$1.28 divided by 48.6Kwh= $0.264 per Kwh

Cheaper BMS- Cost would be $9,350

$9,350 divided by 6000 cycles= $1.55 per cycle

$1.55 divided by 54= $0.29 per Kwh

$1.55 divided by 48.6= $0.319 per Kwh

With tax credit- $6545

$6545 divided by 6000 cycles = $1.09 per cycle

$1.09 divided by 54= $0.020 per Kwh

$1.09 divided by 48.6=$0.0224 per Kwh

Yes ive seen your battery thread, very tidy job indeed , looks professional .




Googling eve 304ah/280ah cells , 6000 is the absolute outside number , most quote 3500 cycles. Or as low as 2000 cycles if you're batteries are getting warm


So $9,350 with cheap BMS, I'm not so interested in tax incentives

3500 cycles @ 48.6kwh is:
$0.055 USD per lifetime kwh

Compared gel batteries:
$0.082 USD per lifetime kwh









interesting, figures show yes lithium is better value for money, but the margin is slimmer than some might imply...., and it's a huge upfront investment. You have to shell out £10,000s on batteries, not possible for a lot of people ,

so you said there's no place for lead acid in solar today, I disagree . There is a place for lead acid, just at the lower end of the market lol... for the people who don't want to / can't invest that much into a system, lead acid is still a viable option.

 

[Blakes]

I have a 48v renogy AGM battery bank wired into 4S2P. 2 years old fed by a 2400w solar array and renogy 48v inverter/charger on the SLD setting


I've babied these things the past 2 years running the generator a lot during the winter and low sun days.

I have never gotten below 49v SOC and often wonder if I have wasted gas on keeping them 'happy' and have over charged then.

 

[SamDeleted]

There is a place for lead acid, just at the lower end of the market lol... for the people who don't want to / can't invest that much into a system, lead acid is still a viable option.

And let's be fair, the majority of people fall into one of those two categories, they either can't or won't spend £10,000 on lithium batteries


But if they still want to go off grid .., a lot of people can / will pay for £1500 of lead acid

LiFePo4 is the best option if money is no object , but there's still a place for lead acid in this world

 

[Zwy]

Yes ive seen your battery thread, very tidy job indeed , looks professional .

Thank you. I always strive to make things very tidy and professional.

Googling eve 304ah/280ah cells , 6000 is the absolute outside number , most quote 3500 cycles. Or as low as 2000 cycles if you're batteries are getting warm

6000 is considered standard and it appears these might even go 10,000 cycles. Plenty of discussion in the archives.

I hit a full cycle once every 4 to 5 days. 365/4=91.25 cycles per year. Even using the 3500 cycles figure you have, that is 38 years. Do that with lead acid, I'd like to see it.

So $9,350 with cheap BMS, I'm not so interested in tax incentives

3500 cycles @ 48.6kwh is:
$0.055 USD per lifetime kwh

Compared gel batteries:
$0.082 USD per lifetime kwh

View attachment 154311

One can find charts all over the internet to support any position.

The expected standard life cycle is 6000 cycles. This chart shows 8,000 cycles and still 80% capacity remains.

interesting, figures show yes lithium is better value for money, but the margin is slimmer than some might imply...., and it's a huge upfront investment. You have to shell out £10,000s on batteries, not possible for a lot of people ,

Not really, it would depend upon the system. Any large system for powering a complete house off grid will require a big investment upfront.

Something small such as an RV, there are cheaper alternatives. I run a pair of 100Ah Zoom's in my boat for the trolling motor, cost was $310 each delivered to my door. I can't even buy AGM for that money per Ah of capacity.

so you said there's no place for lead acid in solar today, I disagree . There is a place for lead acid, just at the lower end of the market lol... for the people who don't want to / can't invest that much into a system, lead acid is still a viable option.

There isn't a place for it unless one wants to waste money and even time over the long term. It isn't economical even from the start.

Add in watering, EQ charging, corrosion and a few other factors. There isn't any benefit to lead acid unless the batteries are free and even then, it isn't an option that is worth the hassle.

 

[timselectric]

so you said there's no place for lead acid in solar today, I disagree . There is a place for lead acid, just at the lower end of the market lol... for the people who don't want to / can't invest that much into a system, lead acid is still a viable option.

But if they do the math, they will actually spend more on led acid.
and the low cycles you are showing is for use in an EV. That's a lot more strenuous on the cells.
6000 is probably the low minimum for solar storage.
If a system is built correctly, I think that 10,000 cycles will be more likely.


Edit: @Zwy beat me to it.

 

[HarryN]

I have a 48v renogy AGM battery bank wired into 4S2P. 2 years old fed by a 2400w solar array and renogy 48v inverter/charger on the SLD setting


I've babied these things the past 2 years running the generator a lot during the winter and low sun days.

I have never gotten below 49v SOC and often wonder if I have wasted gas on keeping them 'happy' and have over charged then.

So the big challenge that you have is with the renogy solar charge controllers.

Those use quite a bit of power from the battery all of the time, 24 hrs / day - at least the rover unit that I tested did.

Probably your best investment would be a midnight or victron solar charge controller to replace it.

A 49 volt minimum is probably as low as you want to go.

Perhaps consider to run the generator for 1 -2 hrs first thing in the morning on those cloudy days and the let the sun do the rest.

__________

Those tend to charge fairly slowly compared to a higher end AGM, so it helps a lot to have some panels facing the morning sun as well as the late afternoon sun.

 

[HarryN]

Out of interest then , what does you LiFePo4 bank work out at price per lifetime usable kWh?



Here's the maths on a gel bank, (trying to keep it simple I'm going to use manufacturer cycle rating)



16 x GF06240V SONNENSCHEIN dry fit gel , 270ah c20 1,620wh / 25920wh total

Rated for 700 full 100% cycles

700 X 25920wh = 18,144,000 lifetime watt/h (18,144kwh)

Paid £1,350 gbp delivered


£1,350 ÷ 18,144kwh = £0.0744 GBP per lifetime kWh ($0.094 USD)





So I understand about all the disadvantages of lead acid, but I think that figure is going to be hard to beat ....

It gets even better if you do 50% soc cycles:

£1,350 ÷ 20,684 kWh = £0.065 GBP per Lifetime kWh ($0.082 USD)

A gel battery is similar - but still different than an AGM.

Not criticizing, just letting you know that you can't make the same assumptions about flooded, cheap AGM, higher end AGM, deep discharge AGM vs marine type AGM. Each is a different entity, nearly as different as AGM vs LiFe.

I am also not an AGM fan boy, I give the info to the customers on how the systems will behave with the choices. Ultimately they choose what makes sense for how they plan to use their van or trailer.

One of the reasons that people are so happy with LiFe based solutions is that they were using the wrong battery in the first place.

 

[SamDeleted]

The expected standard life cycle is 6000 cycles. This chart shows 8,000 cycles and still 80% capacity remains.

Not sure if anyone actually seen 8000 real world cycles?

But if they do the math, they will actually spend more on led acid.

Yea over the long term you're right. But it's not as bigger difference as people might have you believe .



no one is trying to make out lead acid is better than lithium, What I'm saying is there's plenty of people who can't afford to put the big investment in and still need the battery capacity.

If your budget is short, lead acid is a very attractive and viable option


Who knows when the next advancement in battery technology might be, or how cheap lithium will be when these gel batteries are worm out in a good couple of years

 

[Hedges]

My grid-backup system has 20kWh of SunXtender AGM, for 14kWh usable. cost $5000. Based on manufacturer data sheet I expect 700 cycles to 70% DoD or 10 years, whichever comes first. If all cycles used, $0.50/kWh of cycle life, which isn't as bad as it sounds because that's just what is used overnight; during the day loads like A/C are PV direct, use-it-or-lose-it PV power that would cost $0.025/kWh to install today.

I selected these 3 years ago because the only compatible lithium I knew of (LG RESU) was 5x the price for 5x the cycle life, and I anticipate only a couple hundred power failures at most.

What I would like to do is add AC coupled lithium, e.g. with Sunny Boy Storage. The idea would be that by frequency shift power control, LiFePO4 would receive all surplus power and would supply all loads up to it's wattage rating. Lead-acid would supply surge and discharge rate as needed, but would spend most of its life floating.

Straight lithium on grid-forming inverter should work too, if it can supply all surge (BMS issue) and absorb all load-dump (have to keep SoC low enough). I'll look into that eventually for my next system on a different house.

 

[Tomthumb62]

So the big challenge that you have is with the renogy solar charge controllers.

Those use quite a bit of power from the battery all of the time, 24 hrs / day - at least the rover unit that I tested did.

What did you test consumption at and for which Rover model?

For the 30A model, consumption is specced at quite low:

Power Consumption:＜100mA/12V; ＜58mA/24V

 

[timselectric]

Not sure if anyone actually seen 8000 real world cycles?

Not yet. It'll be a few years before anyone can report on that.

 

[wattmatters]

Lead acid must be really cheap in the UK. Here (Australia) lead acid is really expensive.

Those lead acid batteries I have, when bought new, are dearer (A$540/kWh) than the LiFePO₄ server rack batteries (A$400/kWh) I have.
Only reason I have my lead acid is they were second hand and hence far cheaper and at the time I was building an outage backup system, not a daily cycling system.

On an energy throughput basis there is no question, lead is far more expensive than LiFePO₄ here.

Cheaper but still good quality AGMs come in at ~A$415/kWh, while the stupid low price units are more like A$200/kWh but they are really crap quality.

 

[HarryN]

What did you test consumption at and for which Rover model?

For the 30A model, consumption is specced at quite low:

Power Consumption:＜100mA/12V; ＜58mA/24V

One of my van build customers brought the 40 amp rover version and asked to have it built into the 48 volt system project / 600 watt panels.

Controllers like a bogart pull their power from the solar and negligible from the batteries. The smaller Victrons that I tested ( like a 150 / 35 ) also pull relatively little.

The power consumption from the 40 amp rover was similar to an inverter being on. ~ 20 -30 watts, 24 hrs / day.

That was on my test stand with 4 x Battle borns wired 4S and I can set up solar arrays with Vmp 18 volts to 6 in series.

 

[Zwy]

Not sure if anyone actually seen 8000 real world cycles?

I believe the manufacturers have tested using higher C rates for discharge and charging. In a PV system, many member report having over 8 years on LFP with no degradation in capacity.

Yea over the long term you're right. But it's not as bigger difference as people might have you believe .

I already gave you the math, you're in some type of denial stage at this point. The difference is quite large.

Your figure: "£1,350 ÷ 18,144kwh = £0.0744 GBP per lifetime kWh ($0.094 USD)"
My figure: "For usable capacity of 48.6Kwh = $0.0377 per Kwh"
That is over 250% higher over the lifetime which is what wanted for a baseline. That is huge.

If a local bank told you they will give you a 250% return on your money over the next 25 years, would you take it?

If you don't understand how money works and how to make it work for you even while you sleep, then buy the lead acid. Easiest money I've ever made was while I was sleeping after putting my money in the right place.

no one is trying to make out lead acid is better than lithium, What I'm saying is there's plenty of people who can't afford to put the big investment in and still need the battery capacity.

I was being nice in prior responses but as you want to be argumentative, I guess I'll play along.

This comment: "So I understand about all the disadvantages of lead acid, but I think that figure is going to be hard to beat ...."
is either you're trolling or ignorant as I quite easily showed you the figures and even used your cycle lifespan of 3500 and it still beat your lead acid or gel (don't care which) and it would run my house for 38 years if calendar aging didn't play into the equation.

If your budget is short, lead acid is a very attractive and viable option

I already gave cheap alternatives, you just choose to gloss over. Either trolling or not paying attention. First, the cheapest I found the GF06240V SONNENSCHEIN is https://www.battery-direct.com/12v-240ah-battery-gf6240v.html which is 485Euro - $528USD - 415.50 pound sterling

Even though you used sterling, it still doesn't add up that you purchased 16 of these batteries for £1,350 gbp

Even with a quantity discount the price is "from 16 pieces 3% discount = 395.37 EUR"

That is $430USD. That would be $6880 USD plus shipping. 8 of these batteries make 48V battery and 11,520Wh. My bank is almost 5 times that size for less than what those 16 gel batteries would cost.

Who knows when the next advancement in battery technology might be, or how cheap lithium will be when these gel batteries are worm out in a good couple of years

The revolution wen right past you with LFP, I doubt you will catch the next generation.

 

[OzSolar]

Why so much anger towards people who just want to ask questions and have a dialogue? I've been personally involved with dozens of FLA projects that did great for 15 years or longer. Is there anyone that make that claim with LFP's? Bueller, Bueller?