Price Point of lifepo4 batterys.

[tytower]

[
What do you mean by " bottom balancing" ? Manually controlling the individual cell voltages when discharged ? That kind of "human BMS" sounds like fun and completely error free

Bottom balancing at say under 3 volts means getting all the cells down to an equal voltage point before recharging.
By joining each cell in parallel current flows from the high to the low cells and eventually settles down to very little current flowing .
Then the cells can be reconstructed into a series string and recharged until one cell reaches 3.55V or so and the pack is fully charged and balanced.

Notice in the pic the loops which allow you to get a current meter on each to check the flow.

LFP , LiFePo4 cells spend most of their life at about 3.2Volts.

[john61ct]

I would only consider lead, LFP or LTO for the safety aspect if the installation is anywhere near my living space,

Delivered cost from a trusted supplier with local warranty return will vary enormously by location.

North American distribution channels are very immature and risky if buying on price, not advisable IMO.

LFP longevity is many thousands of cycles and at least a few decades calendar life, if properly cared for.

Variables include temperature, depth of discharge, charge & discharge C-rates, tweaking voltages and stop-charge setpoints on charge profiles, balancing & float policies, redundancy layers in protection circuitries etc.

Very easy to overspend unnecessarily, but then again, a single failure event can render the whole bank instant scrap.

Personally I'd look at old-school cheap but good FLA. In NA, the best battery value by far is Duracell (actually Deka/East Penn) deep cycle golf cart batteries,but around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.

Even with lower usable-capacity ratio, comes to ~10¢ per kWh of storage, and may well go 6-8 years if cycled not too deeply on average say 2-3 times a week.

[electrodacus]

Personally I'd look at old-school cheap but good FLA. In NA, the best battery value by far is Duracell (actually Deka/East Penn) deep cycle golf cart batteries,but around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.

Even with lower usable-capacity ratio, comes to ~10¢ per kWh of storage, and may well go 6-8 years if cycled not too deeply on average say 2-3 times a week.

~10¢ per kWh ? How did you got this number ?
Do you have a link to datasheet for that battery?

[Nauris]

Personally I'd look at old-school cheap but good FLA. In NA, the best battery value by far is Duracell (actually Deka/East Penn) deep cycle golf cart batteries,but around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.

Even with lower usable-capacity ratio, comes to ~10¢ per kWh of storage, and may well go 6-8 years if cycled not too deeply on average say 2-3 times a week.

~10¢ per kWh ? How did you got this number ?
Do you have a link to datasheet for that battery?

For example, if you take that battery: https://www.solaris-shop.com/trojan-sind-06-1225-solar-industrial-flooded-6v-1225ah-battery/
Capacity: 1225Ah/6V 7.35 kWh
Weight: 190 kg
Price: 1222 USD
Cycle life: 3600@50% DoD
Then
1222 USD/(7.35 kWh x 0.5 x 3600)=0.092 cents per kWh
Looks suprisingly competitive actually if you dont't mind the weight and why would you if it is just sitting there somewhere stationary.


But does anybody have any information on the Sunica.plus flooded NiCd batteries Saft advertises for solar use? Too exotic and too expensive I guess?

[john61ct]

~10¢ per kWh ? How did you got this number ?
Do you have a link to datasheet for that battery?

Best to just call their support dept for tech details

Here's an overview from Maine Sail
http://www.cruisersforum.com/forums/f14/duracell-gc2-charging-specs-163920.html#post2092450

and a basic list of models
http://www.eastpennmanufacturing.com/wp-content/uploads/Deka-Pro-Master-Golf-Car-Flyer-0248.pdf

As for the math, say 215Ah per pair, 12-13V call it 2.5kWh. Last set I bought cost $220 shop was a 20min drive away, so call it $250 per pair delivered?

Sometimes Trojan can be found cheaper, but rarely.

Other good FLA brands in NA are Superior, US Battery and Crown.

Rolls / Surrette are at a whole 'nother level and priced accordingly, but it is common for them to last 14+ years even cycled daily.

I think quality lead pricing being so low here is one of the factors holding back development of LFP and LTO distribution channels, as opposed to Europe and down under, where lesser quality and more expensive AGM are the norm.

[john61ct]

For example, if you take that battery: https://www.solaris-shop.com/trojan-sind-06-1225-solar-industrial-flooded-6v-1225ah-battery/

Gotta factor delivery costs in, for a small bank would add a lot to the final cost.

Not to mention breaking your back anytime they need moving.

[john61ct]

Will Prowse is not exactly an authority on the technical aspects of DC electrics.

Not bad for a YouTube "influencer" but that's a pretty low bar.

Drop-ins really are for convenience, people that don't want to get up to speed on the details.

I am very skeptical they will have longevity like a properly engineered system based on top quality cells, there's hundreds of makers out there, under a dozen known good.

[john61ct]

What do you mean by " bottom balancing" ? Manually controlling the individual cell voltages when discharged ? That kind of "human BMS" sounds like fun and completely error free

You really need to do more research if you don't know the difference between bottom and top balancing.

A BMS is really just a collection of protective functions, how you implement it is up to you.

There are many methods for maintaining balance at the per-cell level, and in some use cases just checking manually every so often is just fine, good cells treated well just don't need more.

There are very few "all in one" BMS solutions I would consider. I wish fully open hardware and FOSS firmware were more common (shout out to Dacian, just realized who I was talking to 8-)

[john61ct]

As long as you don’t do something stupid, quality deep cycle FLA will last 10- 15 years (large traction batteries longer) and AGM 8-10 years in daily cycling applications.

Yes, LFP make good sense and are financially competitive with LA when one considers lifetime costs. But don’t oversell them, they are not always the best option.

Well stated.

In both cases, top-quality cells and the infrastructure+knowledge to care for them properly are required to make the investment pay off.

Only noobs go all fanboy for one particular solution, there are too many variables involved in each use case.

[electrodacus]

For example, if you take that battery: https://www.solaris-shop.com/trojan-sind-06-1225-solar-industrial-flooded-6v-1225ah-battery/
Capacity: 1225Ah/6V 7.35 kWh
Weight: 190 kg
Price: 1222 USD
Cycle life: 3600@50% DoD
Then
1222 USD/(7.35 kWh x 0.5 x 3600)=0.092 cents per kWh
Looks suprisingly competitive actually if you dont't mind the weight.


But does anybody have any information on the Sunica.plus flooded NiCd batteries Saft advertises for solar use? Too exotic and too expensive I guess?

That seems to be at half MSRP in therms of cost but fair enough as it is available at that price.

The 3600 cycles at 50% DOD means using it that way every day for 10 years and then you ignored the calendar aging that can be very significant in solar energy storage application's where battery most of the time is less than fully charged.
Also that capacity is for 100h discharge rate but if you want to assume a 50% DOD every day then best case charge and discharge need to happen in less than 10h each. 
If you then look at 10h capacity it is just 835Ah significantly less than at 100h
Then if you also consider calendar aging and also the fact that you need a significantly oversized battery capacity for your application compared to LiFePO4 and also the much lower charge discharge efficiency.
They mention a service life of 17 years based on IEC61427 and if you check what that means here https://www.trojanbattery.com/pdf/RE_IEC_61427_Standard.pdf
they consider that 50 + 100 shallow cycles are equivalent with 1 year of service life.
The first 50 cycles are 30% DOD and the 100 cycles at 25% DOD with very low discharge rates just 0.1C (10h discharge rate).
For simplicity I will be generous and say 150 cycles at 30% DOD x 17 years as the max possible life for the battery again excluding most of the calendar aging as that is not considered in this tests that only take a few months.
$1222 / 150 x 0.3 x 17 x 5kWh = $0.32/kWh way to optimistic as calendar aging is not considered in the IEC61427
Now if you do the same for LiFePO4 and ignore calendar aging you get
300 to $400/kWh cost and 3000 to 6000 cycles at 100% DOD but I will take a Winston cell that is just 5000 cycles at 80% DOD so
$400 /  5000 cycles x 0.8 = $0.1/kWh again if you include calendar aging the realistic number I always use is $0.2/kWh.

My battery is made with A123 cells (I fully offgrid) and I use the battery heavily at an average 47% equivalent DOD every day and after first year measured degradation was 0.9% from that around 0.3% is from cycling and 0.6% is from calendar aging. This cells are rated 5400 cycles at 100% DOD.

[NorthGuy]

Even with lower usable-capacity ratio, comes to ~10¢ per kWh of storage, and may well go 6-8 years if cycled not too deeply on average say 2-3 times a week.

I did some modeling for different batteries as applied to my particular system about 7-8 yeras, and FLA Deka (8L16) came at $0.35/kWh, which was second from the last, which was Deka gel (8G4D) at $0.54/kWh. The first place - Surrette 12CS11PS came at $0.14/kWh. I only considered LA batteries back then.

[john61ct]

Of historical interest I suppose. Well L16s aren't GCs, and maybe they weren't flogging the "Duracell" label through consumer retail nationwide back then.

Deka's GEL aren't quite as good as Sonnenschein from whom they licensed the tech.

But can last a **very** long time, just a bit finicky on the charge profile requirements, easy to damage overcharging.

[NorthGuy]

Of historical interest I suppose.

I don't think the prices have changed much. Surrettes actually went down a bit in US dollars. They were $1300, now they're $999:

https://www.solar-electric.com/su12357ampho.html

They're still about the same in CAD

[john61ct]

I meant the Deka GCs being so much cheaper now

[Red Squirrel]

I was curious and found these on Amazon:

https://www.amazon.ca/RUIXU-LiFePO4-Battery-Off-Grid-Applications/dp/B07SZ6LR83

Among others.

Problem with Amazon though is you really don't know what you're getting, it's basically a fancier ebay.   So it's still a lot of money and you don't know if it's just going to fail in a year or explode and kill all your family.  You get 90 day return policy to whatever it is, and that's it. If it fails then you're on your own and there's no contact or company behind it or anything.   

Too bad it seems so hard to find reliable sources for this stuff though.  I want to start experimenting with lifepo4 and regular lithium ion  and eventually maybe even convert over my lead acid systems but without reliable sources I will stick to lead acid for stationary battery plants.

[john61ct]

I think it is likely that vendor Ruixu is indeed selling genuine Sinopoly cells, a well respected maker.

However there's no way to tell in advance whether or not they are QA rejects, or sold out the back door by the night shift, etc.

They also sell through Ali and eBay, which have decent buyer guarantee policies.

If you are ready to go with thorough capacity testing, checking IR matching, voltage sag, self-discharge

then I think odds are pretty good of being able to judge the cell quality within a week or two.

Of course a seller able to accept returns on the same continent as you would be better.

[NorthGuy]

I was curious and found these on Amazon:

https://www.amazon.ca/RUIXU-LiFePO4-Battery-Off-Grid-Applications/dp/B07SZ6LR83

Or directly from China at much cheaper cost, such as:

https://www.alibaba.com/product-detail/Hot-Sales-Lithium-Ion-Lifepo4-48V_955841194.html

Either way, there's no way to find out if the batteries are going to last.

[john61ct]

Or directly from China at much cheaper cost, such as: https://www.alibaba.com/product-detail/Hot-Sales-Lithium-Ion-Lifepo4-48V_955841194.html

Either way, there's no way to find out if the batteries are going to last.

That is a completely different seller. Here is Riuxu https://m.aliexpress.com/store/v3/home.html?shopId=5015059&sellerId=238482081

This is them on eBay
https://www.ebay.com/sch/i.html?sid=bulbman702

Of course contacting a known good manufacturer and buying direct is the best way, but certainly costs a lot more than through the riskier sellers.

[NorthGuy]

That is a completely different seller.

Most sellers sell the same. They pack little batteries into big packs and optionally add BMS. Your luck only depends on how good were the little batteris they used. These may be premium new batteries, or some used junk at the end of their life. Who knows ...

[tytower]

Man thats a big price above .
To get a good sized house bank of say 48 volts wound be $8000 plus delivery, and that's still only 400 Ah.

Hope anyone using them has the good sense to compress the sides slightly to stop expansion.
With a normal BMS these days each board uses a chosen chip with the needed cut off points for each function being monitored.
What your board monitors is defined by the chip specs so its up to you or your manufacturers recommendation.
They are usually back to back Mosets on the board used for switching so both must be on for current to flow. They are always on the negative line.

If a Mosfet is turned off , the whole battery pack is turned off.

Its my conviction that anyone who says run LFP without a BMS has not really used their battery pack and are stuck in the old lead acid era when you start to worry at 80% SOC. hard to get out of but get out of it you must and use your LFP's to full advantage.
The world is catching on.

[john61ct]

Most sellers sell the same.

Yes, but in this case we were discussing sourcing quality LFP from known-good factories - Winston/Thundersky/Voltronix, CALB, GBS, Sinopoly and A123 (now Lithium Werks / Valence / Super B).

> They pack little batteries into big packs and optionally add BMS.

I did not see anyone talking about those, very rare for the above.

In this case, large hard-case prismatics, where 60Ah cells are small, go up to thousands of Ah per cell.

And specifically, the units under current discussion are made by Sinopoly, that's the only reason that specific seller Ruixu is being discussed.

Hence my pointing out that your suggesting some random Ali seller flogging completely different cells as an alternative is not helpful.

Or are you actually specifically recommending that seller, if so then for what, and why?

[john61ct]

Man thats a big price above .
To get a good sized house bank of say 48 volts wound be $8000 plus delivery, and that's still only 400 Ah.

Yes, we're looking for top-notch quality LFP, so if you know of more reasonably priced sources suitable for NA please link to them.

Even for a much smaller bank, the delivery cost alone is usually $600+

Keep in mind they're Hazmat, and Trumps's tariffs may have an impact any day now.


_____
Depending on the use case and your care protocols for checking / monitoring, there are many choices how to implement "BMS" functionality.

Sure LVC / HVC and temp failsafes can be critical, adjustability is key,

but thousands of banks built from new quality cells don't need any re-balancing at all cared for properly, zero capacity loss over thousands of daily cycles, some hitting a decade now.

Yes compression plates are standard.

[john61ct]

I don't think trying to include cycle life across different chemistries yields a clearer picture.

Vendor lab results have hardly **any** relationship to reality.

A 100Ah 12V drop-in Battle Born can't realisticall be compared to 1000+ Ah bare cells from CALB or Winston, or baby 2500mAh cylindricals from K2.

The variation by usage patterns between say propulsion vs solar storage could be 500 cycles vs 6000.

And that's just within LFP!

[NorthGuy]

Or are you actually specifically recommending that seller, if so then for what, and why?

No. I am not recommending any sellers. Moreover, I believe that buying any of these batteries is a huge risk, and I would strongly recommend against that.

[john61ct]

Then it seems you have no interest in the actual topic, won't have anything constructive to add to the thread and I suggest it best you just ignore it.