1400 Ah Lithium from cells

[rom]

Originally Posted by CatNewBee

Smaller cells op to 400Ah are driving around daily in various RV's with no problems, the road is harder then the ocean btw.

in a different way ... everything in a boat can be punched up and down real hard for hours on a passage. I thought the explanation hereunder made sense:
Assembling a Lithium Iron Phosphate Marine House Bank | | Nordkyn Design

But well, good for you your happy with your system. Let us know how it goes on the long run.

[nebster]

Originally Posted by CatNewBee

So what is the point?

His point is that the consensus is that larger cells are probably riskier. He probably wants to know how much that weighed into your decision. That seems like a reasonable question.

[CatNewBee]

I use the larger cell on purpose, because they are built more robust, not to heavy (35kg) and have great connectivity (6 x M12 connection posts, massive bars inside for high amps). It is BS, that bigger cells are more sensitive. the cell is not an empy thing, it is packed inside by lots of foils wrapped tightly around, no spaces, no moving parts. There is nothing inside that moves freely and would be affected by the movement of the boat. Its almost a tight packed and sealed brick, there are no liquids or plates inside like a wet lead acid battery.

Also there are only few connections between the cells ( up to 3 bridges if you want per inter-cell connection, I made 2 bridges for redundancy and power out of solid copper bars 30mm width x 5 mm thick, the remainig connectors will be used for the sensors only.

Lots of small cells are messier to integrate, lots of connections / joints that can mess up the whole system, also potential imbalance and risk of fire because of overpowering a single cell by the grid around in a parallel first design, also necessity of cell-fuses and cross-connections to keep the parallel cells in balance and in the power path. Serial first increases the redundancy, but also multiplies the BMS and the power relays. Its more risky than a clean 4 cell design. I'm for "Keep it simple".

Winston is the only manufacturer that is able to manage the process of building high-capacity LiFeYPO4 cells on the market above 700Ah / cell.

Winston cells have usually 10-20% more power than stated the spec, they promise to keep the specified Ah for 3000 to 5000 cycles, so they have some more capacity upfront. This cells are for industrial use and used in e-mobility projects as well as stationary storage systems. Winston is the market leader in LiFeYPO4 and the cells are used inside of many "branded" products. Winston produces the cells, and the others built the enclosure and the BMS around. http://en.winston-battery.com/index..../power-battery This Batteries delicer constant current of 3C and Impulse current up to 10C on charge and discharge - that means up to 3000A for constant current applications and 10000A short use. Well on the boat, there will be not more then 500A draw / 400A charge, so this will be lazy and operate in a very safe zone - most of the time the current will be around 50A for the electronics / fridges / freezers etc....

So I an pretty optimistic to have made the right decision. You can have a warranty up to 3 years for the cells and the capacity, if you pay some extra, otherwise 1yr warranty. Even is after a time one cell fails, its 1200€, its replaceable. Its unlikely that all 4 cells die the same time.

I believe, the risk to screw up a system of 48 cells is in magnitudes higher then a 4 cell system.

Anyway, you can built your system to your needs / thoughts... Many people complaining about LFP never hat one, they insist to use the out of the box systems, but don't want to pay for them. Some troll around becauuse they want to sell consulting and the expensive stuff of Lithionics, Mastervolt and Victron. Even the reps of Mastervolt and Victron are often reluctant to sell you the components or give you information without consulting and installation, they make the profit on labor.

But you can buy what you need on the market and physic is universal, electrons do not care about brands and marketing bla bla. Electricity is universal science and current flows regardless of a brand.
If you understand how it works and can interpret the datasheets, you can combine any component with something else.

I am fortunate to have the technical background in electricity and electronics, so I have respect but no fear of projects like this one.

btw: The BMS is calculating / measuring the cell resistance, so the voltage is compensated on high loads - but on those 1000Ah bricks it means nothing, they are simply so big and powerfull (can deliver 3000A continously), that loads of 200A or 500A do not make any significant voltage drop (around 50..100mV @ 3V), what is really impressive. In low temperature this is a different game, but still, the BMS will compensate the voltage drop too.

[nebster]

There's no need to be dismissive with your language, CatNewBee. Be nice here.

I don't think a lot of the manufacturing industry agrees with your statement about "BS", and the physics aren't in your or Winston's favor either. But it would still be great if Winston has built something that is better than anything else out there.

A while back, I built a spreadsheet to look at cost and density across a bunch of available cells. The Winston 1000Ah was on my worksheet, but interestingly, it looks like the weight has been decreased slightly (or I mistyped it) in the last year.

With a 20% derate (or max 80% DOD, which is really 15-95), Winston 1000AH achieves 33Wh/lb, which is on par with CALB CA 100Ah, GBS 200Ah and 400Ah, and slightly below the most plastic-shell LFP cells with the highest gravitometric density, like the CALB CA 180Ah.

Comparatively, the aluminum-shell LFP cells achieve about 20%-40% greater energy density per unit mass, coming in at about 40 to 47Wh/lb on average.

Looking at volume, the Winston monster cell achieves 2.81kWh/ft^3, while CALB CA 100Ah is 3.49kWh/ft^3. CALB 180Ah is the king of volumetric energy density in plastic-shell LFP at 3.79kWh/ft^3, or about 34% more. This is may explain why you are seeing 30% over-provisioning... because otherwise, these batteries are really big for their rated capacity.

Now let's look at the aluminum-shells. Adding compensating volume for spacing (because they need air in between each cell), CALB CAM72 achieves around 5.5kWh/ft^3, or about than twice as much energy per unit volume. Other aluminum shell cells, including the ones I am using, come in about the same.

If your delta-voltage numbers are accurate (0.2mOhm IR), that is incredibly good and weighs significantly in their favor. That means your interconnect resistance will dominate, which you haven't characterized for us by the way. Have you placed a 500A load on your pack with full fusing and disconnects in-circuit? They add substantial resistance and will impact your drop.

I think if space and weight efficiency is not as big a concern, and especially if someone is looking for the simplest pack build at about 10kWh, this seems like an attractive cell. I think I would probably still choose a smaller (perhaps Winston 700Ah or 400Ah?) cell and go up to 4s2p, or 8s1p 24v, or 9s1p 28v for flexibility, since wiring is not hard and more failure modes are mitigated with these pack topologies when in remote locales.

But if density is a top priority and/or the storage location is constrained, the aluminum shell options are way out in front. They approach NMC on volumetric density. To my knowledge, no one is willing to make an aluminum LFP cell bigger than 300Ah today. Maybe Winston could figure it out.

[kmacdonald]

I haven't seen much of a reduction in pricing of LiFePO4 over the last 4 or 5 years. I would have thought they would have come down quite a bit in that time period.

[john61ct]

Blue Sky is one of the few charge sources that has NO as an option for Float.

May require the remote/BM add-on.

It is not true that a Float set below resting is known to have no effect sitting on a Full bank. Likely it is fine, but the ideal if you can do it is Just Stop, isolate from the charging buss.

[john61ct]

Originally Posted by nebster

Absolutely. But a bank of 8 or 12 1000AH is likely impractical for the person who selects a 4s1p 1000AH pack for its simplicity and capacity.

many would say 1000AH cells are themselves impractical.

And going to high voltages makes little sense unless propulsion. Maybe 24V for some windlass and long wire runs.

[kmacdonald]

Originally Posted by john61ct

Blue Sky is one of the few charge sources that has NO as an option for Float.

May require the remote/BM add-on.

It is not true that a Float set below resting is known to have no effect sitting on a Full bank. Likely it is fine, but the ideal if you can do it is Just Stop, isolate from the charging buss.

True. LiFePO4 overcharging in the RV market have proven to be a battery killer. LiFePO4 has also proven to eat tow vehicle alternators like children eat candy.

[jbinbi]

Nothing new to add but to say, excellent write up. Thanks.

[nebster]

Originally Posted by john61ct

And going to high voltages makes little sense unless propulsion. Maybe 24V for some windlass and long wire runs.

Depends on the size of your boat (load). 5000kW is the practical limit for 12v systems unless you are really a glutton for punishment.

Once you decide to take the leap across the 12v chasm, you're going to be downconverting for all your legacy 12v equipment, so you might as well go to the safe limit of 50v. All the rest of the equipment is cheaper (and more efficient) in 48V designs.

I believe we'll see most of the mobile house-power space move to 48v over the next few years, at least in any setting where motors or compressors are involved.

[senormechanico]

Originally Posted by john61ct

Blue Sky is one of the few charge sources that has NO as an option for Float.

May require the remote/BM add-on.

It is not true that a Float set below resting is known to have no effect sitting on a Full bank. Likely it is fine, but the ideal if you can do it is Just Stop, isolate from the charging buss.

I have the add on Pro Remote. I didn't see any option to NO float, although it allows several parameters to be programmed.
Got a link?

Ooh, popcorn ! I'm gonna make some.

[CatNewBee]

First of all, you are right, I checked the Data, 35kg per cell seems to light, it was an old datasheet of one supplier I looked up (thanks google). Actually Winston says they are 41kg +/-500g, but this is no big deal either.
Btw, during my research I noticed, they increased the price by 10% this year.

The charging regimes are always done by the sources and not the BMS itself, the BMS creates only some signals to protect the battery. This one has up to 4 independent programmable outputs instead of the usual 2 (over-voltage and under-voltage protection), the standard configuration is to have the opto-coupler and the relays doing the same (OVP / UVP).

I am nice and not dismissive, otherwise I would not participate in this discussion... Anyway.

I also had my checklist end ended up at the 1000Ah cells as the perfect solution for me.

- I wanted the Yttrium cells because low temp changeability.
- They were almost linear in price/capacity at the dealer around
- I wanted as few as possible connections
- I wanted a system for heavy load up to 7kW on inverter
- I wanted batteries with low voltage drop and deep discharge
- I wanted a BMS, where I can set / modify the values and that gives me a lot of flexibility.

The measurement of the resistance and the calculation of the cell voltage is done by the BMS on the cells directly, the voltage drop of cabling, fuses, relay contacts etc. is not relevant for this measuring. Also the Victron Quattro has separate voltage sense wires to the battery to measure the battery voltage prior the drop over the current path to work properly, same for the BMV monitor.

If I figure out, the system needs further tweaking, I can do that. I even have a Victron BMV wit a programmable output, a MPPT controller wit input switch and programmable relay and also the quattro has a built-in battery monitor and programmable relay outputs. So - I can measure Voltages, SOC, count Ah and use any value between empty and full to fire up additional signals / events and switch devices on and off if I want to.

The Charger of the Quattro will run only on purpose (when I start the generator or connect to shore power - it will be not the normal charging of the bank) More important is the charging program of the MPPT controller - because it runs always and starts over daily. I will start with the same settings like the Quattro for the charging regime and will see how it works, what my usage pattern is and if the charging fits to my needs. I have 24/7 running loads on board (Fridges, Freezer, Ice maker, warm water...) There will be a need for re-fill in the morning.

[nebster]

Originally Posted by kmacdonald

I haven't seen much of a reduction in pricing of LiFePO4 over the last 4 or 5 years. I would have thought they would have come down quite a bit in that time period.

Yeah, weird, huh? I guess the material, synthesis, and assembly costs are pretty much optimized already without some special leap that might not come for LFP. Electrochemistry is pretty a staid art compared to integrated circuits.

The real pricing improvements seem to be over in the cobalt chemistries, where there must be a market several orders of magnitude larger.

[nebster]

Originally Posted by CatNewBee

First of all, you are right, I checked the Data, 35kg per cell seems to light, it was an old datasheet of one supplier I looked up (thanks google). Actually Winston says they are 41kg +/-500g, but this is no big deal either.

Ah, okay. Well, that makes mass data match the volume data in comparison to other plastic LFP: it's clear that Winston is overprovisioning these cells by a larger factor. It seems strange that they'd do this for "free," so I wonder if they are doing it to provide cover for degradation related to the larger internal structure.

(By the way, the electrolyte in an LFP cell is a liquid. And the electrodes are super thin and flexible, like tinfoil.)

The charging regimes are always done by the sources and not the BMS itself, the BMS creates only some signals to protect the battery. This one has up to 4 independent programmable outputs instead of the usual 2 (over-voltage and under-voltage protection), the standard configuration is to have the opto-coupler and the relays doing the same (OVP / UVP).

Those REC BMSes look great. A little too expensive for 6 x 16 channels, but plenty reasonable for such a huge 4s pack.

- I wanted the Yttrium cells because low temp changeability.
- They were almost linear in price/capacity at the dealer around
- I wanted as few as possible connections
- I wanted a system for heavy load up to 7kW on inverter
- I wanted batteries with low voltage drop and deep discharge
- I wanted a BMS, where I can set / modify the values and that gives me a lot of flexibility.

Seems like you nailed it.

The measurement of the resistance and the calculation of the cell voltage is done by the BMS on the cells directly, the voltage drop of cabling, fuses, relay contacts etc. is not relevant for this measuring. Also the Victron Quattro has separate voltage sense wires to the battery to measure the battery voltage prior the drop over the current path to work properly, same for the BMV monitor.

Good point, you can go right to the cells. I was thinking of my parallel setup, where things like the inverter and BMV v-sense have to be at the bus, which is already past some substantial fusing and cabling.

[CatNewBee]

No, it's the demand. This batteries are sucked up by the automotive industry, truck, buses, even street scooter use the yellow winston cells. Also large energy storage systems for wind- and solar parks use this as a buffer, large UPS systems too, military is also one of the customers for submarine propulsion energy storage... Also many DIY builder use them in RV projects, some for powerwalls in the garage with solar roofs, there are lots of small to large companies building drop-in LFP batteries with proprietary bms using the Winston cells, also some of the LFP "solution provider" build on Winston cells, they split the balancer and attach them to the cells into the sealed battery while adding the second part of the BMS with the OVP / LVP logic to proprietary external modules - that ensures that the customer sticks to the manufacturer's product range for extensions.

The demand is exponentially increasing and there are only few suppliers around. The Tesla systems bet on LiPo, but the bigger rest of the world uses LFP for safety reasons and larger temperature range. Besides the promised global warming, it's pretty cold in some places around the world, you need batteries working also in sub-zero environments.

I guess, the prices will continue to rise until some other jump on the wagon and flood the market with cheep mass batteries. There is very little competition around for free available batteries on the market. Some "green energy" companies do build batteries as OEM only to the system integrator / car builder, so you cannot buy the cells as consumer.