lithium maganese cells

[donald]

........

Can you make a house-power bank from other lithium chemistries - sure - but you are wasting money and energy (unless you are just cheaping out for some reason) on cells not designed for a house-power "Sub-C" application! Kind of like putting a Chrysler Hemi into a Yugo. Fun, but not the norm.
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I don't get the criticism. He said what it cost, and it should work for a number of years. FLA is hardly trouble free and less expensive. Purpose made li-on battery packs, like the powerwall, still look pricy for the next several years.

Especially in Norwegian with its vast EV %, this seems like a great DIY storage solution.

[jkirkebo]

I guess it is now. It was just trying to protect tasman from mixing and matching different chemistries.

Certainly recycled leaf cells can be used if you know what you are doing. Recycled or not though, the high-current capability of the cell is going to waste for a relatively low-current solar housebank (other than a one-off diy project).

Yeah, the high current capability is not needed. However it is not a drawback either, since the cells have such low internal resistance the charging efficiency is fantastic. I've calculated it to 99.8%, compared to ~94% on my old FLA bank (12V from 3xRolls 4KS25PS).
Also the modules are too big for applications like wheelchairs or ebikes, so they are not very sough after and thus pretty easy to aquire cheaply. They only really work for EVs and stationary storage like solar. To get a 48V (well, really 52.5V nominal battery for a fast ebike one needs to connect 7 modules in series, which will weigh about 55 pounds. Way too heavy and way to high capacity at 66Ah.

For instance, your leaf cells from Norway will differ a bit from those who came from crashes in Arizona: (leaf cells are discussed among others - one of my fav videos)

https://www.youtube.com/watch?v=pxP0Cu00sZs

Yeah, one should definately be aware of the heat problems with these modules. That said, an Arizona Leaf battery degraded to 70% of original capacity should still be very usable if it's cheap enough. Just add some more modules for the same total capacity.

This is not unlike EV forums where the main emphasis was on using large prismatic lifepo4, and suddenly is barraged by guys wanting to power their vehicles with used laptop-pulls. Or wheelchair users thinking that large prismatics are the way to go, when in fact higher-current small cylindrical headway lifepo4 cells (typically 10ah each) are really are what is needed with their huge motor current surge demands. Ideally one fits the battery to the application as closely as possible..

I agree, C-rate must be high enought for the application. I do not however see a problem with high C-rate batteries in a low-C environment as long as they have enough energy density for the application and is reasonably priced. For a 35kWH off-grid battery like mine which will never see a load above 0.2C any battery chemistry will do. So it's better to focus on the other parameters like weight, size, cost, efficiency, durability, maintenance need etc. Here the used Leaf-modules excels in most categories, for solar use.

[PNjunction]

This is the LiMn thread after all?

I guess it is now. It was just trying to protect tasman from mixing and matching different chemistries.

Does any one have any information regarding lithiun maganese battery cells. I'm using lifepo4, was about to order some more when the supplier offered me great prices on lithium maganese cells, half the price of lifepo4. Had a bit of a look around about them and they seem to be much better the lifepo4, other than they don't have the same energy density.

Certainly recycled leaf cells can be used if you know what you are doing. Recycled or not though, the high-current capability of the cell is going to waste for a relatively low-current solar housebank (other than a one-off diy project). Like all battery projects, unless one knows what they are doing, stay away from used batteries like used toothbrushes. Details make the difference.

For instance, your leaf cells from Norway will differ a bit from those who came from crashes in Arizona: (leaf cells are discussed among others - one of my fav videos)

https://www.youtube.com/watch?v=pxP0Cu00sZs

This is not unlike EV forums where the main emphasis was on using large prismatic lifepo4, and suddenly is barraged by guys wanting to power their vehicles with used laptop-pulls. Or wheelchair users thinking that large prismatics are the way to go, when in fact higher-current small cylindrical headway lifepo4 cells (typically 10ah each) are really are what is needed with their huge motor current surge demands. Ideally one fits the battery to the application as closely as possible..

Dunno - maybe to avoid confusion a separate LEAF battery thread could be started with a possible warning or two about their charging differences from lifepo4? Just trying to keep the neophyte from confusing chemistries and making big charging errors ...

[jkirkebo]

And do not forget to make a conscious decision as to whether to bottom balance (best for safety) or top balance the packs. Top balance would be more important if you intended to charge the bank close to 100% SOC, which is NOT recommended for longest battery life.

Yeah, mine is charged to nowhere near 100%, I stop at approx 80%. 80% is also the recommended long-life charging mode in the Leaf. So top balancing these is out of the question. Better to balance at all times, ie. middle balacing. The AESC modules in the Leaf track each other very closely voltage wise and seems to respond well to this. And since neither the top 20% or bottom 7-10% is used perfect balancing isn't very important either.

Here's a snapshot of the cell voltages taken now: Skjermbilde.JPG

[jkirkebo]

Can you make a house-power bank from other lithium chemistries - sure - but you are wasting money and energy (unless you are just cheaping out for some reason) on cells not designed for a house-power "Sub-C" application! Kind of like putting a Chrysler Hemi into a Yugo. Fun, but not the norm.

Except when yuu can get really cheap cells from wrecked cars. Recycling at it's best and it's nice to see a 53V lithium bank only sag half a volt or so under 6kW load
And since I paid only a little over $100/kWh I doubt you can get LiFePO4 any cheaper.

If you did this to GBS cells (which admittedly have a *dash* of mangenese in them), they'd be toast.
PLEASE keep chemistries straight here or someone may get hurt.

Of course. The Leaf cells are refular lithium cells with a max voltage of 4.2V. This is the LiMn thread after all?
Info is readily available on the AESC modules that is used in the Leaf. I know they are popular for building replacement batteries for some electric scooters. They are excellent quality cells that usually never need much balancing, and they are very easy to mount together and build whatever capacity battery one need.

[inetdog]

And do not forget to make a conscious decision as to whether to bottom balance (best for safety) or top balance the packs. Top balance would be more important if you intended to charge the bank close to 100% SOC, which is NOT recommended for longest battery life.

[PNjunction]

Thanks and interesting. The lithium manganese Ive seen, been offered and interested in, are only 3.2-3.4v, half the price of lifepo4 and guaranteed for 2500 cycles.

If those are the true charging specs, then they are NOT LiNmC, but actually lifepo4 with a *dash* of manganese added much like GBS uses. LiFeMNpo4. Still lithium-iron-phosphate at heart, and follows the charging regimen for lifepo4 which means no more than 3.6v typically.

Watch out - many sharks out there to hoodwink the duct-tape-a-pack together crowd with gray market / EV crash / failed warantee reject cells.

[PNjunction]

Warning to newcomers

Don't get your chemistries confused or you will destroy your cells and run in an unsafe environment.

LiNMC (lithium manganese) such as seen in some EV products, RECENT powertools, flashlights, and the like are designed for HIGH CURRENT capability, (regen and so forth) and typically are designed for no more than 4.2v max charge, just like their laptop cousins.

These differ from large prismatic GBS lifepo4 cells, which have a *dash* of manganese in them. Their chemical structure is predominantly Lithium-Iron-Phosphate, but this *dash* of manganese makes them LiFeMnPo4 chemically. They are rated at most for about 3C temporary bursts, whereas the linmc cells are purposely constructed for much higher rates, much of which would be a waste in a solar house power project of any reasonable size.

That means that you do NOT charge GBS cells beyond 3.6v like you normally would with the other types like laptop / flashlight cells.

Ie, the major players in the lifepo4 arena that charge to no more than 3.6v, are GBS, CALB, Winston and a few others. They are all predominantly lifepo4.

Can you make a house-power bank from other lithium chemistries - sure - but you are wasting money and energy (unless you are just cheaping out for some reason) on cells not designed for a house-power "Sub-C" application! Kind of like putting a Chrysler Hemi into a Yugo. Fun, but not the norm.

For example:

Yes, I balanced every module perfectly with a BC168 (6 channel, so 3 modules at a time) to 4.05V before constructing the packs. If not there would have been sparks flying

If you did this to GBS cells (which admittedly have a *dash* of mangenese in them), they'd be toast.

PLEASE keep chemistries straight here or someone may get hurt.

[jkirkebo]

Did you balance the cells individually before constructing the packs? Find any bad cells?

Yes, I balanced every module perfectly with a BC168 (6 channel, so 3 modules at a time) to 4.05V before constructing the packs. If not there would have been sparks flying

I haveb't found any bad cells. The BMS reports very similar internal resistance for each 10P module and the voltages track very nicely. Before balancing the cells also had nearly identical voltages (but two different levels since the modules come from two different Leaf packs).

[donald]

Did you balance the cells individually before constructing the packs? Find any bad cells?

[jkirkebo]

Very cool. These are new cells?

No, I got them from wrecked Leafs. There are maybe 20,000 Leafs in Norway and there is a steady supply of crashed ones. There isn't much demand for complete battery packs so they can usually be gotten at reasonable prices from the wrecking yards.

[donald]

I use Leaf modules in my off-grid cabin. 70 of them for a 35kWh battery of which I use approx. 25kWh. 7S10P which is a 14S battery since the modules are 2S2P.

Charging safety is not a problem. My Outback FM80 is set to 57V which for the 14S battery is 4.07V per cell. The Orion Jr. BMS controls a charger safety relay that cuts the PV input to the FM80 if any cell exceeds 4.10V. The BMS also continously balances above 3.900V for any cells 10mV higher than the lowest. Also the BMS controls a load safety relay that turns off the inverters and most 12V loads if any cell dips below 3.4V.

Thermal management is not neccessary in Norway, we never get Arizona temperatures here (max ~25C where the cabin is located). Also I never draw more than a little less that 0.2C from the battery bank (2x3kW inverters + a 360V 12V DC-DC). Charging is 5kW max from generator or 2.6kW max from solar (8xSunpower 327W).

Price paid for the modules was $3750 for 35kWh, or a little over $100/kWh. What can compete with that, price wise?

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Very cool. These are new cells?

[jkirkebo]

Let me guess, they are advertised as new Nissan Leaf Modules from 2012 right? Along the lines of this ad right?

I use Leaf modules in my off-grid cabin. 70 of them for a 35kWh battery of which I use approx. 25kWh. 7S10P which is a 14S battery since the modules are 2S2P.

Charging safety is not a problem. My Outback FM80 is set to 57V which for the 14S battery is 4.07V per cell. The Orion Jr. BMS controls a charger safety relay that cuts the PV input to the FM80 if any cell exceeds 4.10V. The BMS also continously balances above 3.900V for any cells 10mV higher than the lowest. Also the BMS controls a load safety relay that turns off the inverters and most 12V loads if any cell dips below 3.4V.

Thermal management is not neccessary in Norway, we never get Arizona temperatures here (max ~25C where the cabin is located). Also I never draw more than a little less that 0.2C from the battery bank (2x3kW inverters + a 360V 12V DC-DC). Charging is 5kW max from generator or 2.6kW max from solar (8xSunpower 327W).

Price paid for the modules was $3750 for 35kWh, or a little over $100/kWh. What can compete with that, price wise?

2015-04-25 23.39.41.jpg

[Sunking]

If anything else, I'd recommend GBS to newcomers purely because they come with cell-top covers to enhance the safety factor from the get-go - of course you need to actually use them!

As disclosure I have GBS cells, but they are used in a Golf Cart. GBS is good, but is a High-End LFP product. CALB is trusted and the most bang for the buck even though they just went up in price.

Looks like LFP cells have bottomed out, and now prices are rising. A month ago you could get Calb cells for 34-cents per watt hour. Today just a hair shy if 40-cents or a 15% increase.

[PNjunction]

What makes lithium batteries a bit confusing for newcomers is the industry just lumping all lithium-based batteries together without knowing that there are differing characteristics and charge routines.

It is kind of like walking into a battery retailer and simply saying " I need a lead-acid battery please". Plenty of ways to get ripped off if you don't know if you need a starter battery, deep discharge, flooded, agm etc etc.

Same goes for lithium. To add to the confusion, I have a few small radios that now use a single LiNMc battery like Tenergy and so forth, which are 3.7v cells and NOT lfp. These very same cells go into automotive jump-starter packs, yet the radios themselves only draw something like 75ma in operation. The capability of those cells in the radio application are going to waste, but are cheap enough not to matter. I would have preferred the lower voltage LFP if I was the engineer, but they went with these.

So I can see the confusion when someone considers lithium for a solar setup, and not differentiating between the 3.2v lifepo4, and all the others (3.7v different chemistries) when there is really a mis-application in some consumer devices like my radios. Presumably they did that for that tiny bit of higher voltage and slightly smaller form factor.

All the major players like GBS, Winston, CALB etc are more than good enough for our needs. If anything else, I'd recommend GBS to newcomers purely because they come with cell-top covers to enhance the safety factor from the get-go - of course you need to actually use them!