NMC or LiFePO4 based on kWh price and budget?

[yabert]

IMHO, 12S is pretty worthless for 48V.

Worthless! Well, I can understand your point. Higher voltage of a NMC 14S or 15S battery will lower current for same power output (by 15-20%) and the voltage range is similar to 4x 12V lead acid battery in serie.
Still, with an adjustable inverter low voltage cut-off at 40V, a 12S battery is perfectly fine. Between 40V and 50V a 12S battery will give you access to over 90% of his capacity.
So if someone find high quality/low cost 12S EV battery module, why bother.

I hope nobody on earth will have the bad Idea to take perfectly integrated and high quality 12S battery modules and destroy it to tried to do a DIY 15S battery simply because high voltage is better.
I bet battery fire could happen when a single guy think he is smarter than the hundred of engineers who designed and produce the 12S battery module for an EV warranty 8 years and hundred thousand miles.
Some battery module can be easily rearrange (Ford Energy, Nissan Leaf in mind), but some other are near impossible to rearrange (Tesla, VW, GM, Kia in mind).

But hey, we should all write to EV manufacturers to propose them to build 14S and 15S battery module instead of 12S
Oh! wait, 16S LFP modules in fact ?

 

[SeaGal]

Just wondering... how do people get hold of EV batteries cheaply, especially newer ones like the Volkswagen ID3? Is it from crashed / written off vehicles? If so, surely the act of crashing an EV could cause internal damage to the cells? Or worse still, some internal weakness that doesn't manifest itself until a year or two later.

 

[yabert]

Just wondering... how do people get hold of EV batteries cheaply, especially newer ones like the Volkswagen ID3?

Crashed car.

If so, surely the act of crashing an EV could cause internal damage to the cells?

These days, insurance companies declare total loss for cars with really small damages. Example, an airbag has exploded and there is bumper, a light and a fender to change... this brand new 50k$ EV have now 35k$ in damage and it declare total loss. IT's sad to see all those lightly crash EV been declared total loss.
Also, new EV are really well build and their battery cells are often specially well protect inside car structure, battery pack structure and battery module structure.

 

[Alkaline]

Yeah, NCA chemistry (most Tesla) is quite dangerous in over voltage even.
NMC chemistry (most EV) is less dangerous, but still no safe.
LFP chemistry (some Tesla and other China EV) is safe in most situation.

I would like to use LFP cells for my house, but I bought a Ford Fusion battery module (NMC) for free. In fact, I paid around 50$/kWh and I end with free modules after had sold half of the modules.
My receipt to sleep well at night with my NMC battery is the 3 security steps: Inverter have HV/LV setting, the relay BMS have HV/LV setting at cells level and I add a HV/LV controller to watch the BMS.

what chemistry is ltihium polymer based? I know that is the explosive out of them all.

 

[yabert]

Li-Po is often use to describe RC battery (Radio-controlled aircraft/car). Those are LCO (Lithium cobalt oxide battery).
But in fact:
LiPo technology is used across all the main lithium battery chemistries:

• Lithium cobalt oxide battery (LCO)
• Lithium-ion ternary battery (NCA, NMC)
• Lithium-ion manganese oxide battery (LMO)
• Lithium iron phosphate battery (LFP)

To me there is absolutely no comparison between a 12$ Lipo battery build inside any Chinese factory to serve few months in a Radio-controlled aircraft/car and an EV battery build for biggest car companies in the world and build to be warranty 8 years/100 000 miles.
Still, LFP is king in safety and I can't wait to dismantle high quality LFP battery module out of crash EV.
@Nick0016, if you can put your hand on a LFP Tesla 3 battery I will be the first interested to know how complex they are to rearrange ?

 

[Nick0016]

Thanks all for the comments.

Here (Netherlands) it's fairly easy to get EV batteries, BMW PHEV 60V (2kWh module 16S) goes as low as 25,-- EUR per kWh.
Although no LFP yet from EV's.

But total costs is quite high as the cells are <100Ah which mean more hardware to connect/monitor them all if you go for like 40 kWh and want to monitor all cells (which you should with NMC).
Cells >100Ah are a lot more expensive which then you can go better with LFP.

So even tough the costs for LFP are 1,5-2x more I will be starting with LFP with 20 kWh capacity and grow later on.

Main reason:
Did more research (with the information from here) and hearing more stories about thermal runaway on systems that have been running perfectly for years. The chances is so little but it does happen...

 

[houseofancients]

Thanks all for the comments.

Here (Netherlands) it's fairly easy to get EV batteries, BMW PHEV 60V (2kWh module 16S) goes as low as 25,-- EUR per kWh.
Although no LFP yet from EV's.

But total costs is quite high as the cells are <100Ah which mean more hardware to connect/monitor them all if you go for like 40 kWh and want to monitor all cells (which you should with NMC).
Cells >100Ah are a lot more expensive which then you can go better with LFP.

So even tough the costs for LFP are 1,5-2x more I will be starting with LFP with 20 kWh capacity and grow later on.

Main reason:
Did more research (with the information from here) and hearing more stories about thermal runaway on systems that have been running perfectly for years. The chances is so little but it does happen...

ben je bewust dat in het geval van li-ion je verzekering die niet zal goed keuren en bovendien niet zal uitbetalen bij schade.

ben blij dat je voor lpf kiest

 

[Nick0016]

Not true @houseofancients, there are commercial home batteries available which are also using other chemistry than LFP.

It's more the DIY part why they do not cover you when the sh*t happens.

But it all depends on which insurance you have .

 

[houseofancients]

Not true @houseofancients, there are commercial home batteries available which are also using other chemistry than LFP.

It's more the DIY part why they do not cover you when the sh*t happens.

But it all depends on which insurance you have .

tesla powerwall use li-ion , LG uses nmc i am very much aware.
but, those are new cells, and are seperately approved, a world of difference from the used dit solutions
that being said still dont want any of those in my home, which was again proven by the mishab in my former home .


tesla fires are plenty and simply dont want to run that chance.

anyway, looking forward to seeing you build.
if your looking for local sources of lfp cells, be sure to check out nkon.nl , they are near eindhoven

 

[Nick0016]

So, received my LFP cells

All cell voltage seems to be matched, a max difference of 0.002V and IR between 0.70-0.77 mOhm. Except one cell is 1.22mOhm ?!

Do I need to worry about the cell with 1.22mOhm IR?

 

[sunshine_eggo]

So, received my LFP cells

All cell voltage seems to be matched, a max difference of 0.002V and IR between 0.70-0.77 mOhm. Except one cell is 1.22mOhm ?!

Do I need to worry about the cell with 1.22mOhm IR?

IMHO, yes. 10-20% variation is expected, but > 50% larger is an outlier. Outliers are always the problem.