Use 24kWh Nissan Leaf Battery as powerbank for nightrate electricity

air

You go off on a different tangent every time I try to explain something.
It's well established that lithiums give more cycles when not charge fully to 4.2V - total tangent.

It is a parallel load but it is also a voltage source which opposes he voltage applied by he charger so there is no current through it.
You seem to be missing this completely.

Every consumer electronic device in the world with a lithium battery - laptop, mobile phone etc. has a constant voltage maintained on the battery while it is plugged in and fully charged. Do these batteries overheat or even get warm? No, because there is no current through them once the battery voltage stabilises at the charge voltage.

The starter batteries that you are seeing boiled dry are lead acid batteries, totally irrelevant to this discussion, different charge profile.

air

air wrote: »

You go off on a different tangent every time I try to explain something.
It's well established that lithiums give more cycles when not charge fully to 4.2V - total tangent.

I am taking about the holding voltage after charge completion.

air wrote: »

It is a parallel load but it is also a voltage source which opposes he voltage applied by he charger so there is no current through it.
You seem to be missing this completely.

It is a voltage source of 3.6V

air wrote: »

Every consumer electronic device in the world with a lithium battery - laptop, mobile phone etc. has a constant voltage maintained on the battery while it is plugged in and fully charged. Do these batteries overheat or even get warm?

Yes. Manufactured obsolescence. Your phone probably has an internal battery temp sensor...have a look for it in settings.

air wrote: »

The starter batteries that you are seeing boiled dry are lead acid batteries, totally irrelevant to this discussion, different charge profile.

Also a voltage source, also has an internal resistance. Same profile, different values.

air

Sorry, I've lost my patience, you've no clue what you are talking about.
A fully charged lithium cell has a resting voltage of 4.2v, not 3.6v.
If you connect one to a 4.2v PSU, there will be zero current flow.
Lead acid is charged at voltages above those which the cells can produce when fully charged. Lithium is never charged in this range, never ever.COMPLETELY different chemistry & charge profile.
Have you ever charged a lithium cell?
As for planned obsolescence and battery temperature sensors, more inane off topic rambling.

2011

Technical is welcome once it's civil.
Please bear this in mind when posting.

Thanks you.

I'm sorry air it is not my intention to raise emotions.
I hear what you are saying and after some experiments I must admit you are correct in instances where I have disagreed with you. I see the voltage of the cell does not "bounce down" as I expected it to. So floating a cell at 4.1V would be in fact discharging the cell.


I conducted two controlled experiments one with a dumb charger a 1.5Ah li-ion cell with a CV of 4.15V to see if the current zeros. It was partially charged to begin with and since 19:30 has trickled down to 8mA and holding for the last hour. Temperature rise from the outside is not significant.

The other is using my phone's onboard temp sensor in relation to floating voltage and resting voltage which there's a difference of 50mV and 0.5°C.

To address the issues we have stirred and let's look at the situation objectively:

In answer to the OP's question:
Is their technical merit? Certainly
Is there financial merit? Not as yet at retail prices unless you can source materials at discount and labour costs are negligible.

Lead acid is more complicated to charge than lithium.
I disagree, you agree.
You say Constant Voltage is all you need for lithium. For expected charge rates < C 0.5 this is true.

For lead acid I would want a 4 stage charger with temperature compensation and load compensation.
This indeed is more complex than Constant Voltage.
However I feel it is less complex than a 2 stage BMS with current limiting, thermal management, balancing and individual cell monitoring. It's news to me that none of this is required.

To go all out with making both system as good as it can be FLA will demand electrolyte readings, watering, rotation of cells and sometimes periodic equalisation charging; all rather involved but low tech.
With an all singing all dancing Wi-fi enabled, App in your pocket Li-ion BMS I would see this technically sophisticated and hence less reliable but certainly plug and play.


Tangents:
I am not the only one who made these,

Battery sizing: situation dependant.
Peukert exponent/ Coloumbic efficiency: FLA ~1.3, Li-Ion close to Unity. Swings and roundabouts. Favours Li-Ion for a small battery with a large load...favours FLA for a large battery with a small load.

Accurate Battery SOC reading: Easy for Li-Ion. Black Art for FLA.

End of charge voltage for lithium, I say 4.05V pc you say 4.2V.
The reason I say 4.05v is because the battery will supply far more power over it's lifetime and this addresses another tangent which is manufactured obsolescence...why can't I set my devices to terminate charge at a more ecological end of charge voltage?
I have proved to my own satisfaction that they do not generate heat while floating with your direction air, that is not to say they don't evolve more heat getting to 4.2V than they would 4.05V which does make them grumpy (+6°C for 3Ah @ C1.4 between 4.05V & 4.2V)

When I say FLA and Li-ion have the same profile I mean the same CV - CC charger curve while the voltages differ.
Li-Ion is self current regulating moreso than FLA.

Lithium Ion: low self discharge, more compact, lightweight, doesn't require maintenance charging, 12% recyclable. Scrap value:

Lead Acid: Cheaper (by far) per kwh. Least volatile. durable, gasses, requires periodic cleaning, 99% recyclable. Scrap value: €0.50 per kilo.

Suitability for home power storage solutions: Either is of merit.




Sorry for any frustrations caused Air, at least I learned someat.

I do feel obliged to defend lead while all the hype these days pushes li-ion and compares itself to AGMs to get a leg up. Li-ion versus forklift cells or flooded OPzS is a fair fight imho which is why you never see it.

isnottheword

Sir Liamalot wrote: »

In answer to the OP's question:
Is their technical merit? Certainly
Is there financial merit? Not as yet at retail prices unless you can source materials at discount and labour costs are negligible.

Would it have financial merit if it was used in combination with some sort of renewable system? eg. wind/solar?

It can be if you are frugal with expenses and materials. Sourcing good components at discount or ex-industrial service routine renewal stock. I don't think the numbers yet stack for a plug and play system or buying everything at RRP. I outlined in post 21 the basic parameters for viability assessment.

I run 4 separate systems in various states of completion. My camper has a modest but adequate PV/diesel electric system that is more viable to me than the alternative which is extortionate campsites so as a reflection of markets this system works very well.

My house has a 12volt system running light duty ELV lighting, equipment and isolated control circuits for a larger system in a workshop that I threw together from mostly leftovers of other systems so arguably economic.
I've been building a 48V system with the last year and it might be economic because I'm sourcing everything at mates' rates and ex-service ebay clobber, this takes time and test gear... My intention is to make it a versatile system I can eventually off-grid, that'll pay for itself in other ways.

The only system that actually pays it's way is my 550Wp grid tie that offsets my usage, so even without feed in tariffs I've knocked most of the base load off the house during the daytime at least (with some excess on sunny days). Eventually my grid tie will be assimilated by my 48v system.

They only way it can be viable is with renewables and enough of them, viable micro-wind is a tough nut to crack as it's entirely site dependant.

They other thing is the battery, there's a learning curve, so it can make or break the deal if it lasts or not. My advise is give it a try but start small until this country realises the technology works and starts paying fair price for home-grown power.
As a point of perspective I installed my grid tie system in 5 days. My battery system...well we'll see how long that takes...

Between this discussion and this fellars work (Alpha Nerd alert) I'm almost swayed to the practicality of Li-ion.

Good thing all my chargers are fully programmable.

Aided by the fact I just ran a 26 day deep cycle on my FLA and the drift on my sometimes cromulent SOC meter had me stop believing the % SOC about a week ago. Yurp definite advantages...still though my lot were £88 per kWh new - €10 scrap value with two terminals ready to go his are AUD$162 + insane amounts of time + used per kWh.

I've been sitting on these links because I wanted to watch the entirety before comment, but I just haven't had the time lately.


Full playlist here

He's entirely convinced me if I ever do it I'm getting EV modules that've lived as one cell all it's life. Repurposed laptop cells is nerd insanity. :eek:

As far as I have gotten he's not running a BMS either so I guess it works. In a large part he is the BMS though.

Good watch if it's your cup of tea. I've seen a whole lot worse approaches of all battery chemistries.