scalability of LifePO4, an insane® battery pack.

[mrzed001]

I did find a 3 phase inverter though with all the EU credentials and a standard 10 years of warranty that seem to not accept any less than 106v battery

Growatt SPA4000-10000TL3 BH - Residential Storage Inverters - Growatt

Growatt SPA4000-10000TL3 BHhouse inverters,three phase inverters,solar system inverter

growattinverters.com

Sure it is a Chinese brand with many aliexzpress counterfeit crap. But they do seem legit from the sources I am looking at.
Even a well known professional dealer sells them.

Can one think of additional reasons not to go 48V+?

For HighVdc batteries usually the charger is not part of the inverter, but the battery !
Like with the LG RESU 10H
So the battery system gets "something" from the inverter and its DC/DC Buck/Boost converter transfers it to charge voltage.
Also regulates it for CC-CV charging.
And the same Buck/Boost converter transforms the battery real (like 2x48V) voltage to the high DC voltage.
Usually the battery is directly connected inside the inverter ... like a solar string.


You can use this 3 phase (real) hybrid inverters also.
They have all the needed EU certificates, and use (also DiY) 48V battery:
- Voltronic Infinisolar 10kW (aka MPP Solar MPI 10kW) inverter, 1-3 year warranty, produced almost a decade long.
- Deye 8-10-12kW inverter, 5 year warranty, can even run other Grid-Tie inverters AC coupled. Top seller in the US (there called: Sol-Ark)

 

[brandnewb]

I'll provide the translation fo what @houseofancients wrote (sorry for the poor formatting, translate.google.com)

384v is not legal in the Netherlands, but I think you are overestimating the required voltage. to give you an example : 16 cells in series is 48v (the common voltage for home batteries and inverters) if you put 280ah cells in 1 series, you effectively have 14.4 kW. that means you can use 14.4 for an hour. if you put 32 cells in 2 series, you still have 48v, but you have 28.8 kW at your disposal. this multiplies this so much there is not a single (affordable and approved for residential use as far as I know) inverter available that supports more than 48v nominally. that's not necessary either. if you look at for example the Deye 12kw 3 phase, or the mpp solar 10kw mpi 3 phase , which deliver on each individual phase 12 and 10 kWh respectively. you can stack these, which means doubling, so 2 inverters become 24 kW and 20 kW. there will be few residential ev chargers that can handle more power. you are confusing KW (kilowatt = power) and KWH (power over time)

@houseofancients Can you please help me find some documentation regarding the legality, or rather the illegality, of a +- 400 volt battery in the Netherlands?
It could be that that +- 400V is indeed insane but that for example 96V pack is still allowed. In that case it would explain why I can find inverters for the EU market that seem to only accept a 100V+ battery.

 

[brandnewb]

@houseofancients Can you please help me find some documentation regarding the legality, or rather the illegality, of a +- 400 volt battery in the Netherlands?
It could be that that +- 400V is indeed insane but that for example 96V pack is still allowed. In that case it would explain why I can find inverters for the EU market that seem to only accept a 100V+ battery.

I tried again but I simply can't find anything regarding the illigality of an insane battery pack. So I say all bets or off and lets get syco

 

[time2roll]

Plenty of people are driving a 400 volt battery day to day and park-charge at home. Can't imagine this is not allowed.

 

[brandnewb]

Plenty of people are driving a 400 volt battery day to day and park-charge at home. Can't imagine this is not allowed.

I assume you mean the battery in for example a Tesla electric car? these batteries are really potent indeed. not yet syco but potent non the less. And if that is what you meant then that does makes sense.
I mean why can one drive a 400V battery in and out of the garage but not have one just stationary.

 

[wattmatters]

I mean why can one drive a 400V battery in and out of the garage but not have one just stationary.

These battery systems have sophisticated design, some with inbuilt fluid cooling and heating systems, packaging and redundancies for safety. They are designed by the smartest people in the business. But even they get it wrong.

LG, one of the biggest electronics and battery supply companies in the world, has had to recall many of their batteries because of a small fault with internal welds. With some chemistries, such a fault would cause a performance issue and maybe kill the battery, but it won't kill you. With NMC it can kill you. Thermal runaway.

If you want to build HV system from NMC cells, sure knock yourself out. You may literally do just that. But be very careful if you've never attempted working with such things before. NMC is just not a safe chemistry to be going psycho with.

We really would prefer for people here not to be on the Darwin Awards honour role.

 

[brandnewb]

NMC is just not a safe chemistry to be going psycho with.

one of the best responses ever

 

[Picasso]

Hence keep it pack intact.

 

[brandnewb]

Hence keep it pack intact.

Can you please rephrase? I am not sure what you meant

 

[Picasso]

Getting a used EV battery, Dealing with open and closing the contactors, keeping the installed BMS....Not opening the pack, Stay pack intact with the HVDC thought train.

 

[brandnewb]

We really would prefer for people here not to be on the Darwin Awards honour role.

I stumbled upon

LiFePO4 Prismatic Battery and Charger Package: 96V, Choose from: 40Ah, 60Ah, or 100Ah + BMS with CAN communication

6888

www.batteryspace.com

It features an expandable BMS system. Sure 96V could, and when handled by people like me will, be dangerous but it does seem to suggest that there are ways for the DIY community to get things more powerful than 48V.
Or is that site full of nonsense and I should stay away from that BMS?

Also, if my cells every arrive and are up to specs it will form an 48V 280 Ah pack. But the BMS featured there only seems to go up to 200Ah. or can I ignore that aspect?

 

[wattmatters]

But the BMS featured there only seems to go up to 200Ah.

A BMS is concerned with protecting the battery. The rated energy storage capacity isn't a factor.

What it is concerned with are:
- cell voltages, high and low
- relative state of charge, high and low
- over current, charge or discharge
- temperature, high and low

 

[brandnewb]

A BMS is concerned with protecting the battery. The rated energy storage capacity isn't a factor.

What it is concerned with are:
- cell voltages, high and low
- relative state of charge, high and low
- over current, charge or discharge
- temperature, high and low

So you see no objections to getting this BMS and using it on a 16s 3.2V 280Ah pack? And when I feel confident maybe even getting more extender units to scale up to lets say 96V?

 

[wattmatters]

So you see no objections to getting this BMS and using it on a 16s 3.2V 280Ah pack? And when I feel confident maybe even getting more extender units to scale up to lets say 96V?

I make no comment about that specific BMS.

 

[brandnewb]

whooot, the 16 x 3.2V 280A LifePO4 cells are in. I unpacked only 1 of the 4 boxes and inspected those 4 cells.

no bloating and all 4 in that opened box have a voltage of 3.29DC. I almost can't wait to open the other boxes as well but should not I run a few other tests first?

I do not have a BMS yet or anything related.

I tried loooking for how to capacity test without BMS on this forum and others but I got a bit lost ;(

Can anyone please refer me to a resource or have suggestions on how to proceed making sure these (sold as) brand new class A cells are actually as advertised?

Later down the line when all cells check out I will build an 48V pack in a 16S configuration. If that works I'll add 3 extra 16S in parallel as to create 4P16S. Now that is still not insane® But it is a start

 

[brandnewb]

or 2P32S. there's no end to the possibilities

 

[brandnewb]

these are the specs as they are sold.

Product name: lithium iron phosphate cell（3.2V 280AH LIFEPO4)
Typical capacity: 280Ah（25±2℃,fresh cell, 0.5C discharge）
Minimum capacity: 280Ah（25±2℃,fresh cell, 0.5C discharge）
Internal impedance: 0.1 ~ 0.3mΩ
Nominal voltage: 3.2V
Dimensions(L*W*H): 174*72*203mm
Shell Material: Aluminum
Weight: 5.3 ± 0.1 kg
Recommend constant current: 280A (1c)
Discharge end voltage: 2.5 v
Recommend constant current: 140a (0.5c)
Charging voltage: 3.65 v
Maximum continuous discharge current: 280A (1c)
Life cycle (80% dod): 25℃0.5C/0.5C 80% ≥3500Cycle &
25℃0.5C/0.5C 70%≥4000Cycle
Standard charge temperature: 25±2℃
Absolute charging temperature：0~55℃
Absolute discharge temperature: -20~55℃
Operating：-20~60℃

Can I also test the resistance with my mmeter without an issue?

 

[brandnewb]

I could not resist and opened the other 3 boxes as well. All 16 cells read either 3.30Vdc if I use the black (COM) probe on the + pole and the red probe on the minus pole (or the other way around, I already forgot ) amd 3.29Vdc if I switched the probes on the poles.

Anyway I think it is fair to say they are all fully and equally (over)charged. @Hedges, does that still mean I need a CV/CC charger now before I can test other aspects of those cells?

 

[brandnewb]

Please stop me if I am going in the wrong direction.
I'll test the 16S configuration from the get go as all cells seem fully charged and thus already balanced.

I did not get any readings yet when testing for resistance. Can anyone please advise how to do that?

48V * 280A = 13.44 KW. Since the max discharge rate is listed as 1C (280A) i'd like to hookup a load of that size and see if I can run that load for 45 minutes or so (i'll need to do a calculation of when it is time to stop the test as to not completly over deplete the pack)

 

[wattmatters]

Can I also test the resistance with my mmeter without an issue?

Per se? No.

You could do it by applying a known resistance/load, measuring loaded and unloaded voltages and using Kirchhoff's and Ohm's law. You may not have equipment with sufficient precision as LiFePO4 has very low internal resistance.

Anyway I think it is fair to say they are all fully and equally (over)charged.

3.29/3.30V is not fully charged, let alone over charged. All you know is the voltages are the same. You don't know their state of charge. The LiFePO4 voltage-SOC curve is very flat.