Discrete Large Lithium Battery Control

[MEXICOWANDERER]

This gets a bit involved so grab a cup of coffee.

There are dime size discs that have been around for decades that shut off AC power when a certain temperature has been reached. Most are guaranteed for 30,000 cycles minimum. 30 amp capacity. One per cell Meanwell makes a huge variety of adjustable FIVE VOLT power supplies that can be adjusted to exact tolerance for lithium batteries -- from 5 amps to 150 amps depending on the model. One per cell. The low voltage cutout can be installed on the pack load output::A high quality low voltage disconnect can be paired with a 200 or even a 500 amp relay.

What kind of low voltage disconnect does the Tesla use? It would be nice if the relay used milliamps not full amps when energized.

The temperature cut outs are connected in series.

By correctly selecting the power supply capacity it limits the per cell amperage automatically.

[MrWizard]

24v Tesla battery for RV

Tesla battery Module in the RV

[MEXICOWANDERER]

Has anyone here examined the BCU battery control unit

For the various electric cars? Are they entities separate from the chassis control and drivetrain control or is everything integrated?

My thoughts are China is going to be forced to build good lithium batteries for their transportation because the Politburo and Central Committee has eyeballs on this endeavor. They are committed to build world class automobiles. When they put the effort into something they can build decent stuff. For instance at the moment heads are rolling because of fin failure on jet engines for aircraft carrier war planes.

Building tens of millions of electric cars and trucks is an ego plumb for the communist government and if they have to Darwin a few hundred engineers in the process my bet is it will be done. This is what will bring the price of large lithium down. The country has a billion and a half mouths to feed and those mouths have fangs. China has advanced so much in urban development any step backward will have politburo and committee heads rolling.

[MrWizard]

Ok ok charger, sorry
But I could build a 100 ampHr lithium cheaper than $1600
Cost $600_$700 using 10 amp HR, lithium 12v batteries
I linked to in your other thread
And at that price some ready built drop in are available,
Although there are many closer to $1000

[MEXICOWANDERER]

Battery CHARGER. Remember the title of the thread por favor.

And there's nothing wrong about using the concept on Tesla Batteries. $500 for two controller for a pair of Tesla batteries.

Or a U1 size lithium for a CPAP.

BTW. For 49 dollars I adapted a brand new CPAP circuit board into a BiPAP machine. Respironics obsoleted the machine and the psychotic USA medical system forces a person to milk MediCare for a grand in order to get a Sleep Study Rx for another machine. And three trips to the MDs. I am getting therapy again for the first time since June, and have utterly lost the utter exhaustion.

People wonder why I have a propensity to do stuff myself. A new board had they been available was almost three hundred dollars from OEM. A CPAP repair place wanted $500. I have gnus for them.

Individual cell management is warranted when individual cells are hypersensitive to imbalance and overcharging both. Lithium's trademark. If cells must be managed MANAGE THE @#$%&! things, not screw around with them. Like anything else in the electrochemical world the unschooled cry out "Why? They're going to last "X" amount of time anyway.

I doubled and even treble my lifetime of flooded and absorbed glass mat batteries by strictly controlling charging regimens. Cherry picking lithium battery packs may be acceptable for some people but not for me. Not with MY personal lithium battery packs. Land Yacht listened to common sense and is enjoying the benefits. I was spitting nails as I forked over $110+ dollars last week for a replacement to a car battery that was babied and lasted less than four years. GOHNER has a deserved evil reputation down here.

Yeah I am managing several different chemistry (computer) battery packs used for wireless emergency LED lighting. And yeah even those cells get imbalanced and need babysitting electronics.

[MrWizard]

PT thanks,, but does NOT compute
that would cost $1600 to build a 100amphr 12v battery

Mexi said $200 to $275

[pianotuna]

Hi MrWizard,

https://www.batteryspace.com/polymerli-ionmodule37v50ah185wh7aratewithpcbandpolyswitch.aspx

50 amp $160.00

MrWizard wrote:
where are you going to get 100ampHr 3.7v cells ?

i would bite the bullet for a 100ampHr lithium for $200+
and buy several

[MrWizard]

Duplicate

[MrWizard]

where are you going to get 100ampHr 3.7v cells ?

i would bite the bullet for a 100ampHr lithium for $200+
and buy several

[MEXICOWANDERER]

Yes I do a static and a dynamic cell per cell voltage test. And a home built 200 amp 50 pound transformer that peaks 3.9 voc. Thanks to Lockheed advanced projects.

What I propose is most useful on single series string 3.7 volt cells.

Take a 100 amp hour battery and charge it at 50 amperes, and throttle the current by limiting the voltage. If lithium HAD to be current regulated meaning constant current charged it would be a first for me to see it. 250 watt Meanwell power supplies are cheap. And they adjust down to 3.15 volts. So are the temperature cutout switches inexpensive.

Three N/C temperature cutour switches rated to 45c.

Three 5 digit panel volt meters.

I can build one of these gizmos for around $200 to $275 NOT INCLUDING THE ENCLOSURE.

And from what you are describing (inadequate control and monitoring) only a PC based A to D to A data acquisition board to PC interface would be superior.

The BORG was supposed to be "impossible". I hear it chuckling at me next to the bed after 7 years 24/7/365. Or is there some other 100+ amp charger out there that operate with the smallest generator sold? All it takes is experience designing this stuff then some classroom time learning the in's and out's.

Engineers have an advantage over DIY

And one Intermatic 4 hour wind up timer.

[MrWizard]

do you charge 'each' 2v cell with its own charger ?
as i recall you have them on a 24v system

a BMS for each Lithium cell, would be like having a 2.4v charger on each of your 2v Rolls cells

yes i know you check the SOC of each one ,

a 4 pack 10 pack or 20 pack or 100 pack of 3.7 parallel is still 3.7v

IIRC and 3.7v cells are charged at 4.2v , NOT 5v
i know the mean well is adjustable

i'm not saying you can't do what you want
i'm saying its going to cost a lot to implement
and be a lot of work, i don't think an OEM is going to do it

the law of diminishing return on investment

i have not seen a DIY builder do it
not with 18650 cells, which telsa and others are using
maybe with the larger pouch cells
but there are less cells involved
more problems more possible damage if one fails

[MEXICOWANDERER]

The cells I am writing about are 3.7 volts. I guess they figure that if a voltage module goes offline because of a bad cell then retaining the remaining batteries of that module is a waste of time.

My concept is to maintain each cell much more carefully and not allow it to stray too far from optimum charging quality.

Unless the lithium came from a different universe an optimum routine cannot help but extend cell life thus, module and battery life. This is a universal rule in electro chemical applications.

If trying to argue the point remember decoupling alternator pulleys that offer .00000012 miles per gallon gain and ECU voltage regulators that hunt all over the map and new vehicle ECU analysis of alternator/battery parameters. All combined in the same bucket they're not worth half a honk of snot.

OEM engineers continue to lose focus in order to justify their salary.

Individual monitoring and maintenance is what I give to my two volt Rolls cells. This does not differ in concept from Word War II submarine 380 volt fore and aft battery maintenance and control.

Discrete amperage monitoring is useless re: Kirchoff's Law.

[MrWizard]

i'm PRE-neophyte all i have been doing is reading, watching videos, looking at wiring drawings (no hands on)

it seems everything i have seen regarding large scale
goes to 'cell groups', cells in parallel packs, or cells in series packs
treated as one larger cell
for 12v, 3-4 cells arranged series depending on chemistry, and parallel the needed number of packs needed for the 'pack size'
some use individual BMS units on each 12v group wired to each cell
it is charged with a 14.x charger, not with a 5v charger

some parallel a number of cells then series them for 12v ? bank voltage
the BMS goes to each group of parallel cells, but not too each individual cell
they also use a 14.x bank charger not 5v

i have not seen anything using a 5v charger running to BMS or cells
to charge a bank wired for higher output voltage 12, 24v, etc

i saw a video discussion on tesla batteries
the cells were connected with 'fuse wire' to a buss bars
no individual BMS per cell
buss bars arranged the cells in large parallel packs that are series
for high voltage
if a cell goes bad, takes too much charge power or too much output
it takes out the fuse and that single cell goes off line
these parallel packs are very large so loosing a few cells will not cause a noticeable affect on performance
loose to many and you a 'alert' regarding battery capacity and service

there is a BMS of some sort, but i 'think' it deals with each large parallel group as one large cell

BMS is concerned with cell group voltage and total power out or total input needed , which indicates too many 'individual' cells are offline

[MEXICOWANDERER]

To a pessimist a glass is half empty
To an optimist a glass is half full

To an engineer, the glass is twice as big as it needs to be.

A large capacity Battery control and charging circuit cannot be anywhere near the price of these discrete components. The design has one weakness. It cannot determine when the battery is full - then shut off automatically.

So individual cell monitoring is mandatory. A bit of experience and a wind-up timer should fill the bill in this area. The Meanwell power supply is switchable 120/240 so larger 5 volt Meanwell power supplies can support battery banks rated in the thousands of amp hours.

[hawkeye-08]

I see MEX has been thinking on things again..