PINNED - Lithium battery conversion/info

[Burgerman]

Tesla battery is:
85-kWh = 16 modules with 6 groups in series (402 volts, 7104 cells)

So to charge to HALF in 20 mins means he needs to feed it 14,200 Watts, for 20 mins.

Heres the actual spec for a large 20 car charge array. https://electrek.co/2016/07/20/tesla-su ... se-145-kw/

To charge it in 10 mins, to full, means he needs 510,000 Watts. Half a million watts!!! PER CAR! So on a 20 bay charge station, 10 million watts! Seriously??? The peak demand (highest ever) in the whole of the UK was 75.3 GW. (Thats 75.3 million watts)

So 10 of his new charging stations will need 10GW? Thats already more than the total UK highest ever demand. https://www.google.co.uk/url?sa=t&rct=j ... Fw&cad=rja

Which will melt the grid in most places at once! He has plans for upgrading a few to 350KW so many cars can fast charge at once.


The future will need a lot of new power stations and a new grid. Thats about 10x my house needs per car, per day!
If we all drove electric cars, we will need TEN TIMES the power of today's power grid.

Still its less than this https://www.youtube.com/watch?v=I5cYgRnfFDA

[expresso]

3.182 V -

pack is 25.457

from what i add up - its close to about 90ah discharged now -

seems as if it will drain past 95ah ? to get to 2.9V

is charging at 35amp when the pack is down low after a days ride - OK ? or should i lower the charge rate ?

[Burgerman]

Its better to choose a rate that matches the time available.

Discharge to 2.9v...

[expresso]

Finally done discharging to 2.9V - i added up all the discharge graphs - i get a total of 103,945 ah discharged

here are the graphs - i had to break them up - over 4 days of doing this - - 6 graphs -

[expresso]

going to bed - will start the charge in the morn. - i hope to wake up to good news from you BM on my pack - turns out from what i can see - group Cell 3 is the weakest and Cell group 6 the strongest -

[shirley_hkg]

We can't expect BM's results in our packs , as he spent months in measuring capacity , self discharge rate , ir ; and even them through out his pack . His is safe to discharge to its last drops of juice . Down as 20V .

Instead , you and I built ours blind folded . My 200A pouch cells reached the dangerous point early as @ 25.1V , that cell 3 is 3.00V already .

I insist a deep discharge when assembled to let myself an estimation of the furthest I should discharge .

Also won't leave home without a 4-digits voltmetre , and a cell monitor .

Voltmetre tells me a lots , say anything is dragging , larger current up an incline that I should be easy on throttle , and when I should turn the cell monitor on .

Cell monitor tells me when to . . . . . STOP . . . . .

The 9pins XH 2.54 connectors can be found at any RC shop .

[Burgerman]

Theres nothing wrong with that pack. Although you should really turn off the discharge to CV as it isnt needed here and pulls cells lower.

And differences in charge curves is down to slight differences in cell resistances or cables.

[expresso]

[quote="Burgerman"]Theres nothing wrong with that pack. Although you should really turn off the discharge to CV as it isnt needed here and pulls cells lower.

And differences in charge curves is down to slight differences in cell resistances or cables.[/quote

thanks thats a relief - i can charge it up now and pack it to reinstall in the chair


Discharge to CV ? i havent touched those presets since you made them for me - i only changed the Discharge to a lower Volt to test now - or else i left them alone


Tell me where do i go to make this Change ? i need to make this change to all my presets then ?

i think i made the cables pretty decent - was first time so anything can be -

another thing - i have the Volt cutoff on my Rnet set to 22.5V - is that still a good spot to leave it ? if it ever went down to 22.5v - - would that be too low and kill the whole pack ?

[expresso]

Thanks Shirley - thats a good idea - from now on - built it and deep discharge like this one - at least i would have an idea of the lowest pack Volt to reach - lowest Cell to monitor etc,

i will search for those white connectors and do the wires come already made to just stick them in there ?

how do i go about adding in a Volt meter along with the Cell monitor in one loop - all together ? i think i may even have a volt meter but its bare - if i make the Cell monitor - i would have to unplug it to check the volts and plug it back etc, -

i like to do the way i think you did - all tied together -

any links to ready made Cell monitors - Volt meters etc, - just to have in case

thanks - i really hope this is fixed now - and turns out the Bad group Cell 1 is not a bit stronger than Cell 3 - that turned out to be the weakest group when drained down low enough -

[expresso]

BM - do you mean to change the CC CV discharge to NO ?

the setting right under discharge Volt ? - should i do this to all my presets ?

thanks

[Burgerman]

If testing cells or pack for actual rated capacity you need it set as it is, to yes. It then reduces current, rather than pulling cell below X volts that you set.

So on a lithium ion phosphate battery you would set 2.500V and CC/CV discharge to Yes. To get the full capacity from the cell.
Since we only wanted to know which group dropped first, and not interested in actual capacity, we set a safe 2.9V and just needed it to turn off rather than continuing to discharge at an ever decreasing rate. Just like on CC/CV charging.

So neither is wrong, depends on what/why you are doing what you are doing...

i like to do the way i think you did - all tied together -

Parallel connect the voltmeter and the cell meter + and to the - wires.

[expresso]

Ok - So i dont have to change anything on the presets then ? leave them just the way you made them for me - i can leave the discharge rate to 2.9v also - thats the only thing i changed -

do you think it could have been just a bad cell from the start ? Since it turned out that Group 3 was the weakest of the bunch - but Group 1 gave me the problem - its possiable i never went below the Min. Volts during riding if thats the case ?

i only have one connector for the cell monitor - i can use either one or the other - can unplug one if i wanted outside and plug the other - either way i have to first make a Subd - add my own wire long enough so if make mistakes - can just cut off some and connect new wire with connector - i dont want to waste the Subd -

this is getting interesting now for me - i have alot to do still - but good thing i used the PL 8 - i wouldnt have know anything if i hadnt - it saved me from taking the whole thing apart and hopefully it will be just this one Cell - glad i got a few spares

[Burgerman]

do you think it could have been just a bad cell from the start ? Since it turned out that Group 3 was the weakest of the bunch - but Group 1 gave me the problem - its possiable i never went below the Min. Volts during riding if thats the case ?

Yes probably. Or a loose bolt allowed it to go low.

I consider the PC software, graphing, control etc, and the PL8s charging and discharging adjustability and its 1A balance capability as well as its 40A charge capability pretty much essential as a tool to maintain, understand, and look after a lithium pack in a powerchair. Theres no other alternative thats as good. When you start looking at 120Ah to 180Ah even the 40A is important.

[expresso]

the bolts were all good there - but i did find a few along the other lines where i didnt have locktite on them for some reason - but not on group 1 with the problem - its a mystery - i am happy its at least fixed now -

i can set the alarm on the monitor to go off at 3v - that would go off if any one group hits the mark ? at least that can give me a heads up - but i bet i be home by then i think before it goes off -

[Burgerman]

The alarm will give some false alarms. It will go off when the battery is loaded hard. Like on a ramp. Or hill climb. As the voltage goes lower at these times. So you kind of get an early warning with short beeps as you work it hard.

[expresso]

how do you tackle hills then ? i was under the impression that lithium wasnt going to have the same issues as Lead going up hills etc, - and it dosnt to some extent - i understand it has to drop some under load - no matter what kind of battery is being used - but i didnt think i needed to be worried about the hills -

i do run into hills now - and some may be steep - a good two blocks long going up - dosnt look bad at a distance then when going up - you feel it - - i usually go full throttle the whole way - i see my speed drop to maybe 8.2 on the JS - around there - i know the JS isnt accurate for speed etc, - just saying its normally at 8.5 flat out - and up hills it drops some and i feel it also -

i wonder if the bad cell had anything to do with how it felt going up hills - when i repeat it in the summer - i see how the chair reacts - with the monitor this time if i can keep an eye on it while going up at the same time -

[Burgerman]

how do you tackle hills then ?

Same as before!

i was under the impression that lithium wasnt going to have the same issues as Lead going up hills etc, - and it dosnt to some extent - i understand it has to drop some under load - no matter what kind of battery is being used - but i didnt think i needed to be worried about the hills -

You dont. The voltage drops under load because of resistance, so you ignore it. Its not real.

i wonder if the bad cell had anything to do with how it felt going up hills - when i repeat it in the summer - i see how the chair reacts - with the monitor this time if i can keep an eye on it while going up at the same time -

If that one cell group was high resistaance you would see a greater voltage drop on that cell group than the others. But to see how charged they are you have to stop, or go on a flat level surface. The voltage drop thing making the thing beep will only begin to happen when the battery is quite close to being empty. And will happen more and more the closer it gets to being empty. Until it is on even when you do nothing...

[expresso]

ok - so not to worry and just ride as usual - stop to check it if curious - to get most accurate reading of the cells - pack volt etc, -

[Burgerman]

Its an advantage. It will begin at some point and happen occasionally. Once it starts happening every time you accelerate or turn you can know its getting lower. When its doing it most of the time you know its almost expired! When it does it when you are stationary, thats it...

[expresso]

ok got it - but mostly wont happen at all before the 30 mile mark - i plan on adding a 30ah ADD ON to it also now - leave it there for good - charge separate when i get home - that should make me not worry about it all i think -

when i did the 44 mile ride - i had a 36ah ADD ON - just to be safe and i used about 75ah of the Main pack that day according to the charger - i might as well - since i have a backpack there anyway with nothing in it - i get one to fit the 30ah pack and thats it - 135ah would be the total this summer

[Burgerman]

By now, you will be realizing that things like cell logs, multi meters, advanced chargers, and loads of understanding, is key to having a ton of range, and a good understanding of things.

Always in life, knowledge, and understanding is power. Its what enables us/you. Its what makes everything possible, and understandable. Right now you are 50% there with lithium batteries and beginning to understand why getting a friend to do a system, or buying some straight swap lithium system with a BMS will be guaranteed to end in tears.

You are learning. You fixate on things (still) and you worry about things to excess because you still want a plug and play system. Its not going to happen! You need to understand and fix/monitor what is going on as you just have. And maintain or fix as required. It never ends. The more you learn the less you worry and the better you understand and the less issues you will have.

[expresso]

yes your correct - as long as i learn from my mistakes and keep asking questions when i dont get it -

finally done - looks good - very happy with the results - i think this one is resolved now - i didnt think it was going to be - but glad i was wrong

graphs looks great i think - will be packing it up and install it back this week - will make monitor and start on making the 30ah pack - been sitting here 3 months discharging - its ready to be made -

will also get that divert dump load thing to discharge faster for the next time - if i ever need to test again - using the PL 8 to monitor it also - and start making more charge cables - etc,


that was a close call - glad i got it very early on - in time - and glad the bad cell was in the top row -

[Burgerman]

Thats perfect, and as I expected...
And 107Ah returned, so a pretty full discharge/charge

You have no faith in me!
Now, STOP WORRYING!

[expresso]

Thats perfect, and as I expected...
And 107Ah returned, so a pretty full discharge/charge

You have no faith in me!
Now, STOP WORRYING!

didnt you say you didnt believe in Faith ? haha - i do have in you and others here also - i get very panicky because i cant do it myself right away - so i start to brainstorm what i will need to do etc, - stressful - hey this is NYC after all - now i will pack it up nicely better if i can - maybe try to lift the chair divider up a bit to make it easier to slide in there - with Quickies help and my other girl here - will be back in chair this week

why do you think i am stocked with whisky - volka - wine - tequila - i can relax now and get myself back on track

[shirley_hkg]

Maybe 180Ah is feasible .

Also by ATL .

IR @0.4mΩ

£22.70

[expresso]

180 ah that would be great - never have to worry about going to low - if this is ever figured out and they are new cells -etc,

maybe a good choice for my next future chair -

[Gnomatic]

;) Maybe 180Ah is feasible .

Also by ATL .

IR @0.4mΩ

£22.70

Don't think those above will fit. Can you get the ones you mentioned a couple days ago? The 75Ah cells.

Found this too , and think you'd give it serious thought .

Look at the super low internal resistance , and tested capacity .

I'm quite confident that you can fit 16 of them in it , and that's 150Ah .

Should be good stuff . 0.36mOHM @ 2.65V That's really good , itsn 't it ?

@£17.00

[shirley_hkg]

Yes , they are still available . You have to judge its quality basing on the superficial information , IR and recharged capacity . Risk on / off .


http://c.b0yp.com/h.5mdPXP?cv=TvGoZtJH23z&sm=7abfba

Seller's reply is standard : THIS is NOS , and stored at 2.7V from factory .

[Burgerman]

Wont quite fit 16.

The ones I linked to are perfect! Need supplier.

[Gnomatic]

Yes , they are still available . You have to judge its quality basing on the superficial information , IR and recharged capacity . Risk on / off .


http://c.b0yp.com/h.5mdPXP?cv=TvGoZtJH23z&sm=7abfba

Seller's reply is standard : THIS is NOS , and stored at 2.7V from factory .

I can fit 16 of these easy in any of my chairs. I know there's a risk that these cells might not be top quality, given the limited information available. But for the price, I'm will to take a chance.

What's the best way to buy something off Taobao and have it shipped to the US? I don't speak Chinese and Google's translator isn't perfect.