Sinopoly Cells - Info -

[expresso]

i didnt know at the time but i do now - i guess it was a good fuse to hold off for over a year - the chair has a 70A breaker - which never tripped so i can assume its not going over 70A for long periods if at all

i never understand why they put 70A breakers on chairs with 100A controllers etc, - dosnt make sense to me but still they work fine makes me thing how long or often are we using up 100A or 120A on our chairs -

[Burgerman]

Because just like a fuse a breaker is a thermal device. Your power module can draw 240A max peak as you accelerate up a steep slope.

A 70A breaker or a 100A fuse can do that current for the few seconds needed.

HERES a chart for a fuse
NOTE that it can do its 100% rated 70A forever.
And tat it can do 200% of 70A (140) for a long 10 seconds.
And that it can do 400% or 280A for 1 second.



And note that this is a push button breaker. And that it can take even more current for longer. So your R-Net pulling an intermittent 200A at the battery will never trip it. It behaves the same as the fuse, only more so.

i never understand why they put 70A breakers on chairs with 100A controllers etc, - dosnt make sense to me but still they work fine makes me thing how long or often are we using up 100A or 120A on our chairs -

Look at the graph of a breaker above. It wont trip, unless you take 70A plus 125% to 150% extra for 500 seconds. 9 minutes solid at 100A plus. No mobility controller can do that, they reduce power after a few seconds.

[expresso]

Nice 70A I have on my pilot chairs 100A. Rnet not sure what it had stock but I added 100A breaker. So far so good. And. None on add on pack. I read somewhere that 120A for rnet is recommended. Rnet manual I believe. I already had 100A for few years now. And see no reason to change it

[LROBBINS]

Diodes generally have a maximum (non-repetitive) peak current rating far higher than their continuous rating. From a Vishay spreadsheet for one example: A 5A diode may have a 200 A max peak rating a very short time single pulse. That same diode may be able to handle 30 Amps for 1.5 seconds, however. For Schottky's at least, the forward voltage drop also goes up with current, so draw will tend to further shift from the add-on to the Pb at high currents.

[Burgerman]

Then adding say a 40A to 60A shotky diode may work even better as when not under load will tend to top up the lead again slowly and lesser/no-heat sink may be needed.

The lithium still takes the majority of heavy loads though. Since the voltage drop on lead is quite extreme compared to the very "solid" 25.6V we see on lithium, that typically drops just a single volt under similar loads.

Watch...
This Lead drops from 25.5 approx, to 18.9V in an instant when turning, and just a tiny wheelie in 1 foot of space!
Thats a SEVEN VOLT drop!!! By doing something simple in literally a fraction of a second.

There are 4 readings on the meter.
Big digits are real time volts. 25.5 plus?
Small digits below are peak readings at 100k samples per sec.
Peak HIGH volts...
Peak volts Averaged over time from when started.
Peak LOW volts...

Watch the peak low volts drop as I wheelie 6 inches...
A lithium would take over almost completely here, at about 24.5V under load (at approx 150 to 200A. For an instant).

http://www.wheelchairdriver.com/gopro/voltdrop.mp4

[expresso]

If i understand correctly - 90ah Cell rated at 2C - that means it will do constant discharge 180A - maybe more peak - but forget peak for now -
if you used 16 of those 90ah Cells at 2C rated - then it a bit more than borderline min. for our chairs at 360A

if this is correct - you can use a 2C cell if 90ah and using 16 of them ? this would be OK ?


Now of course if a 90ah Cell at 3C is used - would be much better at 270A for 90ah Cell at 3C

and of course you would use 16 Cells giving 180ah of battery at 540A discharge rate ? is that correct ?


i am curious to know because i do find many 90ah Cells but are 2C rated - which is still ok if the above figures and my understanding is correct .

i founds some 90ah Cells at 5C - which would be great but too tall at 280mm -

[Burgerman]

It doesent matter what you use. It will work.

The further you stay away from the max allowed C rate, the longer they will last. And the difference isnt small.

So if we could buy 20C cells, I would.

If we use cells that are 2C but use plenty of them, then 2C is ok.The lower the C rate, the bigger the pack must be to survive a long time.

You can take 10C from a 2C cell, for a few cycles... Or you can take 2C fro a 10C cell for 3 or 5 thousand cycles.

C = Capacity in Ah x Amps.
So a 10C 10Ah battery will allow 100A.
And a 2C 50Ah battery wll allow 100A.

In both cases they wont last long if you do that! - 200 cycles?
Take 50A and get say 1000 or 1500 cycles.
If you take a max of 10 or 20A from the above they WILL last a long time 2000 to 3000 cycles? if not charged too high, or discharged too low.

But its a guide, theres no hard limits, its a curve. it just to give an idea of how good that cell is at high rates. Never go near the max C if you want them to last. Its easy to fit more Ah into a cell if its low C rate, higher impedance. Conversely high C rate cells are either lower Ah or larger.

[expresso]

ok - i just wanted to know if i was correct how i come up with the numbers - 2C 90ah cell x 16 cells would be 360A discharge which is more than enough

i would say its barely over the boarder line - anything higher C always better -

i am using 90ah as an example - its easier to find 75ah and 80ah Cells that will fit - 90ah are harder to find that will fit - but if you look hard enough you can find one that will

i am thinking about it always - if i have a few people who want an ADD ON for there chairs - i am considering taking my 135ah pack apart this winter

making 3 45ah ADD ON to sell -- - and getting 90ah cells to make a huge pack and then no need an ADD ON - - just an idea - most likely wont happen

[Burgerman]

Its like this.

If you have say 100Ah of 4C cells, you could replace that with 200Ah of 2C cells, and both could provide the SAME current in Amps.

Likewise if you wanted a small pack, you could get a 50Ah pack, but it would need to be 8C capable to be the same capability or same Amp delivery. All would live as long, only range would change.

So as you can see, its better to use high C rate cells in smaller packs. Like an addon. But an addon shares the load with the lead. So its not as serious as it seems, as its not working alone.

What to avoid. 2C 70Ah pack for eg. Wont live long, and may experience a lot of voltage drop under load.

Also all 2C packs will be slower at CV when charging as they are higher impedance. Maybe twice as long. Is that important? Up to you to decide!

I use 50C and 70C cont 130C pulse 5Ah lipo batteries in my hobby heli stuff.
I fully discharge them in 4 minutes in violent flight.
I charge them from all but dead, to completely full, at 8C with the PL8 (and thats at 40A) and they take a fraction over 8 minutes total!

If those Lipos were on a powerchair, and 200Ah rather than just 5Ah, it would need a 1,600A charger to charge in 8 mins. And cables 4 inches across! And your own power station.

And thats why I laugh when I hear that they have invented a new battery that can be charged in 1 minute. Because in a powerchair that would need a 12,800A charger...
Thats 25.6V X 12800A = 327,680 Watts! A third of a million watts!!!

Now musk uses a battery around 30X bigger than my chair, in his model3 car. So now thats going to be 327,680 Watts x 30, = 9,830,400 watts... 9.8 MILLION watts! needed to charge musks car in 1 minute. They plainly didnt think it through.

A town of around 1000 houses 3000 people needs 1mW. The car needs almost 10mW on its own! Thats the equivelent of 10,000 homes, 30k people, and thats no longer a small town.

[expresso]

the new cells i just purchased - if they are not lying to me about the specs - its 5C - 60ah Cells - thats great -

i really wont know anyway - i will make it - and use as an ADD ON and thats it - i am sure they will give me some more range and last many years - this chair wont be used as much -

i may have to make connectors with wires - dont think i am getting any - i asked for them but they said they will try - so means they dont have them and may not get -

[Burgerman]

Connectors are easy. Just loops of cable with a ring terminal at each end. 7 needed.

[shirley_hkg]

If i understand correctly - 90ah Cell rated at 2C - that means it will do constant discharge 180A - maybe more peak - but forget peak for now -
if you used 16 of those 90ah Cells at 2C rated - then it a bit more than borderline min. for our chairs at 360A

if this is correct - you can use a 2C cell if 90ah and using 16 of them ? this would be OK ?


Now of course if a 90ah Cell at 3C is used - would be much better at 270A for 90ah Cell at 3C

and of course you would use 16 Cells giving 180ah of battery at 540A discharge rate ? is that correct ?


i am curious to know because i do find many 90ah Cells but are 2C rated - which is still ok if the above figures and my understanding is correct .

i founds some 90ah Cells at 5C - which would be great but too tall at 280mm -

Draining all 180Ah of these 2C cells in an hour is phenomenal for a wheelchair .
Please let me know what stocK chair had survived such abusive use .

Yet , it's 1C still .

So what's the meaning of this C rate discussion lingers ?

[Burgerman]

Because many chairs can take 200A or more from the battery at times such as climbing a slope as you accelerate. Measured. Its not a matter of in 1 hour. Its a matter of intermittently for 3 to 5 seconds. Or 150A for 15 secs or so.

Measure battery current as you turn left/right on your own brushless chair. It will be 200A.

[elryko1992]

the new cells i just purchased - if they are not lying to me about the specs - its 5C - 60ah Cells - thats great -

i really wont know anyway - i will make it - and use as an ADD ON and thats it - i am sure they will give me some more range and last many years - this chair wont be used as much -

i may have to make connectors with wires - dont think i am getting any - i asked for them but they said they will try - so means they dont have them and may not get -

Expresso when you build your new cells make photo to see the steps if you want like a tutorial i want to see, when my MK is gone i want to buy this cells 60AH.

[expresso]

the new cells i just purchased - if they are not lying to me about the specs - its 5C - 60ah Cells - thats great -

i really wont know anyway - i will make it - and use as an ADD ON and thats it - i am sure they will give me some more range and last many years - this chair wont be used as much -

i may have to make connectors with wires - dont think i am getting any - i asked for them but they said they will try - so means they dont have them and may not get -

Expresso when you build your new cells make photo to see the steps if you want like a tutorial i want to see, when my MK is gone i want to buy this cells 60AH.

Sure no problem - i was thinking of that also - take it slow and try to make it simple steps - with pictures - will try to make it simple to understand and easy to follow with pictures step by step -

if you used this 60ah Cell for the whole chair - you would have 120Ah pack - 16 of them - the seller has been helpful and making an effort to make me the connectors - hopefully they work out - i should expect this order sometime in July if all goes well - free shipping takes up to 36 days - maybe sooner - they havnt shipped yet

[expresso]

Connectors are easy. Just loops of cable with a ring terminal at each end. 7 needed.

yes if i have to - thats was the idea - But turns out they are making an effort to make me the connectors - - so with luck - i may just get them - i asked to make the holes a bit larger for wiggle room - will add maybe .05mm sheet of silicone between each Cell - or 1mm - not sure - since i do want to keep it compact as much as i can

if i did my math - 36mm is the max thickness to fit in my famous plastic shoe box i use

only this time - i hope to be able to seal the lid on it - cut a opening in the middle to snake the charge cable and ADD ON connector outside with the lid closed - if all goes well - will to to wrap it like snaker did - rice cake style - wont be as good as his for sure

[Burgerman]

Now I feel hungry again.

[Gnomatic]

Haven't replied me about shipping to US yet .

Shipping to UK , USA , AUSTRALIA are OK. Same rates .

Thanks for checking, shirley!

I'm interested, in cells like this

https://item.taobao.com/item.htm?spm=a2 ... =14#detail

or this .....

https://item.taobao.com/item.htm?spm=a2 ... =14#detail

I'm not in a hurry. But can order anytime, whatever works for you. Thanks!

[shirley_hkg]

You must be prepared and willing to take a risk . You are gonna be the first crab-eater .

[Burgerman]

[elryko1992]

the new cells i just purchased - if they are not lying to me about the specs - its 5C - 60ah Cells - thats great -

i really wont know anyway - i will make it - and use as an ADD ON and thats it - i am sure they will give me some more range and last many years - this chair wont be used as much -

i may have to make connectors with wires - dont think i am getting any - i asked for them but they said they will try - so means they dont have them and may not get -

Expresso when you build your new cells make photo to see the steps if you want like a tutorial i want to see, when my MK is gone i want to buy this cells 60AH.

Sure no problem - i was thinking of that also - take it slow and try to make it simple steps - with pictures - will try to make it simple to understand and easy to follow with pictures step by step -

if you used this 60ah Cell for the whole chair - you would have 120Ah pack - 16 of them - the seller has been helpful and making an effort to make me the connectors - hopefully they work out - i should expect this order sometime in July if all goes well - free shipping takes up to 36 days - maybe sooner - they havnt shipped yet

ok good i waiting! Thanks!

[Gnomatic]

You must be prepared and willing to take a risk . You are gonna be the first crab-eater .

I like crab cakes.

[Gnomatic]

shirley let me know when you are willing to purchase and ship some battery cells. I will pay. Like these you posted earlier in this thread. Or other if better if you know.

https://item.taobao.com/item.htm?spm=a2 ... =14#detail

I'm in no hurry. happy to wait for good crab.

[shirley_hkg]

shirley let me know when you are willing to purchase and ship some battery cells. I will pay.

Check PM .

[Furio]

Hi all,

Today completed assembly of 8 nos. 120Ah cells into a pack. I followed snaker's mode of "Rice pack",though not so perfect. Used 1mm silicone sheet (cheap and quality in India)and glass fiber tape for cricket bats.

https://www.zenithrubberstore.com/shop/ ... ansculent/

I would like BM to give a preset for charging the set.

Furio.

[expresso]

Hi all,

Today completed assembly of 8 nos. 120Ah cells into a pack. I followed snaker's mode of "Rice pack",though not so perfect. Used 1mm silicone sheet (cheap and quality in India)and glass fiber tape for cricket bats.

https://www.zenithrubberstore.com/shop/ ... ansculent/

I would like BM to give a preset for charging the set.

Furio.

Nice - Snaker is on to something - i plan to do the same thing and try the Rice Cake wrap also - mines wont be as good as his or yours - looks good

[Burgerman]

Single cell and 8 cells.

[Gnomatic]

Just for example, if you take one of those 120A cells that is fully charged, and discharge it @10A with a PL8 down to 2.9v - at that point, what would the % of remaining capacity be, roughly?

[Burgerman]

About 10%? VERY roughly. Because of resistance that voltage point comes earlier at high discharge rates. And later at low rates. To measure full capacity you set a CC discharge with a 2.5V CV low current end point say 0,1C. Will that damage a cell? It may, or may not.

Max rated capacity at 100% is when its down to a dangerously low level.

[Burgerman]

With ead, you can take more than the batteries capacity from it. Ie you can go past 100Ah from a 100Ah battery. Its voltage drops to 9 or maybe 6 volts. That does a little damage but you can recharge and get back maybe 97% of what you had before.

With lithium you cause a lot of damage going below 2.5V. Or above 3.65V per cell. Theres no actual figure. They dont much like below about 2.7, or above about 3.5V. And dropping to 2.0V under load once or twice may not hurt if you either. So its always best to just keep away from each end.

If you are a manufacturer you will charge to 3.65V, and discharge to 2V to measure ultimate capacity. But YOU should not! Althought thats exactly what a BMS does. Or much worse!