Sinopoly Cells - Info -

[shirley_hkg]

Haven't replied me about shipping to US yet .

[Gnomatic]

Thanks for checking!

[expresso]

Yes a 100/200A heavy diode in series with the lifepo4 cable saves the lithium, and uses more lead. So you dont just lean on the add-on most of the time. Also means the battery meter will make more sense.

Say 2x these in parallel, would do it. They will drop .7V approx, so your lithium will be 25.6 less .7 = 24.9V most of the day.
https://www.ebay.com/p/50-X-Vishay-Powe ... 1021668224

Oh thats nice - didnt know - i still not sure how i would connect them -

cable is already made - i most likely wont do it now - but on a new cable if i have to make one again - i solder one of these in between the Pos. cable like a fuse ? and do the same to the Neg. cable - and thats it ?

[Burgerman]

In one end, out the other!

[expresso]

In one end, out the other!

you mean solder it between the cable both ends - like a fuse ?

i dont see where it would go inside - i see a screw on one end - giving me the impression it needs to be screwed in something

and i just pulled the trigger on some Cells from Aliexpress - - free shipping so i am looking at July before i get them - hope they are as they stated with specs etc, it shows 5C constant discharge - i emailed to ask and was told yes 5C - peak 600A -

hope i get the connectors also - never got an answer to that one -

Oh wait you mean solder the cable thru the hole on top ? disregarding the screw ?

[Burgerman]

If fitted like a fuse it will get hot and fail. So one end is threaded so it can screw into a lump of aluminium, or a heat sink. Then the heat sink is the other wire...



Heres 2 fitted to a big heat sink...

[Burgerman]

This also means that any regeneration current will be blocked, so it will all go into the lead. A diode is like a one way valve. Like a tyre valve. Electricity can only go one way. In the soldered part, out of the bolt / thread (ring terminal). But it also needs a heat sink.

But it loses .6 to .7 of a volt. So we will be using its normal disadvantage to our advantage.

[expresso]

Ok so i am wrong again - and yet not clear to me how it will go between the cable -

the cable we are talking about also is the POS and NEG coming from the ADD ON pack - ? this is where this item should go ?

i see how they are fitted to the heatsink - in this case - there wont be a heatsink or anything other than the cable wire ?

i cant vision any other way than what i though with the wire going thru the HOLE on the top - according to the pictures its not that way - but dont see how it would be done for the ADD ON cables

[expresso]

This also means that any regeneration current will be blocked, so it will all go into the lead. A diode is like a one way valve. Like a tyre valve. Electricity can only go one way. In the soldered part, out of the bolt / thread (ring terminal). But it also needs a heat sink.

But it loses .6 to .7 of a volt. So we will be using its normal disadvantage to our advantage.

ah ok - so i am correct then if you solder the wire on the HOLE on top and then solder on the bolt or ring terminal - thats inline with the cable - but if you need a heat sink to make this work - then what ? i have to add a heatshink also ?

wouldnt that be so bulky -

in any event the cells i ordered are 5C - maybe wont need to worry then too much -

do you have any thing already made with this inline to show a picture of how it needs to be - ? pictures work wonders

[Burgerman]

Bulky? Yep a bit. You will be fine without.

[expresso]

Ok but i like to know so i understand for myself - i see how you connect it now - but with a heatsink -- what size would be used for this purpose ? - then heatshrink over the whole thing ?

and this would have to go on each Cable Pos and Neg. which are attached to the ADD ON pack ? inline


has anyone ever done this or used an ADD ON this way before ? i dont recall hearing a discussion about it - maybe you mentioned it before - or Shirley may have since hes the king of ADD ONs - and does well with them

[Burgerman]

Heatshrink over the whole thing will prevent the heat from escaping! Those diodes are normally fitted through a metal case or something.

[expresso]

Ah ok - so this isnt going to work really -

at least i know now - with any luck the specs are real 5C - - i just want to extend the range some and keep the new leads strong for years since i wont get them free any more for this chair - and dont have any other chairs with lead now - only my very first chair which is used indoors only - 15 years old now but i feel good indoors with it - better than my other chairs -

outdoors suck with it - i will test it to show how much i can do a few times - but then it wont be used as often or as much -

[shirley_hkg]

Or my novice way .

Twist 3 , 4 , or 5 these small 5A diodes together . Solder / terminal to the negative cable . Expose it to open air and they dissipate heat .

I tried for years without problem . It is not that hot as thought actually .

[Burgerman]

15A max? He already blew a fuse 3x that size! And I would expect 100A or so to flow at times for short period.

[shirley_hkg]

15A max? He already blew a fuse 3x that size! And I would expect 100A or so to flow at times for short period.

ADD--ON !

I use only Canon plug and a 20A fuse . They all survived .

[shirley_hkg]

Haven't replied me about shipping to US yet .

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

Australian need to bear tax themselves , too high to include .

CROATIA , SLOVENIA ~ no service .

[Burgerman]

Yes, I am amazed you manage with 20A fuse. If I connect an add-on to my chairs, stick a clamp meter over its cable then I see easy 100A peaks in curbs/ramps/turning with high acceleration. And expresso blew a 30 or 40A fuse... On an add-on.

[expresso]

15A max? He already blew a fuse 3x that size! And I would expect 100A or so to flow at times for short period.

At first i had a marine boat fuse - i think 25A or 30A - on the cable i have on the LEAD going to my ADD ON pack - it worked fine for a year or more - till one day - i realized my green lights went out too soon - i knew something was wrong

when i checked it was the fuse - first time it happened - removed it - reconnected the cable and all good since - the chair has a breaker - 70A i believe and never tripped once in 6 years - hopefully never will -

[Burgerman]

Buy you do realise that say a 50A fuse will flow 100A for anything from seconds to minutes. And 200A for say up to a second or so. Depending on if fast blow or slow.

A 25/30A fuse, can likely take intermittent 50A loads indefinitely. So if that blows, and it did, then its highly likely you are taking more than 50A intermitently.

[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 -