PINNED - Lithium battery conversion/info

[Burgerman]

I used to have one of those helpers.

http://www.wheelchairdriver.com/images- ... ir-700.jpg

But she moved out!

[expresso]

I used to have one of those helpers.

http://www.wheelchairdriver.com/images- ... ir-700.jpg

But she moved out!

Difference is - YOU know what your doing and how to do it - i dont never hurts to have a pretty girl to look at while working -

i see how to connect in series - Neg to Pos to Neg to Pos down the roll of 8 cells - - two rolls of 8 Cells same way side by side - in series

then 2 parallel - thats the little tricky part for me - - series would make one large battery - parallel is what doubles the AH - at the same Volts 24v

the balance cables - Pos on one end and Neg on other - then each other balance wire would go to each pack of series Cells - so one balance wire would balance the one pack in series as one battery Cell -

- i need to handle the cells and do it to actually see - and i can use the volt meter to check the volts at the end etc, - my mind is in overload - and on top of that - i am not feeling well the past few days - weather and holidays in the mix - dosnt work for me - or i am coming down with a cold or something - i am trying to get the parts together i need - as i try to learn and read here and listen to your advice as best i can -

i have my other girl or girls that work for me - but to be honest - Jessica - wheelchair Ny - understands me much better - she gets it and very helpful when it comes to doing things - she can and has been the one to remove my batteries etc, my other girls forget it - you think i am bad - haha - they are worse than me when it comes to doing anything - so my frustration gets to me - and i have to watch what i choose to try to do depending on the help i have - i figure this would be good way for me to learn on a small scale -

[Burgerman]

It is.

Series, and all the balance wires is the hard bit.

Once you do that then parallel just means adding more cells connected to your existing ready built battery. That's the simple bit!

[steves1977uk]

This is my balancing wires diagram that I had to give the guy who helped to build my pack...

This is a 8s 5p pack, the green dots are the solder points for the balancing wires. Obviously each second one is on the opposite side. The yellow buss bars are on the top side and blue at the bottom.

Steve

[Burgerman]

You soldered them?
I just fitted ring terminals.

But that diagram would certainly confuse me! Its easier if you start simple as in my link, so you can see and understand where they go yourself.

[steves1977uk]

Yes, I thought that was the best way at the time so that the balancing wires couldn't come loose. But I agree your way is much better

Steve

[Burgerman]

Questions for expresso...

If you connected only 4 of your cells in PARALLEL.
1. How many Ah is that?
2. And how many volts?

If you only connected 2 in parallel.
3. Ah?
4. Volts?

If you connected 2 cells only, in series.
5. how many Ah?
6. how many volts?

Do you realise that 1, 3, or any number of PARALLEL cells just makes one big cell?
7.?

[expresso]

Ok let me see if i can answer your Quiz BM

first one -

4 cells - 3.2 V each 12ah - in parallel means just connecting them Pos to Pos and neg to neg . making one big battery - the AH will double as you add each battery - the end Volts will still be only 3.2 Volts

i think this one would be 3.2Volts and 48Ah -


2 Cells 3.2 V each 12ah - in parallel would be - same 3.2 Volts and 24AH -

2 Cells 3.2 V each 12ah - in Series would be - 6.4 Volts and 12Ah -

and i agree about the balance wires etc, and series - i was thinking about it a short while ago - i always take a short nap with music after i eat - and drink

I hope i passed this test - but even if i did - i always get thrown off - - i got used to see Two Lead Batteries with Pos and Neg. on top - two of them together i get it - simple to connect and make 24V - with same 73ah -

just seeing so many cells - Pos on top - Neg on bottom - then arranging them etc, etc, - has a different look and i go blank -

the balance wires is even more worrisome for me - after i get the big stuff done - which is the easy part -

how did i do ?

heres my utility cart i got so i can put all the new toys on it for this simple 16 cells 24ah - 24 Volt pack - and still have many things yet to get -

[shirley_hkg]

What size of tab screw with 38140 is it ? M6 ?

[Burgerman]

how did i do ?

You did right. And so dont need drawings etc. Yes M6.

[snaker]

I have something still confusing:
- To build a 24V pack, I know theoretically I should connect 8 cells in parallel. But practically should I connect 9 cells in parallel to make sure the pack having a bit higher voltage (~30V)? And then the chair could operate a bit faster?
- I see everybody here prefer cells in 'tube shape' (sorry if I use wrong words). I think that will require some tools to connect them and also a handmade case to hold them together. Maybe many of us cannot do all those without some help from others. I see evassemble.com is selling cells in 'cube shape' and the 'cubes' have more advantages than the 'tubes' in connecting. For example, supposing that I ask evassemble.com to make 8 or 16 cells in a custom size to barely fit a GP24 battery box. I also ask them to make each cell close as a black box and expose only 2 solid cables with tough anderson connectors. Those cells will be easily connected via anderson connectors and also easily arranged inside a battery box. I still wonder what are the defects of the cells in 'cube shape' so that nobody choses them?

[Burgerman]

I have something still confusing:
- To build a 24V pack, I know theoretically I should connect 8 cells in parallel. But practically should I connect 9 cells in parallel to make sure the pack having a bit higher voltage (~30V)? And then the chair could operate a bit faster?

Parrallel 8 cells = same 3.2V.
SERIES 8 cells = 25.6 NOMINAL voltage. Thats 28.8V charged fully. Same as lead.

Mobility ststems will give an over voltage error at 32V or some at 35V and shut down or stop.

9 cells will give you 28.8 nominal, plus a couple of volts pulse on regeneration as you decelerate. Very close to the limit.
But on a fully charged battery thats 32.4v if charged at 3.60V (32.85V) and before you get any regeneration pulses when decelerating. So will definitely give an error.

The rectangular cells are called prismatic cells and are less good in a wheelchair than the cylindrical cells for several important reasons.

Unless you mean allow EVASSEMBLE to build your Headway packss? You can do that. But the cells wont be matched, and half the bolts will be loose, and they fit a generic unsuitable BMS. Read here. http://www.wheelchairdriver.com/BMS.htm
1. Capacity. Its very important to maximize the capacity when you move to lithium to actually get the benefits it offers. One benefit is increased range. Obviously then you need to fit as many Ah in the place your lead battery used to be. Thats easy with lithium with a little planning. For EG I am fitting 120Ah in the space my 68Ah lead batteries were removed from in my BM2 powerchair. This is only one advantage. You cant often do this with prismatic cells as they are the wrong size/shape and space is wasted.

2. Cell Life. Lithiums that are charged half as often, or discharged half as deeply will last twice as long. So again if you really want to get the advantage of long service life capacity should be maximised. So prismatic cells are often the wrong choice.

3. C rating. The Headway cylindrical cells are capable of higher continuous C rating. Typically 2 to 3x higher. Lithium batteries last much longer if charged gently, or discharged gently in comparison to their C rating. That 2000 cycle rating for cycle life is at typically just 0.3C on a prismatic and 1C on the headway cells. See http://www.evassemble.com/index.php?mai ... ucts_id=21 for C rating or max Amp capability of 10C for headway. And these are typical or better than most prismatics are only 3C cont current. http://www.evassemble.com/index.php?mai ... ucts_id=29

4. Temperature. Has a very bad affect on service life. And prismatics have no air gap, so get warm and stay warm as you charge or use them hard. They have a high thermal mass and low surface area. This is one reason they specify a lower continuous C rating.

This said they will still work. But will likely show a shorter lifespan, less range since you can not normally get as many Ah into the same fixed space we have in a chair, and so less of the advantages that lithium offers. They make lots of sense in a full size EV however.

[expresso]

What size of tab screw with 38140 is it ? M6 ?

i will be getting my next shipment on monday - but no rush - since i am not going to start this till my Friend helper can be around to do it with me - after holidays -

PM me when your ready so we can proceed -

[expresso]

how did i do ?

You did right. And so dont need drawings etc. Yes M6.

Relieved i passed the test - but still i like to see pictures at the same time - just helps me see it already done correctly while at the same time learning about it - i still dont fully get it but understand that much at least -

I was so ready to buy the Ready made 20ah pack from EV instead of doing it this way - but from what you been saying and what i been reading here - i got a better understanding of why i shouldnt get that pack - it was a hit or miss - i am sure it would have worked but for how long and how good -

that would have been alot cheaper for me to do - instead of what i did now - but i will learn a few things doing it this way - first i get to size my other chair with the cells i have - i want to really make sure i can make them fit - so i will know if i decide later to do the whole chair - thats one reason i wanted the cells in my hands first -

next reason - i get to learn a little bit also - - with your help and shirley helping me - hopefully in the end - i have a decent little pack - and see how i feel about it after i use it in the summer to be sure how useful it is - but at least - its a little experince doing it and understanding more -

its an learning experince which i dont fully get it yet - but will try - - the other way - i would have to just gotten the pack - plugged it in - and thats it - i would have saved alot of money in the process - but i loose out on the knowledge i will learn from doing it myself - not really by myself - cant do it without you guys here - BM and Shirley -

and with out this site - i would have never even gotten a faster charger or added cables for it etc, - no programming the chair - all that came from this site - which i pass along the info i learn here to others if they are interested -

good work everyone here

[Burgerman]

The knowledge you gain is always worth the most. Knowledge is power. Once you have that everything else is easier and you are in control.

I HAVE to know everything. I am a total control freak. I don't own anything that hasn't been apart, or improved. Right now I am fitting a proper balance connector to my robotic mower.

I discovered its BMS allows the pack to discharge and do so unevenly if you leave it unused. That's normal for lithium batteries. As in now, since its winter. So when you try and charge it, its feeble BMS keeps cutting power and stopping it from fully charging as a single cell is already full... Its got a weedy balance circuit. No doubt after 3 days charging it would manage it. But by then we will have cooked the high cell repeatedly. Mass produced stuff is crap.

[expresso]

The knowledge you gain is always worth the most. Knowledge is power. Once you have that everything else is easier and you are in control.

I HAVE to know everything. I am a total control freak. I don't own anything that hasn't been apart, or improved. Right now I am fitting a proper balance connector to my robotic mower.

I discovered its BMS allows the pack to discharge and do so unevenly if you leave it unused. That's normal for lithium batteries. As in now, since its winter. So when you try and charge it, its feeble BMS keeps cutting power and stopping it from fully charging as a single cell is already full... Its got a weedy balance circuit. No doubt after 3 days charging it would manage it. But by then we will have cooked the high cell repeatedly. Mass produced stuff is crap.

Are you referring to the BMS in the EV Ready made packs ? i understand it better now how the BMS works on that Ready Made Pack - and i see what you mean how the cut off is too high for over charging etc, etc, -
but if you are using a charger which is 28.8V - if it dosnt charge past that - it would never reach those higher levels of over charging ?

if you use the chargers they sell - which i notice are all 29.2V - something like that - then i can see how it chargers higher than it should and the BMS allows it to happen because the cut off is higher on the BMS before it stops it -

for a moment lets forget the BMS cut off - etc, - if the charger is 28.8V - the cut off on the BMS really wont matter right ? it wont reach those levels because the charger dosnt charger higher - that its 28.8v

i understand what your saying how a BMS affects the whole process and its intentions are good but just not perfect enough -

knowing this - i know why you would hate them - i agree - BUT for a moment - remember - Only a handfull of users - YOU being one - and maybe a few hundred lets say who can do what you do - understand what it being done and why - and able to take care of a Pack with out a BMS -

The rest of us - and i know i am not that smart - but many are even less smarter than me - so for the masses - i dont think we ever will see a pack in production without a BMS of some sort - - no one will do or can do what you and a few others do here - Everyone needs and wants a Plug and Play - the BMS gives them what they want and need - they need it because they dont have the knowledge - the power - the funds - Time and really i am sure alot of them - dont care anyway - they just want to plug in charge and go -

i love that option myself - but i get it now -

AS for me - i decided to do it this way - with Shirley doing the BMS for me - - i just have to see how it works out in real life use - i hope its a good experience for my first time - now if i ever get to the point that i want to do the whole chair -
i wont use a BMS with that - and would have to get the charger - PSU etc, all the other stuff to keep that working the way it should be -

when i get this completed and start to charge it - being that i wont be using it much - i should charge my chair normally - each time i use it because still have lead in there - or should i just leave the add on pack off the chair for winter time and can charge that on its own ever few days or once a week maybe

the only reason i am using the 28.8V charger now is because i have the AGM batteries in there now - or else i could use the other charger set for GEL - at 28.2V - which would be better for the ADD on Cells also ? wont over charge them that way for sure -

[expresso]

i am getting a little confused on which anderson connectors i need to purchase that would fit the current ones i have also -

i have gray connectors SB50 - they were made for me when i purchase the charger - which already had it - http://www.chargingchargers.com/charger ... c2024.html

i want to purchase some - was going to get 8 AWG Wire and the connectors so i can make a lead - but i would want them to fit on the current connectors i have also

Would any Anderson SB50 Gray connector work ? i seen some say 50A - etc, and etc, - and some dont -

http://www.ebay.com/itm/10-GENUINE-ANDE ... 6Mp0nrlFoQ

would this be correct - - good deal ? i cant seem to find a large roll of silicone wire - -i find many 3 feet and 5 feet etc, -

Also would this be a good size to get - 1/2 inch ? if using to cover a lead both cables - -

[Burgerman]

You don't need or want silicone wire really. Marine, tinned, is harder to damage. Silicone is heatproof but fragile and tears and cuts easily.

All same colour sb 50 andersons fit...

[expresso]

ok good thing i waited for your answer -


this would be good then ?

http://www.amazon.com/gp/product/B00TAN ... o_pC_S_ttl

or this one - http://www.amazon.com/dp/B016LH89NA/ref ... 4NBE&psc=1

how about this size for the cover -

http://www.amazon.com/dp/B0008JIQ18/ref ... ESAG4HO2M0

i never know the correct size when i get these things -


these would be fine ? - http://www.ebay.com/itm/10-GENUINE-ANDE ... 2518.l4276

with this crimper ? - http://www.ebay.com/itm/8-Ton-Hydraulic ... 2518.l4276

- thanks

[Burgerman]

yes

[Scollard]

BM, what gauge did you use for your balance wires?

[Burgerman]

http://www.store.revolectrix.com/Produc ... sion-Cable

This from charger to SubD connector.
Same size plus 1 for battery to Chairs SubD connector.

No idea what that actually is.

[snaker]

@Burgerman: Many thanks for your clear analyzing and comparing between the prismatic and cylindrical cells. I think I could not find these valuable infos outside the board.

[shirley_hkg]

expresso, stick to grey and black.

Keep your cables as short as possible too.

[expresso]

expresso, stick to grey and black.

Keep your cables as short as possible too.

I just ordered a pack of Grey SB50 - black wire only - if thats what you mean - or you mean black SB50 ?

i am goin to start a new thread of this build once i start after the holidays -

thanks everyone - Merry xmas and Happy New Year

[flagman1776]

I prefer to use different color wires... I usually find enough left over wire from my salage at the Marine Electronics shop... but not always. If I must use like color wire, I use colored tape at each end of the wire (like red tape for +) to avoid smoke & flames.
I really should buy some uninsulated crimp terminals (I always solder & heat shrink after anyway) but I usually wait until last minute & then end up removing the plastic from insulated ones.

[expresso]

I prefer to use different color wires... I usually find enough left over wire from my salage at the Marine Electronics shop... but not always. If I must use like color wire, I use colored tape at each end of the wire (like red tape for +) to avoid smoke & flames.
I really should buy some uninsulated crimp terminals (I always solder & heat shrink after anyway) but I usually wait until last minute & then end up removing the plastic from insulated ones.

I am also used to seeing two colors - red and black wire - but i found 50 foot roll of black - figure why buy two rolls - but i also got Red tape also - to do just that - put it on the end of the Pos - i like to see the color difference

i figure if i use the black sleeve to cover both wires anyway - dosnt make a difference having Two colors - as long as its connector the proper way on the Connector - little Red tape at the end for a visual -


http://www.amazon.com/gp/product/B00DVC ... ge_o00_s01

i got in black also - can come in handy for that purpose on many other things also -

[Burgerman]

I normally use all red or all black but use red heat shrink on the pos. terminals.

[ex-Gooserider]

Looking at the pictures I'd say somewhere between AWG 20 and 26.... The connector on the end looks like a JST-XH series plug, and the official spec on that series is AWG 22-28. Given the length, I would hope that it was AWG 22....

I like to use color coded wires if possible, but if not, I will also do colored shrink tube on the ends - Avoid tape, as it can fall off.... I also use color coded (even if it's my own code) Anderson power-pole connectors in addition to attempting to use different plug configurations to the extent that I can...

IMHO It is best to have redundant information on wiring just to avoid any confusion....

ex-Gooserider

http://www.store.revolectrix.com/Products/Cellpro-PowerLab-Adapters/Cellpro-PowerLab-36-Extension-Cable

This from charger to SubD connector.
Same size plus 1 for battery to Chairs SubD connector.

No idea what that actually is.

[flagman1776]

All good. For gosh sakes, draw out your wiring diagram... even make copies. Label everything. Keep one with the chair & another in a safe place. Years from now, if something needs fixing or replacing you'll be glad you did.

I used the JXT series to make my own charging loom for the Hyperion 1420i I charge with... merge the output from both Hyperion balance ports into a single balance plug for my 8S LiFePO4 TravelScoot (Conversion) pack.