Battery ADD on pack - First Attempt -

[shirley_hkg]

I worry about it's incompetent BMS too.

[Burgerman]

I worry about all BMS. Never saw a good one yet. The idea of one is fundamentally flawed. They are in the wrong place, and do 2 jobs badly. The only purpose they serve is to allow some retard to use lithium cells in a badly thought out way, or in a place (like an eBike) where a non sophisticated controller can abuse the too small pack. And to sell lithium to the masses that don't understand.

Go on any ebike/ev forum and read about the mass of cell damage, short lifespan, fires and reliability issues and endless problems. In every case BMS caused...

They attempt to fix the symptoms, (over current, under voltage etc) in the wrong place rather than address the problem to begin with. Even if working "correctly" they do things we don't want! They make a mess of charging with inadequate accuracy, inadequate current handling with feeble 100mA balance circuits, trying to balance below 3.4 or 3.5v, allow repeated over volt then cut off during charge and cannot control the charger proportionally on/off as it bounces the cell voltage up and down - often for days... And cuts power at the wrong (dangerous) times in use. Worse, they fail, cause fires, and add another layer of complication that simply isn't needed.

With a properly thought out system, and a current limiting controller as we already have on a powerchair (in the correct place), That already will not allow too low voltage, or over current. And it addresses this proportionally under proper control, a BMS functions are redundant. They exist only to fail. That just leaves the cell balancing and charge control, the other thing BMS do very badly...

Want your cells to have half the life they should? Want to wait days to balance a pack that's been stored a few months and is out of balance? A BMS is the answer! Some that balance ALL the time will even unbalance it for you!

Simply not needed. My small quality hobby charger does a massively better job, far more accurately, to the figures you tell it, and its kind to the cells with full proportional charge and balance circuitry to 0.003mv accuracy. And it can charge from a car or in your house at 40A if you want. And has 1A balance circuits so the highest cells on charge spend 10x shorter time at 3.550 or 3.600v as you choose.

Why on earth would you want a BMS???

What useful purpose does it serve?

[shirley_hkg]

I knew it all !

However , I want to use my dumb charger , because :

we want to share our chargers among wheelies during outing ,
I want to be able to recharge battery , when I'm away from home ,
it can be handled by carer,
it is cheaper,
it lasts for years.
it can charge the lead bricks together , in one go , with the lithium as an add-on.

REMEMBER . Full lithium is not trivial and need constant T L C . Add-on is the best shot for novice .

Now the price, per usable amperage, of lithium cells is only 1/3 of that of new MK GEL battery , so it becomes expendable .

[Burgerman]

>>we want to share our chargers among wheelies during outing ,

PL8 can charge anything, at .010A to 40A. And ALL chemistries, all capacity, inc lead bricks, lithium, Nickle metal, and any other! And so nothing changed. And also from 12V, or 24V, or from a car, or from another powerchair... It can (or not - you choose) balance cells, discharge, graph, monitor, measure resistance, and be controlled by PC if you wish... You lose nothing.

>>>I want to be able to recharge battery , when I'm away from home ,

PL8 from wall with a small power supply, from another chair, from a car...

>>>it can be handled by carer,

Yes... Its easy. Pre programmed. Plug in press go.

>>>it is cheaper,

Is it? Not so sure.

>>>it lasts for years.

Battery? Not with BMS...

>>>it can charge the lead bricks together , in one go , with the lithium as an add-on.

So can PL8. Or charge it PROPERLY on its own. And can ALSO do a much better job of charging your lead batteries too, with user chosen termination current, and accurate CC/CV levels that you decide, and at up to 40A... 12V or 24v in parallel or series...

>>>REMEMBER . Full lithium is not trivial and need constant T L C . Add-on is the best shot for novice .

Not so with hobby charger. Just connect and press go. Yes with BMS it DOES need lots of massing about to keep it working...

[Burgerman]

Just starting a discharge test on my NEW 120Ah headway pack.
Initial charge at 40A inc balance took a few mins. All cells were sat at 3.600V until 100mA reached. Nothing exceeded 3.652. Balance started at my chosen 3.500V and not before.
Initial charge 3.650V
All future charges will be at 3.600V or 3.550V and at 40A. Balance on a carefully built pack with 1A cont proportional variable balance and variable charge rate means full charge and balance achieved for 120Ah is 3 hours 5 mins (+/- 3mins) from 100% dead to 100% full.

Two mouse clicks, one connector. No BMS.

[Burgerman]

Wiring not yet tidied up yet but already under test!
120Ah, 80 cells, in 2 parts.

Each of the 8 groups have matched self discharge levels, (tested as individual cells over 6 weeks) and equal capacity. Actually they were all so close to within around 20mAh to 2.800V at 1C that measuring that was a waste of time. But at least I know.

[flagman1776]

I have to agree with Burgerman. I'm using the Hyperion "smart charger" instead of the PL8 "smart charger" he's switched to but they are comparable. I just plug my pack in. Power up the charger, press the same button as the charger comes up... It's already programmed.
The charger beeps when it's done. Shut the charger off, disconnect.

The "complicated part" if you want to call it that, was building a wiring harness. But a BMS will need basically the same balance harness. So that's even.

[Burgerman]

It actually needs more. You need to route the chairs supply and the charge supply through it too. (Adding resistance and heat from its Mosfets on the way) So it can keep cutting off the charger when its tiny 100mA balance circuit cant cope. Or so it can cut the power when the voltage drops or current is exceeded as you try to climb a curb and not be killed...

And needs to be found somewhere to "live" until it catches fire, or its wiring does, or until it ruins the batteries or causes you to breakdown, or wonder why you have no range... Ore why the charge never ends!

Oh the fun. I don't like, don't need, don't trust, BMS. Because I have seen what they do. And have yet to be shown any single good reason to use one on a powerchair? Other than it means you can use a cheap weak slow 7A heavy mobility type charger that takes forever. That only works on the AC supply. While the BMS ruins the batteries!

[expresso]

Oh dosnt sound good now - - i guess i will find out the hard way or maybe i be the lucky one and works fine - well i guess i let you guys know how it works for me soon - i hope to receive it - the BMS next week - or latest end of month -

i may end up with the PL8 etc, sooner than later anyway - i am leaning on doing my other chair full also - once i work out a few little things first -

[Scollard]

Oh dosnt sound good now - - i guess i will find out the hard way or maybe i be the lucky one and works fine - well i guess i let you guys know how it works for me soon - i hope to receive it - the BMS next week - or latest end of month -

i may end up with the PL8 etc, sooner than later anyway - i am leaning on doing my other chair full also - once i work out a few little things first -

You have to put everything in context. When we poo-poo the BMS it's because we're talking about building packs which will probably outlast the chair. The cost of a full replacement pack is 3x the cost of lead. So you need to get 3x the length of life for just the ROI. There are also other advantages but that should be bonus features, not ones you need to pay for. In 10 years time, when BM retests his 120Ah pack, it will still be in terrific condition. In 10 years time when you check your add-on, well, it won't be around in 10 years time.

[Burgerman]

BMS will be OK on the add on. Don't worry its cheap!

But I wouldn't run one on a proper battery. with a few exceptions that is too complicated to explain here.

[snaker]

I still agree with Shirley that PL8 only suits hobby stuff. That means it's perfect if you use it yourself. It will cause troubles if others (i.e carers) use it to charge your battery pack. Even it can be pre-set and operate with a press, I doubt that anyone around me (like my dad) could do it correctly everytime. For him, reading some simple English worlds on the PL8 LED screen is confusing as you (Westerners) read Chinese characters. But he or anyone can easily charge a plug-and-play battery pack with BMS. So BMS is not too bad in every cases.

[Burgerman]

Everyone is different. But I saw too many ruined battery packs, that I have rebalanced to get them working again after changing out cells etc. And read about too many fires, and endless problems and reliability issues all caused by BMS. They mostly do a lot of stuff we do not even WANT them to do.

You can get over some of that by connecting the chair directly to the battery. That only leaves them in control (if that's the right word) of charging. Which they are dangerously bad at. But hey, if you can afford the replacements, and don't mind the problems and messing about trying to get it working when it doesn't, that's great. Too me its not worth the risk or the trouble. For an add on pack then it is probably worth it if you cant work a proper charger.

[expresso]

I agree with SNAKER - - My father couldnt do the PL8 for real - i dont trust him with the plug and play either - haha - My girls - i can do plug and play easily - but still have to watch all the time - depends which one is doing it - i have a few

i would be the only one to touch the PL8 - when i get there -

i wont be using any BMS with the full pack - its only going to be used on the ADD ON Pack - if that lasts 5 years i be happy - for the first time - once i get used to the PL8 - and the full pack done etc, - i can feel better then if i have to not use a BMS in the future for any other ADD ON packs i may make or do for a friend etc,

i have a friend or two who once i get the ADD ON pack done - they may be interested in that - but like me - they would want it simple plug and play and that means BMS for them also - i know they wont invest or get too involved in doing the PL 8 and computer etc, etc, - but who knows - they may change there mind also like i did now -

[Burgerman]

if that lasts 5 years i be happy

Could be 3 days. Or 10 years... That's the problem. Or it could just be slow, etc, and no information so you cant see what its doing or not doing... Shirley can, and then he can administer his TLC to massage it and make it behave...

[expresso]

i See what your saying - in my case - i wont have to know how to see whats going on and take care of it the way you and Shirley can - i hope it hangs in there for sometime at least -

[Burgerman]

Well you better hope! Because you wont know.

Whereas I can see everything on my laptop in detail

[expresso]

You have to have Faith like they say people love to use that word when they dont know the answer - haha - but i am going to give it a shot - have faith in Shirley's BMS and its only for the ADD ON pack -

[Burgerman]

Faith = irrational belief in something without any logical reason.

Its not a GOOD thing no matter what the delusional religious nuts may tell you.

Here for eg, I can see a lot of things as I discharge.
All cell voltages stay together as I discharge the battery with the charger. That means equal resistance, equal state of charge, and t is staying that way. If I keep going till they drop to 2.5 to 2.6V I can see that some cells will drop first, and read actual Ah out. Now when new, and again every 6 months or so to keep a check on battery condition, cell resistance, capacity, balance, etc. I also see that they are at 3.315V for every cell. And that I am discharging at 3.5A. And how many Ah I have removed so far. (not many!) And so on.

I see similar only more interesting when I charge.

download/file.php?id=4285&mode=view

[Scollard]

Once you build the full pack and get a PL8 you can always go back and remove the BMS from the add-on.

[expresso]

Faith = irrational belief in something without any logical reason.

Its not a GOOD thing no matter what the delusional religious nuts may tell you.

yes i agree - i dont get too involved in that area - its nice to want to believe something - but i need some sort of Facts also - to get my attention

[Burgerman]

Or leave it temporarily, and use the PL8 to just monitor instead and graph the cell voltages as they go beserk and bounce around as the BMS tries to charge/balance and so see why they are so crap!

[Burgerman]

its nice to want to believe something

No! Its really not.

Right now there are thousands of deaths and suffering and mangled, or beheaded bodies and worse, all over the middle east and even in Europe because of this garbage. Same shit all through history. Everywhere there is this confused irrational thinking you get the same thing. Stick to logic and reason. Sane people don't go around murdering and torturing, blowing up the innocent, or cutting up children's genitals or any of the other ridiculous things that the delusional do.

[expresso]

Once you build the full pack and get a PL8 you can always go back and remove the BMS from the add-on.

that would be an option then - but then i would have to charge that alone and the chair separate - not end of the world - just sounds good to plug it in and leave it as before - either way - i wont mind but i do want to give this BMS a try - i didnt get it yet - - i have to give it a shot - i want to see it myself - i guess the ADD on is a Test for me -

you know you have to really guide me along step by step when i do the full pack - i hope your ok to help me that way

[expresso]

its nice to want to believe something

No! Its really not. Right now there are deaths and suffering all over the middle east and Europe because of this garbage.

yeah but thats stupid to me - its ok to believe something - but not kill people for it - Peaceful beliefs - anyway off topic - i dont follow that stuff much - more science guy here - i am open to many theory's -

[Burgerman]

yeah but thats stupid to me - its ok to believe something - but not kill people for it - Peaceful beliefs - anyway off topic - i dont follow that stuff much - more science guy here - i am open to many theory's -

ANY bewildered muddled thinking, any odd belief, is simply the thin end of the wedge. Its all evil. Even if indirectly. No matter how unintended the consequences. Its impossible to allow any type of illogical irrational thinking not to affect your world view. And so also impossible not to allow your confused world view to further affect your decisions. One day you may be in a position to make rules, laws, or just meet me or someone like you. And all of this affects me. And other sane people worldwide. Today for eg, I go to my local model shop, and its closed. Why do you suppose this is? Religion and its members, stopping me buying some connectors... Someone's imaginary friend is stopping me finishing my powerchair. It directly affects me. One tiny example.

A more serious one, ignoring all the violence over the centuries, stem cell research was held back decades. I may have been walking rather than paralysed now. There are countless others. For these reasons I do not think irrational beliefs should be respected, but ridiculed as much as possible.

[Scollard]

Once you build the full pack and get a PL8 you can always go back and remove the BMS from the add-on.

that would be an option then - but then i would have to charge that alone and the chair separate - not end of the world - just sounds good to plug it in and leave it as before - either way - i wont mind but i do want to give this BMS a try - i didnt get it yet - - i have to give it a shot - i want to see it myself - i guess the ADD on is a Test for me -

you know you have to really guide me along step by step when i do the full pack - i hope your ok to help me that way

No difference between a big pack and the add-on. It's just bigger. You know how your add-on has 2 rows of 8. The bigger pack will just have 6 rows of 8. Connectivity is all the same. I suppose it's a little more complicated if you go with the extra 8 cells on top.

[expresso]

BM - I agree - i rather be walking also - if they can do something already -- i dont mind respecting anyones beliefs - as long as its peaceful and not forced on anyone else etc, - but i get it - thats a never ending subject - winter is good for Netflix Documentaries of all sorts -

i rather learn to make a charge balance cable instead

[expresso]

Scollard - - i dont mind doing the basic 6 x 8 - 15ah cells - if the extra 8 on top is too complicated to do - i dont have to do them - i can always make another ADD on back for that chair also - make a 30ah ADD ON - same 15ah cells

that would give me 120ah - if i used the ADD ON with the 90ah in the chair - still very good - i be happy with the 90Ah - i know BM wont be - to me whats more important is if i start it - i like it done - simple - easy - neat and want room to move the tray back and forth -

i am going to work on that divider thing - i can see how i can get it fixed better and more stable than it is now - with a little extra headroom once done - still not enough to my liking -if you ask me - the 90ah pack seems easier to connect etc,

i will still be at least 2 x the range ? to me thats a huge improvement - and i might not even use that much daily - and can use the ADD ON when i do want to take a longer ride - once i get the feel of how much i can do with the 90Ah pack
then i can adjust as i learn what the limits are -

what do you think ? is that something you can walk me thru - remember i never done it - and my helper - shes great but knows less than me - so she will do what i explain to her to do - and i will do what you explain to me

hopefully with pictures -

[Scollard]

Very Easy. We will get the add-on done first and you will see. You can decide afterwards if you want to do a 90Ah or 105Ah pack. As I said before, adding the extra 8 cells will mean having to make nine 8 AWG wires with ring connectors. You're going to have to make 9 balance wires anyways, plus the power wires and charge wires.