Revolectrics

[sacharlie]

https://www.industrie-techno.com/article/le-lithium-fer-phosphate-la-plus-sure-des-technologies-de-batteries-au-lithium.44982

Well here again I read lifepo4 has no danger of fire even with a BMS.
BUT as BM now explained its the BMS wiring and other material that can catch fire.

[Burgerman]

Correct. Thats exactly what happened to the 4 wheel drive chair I linked to. Net result was that the initial fire was wiring, plasticks and seat cusion. Then a little time later tyres. And then it boiled the electrolyte out of the cells. Which burns very well...

[Burgerman]

I know this happens.

I posted a link to an example here https://www.wheelchairdriver.com/board/ ... =40#p84092

Take the time to actually read the first few posts. Where I correctly predicted the cause...

Re: TerrainHopper

First time we used it it caught fire

Burgerman: What exactly caught fire? Let me guess. A lithium battery with a BMS system on it

And...

You guessed it Quite an experience trying to get your disabled son out while its on fire. Good job we where on the beach, sand does put out fires quickly

So dont tell me its not a risk for someone that cannot get out. Or if indoors and you are not watching it.
It had 2x 80Ah grp22 drop in replacement overpriced lead brick replacements. LiFePO4. They dont offer those now!

[Fred005]

Your link is a bit more than 5 years old.
I can imagine, since 5 years, BMS technoligy is a little bit better. Only a little bit !!! Lol.

BTW, with a Daly BMS, for exemple, waterproof, dustproff, even if a nasty mosfet whent to burn, fire will not go far.
Ah ... Ok ... The wires ... Fucking wires, more nasty than BMS, so.

[snaker]

The danger is not about what material a BMS is made of. It is about SHORTED caused by BMS. And a shorted circuit would toast everything. And in VN, Daly BMS is known as a fake/clone of another Chinese Daily BMS which is also not great.

[sacharlie]

So why isn't there a good BMS?
Why isn't the pl8 subject to failure that can cause a fire?
Guys here have pl8s that no longer function, no?

[snaker]

There are good (or good enough) BMS for stuff other than powerchairs.
PL8 could fail but it was well designed and made for safety. A broken PL8 does not cause SHORTED or fire.
I have a broken PL8, all its mosfets were toasted but did not cause any danger. If I plug it to a power supply or a battery, it simply does not work and keeps quiet.

[expresso]

i had only ONE fail on me when it was new - and i smelled smoke and flames shot out the back from the fans -

since then i finish my charging while i am still awake - nothing happened - was replaced - that was the only time i had one fail at all so far

i have used it overnight many times also - but i like to always finish before i go to sleep

the times i leave it going were mostly when testing new Cells - charging discharging a new large pack

[Burgerman]

So why isn't there a good BMS?

Because its in the WRONG PLACE.
Doing mostly stuff we dont want it to do.
And it cannot control the charger output or the termination point, or the charger voltage.

Why isn't the pl8 subject to failure that can cause a fire?

Technically it could. But you have that disconnected when you are using the chair. And it is therefore no danger to the user. Its also designed in a different way and if its main mosfets failed shorted it will take out a fuse in the charge cable of 40A. Its balance mosfets are through resistots that limit it to 1A drain. So hard to see how it can cause a fire in the same way. And 2 cooling fans on board to cool those components.

Guys here have pl8s that no longer function, no?

Yes as mentioned may times. They dont like cheap spiky power supplies. So buy spare ones. That said I have 4 of them and never had any failures. Expresso had one go bang when first used. Replaced. But the difference is that you dont sit on it.

[Fred005]

PL8 and its company were so good that they couldn't pass the COVID crisis .....

BMS is ''not in the right place'' ?
That's not what are saying (except some ones here) plenty of cells/batteries/electric vehicules (all kinds) builders/sellers/engineers/users ....

BM wrote "Doing mostly stuff WE dont want it to do.", for the moment I can say BMS will do mostly stuff I want/need.
So, maybe it's time to change your mind.
Time too, to see what are all the settings you have in a 2021 BMS instead having ideas/exempls old for more than 5 years.
Remember BM, when you helped me (and I thanks U again) with my PM settings you wrote:

What do I think? Looks like you would be hard pushed to control or drive it.
You have everything exacty opposite what I would do.

Yes, I have everything exactely opposite what YOU would do. But exactely what I need. If today I send you my PM settings you'll be .
But MM have been interested by these ''strange'' settings.

Today a spinal cord injury can't be solved. In a few years, for sure, it'll be possible.
In all domain, progress they are, even in the BMS world.

[Burgerman]

You are welcome to your views. Wrong regarding BMS but welcome to it anyway.

A question for you.
How does your BMS know the battery balance has completed, and that the battery charge has completed?
I can tell you the answer, it doesent, But more importantly even if it did it has no way to tell the charger this. Which in turn has no idea what the BMS is doing... They cannot talk to each other.

Next question, how does the charger know when battery cell balance has ended. It can take days or minutes. How then can it determine if its time to stop charging? I can tell you the answr to this too It cant!

Next question... How does the charger know when to stop charging. The BMS doesent do that and it cant?
The correct time to do this has a need of a little logic.
1. When all cells are balanced and sat at x volts. And at x (low to almost zero) balance current. Then 2 below.
2. And at a specific current. The current, typicaly 350th of capacity should mark charge end by the charger. But it cant know this if the BMS is chopping off power to prevent a cell going too far above the correct charge voltage.

All because the balancer and the charger must be able to talk to each other. The balancer has to be able to control charger output current to below balance current to kepp a high cell from going abive the chosen point. And be able to tell the charger when balance is complete. And because its only got 2 wires with a dumb charger it cannot ever know any of this. Because the BMS is in the wrong place. It needs to be part of a integrated charger to do this properly. So the two parts can communicate as needed.

I know that you "feel" its all ok, but thats just because you do not understand how it all works. Feelings and scientific and engineering ignorance is no substitute for engineering and electrical knowledge. Sorry if you dont like that. But it remains true anyway. Does it work? In a fashion. Does it do it correctly? Absolutely not! All kinds of incorrect shit can happen. And does.

As I have said many times. Its good enough to prevent cells getting returned under warranty (most of the time). And thats really all its sold and good for. Its there to prevent ignorance murdering the cells. If you dont care about all the details thats fine. The trouble is details matter. The vast majority of people have no idea how most of the stuff in the world works. They are the very same ones that get a year out of their laptop batteries. Or who get ripped off every time that want a car or a chair repaired.

Or children set on fire...

[steves1977uk]

Well I certainly won't be using a Failly (oops sorry Daly) BMS... https://diysolarforum.com/threads/daly- ... nce.27086/

Looks like a POC to me.

Steve

[Burgerman]

Its not just that BMS. That is the result of how they work. They cannot control the charger. This is why I never want anythng to do with any BMS.

I read those 2 pages in your link. This is typical. The one in my mower was doing the exact same thing. They can work ok on lithium ion cells. But on lifepo with a completely flat or even resversed voltage/charge level across most of the discharge/charge ange a BMS doesent stand much chance of balancing properly. Unless its very well configured, and with a equally well matched charger and a lot of user montoring. This doesent happen so the net result is exactly what you see in your link.

[fishinjunky]

Man this sucks not sure what to do I planned on building a lithium pack for the bounder this winter.

[expresso]

Man this sucks not sure what to do I planned on building a lithium pack for the bounder this winter.

one way or another you will find a way to charge it - if you dont have a PL8 now - start looking at a different charger -

and or another option - external BMS - thats worse case situation - this way it wont affect you while riding at all - with a large pack
you shouldnt have to worry about getting too low -

when you get home - connect external BMS - connect charger to that and let it go - may take all night - i would shoot for a 20A charger at least -

my bounder uses a BMS - i charge it at 20A with the PL8 -

[Burgerman]

But how do you know if its balanced the cells before you stop it? How do you know if its even tried like my mower or the one in the link above? How do you determine if its fully charged? How can any charger? And thats one of the problems. At best it is guesswork and hope.

[expresso]

you dont know - but what you do know is either that nothing - then you know nothing -

its the last case resort - thats all i am saying - if its that or nothing - which do you choose - or go back to lead haha - not going to happen here

all my chairs are lithium now - just one indoor chair has lead with an add on - i am charging that one now - so one way or another - i have to charge - i am ok i have spares- but if i didnt have them -

i would have to try any other charger out there - or an external BMS - last resort

maybe - start a section - BMS - and let the expert BMS here lay it out - what can be used - the differences between BMS - etc, etc, - a Section just for BMS and New Chargers -

[Burgerman]

Well theres not much to know. They are all the same, work in the same flawed way give or take some fancy graphics and blutooth.

Yes you are right. You have 2 choices. Explore a lot of hobby style chargers till you find one thats good to go as I did originally with hyperions and revolectrix, or use a BMS.

But the more you understand about both the better position you are in to do both of those things.

[expresso]

yes thats true - thats why a new section just for New chargers and BMS -

so we can explore and give feedback there - also who ever is more involved with BMS stuff or has been or still is - can give feedback -

anyone doing lithium now will benefit from the feedback on new hobby chargers and BMS details etc, - from my little bit of understanding with the BMS - we would like it to just balance - keep the cells at 3.6 at most during the process - and start the balance at 3.5v ? and hold it till all cells reach 3.6v ?

is there ANY BMS that comes close to whats needed as a last resort ?

[Burgerman]

keep the cells at 3.6 at most during the process - and start the balance at 3.5v

Thats not how they work. In order to do that they would need to throttle the charger back so that the cell that is high, that they are trying to pull power from, does not keep rising. All they can do is chop off power completely while that keep on dragging a high cell down from 3.7 or 3.8V down to 3.5. Then rinse and repeat. They can only CHOP OFF charge power. Meanwhile the charger may do 2 things. Stop charging as it sees no battery. Keep going but voltage rises due to no load. Or think the charge should end. Due to low current. All depends on the charger. This all happens because the charger has no way to know what the BMS is doing. And the BMS cannot slow down the charge as it balances as it cant talk to the charger.

So it just does what it does. Which kind of works, but not very well. And bad for cells. And unknown state of balance. Etc. The problem isnt "how good" a BMS is, its where it is located. It needs to be in the charger. Theres many hobby chargers around. Maybe hundreds. You just need an 8S one that works.

BMS or CHARGER specs:
To charge a big 200Ah lithium pack you really need a 30 to 40A capable charger. Unless time doesent worry you. 200Ah at 20A takes 10 hours and another for CV and balance. Your choice here.

Balance current on a large pack, esp when cells are less than new, or on a freshly built pack, or with less that A GRADE cells needs to be 1 to 3 Amps minimum. Not a few hundred mA!!!

It must be voltage compatible. What exact voltage is needed depends on the BMS if you Use one.

The balance must never be active below 3.5V and maybe better only at CV voltage of an accurate 3.550V to 3.600V.

The charger used with a BMS must magically know when to stop... Dont ask me how you are going to do that.

[sacharlie]

anyone doing lithium now will benefit from the feedback on new hobby chargers and BMS details etc, - from my little bit of understanding with the BMS - we would like it to just balance - keep the cells at 3.6 at most during the process - and start the balance at 3.5v ? and hold it till all cells reach 3.6v ?

Is this the magic of the pl8?
When charging a group of cells like 4/12v or 8/24v if one cell only charges to 3.5v all the others are then brought down to 3.5v?

[expresso]

keep the cells at 3.6 at most during the process - and start the balance at 3.5v

Thats not how they work. In order to do that they would need to throttle the charger back so that the cell that is high, that they are trying to pull power from, does not keep rising. All they can do is chop off power completely while that keep on dragging a high cell down from 3.7 or 3.8V down to 3.5. Then rinse and repeat. They can only CHOP OFF charge power. Meanwhile the charger may do 2 things. Stop charging as it sees no battery. Keep going but voltage rises due to no load. Or think the charge should end. Due to low current. All depends on the charger. This all happens because the charger has no way to know what the BMS is doing. And the BMS cannot slow down the charge as it balances as it cant talk to the charger.

So it just does what it does. Which kind of works, but not very well. And bad for cells. And unknown state of balance. Etc. The problem isnt "how good" a BMS is, its where it is located. It needs to be in the charger. Theres many hobby chargers around. Maybe hundreds. You just need an 8S one that works.

BMS or CHARGER specs:
To charge a big 200Ah lithium pack you really need a 30 to 40A capable charger. Unless time doesent worry you. 200Ah at 20A takes 10 hours and another for CV and balance. Your choice here.

Balance current on a large pack, esp when cells are less than new, or on a freshly built pack, or with less that A GRADE cells needs to be 1 to 3 Amps minimum. Not a few hundred mA!!!

It must be voltage compatible. What exact voltage is needed depends on the BMS if you Use one.

Ok but there are no chargers with built in BMS - we have to deal with what we have or can get -

The balance must never be active below 3.5V and maybe better only at CV voltage of an accurate 3.550V to 3.600V.

The charger used with a BMS must magically know when to stop... Dont ask me how you are going to do that.

[Burgerman]

Ok but there are no chargers with built in BMS - we have to deal with what we have or can get -

Of course there are. You have 4.

[expresso]

your confused - yes i have the PL8 - but they are not being made anymore - i was not referring me only -

in general - for everyone as of right now - they are none that you know of that works as good as the PL8 or close to it - you have to buy a charger what ever you think may work and try it - or use a BMS -

you said the BMS is in the wrong place and needs to be in the charger - i dont know of any other charger that has a BMS installed inside or works like the PL8 - the PL8 was doing the job of a BMS without all the bad parts of the BMS -


but its over - done - PL8 dead - Covid got it - PL8 should have taken the vaccine

[Burgerman]

But a PL8 is one of hundreds of hobby style chargers. I was using it as an example.

[expresso]

But a PL8 is one of hundreds of hobby style chargers. I was using it as an example.

ok i see all those hobby chargers have a BMS built in - they just dont do a good job at it - like the rest of the BMS out there -

the trick is now to find a good hobby charger and start from there ?

for new users now -

[Burgerman]

They all do a much better job than a BMS. But many are super cheap, low powered, dont allow large packs or dont allow the settings a large pack needs. They are primarily designed for small batteries, hobby stuff. Mostly lipo. rather than 200Ah lithium phosphate. So while many can charge that chemistry not many people use that. So it remains pretty underdeveloped. The secret in all these chargers is the firmware. Code. Phone books of it. Hence me spending over a year each getting the hyperions and later on the pl8 sorted out with dozens of test firmwares, and updates.Till they did as we needed.

For e.g. the majority cannot set a termination current properly. They use a percentage of charge current. And too large a percentage at that. So while charger like the ichargers can work they will end charge too soon. Unless you restart the charger and charge at a low current afterwards. Again it can work but needs a little user knowledge and messing about. It may be that they would fix that. But since they have a warning about not using them for non hobby stuff probably not...

[expresso]

Ok so a good hobby charger will work better than using an external BMS ?

if thats the case - then we have to get a hobby charger that can work for large packs - if they cant - then we are back to an external BMS

[sacharlie]

anyone doing lithium now will benefit from the feedback on new hobby chargers and BMS details etc, - from my little bit of understanding with the BMS - we would like it to just balance - keep the cells at 3.6 at most during the process - and start the balance at 3.5v ? and hold it till all cells reach 3.6v ?

Is this the magic of the pl8?
When charging a group of cells like 4/12v or 8/24v if one cell only charges to 3.5v all the others are then brought down to 3.5v?

Asking again what does the pl8 do when one cell in the pack will only charge to 3.5v?

[expresso]

If it's set to 3.6 target. Pl8 will bypass the rest of the cells till the lower cell catches up. It does it to each cell in real time. till all r 3.6. If it's set to go to 3.6. Once there it holds it till term. Point.