Do I really need a bms?

[Samsonite801]

some comic relief for the topic

View attachment 107358View attachment 107361View attachment 107362

upset pillows ?

Ha, those pillows look just like my old Macbook batteries when they started bludging and bowing the keyboard up...

Can you tell which ones are the bad ones?







And these even come with a BMS...

EDIT:
I saw some guys on You Tube who would just poke a hole in each cell and squeeze all the gas out of them and put a piece of tape back over the hole, and keep using them, but I didn't really feel like trying that, I just decided to replace the pack hehe...

 

[curiouscarbon]

mmm lipo soufflé ?

today i learned:

The word soufflé is the past participle of the French verb souffler which means "to blow", "to breathe", "to inflate" or "to puff".

 

[timselectric]

Ha, those pillows look just like my old Macbook batteries when they started bludging and bowing the keyboard up...

Can you tell which ones are the bad ones?
View attachment 107375

View attachment 107376

View attachment 107377


And these even come with a BMS...

EDIT:
I saw some guys on You Tube who would just poke a hole in each cell and squeeze all the gas out of them and put a piece of tape back over the hole, and keep using them, but I didn't really feel like trying that, I just decided to replace the pack hehe...

I've done that several times with cell phone batteries.
Saved a lot of money.

 

[Samsonite801]

I've done that several times with cell phone batteries.
Saved a lot of money.

Yeah I had contemplated doing it, but I had already bought the new battery and had it here in front of me before I saw the video about poking them and bleeding the gas out. I guess you also gotta be careful poking them (like kind of poke through the plastic where it's puffed out, kind of with the needle sideways at a sharp angle), make sure not to poke through the core of the cell itself, or you could short the anode and cathode with the needle and start sizzle-fry reaction...

 

[timselectric]

Yeah I had contemplated doing it, but I had already bought the new battery and had it here in front of me before I saw the video about poking them and bleeding the gas out. I guess you also gotta be careful poking them (like kind of poke through the plastic where it's puffed out, kind of with the needle sideways at a sharp angle), make sure not to poke through the core of the cell itself, or you could short the anode and cathode with the needle and start sizzle-fry reaction...

Yes, it's a bit tricky. I use a brand new razor blade, almost laying flat. And I do it outside, far from everything. This way if it goes badly, I can just run away and watch the show.

 

[Thisguy80]

oh for sure dont get inline, but do post the pictures when you stuff burns to the ground..

'come on dude all jokes aside ;

there a whole forum section dedicated to "crap i done stupid", but it's always your choice and responsibility, just dont get on a high horse when people give you advise/try to help you

The DIY crowd generally isn't interested in having their entire project ruined, or potential house / RV fire. I find it odd that somebody would use super high-tech modern lithium batteries, and not be willing to use the same high-tech monitoring systems that they require. To use a car analogy, this is like buying a 2022 Corvette, and saying that you don't trust the computer, so you put a carburetor back on it.

Just out of curiosity, how would your system handle a failing, low voltage cell if you weren't right on top of it? ALL cells WILL eventually fail, 100% of the time, it's just a matter of when it happens.

One cell starts to dip voltage, your pack appears to have a lower voltage than it "should" be, and now your charger is trying to put 14.4 volts on a 3S pack, which overcharges the remaining cells to 4.8v each. Now instead of a battery, you have a balloon (and hopefully not worse), all in the name of saving a fraction of a percentage of the total battery cost.

I just can't see a single reason to justify not having a BMS. I understand that you feel your situation is unique, and it very well may be, but I wouldn't suggest that ANYBODY try and build an unmonitored lithium pack.

No idea we’re to start or how answer but the Corvette analogy, no I personally wouldn’t but some may do to there end goals and knowledge of different technology.
That’s comparing a technology that’s from my view has been mastered for consumer use while THE BMS is in early stages, one look at the endless posts of issues(here) with them is major point of failure in any system.
Which could lead to all the comments above as well then.
The use of the word lithium, lithium polymer is far more volatile chemistry vs iron phosphate, dense at higher voltage so saying lithium is dangerous doesn’t tell the whole story but leans towards message of saying just as dangerous as it’s big bother ion polymer. It’s much more stable.
I’m no electrician just have few years hands on experience and proven ways of working without labeled BMS.
My head still gets turned around wiring panels but I don’t take shortcuts if I think will add points of failure, I’m in finance and name of the game is minimize risk -DONT LOSE MONEY.
I like to simplify things if possible to do this.
I’ve overly analyzed my interlocking comments, wire breakers, busbar for minimum resistance and at first heavily monitored system but over time have become fairly confident in them.
Like I’ve said temp controlled building.
But what I think is largest contributor to my success is capacity usage and operating range, including how hard I will tap it(discharge amps)
I compare capacity to bank account, more I have more I can withdraw with out but never wanna take them down to low which puts me at risk.I don’t ever swear I label I’m sold that’s likely overly optimistic.

Do some balancing don’t do some balancing and only use flattest part of curve, stay away from any run off points, emptying your account only exposes you.
I’ve never understood using every last amp hour mentality or dollar.
I also have lots of sun here, so batteries seldom need to be my only source of power so can afford to not tap it for everything it has. Run in very tight range.
Like I said BMS use it, it will ultimately be very reliable standard piece of puzzle without question, especially with all the free consumer driven advertising.
Especially use it if your mindset is to withdraw every last amp hour and push high SOC or low DOD, the well established trouble area’s. Most do.
I do little Rc flying at times and made a switch to electric use lithium polymer as main source, while I will charge my cells to 4.06v cell and land at 3.8v(reading 50%) and have trouble free lasting cells nearly all the rest just had to max charge to 4.2v for what gain I have no idea and land with 20% or under reading. Sometimes not even able to land, cells at 140F(mine are cool to touch, air temp)they also love to push labeled discharge rate(another thing I don’t do)complain if there $100 charger says it only charged to 99% lol
I tend to always take a more hands on approach with what ever I’m doing and have head I DONT HAVE TIME more times than I can count, even tho we all have 24hrs to allocate our time. But that’s another story that will surly stir things up.
Since average mindset is typical to buy 200ah batteries or what ever and use 200ah then I’d highly recommend using a BMS or your going to have trouble.
I’m not reiterating what I’ve heard others say or what I’ve been sold just my first hand experience while using these cells, that from my opinion and experience are very reliable, whats contributing to this idk know can only estimate that my process plays a heavy role or I’ve just got some of the best cells ever made idk.
It’s not about saving a dollar, product price point is well established game, cost can lead to better product but saying you get what you pay is true but also played so doesn’t always correlate with quality but diluted quality that can lead to same problems as lower cost product. But also vise versus when smaller company aims to take market share by offering lower cost points with less margins to gain it.

 

[Thisguy80]

No idea we’re to start or how answer but the Corvette analogy, no I personally wouldn’t but some may do to there end goals and knowledge of different technology.
That’s comparing a technology that’s from my view has been mastered for consumer use while THE BMS is in early stages, one look at the endless posts of issues(here) with them is major point of failure in any system.
Which could lead to all the comments above as well then.
The use of the word lithium, lithium polymer is far more volatile chemistry vs iron phosphate, dense at higher voltage so saying lithium is dangerous doesn’t tell the whole story but leans towards message of saying just as dangerous as it’s big bother ion polymer. It’s much more stable.
I’m no electrician just have few years hands on experience and proven ways of working without labeled BMS.
My head still gets turned around wiring panels but I don’t take shortcuts if I think will add points of failure, I’m in finance and name of the game is minimize risk -DONT LOSE MONEY.
I like to simplify things if possible to do this.
I’ve overly analyzed my interlocking comments, wire breakers, busbar for minimum resistance and at first heavily monitored system but over time have become fairly confident in them.
Like I’ve said temp controlled building.
But what I think is largest contributor to my success is capacity usage and operating range, including how hard I will tap it(discharge amps)
I compare capacity to bank account, more I have more I can withdraw with out but never wanna take them down to low which puts me at risk.I don’t ever swear I label I’m sold that’s likely overly optimistic.

Do some balancing don’t do some balancing and only use flattest part of curve, stay away from any run off points, emptying your account only exposes you.
I’ve never understood using every last amp hour mentality or dollar.
I also have lots of sun here, so batteries seldom need to be my only source of power so can afford to not tap it for everything it has. Run in very tight range.
Like I said BMS use it, it will ultimately be very reliable standard piece of puzzle without question, especially with all the free consumer driven advertising.
Especially use it if your mindset is to withdraw every last amp hour and push high SOC or low DOD, the well established trouble area’s. Most do.
I do little Rc flying at times and made a switch to electric use lithium polymer as main source, while I will charge my cells to 4.06v cell and land at 3.8v(reading 50%) and have trouble free lasting cells nearly all the rest just had to max charge to 4.2v for what gain I have no idea and land with 20% or under reading. Sometimes not even able to land, cells at 140F(mine are cool to touch, air temp)they also love to push labeled discharge rate(another thing I don’t do)complain if there $100 charger says it only charged to 99% lol
I tend to always take a more hands on approach with what ever I’m doing and have head I DONT HAVE TIME more times than I can count, even tho we all have 24hrs to allocate our time. But that’s another story that will surly stir things up.
Since average mindset is typical to buy 200ah batteries or what ever and use 200ah then I’d highly recommend using a BMS or your going to have trouble.
I’m not reiterating what I’ve heard others say or what I’ve been sold just my first hand experience while using these cells, that from my opinion and experience are very reliable, whats contributing to this idk know can only estimate that my process plays a heavy role or I’ve just got some of the best cells ever made idk.
It’s not about saving a dollar, product price point is well established game, cost can lead to better product but saying you get what you pay is true but also played so doesn’t always correlate with quality but diluted quality that can lead to same problems as lower cost product. But also vise versus when smaller company aims to take market share by offering lower cost points with less margins to gain it.

I’d also like to say this site is my favorite source to gather ideas, and most have there own of what’s best for their cells.
I’ve seen posts I strongly disagree with while others I a-line with.
Props to anyone assembling there own systems and going along with such a steep learning curve, that most won’t attempt and will seek a professional.
DIY banks will be thing of the past at some point along with the basic understanding.
This is sad to me has it only fuels consumer dependence and division of labor goals.
Pre-assembled banks have become very price competitive now making it more suited for masses to gain entry.
I try to end on a positive but will still probably get backlash for not aligning with popular opinion.
So have it and tell me I’m going to burn down my house or ruin things, which I don’t count out as possibility with or without labeled BMS.
Anything of value brings risk. My system basically runs small business without many issues to speak of so disagree you may, but it’s obvious here I’m doing something right.

 

[BradCagle]

What about using the right charger at a set voltage e.g lithium ion or LifePO4 at d right settings with a bms - 12.4v and 13.7v respectively?

One of the most important safety aspects of a BMS is to monitor the cells while charging, to make sure one cell does not overcharge.

Now it's easy to fall into a false sense of security by only charging to 13.7. You can do it, and check each cell, none get out of whack, you feel you've got it figured out. We'll it's all fine until the pack gets out of balance, or one cell goes bad (which I've had). Of course this will happen sometime later when you least expect it.

Now that being said, I do use some packs without BMS on my ebikes. But I use a balance charger that has sense wires to each cell.

 

[A.Justice]

No idea we’re to start or how answer but the Corvette analogy, no I personally wouldn’t but some may do to there end goals and knowledge of different technology.
That’s comparing a technology that’s from my view has been mastered for consumer use while THE BMS is in early stages, one look at the endless posts of issues(here) with them is major point of failure in any system.
Which could lead to all the comments above as well then.
The use of the word lithium, lithium polymer is far more volatile chemistry vs iron phosphate, dense at higher voltage so saying lithium is dangerous doesn’t tell the whole story but leans towards message of saying just as dangerous as it’s big bother ion polymer. It’s much more stable.
I’m no electrician just have few years hands on experience and proven ways of working without labeled BMS.
My head still gets turned around wiring panels but I don’t take shortcuts if I think will add points of failure, I’m in finance and name of the game is minimize risk -DONT LOSE MONEY.
I like to simplify things if possible to do this.
I’ve overly analyzed my interlocking comments, wire breakers, busbar for minimum resistance and at first heavily monitored system but over time have become fairly confident in them.
Like I’ve said temp controlled building.
But what I think is largest contributor to my success is capacity usage and operating range, including how hard I will tap it(discharge amps)
I compare capacity to bank account, more I have more I can withdraw with out but never wanna take them down to low which puts me at risk.I don’t ever swear I label I’m sold that’s likely overly optimistic.

Do some balancing don’t do some balancing and only use flattest part of curve, stay away from any run off points, emptying your account only exposes you.
I’ve never understood using every last amp hour mentality or dollar.
I also have lots of sun here, so batteries seldom need to be my only source of power so can afford to not tap it for everything it has. Run in very tight range.
Like I said BMS use it, it will ultimately be very reliable standard piece of puzzle without question, especially with all the free consumer driven advertising.
Especially use it if your mindset is to withdraw every last amp hour and push high SOC or low DOD, the well established trouble area’s. Most do.
I do little Rc flying at times and made a switch to electric use lithium polymer as main source, while I will charge my cells to 4.06v cell and land at 3.8v(reading 50%) and have trouble free lasting cells nearly all the rest just had to max charge to 4.2v for what gain I have no idea and land with 20% or under reading. Sometimes not even able to land, cells at 140F(mine are cool to touch, air temp)they also love to push labeled discharge rate(another thing I don’t do)complain if there $100 charger says it only charged to 99% lol
I tend to always take a more hands on approach with what ever I’m doing and have head I DONT HAVE TIME more times than I can count, even tho we all have 24hrs to allocate our time. But that’s another story that will surly stir things up.
Since average mindset is typical to buy 200ah batteries or what ever and use 200ah then I’d highly recommend using a BMS or your going to have trouble.
I’m not reiterating what I’ve heard others say or what I’ve been sold just my first hand experience while using these cells, that from my opinion and experience are very reliable, whats contributing to this idk know can only estimate that my process plays a heavy role or I’ve just got some of the best cells ever made idk.
It’s not about saving a dollar, product price point is well established game, cost can lead to better product but saying you get what you pay is true but also played so doesn’t always correlate with quality but diluted quality that can lead to same problems as lower cost product. But also vise versus when smaller company aims to take market share by offering lower cost points with less margins to gain it.

You can do whatever you want, good luck.