What will happens if without BMS?

Hello every budy!
I'm a new player,I have a lot of question.
When I was going to build the 18650Battery group,I have a question----How can I charger them?
Then I got a lot of solutions.
But....
All of them use BMS
Then.....
I want asking why??
I found a lot of answers
But
All the answers ....They are not the right one.I means I still did't understand the principle.
Let me show you why?
1,there're some batteries,18650,some 3.2V,some 3.3V ,some 3.6V and so on,may be 15 batteries
2,there is a charger,actually, it's not a charger,it's a computer power transformer.It's can output 12V,3.3V,5V

Okay,Let's starting the show!
every 5 batteries in parallel as a group.So,I got 3 groups,One of them may be 3.3V,and ohter may be 3.1 V.
Stop!!the strange things happened!
did you remeber the 15 batteries? every group has 5 different batteries,some of them may be 3.0V or 3.1V,But now they are connected in parallel.The current flows like water between them,High flow to low,They are balanced?
Then I use TP4056 charger them,very slow,but it's work.
Okay,Let's go on
after that?I put 3 batteries groups in series.
so,It's become a 3S5P battery,But the voltage only 9.7V
right now,I was thinking! 5 different batteries in parallel can get balance,That's means the current like water,high to low.
what will happen if I give 3S5P battery 12V power? Can I see magic smoke? Or I'll get a C4? Or .....?
I was thinking,3 batteries in series,what is looks like?Can I think of it as a 12V battery? Of course not, the exterior looks like they are 3 batteries.But,If we use differrent angle,3 batteries in series with the power cord up.When charging, each battery is inside a chemical reaction.that means 12 volts will be evenly distributed to each battery.
But,it's juest a idear.I never do that....
anyway,I decided to give it a try
Then I connected in series with a ammeter
At the beginning,the charger current was 12 A
But it quickly become lower,10A...8A...6A....
4-8 A It lasted a long time
when the 3S5P battery voltage reaches 12V,the current less than 1A
when voltage reaches 12.36V,the current only 0.36A
then I stop
after 24 hours,the 3S5P battery still has 12.34 voltage.

So??????I'm thinking
Can I charge 14S battery pack directly with 58V power supply?
I mean...without BMS!
I want to make a 40-kilowatt battery pack to power a 4-kilowatt motor.

First of all your thread or question was way longer than needed.

Simple answer Yes you can charge your battery with any charger that can limit voltage and current to max what the battery takes.
Is it recommended to do it that way? NO.

You need something that keeps track of the balance between the packs. If you got a 14s string you got 14 individual packs. The total can be 58V yes but the packs internally can be all from 0 to 58 in real life. (Not really true.. )

Lets say you have 2s. ie 2 cells in series. Max volt per cell in generall is 4.2V. so max total should be 8.4.

But what if 1 cell have 3V when starting and the other 4V. If you start to charge to the total of 8.4... You will in theory end up with 4.7V and 3.7V.... Because energy is distributed evenly in most cases one of the cells is overcharged and you will destroy it and in worst case it will result in fire!!

This is where the BMS come in play. It will balance the packs if they get to high. They can also make sure that no cell actually can go above 4.2V that is max for most Liions. They also protect against under voltage and over current.


So either you charge it manually to 58V but then you manually also need to crosscheck ALL cells DURING charge.
Or you install a BMS that sorts it for it.

Note that a BMS as such is not a charger nor controller to a charger. It is a PROTECTION in case of failure. The charger chould in best cases take care of the charging alongside with the BMS. With that said there are some BMS systems out there that do controll the charger too. But they cost.


I would NEVER charger a lithium pack without BMS or balance charge that RC chargers do.

Well, the fast answer is yes, you can charge it without BMS.
Keep a full 14S system made of 18650 cells working without BMS? I won't do that. Even with goods cells, every pack of the 14 have different internal resistance, and I'm sure different capacity, even using a pack builder to ensure all have the same. That causes your packs go unbalanced at high loads charging or discharging. That will make that close to max voltage ot minimum voltage some pack will reach that level first. What if this pack continues to overcharge or overdischarge far than a recomended value?

Here is where a BMS interferes, cut the charge or discharge, or balances with some active or passive method, making high voltages packs waste some energy and wait until the rest of packs reach the high voltage. You have what you pay, a BMS as Batrium can control the inverter or toggle a relay and a lot of other possibilities to make your system safe to critical fails.

Only if you have identical cells in your serie, packs will keep at same voltage with the battery fully charged or discharged. And I can assure you this won't happens with recycled 18650.

With goods packs without self discharge you can ommit the BMS for some time, but finally some packs wlll unbalance maybe in a year? Then maybe a pack of the 14 will suffer undervoltage with empty battery and the rest overvoltage with full battery Will you left a system unmonitored that maybe provoke a fire?

Is up to you.

Edit: almost same answer as Daniel, when I started responding Daniel was ending

Another way to look it is, the BMS is like a Gate Keeper. It controls what comes in, and what goes out. That way the roads don't get overwhelmed and over taxed (overvoltage/current) in either direction.
Now, if your charger can only handle a max voltage/current of what is less than the max/current the pack can handle, then you might be ok. The problem comes in when voltage isn't arranged in a balanced manner.
Think of charging a 2 cell string as a teeter-totter (aka see-saw) (the plank of wood balanced across bar/log). Charging will always put even amounts of charge across the string. So, in the teeter-totter example, lets say there is 15 lb/kilo sack on one end, and 12 lb/kilo on the other end, which gives an average of 13.5. The teeter-totter can safely hold 20 lb/kilos. So, as you add weight, it's added evenly. So when 6.5 lb/kilos get added, the average will be 20. However, one side is now 18, the other side 22. It won't be balanced.
A BMS would take weight off the heavier side and toss it (a passive balancer) or take weight from one side and add it to the other (active balancer)