# 4s lithium ion 16850 batterypack bms, charger, discharge.

#### Storro

Aug 11, 2023
8
I have tried to make a picture with the planned wiring of my battery and charging. It is based on 2.5-4.2V. I put them together in 4S, 10v-16.8V. I plan on charging them with a 120w charger, see link, it is rated at 20v, 6a, maximum. I see each cell has a discharge maximum of 30A continious. This might be a noob question, but is this the highest safe output for my batteries when they are connected in 4S 16.8v configuration too? I would not be able to power an electric motor with these batteries if the motor and the motorcontroller, vesc, is set to discharge 40 amps continiously? I see the 4S bms has a limit of 40 amps. What about a motor pulling 70 amps at 12-16V. If I was to use the batteries for Ebikes I would probably make the batteries higher voltage, but would this increase the amps too? does it increase the total wattage the battaries can handle watt = ampere x volt. If the 1s 3.7v battery can handle 30a x 3.7v = about 120w, would I be able to do more than 120w if I go up to higher voltage with 4s, could I expect more than 120w, lets say 40a x 16v=640w, or would it allways be maximum 30amps? If I put the batteries in parallell, does this increase the amps i can discharge/charge? If I have two batteries of 3.7V in parallel, does this make 3.7v x 60a = about 240w discharge?

#### Attachments

• battery example.pdf
1.6 MB · Views: 5

#### Bluejets

Oct 5, 2014
6,977
Think you'll find those cells are 18650 but to expect such high continuous currents is flying in the clouds with the fairys.

#### kellys_eye

Jun 25, 2010
6,514
Note to OP - using paragraphs make it a LOT easier to read.

Batteries connected in series have a current limitation equal to that of a SINGLE cell.

Batteries connected in parallel have a current limitation equal to that of the SUM of the individual cells.

The equipment under power determines the current that is drawn, not the batteries themselves (except where the limitations of the batteries come into effect)..

Batteries cannot deliver more current than they are rated for.

Lithiums require (for safe use) a charge BALANCING system and a properly regulated (controlled) charger.

#### Storro

Aug 11, 2023
8
Note to OP - using paragraphs make it a LOT easier to read.

Batteries connected in series have a current limitation equal to that of a SINGLE cell.

Batteries connected in parallel have a current limitation equal to that of the SUM of the individual cells.

The equipment under power determines the current that is drawn, not the batteries themselves (except where the limitations of the batteries come into effect)..

Batteries cannot deliver more current than they are rated for.

Lithiums require (for safe use) a charge BALANCING system and a properly regulated (controlled) charger.
Do you actually need a bms attached to the battery at all time, isnt it sufficient to have a bms between the battery and the charger while the battery is connected to the charger. If you have an electric motor controlled by a motorcontroller and it is configured to not pull more amps from the battery than what it is rated for and you also have a suitable fuse between the battery and the controller/motor.

So a 4pack 4s battery, each cell is 4v and max 30amp discharge/charge, 20 amps is recommended for continiuous discharge. I get 16v 60amps. If I want 300 amps continious I would need a controller taking 60v and put the batteries in a 15s configuration to get 60v and 300amps batterypack?

Is it possible to connect a 4s 16v batterypack and a 2s or 3s batterypack in series or parallell, or maybe one of each or would they all have to be 4s when connecting them together in parallell?

#### Bluejets

Oct 5, 2014
6,977
Do you actually need a bms attached to the battery at all time, isnt it sufficient to have a bms between the battery and the charger
Yes
No
Discharge cut off is just as important as charging.

Best you do some reading at battery university web site.
For one thing it will negate having to repeat/explain every detail here.

While you are at it, look up some basic English on structuring paragraphs and sentences for better/easier reading/understanding.

#### Storro

Aug 11, 2023
8
While you are at it, look up some basic English on structuring paragraphs and sentences for better/easier reading/understanding.
pls show me what was incorrect english paragraph structuring in this text "
Do you actually need a bms attached to the battery at all time, isnt it sufficient to have a bms between the battery and the charger while the battery is connected to the charger. If you have an electric motor controlled by a motorcontroller and it is configured to not pull more amps from the battery than what it is rated for and you also have a suitable fuse between the battery and the controller/motor.

So a 4pack 4s battery, each cell is 4v and max 30amp discharge/charge, 20 amps is recommended for continiuous discharge. I get 16v 60amps. If I want 300 amps continious I would need a controller taking 60v and put the batteries in a 15s configuration to get 60v and 300amps batterypack?

Is it possible to connect a 4s 16v batterypack and a 2s or 3s batterypack in series or parallell, or maybe one of each or would they all have to be 4s when connecting them together in parallell?"

Also, you dont rly need a bms attached to the battery to protect from overdischarge.

#### Storro

Aug 11, 2023
8
dddddddddddddddddd
Yes
No
Discharge cut off is just as important as charging.

Best you do some reading at battery university web site.
For one thing it will negate having to repeat/explain every detail here.

While you are at it, look up some basic English on structuring paragraphs and sentences for better/easier reading/understanding.
you shouldnt look up english at all, language is flowing and you should allow it to evolve on its own. we have way to many silly grammar rules.

#### Storro

Aug 11, 2023
8
Yes
No
Discharge cut off is just as important as charging.

Best you do some reading at battery university web site.
For one thing it will negate having to repeat/explain every detail here.

While you are at it, look up some basic English on structuring paragraphs and sentences for better/easier reading/understanding.
pls answere. "Is it possible to connect a 4s 16v batterypack and a 2s or 3s batterypack in series or parallell, or maybe one of each or would they all have to be 4s when connecting them together in parallell?" I bet you have no idea.

#### Delta Prime

Jul 29, 2020
2,033
I bet you have no idea
I'll take that bet!
Welcome to Make Pro.
The ongoing battery technology has prompted many newcomers (Like yourself) to learn about designing a battery management systems.
Obviously you know nothing about it. You're asking the questions, therefore, a beginner’s guide to the battery management system (BMS) architecture.
A battery management system can be comprised of many functional blocks including: cutoff FETs, a fuel
gauge monitor, cell voltage monitor, cell voltage balance, real time clock (RTC), temperature monitors and a
state machine.
There are many types of battery management ICs available.
The grouping of the functional
blocks varies widely from a simple analog front end that offers balancing and monitoring and requires a microcontroller
(MCU), to a standalone, highly integrated solution that runs autonomously.
FET driver functional block is responsible for the connection and isolation of the battery pack between the load and charger.
The behavior of the FET driver is predicated on measurements from battery cell voltages, current measurements and real-time detection circuitry.
Battery packs with one to four batteries in parallel and three or more in series benefit the most from balancing.
As the parallel combinations increase per cell, the weak cell’s performance is averaged with other cells in parallel.
The performance distribution between cells is tighter.
The benefit of having more cells in parallel is also a detriment because it is harder to find the weaker cell in a battery pack.
A battery pack sitting idle could be burning charge due to the strong cells propping up the weaker cell.

#### Bluejets

Oct 5, 2014
6,977
pls answere. "Is it possible to connect a 4s 16v batterypack and a 2s or 3s batterypack in series or parallell, or maybe one of each or would they all have to be 4s when connecting them together in parallell?" I bet you have no idea.
Well, so sad to disappoint you but yes, I do have the knowledge.
No
Yes
Yes, plus ideally the same Ah .
There you go then, chew on that.

#### Storro

Aug 11, 2023
8
Well, so sad to disappoint you but yes, I do have the knowledge.
No
Yes
Yes, plus ideally the same Ah .
There you go then, chew on that.
I blame the school system. We didnt learn shit.

#### Storro

Aug 11, 2023
8
I make batteries like this with 4s 16v. I can put them in parallell to create a larger 16v battery. But if I take the same batteries but connect them in series, for example three times 4s 16v, I can get 48v? would that be a 12s 48v battery? So I can use the same batterymodules in a 12-16v project and a 48v project?

#### Attachments

• 1693657315714.png
13.3 KB · Views: 1

#### Delta Prime

Jul 29, 2020
2,033
If these are lithium ion cells then it's 4.2 volts for a fully charged cell 4.2 * 4 = 16.8 volt that .8V matters.
I see 4 parallel, 4 Series connected Network(4s4p). This is very dangerous project!
For 48 volts you going to need (13s 4p) 4.2*13=54.6V and that's fully charged batteries nominal voltage is 3.7V.
Therefore 3.7v*13=48.1Volts so a battery pack which is what you are making if it is stated as 48 volts it is the same as an 54 volt battery pack. You will need a battery management system (BMS) your system as is will blow up,
catch fire, burn a hole in the ground all the way to China!

#### Delta Prime

Jul 29, 2020
2,033
If your project requires a 48 volt controller than that controller is going to expect to see 54.6 volts that's fully charged 13s 16850 in series for safety reasons cuz 48 volt controller will not discharge past approximately 48 volts. 48 volts is the nominal voltage of 13
16850's. Or put a different way.
If they reach 48 volts you have to recharge them.

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