DIY pack 18650 lithium safe

Batteries, Chargers, and Battery Management Systems.
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EMX_USD   10 mW

10 mW
Posts: 28
Joined: Jan 09 2020 1:41pm
Location: Belgium

DIY pack 18650 lithium safe

Post by EMX_USD » Apr 13 2020 5:45am

What gives me problem to domyself a pack in 18650 with cells 30A and 3000mah:
If I put two rows of (+) and two rows of (-) in my 16S 5P configuration, does that change anything? instead of having a 16S bms, would you need an 8S bms? Thank you for your information.

I do not know what burns a brushless motor: much more amps than what the manufacturer recommends or much more volts? On the description of a brushless motor it says above all not to exceed the maximum number of volts recommended but for amps is it the same?

obcd   100 W

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Re: DIY pack 18650 lithium safe

Post by obcd » Apr 13 2020 8:15am

The way batteries are normally assembled is that they create several groups of parallel cells (in your case 5) and put those groups in serie. (So that would mean 16 groups) If you don't want to burn your house (bad moment as corona regulations tell you to stay inside), you would choose a quality BMS with bluetooth interface so you can verify the cell voltage of every cell group. Those usually have an option to adjust the number of cell groups that are connected to them. (up to some maximum so less shouldn't be a problem.)

The thing that burns a motor is heat. Motor windings have a resistance, and if current passes trough them, they will produce heat.
The winding losses P = I^2 * R will end up in heat.

Voltage is important for maximum speed. If a motor runs, it works as a generator and will produce voltage. Due to that, you need a higher voltage to make current flow trough the motor windings. If you increase the voltage, you can push more current trough the windings and you have a higher chanche of overheating your motor as well.

EMX_USD   10 mW

10 mW
Posts: 28
Joined: Jan 09 2020 1:41pm
Location: Belgium

Re: DIY pack 18650 lithium safe

Post by EMX_USD » Apr 13 2020 11:09am

obcd wrote:
Apr 13 2020 8:15am
The way batteries are normally assembled is that they create several groups of parallel cells (in your case 5) and put those groups in serie. (So that would mean 16 groups) If you don't want to burn your house (bad moment as corona regulations tell you to stay inside), you would choose a quality BMS with bluetooth interface so you can verify the cell voltage of every cell group. Those usually have an option to adjust the number of cell groups that are connected to them. (up to some maximum so less shouldn't be a problem.)

The thing that burns a motor is heat. Motor windings have a resistance, and if current passes trough them, they will produce heat.
The winding losses P = I^2 * R will end up in heat.

Voltage is important for maximum speed. If a motor runs, it works as a generator and will produce voltage. Due to that, you need a higher voltage to make current flow trough the motor windings. If you increase the voltage, you can push more current trough the windings and you have a higher chanche of overheating your motor as well.
ok thanks for your answer.

EMX_USD   10 mW

10 mW
Posts: 28
Joined: Jan 09 2020 1:41pm
Location: Belgium

Re: DIY pack 18650 lithium safe

Post by EMX_USD » May 06 2020 7:12am

:( Hello guys, i have problem with the pen of that spot welder bought on aliexpress. How to assembly that?Image[/img]
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IMG_20200418_083156.jpg
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goatman   100 MW

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Location: Surrey, B.C.

Re: DIY pack 18650 lithium safe

Post by goatman » May 06 2020 7:24am

EMX_USD wrote:
Apr 13 2020 5:45am
What gives me problem to domyself a pack in 18650 with cells 30A and 3000mah:
If I put two rows of (+) and two rows of (-) in my 16S 5P configuration, does that change anything? instead of having a 16S bms, would you need an 8S bms? Thank you for your information.

I do not know what burns a brushless motor: much more amps than what the manufacturer recommends or much more volts? On the description of a brushless motor it says above all not to exceed the maximum number of volts recommended but for amps is it the same?
16s is 56v and 8s is 28v. what are you trying to build?

EMX_USD   10 mW

10 mW
Posts: 28
Joined: Jan 09 2020 1:41pm
Location: Belgium

Re: DIY pack 18650 lithium safe

Post by EMX_USD » May 06 2020 7:50am

Finally, i trying to build 16s. But two 8s in series is 56V too. No problem with that i have the solution but I will post this when it works safely. Trust me.

EMX_USD   10 mW

10 mW
Posts: 28
Joined: Jan 09 2020 1:41pm
Location: Belgium

Re: DIY pack 18650 lithium safe

Post by EMX_USD » May 06 2020 7:57am

The spot welder is assembled and battery re
IMG_20200418_083156.jpg
IMG_20200418_083156.jpg (228.67 KiB) Viewed 313 times
charged but it's the pen who don't work!

goatman   100 MW

100 MW
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Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: DIY pack 18650 lithium safe

Post by goatman » May 06 2020 8:10am

I know nothing about spot welders but have you checked the trigger to make sure its working

EMX_USD   10 mW

10 mW
Posts: 28
Joined: Jan 09 2020 1:41pm
Location: Belgium

Re: DIY pack 18650 lithium safe

Post by EMX_USD » May 06 2020 9:15am

goatman wrote:
May 06 2020 8:10am
I know nothing about spot welders but have you checked the trigger to make sure its working
Yes, it work

EMX_USD   10 mW

10 mW
Posts: 28
Joined: Jan 09 2020 1:41pm
Location: Belgium

Re: DIY pack 18650 lithium safe

Post by EMX_USD » May 06 2020 12:08pm

ok it work! :) one mosfet not welded and one nut out of 6 not tight enough .

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