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### Topic: Lithium ion charging (Read 208 times)previous topic - next topic

#### tjones9163

##### Sep 01, 2019, 05:07 pmLast Edit: Sep 01, 2019, 05:07 pm by tjones9163
Hello, i have a 2-part question about charging lithium ion batteries.

1- Do i need to balance charge a 1s 3p setup with something like a BMS or is that only when they are in series?

2- Is the different connection points of my 18v drill battery connected to a BMS inside the charging unit?

#### raschemmel

#1
##### Sep 01, 2019, 06:30 pmLast Edit: Sep 01, 2019, 08:16 pm by raschemmel
Part-2 (ONLY)

Let's look at the facts:

1. Each Lithium ion cells has a nominal voltage of 3.6V

2.  Your drill battery has 18V/3.6V =

MATLAB
>> 18/3.6

ans =

5 cells

FYI, (5>1)

3. Lithium batteries should not be charged without a BMS:
Quote
Using a lithium ion battery without BMS is not possible with safety. You can have one cell with overcharge protection. But 2 cell (7.4 V) or 3 cell (11.1 V) packs require a BMS to charge the battery fully without any problem.
4. The charged voltage of a 3.6V cell is about 4.3V

5. The drill battery connector has one GND and 4 positive terminals.

6.  4 * 4.3 = 17.2V

#### tjones9163

#2
##### Sep 01, 2019, 07:18 pm
Let's look at the facts:

1. Each Lithium ion cells has a nominal voltage of 3.6V

2.  Your drill battery has 18V/3.6V =

MATLAB
>> 18/3.6

ans =

5 cells

FYI, (5>1)

3. Lithium batteries should not be charged without a BMS:
4. The charged voltage of a 3.6V cell is about 4.3V

5. The drill battery connector has one GND and 4 positive terminals.

6.  4 * 4.3 = 17.2V

my first and second question have nothing to do with each other. It make since that the drill battery has a bms,
but i dont see anywhere on the web where they sell a 1s3p BMS?

#### raschemmel

#3
##### Sep 01, 2019, 07:53 pm
Quote
1s3p BMS?
I don't know how to tell you this but you don't need a BMS if all the cells are in PARALLEL, for the OBVIOUS reason that they are SHORTED to EACH OTHER and therefore ALL CELLS will (MUST) have the SAME voltage. If you can figure out how it is possible for 3 cells shorted to each other to NOT have the SAME voltage I would certainly be curious to hear it.

#### tjones9163

#4
##### Sep 01, 2019, 08:09 pm
I don't know how to tell you this but you don't need a BMS if all the cells are in PARALLEL, for the OBVIOUS reason that they are SHORTED to EACH OTHER and therefore ALL CELLS will (MUST) have the SAME voltage. If you can figure out how it is possible for 3 cells shorted to each other to NOT have the SAME voltage I would certainly be curious to hear it.

ya it just confused me because my first question was "do i need a bms for a 1s3p?"
and you replied " Lithium batteries should not be charged without a BMS:"
but thanks for the explanation.

#### raschemmel

#5
##### Sep 01, 2019, 08:15 pm
I only answered part 2 of your question. I actually did not notice the 1s3p part of your first question. My bad. So, by accident, I just answered part 1 in my last post, somewhat belatedly...

#### tjones9163

#6
##### Sep 01, 2019, 08:23 pm
I only answered part 2 of your question. I actually did not notice the 1s3p part of your first question. My bad. So, by accident, I just answered part 1 in my last post, somewhat belatedly...
no problem, thank you for the explanation

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