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Author Topic: i have a problem charging the battery  (Read 1725 times)
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naeim golshekan
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« on: August 18, 2021, 11:39:05 11:39 »

I want to charge 12 volt battery by 12 volt charger but when i restrict the current by a resistor, the battery charging  voltage drops.
Can anyone help me?
The picture of circuit is as below
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vern
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« Reply #1 on: August 18, 2021, 12:29:06 12:29 »

it is quite simple.
First of all there is a voltage drop on the diode, about 0.6V
Next you have the voltage drop across the resistor.
Example: Power source 12V, resistor 1 Ohm
Depending on the state of your battery there is a charging current flowing through the diode and the resitor.
If we assume that the current is 1A, there will be the voltage drop across the diode 0.6V, across the resistor 1V, that means you only have 10.4V at your battery.
Since I assume you are just starting with electronics: make yourself familiar with Ohms law, you need it!
You should also be very careful with charging batteries, they can catch fire or explode when not charged properly.
If you have a power battery you can not charge it with the circuit above!
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Sideshow Bob
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« Reply #2 on: August 18, 2021, 12:45:18 12:45 »

MS/LM/TS batteries are all of lithium type most often. Given they are of  lithium type. Your approach is VERY dangerous and irresponsible. Lithium batteries must be charged in a very specific way in order to safe. If not they are just an accident waiting to happen. They will catch fire most probably. A beginner like you, should not play around with homemade lithium charging at all.
« Last Edit: August 18, 2021, 12:50:39 12:50 by Sideshow Bob » Logged

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Old_but_Alive
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« Reply #3 on: August 18, 2021, 01:21:01 13:21 »

has he never heard of Ohms law ?
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Sideshow Bob
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« Reply #4 on: August 18, 2021, 01:35:29 13:35 »

has he never heard of Ohms law ?
At least points for clean drawing Smiley
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naeim golshekan
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« Reply #5 on: August 18, 2021, 03:21:48 15:21 »

it is quite simple.
First of all there is a voltage drop on the diode, about 0.6V
Next you have the voltage drop across the resistor.
Example: Power source 12V, resistor 1 Ohm
Depending on the state of your battery there is a charging current flowing through the diode and the resitor.
If we assume that the current is 1A, there will be the voltage drop across the diode 0.6V, across the resistor 1V, that means you only have 10.4V at your battery.
Since I assume you are just starting with electronics: make yourself familiar with Ohms law, you need it!
You should also be very careful with charging batteries, they can catch fire or explode when not charged properly.
If you have a power battery you can not charge it with the circuit above!

thanks
when the battery is fully charged the diod is turned off so the charging operation is stoped and the battery remains safe. isnt true?
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« Reply #6 on: August 18, 2021, 03:29:26 15:29 »

Check for >> Circuit Board Module PCB BMS Charger Li Ion Lipo Lithium Battery And Protections
I bought 100 mixed very cheap, and well worth the money.


Posted on: August 18, 2021, 04:28:09 16:28 - Automerged

thanks
when the battery is fully charged the diod is turned off so the charging operation is stoped and the battery remains safe. isnt true?

No not safe - your fire insurance cliam will be rejected.


https://www.youtube.com/watch?v=ySXtBuawf70
« Last Edit: August 18, 2021, 03:32:06 15:32 by pickit2 » Logged

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vern
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« Reply #7 on: August 18, 2021, 03:37:14 15:37 »

The voltage of the battery will rise, the charge current will fall and stop at some point when the battery is charged to almost 12V.
But as me and others here have already pointed out:
it is very dangerous to charge a battery this way! You should use a professional charger!
These chargers have a constant current source that has a voltage limit build in where it shuts off charging when the battery is full.
It's safer!
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« Reply #8 on: August 18, 2021, 03:45:13 15:45 »

Always reminds me when the painters were in the Telephone Exchange, and one put his metal paint pot on the power buss rails.
he had no pot to piss in (english joke) but there was paint every where.
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