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Author Topic: Charge 18650 lithium batteries  (Read 1281 times)
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babisko
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« on: July 22, 2019, 03:15:41 03:15 »

I have a device (FM radio, Mp3 player, mini amplifier) that I want to make it portable and power it with 4 18650 lithium batteries. I have a BMS 4S in which I have connected the 4 batteries as usual.
I connected to the BMS the laboratory power supply (0-30VDC, 0-10A) set to 24VDC by inserting a LM2596 module whose output is set to exactly 16.80V. If I increase the current from the power supply, the charging current increases above 2A, resulting in the LM2596 module being destroyed (it can only supply up to 2A).

Can I connect a 24VDC power supply but with a lower current supply (eg 1A or 1.5A) to the BMS by inserting a LM2596 module to have the charging voltage exactly 16,80 VDC to charge the batteries while supplying the device with the required current operation without risk of damage to the batteries or the power supply? It is safely understood without the risk of damaging the batteries or the power supply.

Another suggestion of implementing the construction, with some links if possible, to charge the batteries without being removed from the device?

I searched the internet for information but I'm confused ...  Cry

Thanks in advance for any answers or suggestions

PS Sorry about my bad english

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Sideshow Bob
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« Reply #1 on: July 22, 2019, 04:28:07 04:28 »

Let me suggest some reading
https://batteryuniversity.com/search/search&keywords=Lithium+Ion/
https://www.edn.com/design/power-management/4458421/What-is-a-BMS-anyway-
https://www.google.com/search?q=Lithium+Ion+charge+ic
https://www.google.com/search?q=is+a+bms+a+charger (clearly not Wink )
What also is somewhat uncertain is how you connect the batteries for providing the voltage to your unit.  I.e what is your voltage requirements for your media player. As you may now understand a BMS is not a charger. And also a BMS must be fitted to your battery pack specs. For charging while using the media player. I may have solution but I think more information on your setup is needed
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pickit2
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« Reply #2 on: July 22, 2019, 05:13:30 05:13 »

by using LM2596 you are setting Voltage only. you need to limit the charge current too.
you could use a as an example LM317 set up as a current limit. set by Battery data for charging.
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Checksum8
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« Reply #3 on: July 22, 2019, 12:20:50 12:20 »

This will give you a constant current. Look around there are different modules and prices

https://www.ebay.com/itm/Constant-Current-Voltage-LED-Driver-Batery-Charging-Module-LM2596-1-25-30V-Input/171907258940?hash=item2806789a3c:g:sjkAAOSwpdpVVfxy
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« Reply #4 on: July 23, 2019, 12:55:24 00:55 »

Hi Babisko,

Do you have independant feedback from each cell?

You need a SBM to a cell balancing each cell. Personally i use Imax B6 for charging each battery the first time before making my pack.

++
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Old_but_Alive
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« Reply #5 on: July 23, 2019, 01:06:27 01:06 »

search ebay for

4S 14.8V 30A 18650 Lithium Battery Cell BMS PCB Charge Protection Board Balance

check this out

https://www.youtube.com/watch?v=rYFT4g292jU

you need

https://www.ebay.com/itm/Constant-Current-Voltage-LED-Driver-Batery-Charging-Module-LM2596-1-25-30V-Input/171907258940?hash=item2806789a3c:g:sjkAAOSwpdpVVfxy
set this to the required constant current, set the output voltage to say 18V. The BMS booard shut cut off at 16.8V
so the input voltage can be 24V

« Last Edit: July 23, 2019, 11:50:46 23:50 by Old_but_Alive » Logged

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Sideshow Bob
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« Reply #6 on: July 23, 2019, 02:52:10 02:52 »

Can you use a another  Battery Chemistry instead of Lithium Ion. These cells behave as grumpy primadonnas regarding charging and discharging. And if not threated correct they just go off (literally) or just refuse to work any more. There are more forgiving batteries. You could as an example use a small sealed lead acid battery. The charge circuit can be as simple as a transformer and a rectifier. And charging while using them is not a problem. Lithium Ion battery packs are much much more complex than some batteries connected together.
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sadman
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« Reply #7 on: July 23, 2019, 11:50:27 11:50 »

Can you use a another  Battery Chemistry instead of Lithium Ion. These cells behave as grumpy primadonnas regarding charging and discharging. And if not threated correct they just go off (literally) or just refuse to work any more. There are more forgiving batteries. You could as an example use a small sealed lead acid battery. The charge circuit can be as simple as a transformer and a rectifier. And charging while using them is not a problem. Lithium Ion battery packs are much much more complex than some batteries connected together.

In some cases you are right But compare to sealed lead acid battery they More power full such as size and out put current a 4000maH is small in size and required less space.
Further a well design CV/CC charger can handle them easily I have made such charger based on lm2596 lot of clone  are on ebay but all have fake lm2596 I will my design when back from  tour

Sadman
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babisko
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« Reply #8 on: July 25, 2019, 01:41:45 01:41 »

Can you use a another  Battery Chemistry instead of Lithium Ion. These cells behave as grumpy primadonnas regarding charging and discharging. And if not threated correct they just go off (literally) or just refuse to work any more. There are more forgiving batteries. You could as an example use a small sealed lead acid battery. The charge circuit can be as simple as a transformer and a rectifier. And charging while using them is not a problem. Lithium Ion battery packs are much much more complex than some batteries connected together.

I do not want to use a lead battery due to weight and volume

Posted on: 25-07-2019, 02:31:43 - Automerged

In some cases you are right But compare to sealed lead acid battery they More power full such as size and out put current a 4000maH is small in size and required less space.
Further a well design CV/CC charger can handle them easily I have made such charger based on lm2596 lot of clone  are on ebay but all have fake lm2596 I will my design when back from  tour

Sadman


Thank you, I would appreciate and wait for your circuit if you would like to share it with us

Posted on: 25-07-2019, 02:35:17 - Automerged

Hi Babisko,

Do you have independant feedback from each cell?

You need a SBM to a cell balancing each cell. Personally i use Imax B6 for charging each battery the first time before making my pack.

++

Yes, I use a BMS 4S for battery pack

Posted on: 25-07-2019, 02:37:42 - Automerged

At the moment I am thinking of using the LM317 as a current limiter until I receive the following module I have already ordered

https://www.ebay.com/itm/5A-Lithium-Charger-CV-CC-buck-Step-down-Power-Supply-Module-LED-Driver-New-Z2/171907199469?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Thank you all for your answers and suggestions, I will brief you soon
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sadman
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« Reply #9 on: July 25, 2019, 08:16:17 08:16 »

here are the circuit as i promise i have made LM2576 CV/CV power supply cum lion charger one modification required use a 1k 1 watt resister with 7.5 volt zener to supply the voltage to 7805 voltage regulator this will prevent the voltage regulator from thermal shutdown.

i also share a Chinese version of XL4016 CV/CC module which is better then LM2596 reverse engineer by a Russian forum this circuit is better then mine and required same modification for 7805 voltage regulator for stable and trouble free operation of the module, not least but last i have share a link to a very simple and nice design for CV/CC lion charger based of Arduino.

https://circuitdigest.com/microcontroller-projects/two-step-lithium-battery-charger-circuit-with-cc-cv-mode

sadman
« Last Edit: July 25, 2019, 11:55:32 23:55 by sadman » Logged
zac
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« Reply #10 on: July 31, 2019, 05:07:38 17:07 »

For general purpose use, I recommend LiFePo4 which is much less sensitive to overcharge and much safer as it is nearly impossible to create combustible lithium metal by overcharging.  The cycle life is also at least 4x that of conventional lithium ion.  The downside is the energy density (by weight) is only 60-75% that of lithium ion.  

https://batteryuniversity.com/learn/article/types_of_lithium_ion
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