Making a 12v Battery pack for a portable bluetooth speaker and I want to charge the batterypack via mini-usb or USB-C

[Ploooopp]

I got some NCR1 182650B batteries this BMS a battery level indicator and a female micro-USB jack (also should I wire an on/off switch to the battery pack?) 

Parts I got: are some stepdown converters from 12 to 5V a charging circuit from a standard 5v powerbank for phones 
I'm unsure how to make this so I'm just reaching out, thanks in advance
I'll post another thread with pics and stuff when it's all done

[mariushm]

In order to charge the battery pack, the input voltage must be a bit higher than the charging voltage, so your input voltage should be a bit higher than 4.2v x 3 batteries = 12.6v ... so I'd aim at around 13.5v

So you would use a step-up / boost dc-dc converter to boost 5v from a power bank or a phone charger to 13.5v to charge the battery pack, or power the charging mechanism directly with a power adapter with a barrel jack connector.

 

The charging circuit from standard ...  is useless ... those boards contain a chip which check a single battery and if the voltage is too low and there's power on a input usb connector, it will charge the battery. But that chip can only do one battery, it can't be used to charge the 3 battery pack.

 

The stepdown converter would work, but it's not ideal, you don't want a regular with so wide input range because the components on the circuit board won't be 'optimal' for your use and the converter would be fairly low efficiency. That big inductor (the copper wire winded in a circle) also tells me it's a low frequency chip, which again means it's older design, low efficiency.

You'll want something like this :

https://www.amazon.se/DollaTek-MP1584EN-steg-ned-justerbar-omvandlare/dp/B07DJYW6P3/

https://www.amazon.se/DECARETA-MP1584EN-Converter-justerbar-6-pack/dp/B07QMCW2LY/

if it bothers you, you can replace the small trim potentiometer with a regular potentiometer or a single resistor (to make it fixed output voltage)

 

example step-up converter to connect to the bms : https://www.amazon.se/Converter-Voltage-Regulator-Högkvalitativ-Industrial/dp/B094NCTK8P/

 

[Syze00]

This video might not cover exactly what you were looking for, but I think it might be worth a watch since he goes over premade boards, IC's designed for USB C PD and even some schematics.  His videos are very technical but I can still understand them (to a degree)

[Ploooopp]

1 hour ago, mariushm said:

In order to charge the battery pack, the input voltage must be a bit higher than the charging voltage, so your input voltage should be a bit higher than 4.2v x 3 batteries = 12.6v ... so I'd aim at around 13.5v

So you would use a step-up / boost dc-dc converter to boost 5v from a power bank or a phone charger to 13.5v to charge the battery pack, or power the charging mechanism directly with a power adapter with a barrel jack connector.

 

The charging circuit from standard ...  is useless ... those boards contain a chip which check a single battery and if the voltage is too low and there's power on a input usb connector, it will charge the battery. But that chip can only do one battery, it can't be used to charge the 3 battery pack.

 

The stepdown converter would work, but it's not ideal, you don't want a regular with so wide input range because the components on the circuit board won't be 'optimal' for your use and the converter would be fairly low efficiency. That big inductor (the copper wire winded in a circle) also tells me it's a low frequency chip, which again means it's older design, low efficiency.

You'll want something like this :

https://www.amazon.se/DollaTek-MP1584EN-steg-ned-justerbar-omvandlare/dp/B07DJYW6P3/

https://www.amazon.se/DECARETA-MP1584EN-Converter-justerbar-6-pack/dp/B07QMCW2LY/

if it bothers you, you can replace the small trim potentiometer with a regular potentiometer or a single resistor (to make it fixed output voltage)

 

example step-up converter to connect to the bms : https://www.amazon.se/Converter-Voltage-Regulator-Högkvalitativ-Industrial/dp/B094NCTK8P/

 

Okay that's very good to know! I'll order the more updated converter designs, I may just charge the battery pack via a barrel jack and a 12v power supply for now and try the USB method on an upcoming 18350 build 

[mariushm]

If you want to charge the batteries at 100%, you'll need a voltage higher than 12v. 

As I said .. the last few percent of a battery will be trickle charged with a voltage close to 4.2v, so the chip needs to output 3 x 4.2v = 12.6v to the chain of 3 batteries. 

In order to measure the voltage it sends to the batteries and regulate the voltage to that level, the chip contains some transistors inside and some resistors which cause a voltage drop, let's say at least 0.3v but probably closer to around 0.8v - 1v - it depends on the charger chip.

 

The BMS you linked doesn't do the charging - the chip on it is just a protection chip for the batteries - the one in the BMS link you posted is Ablic S-8254 : https://www.ablic.com/en/doc/datasheet/battery_protection/S8254A_E.pdf

 

Here's an example of a charger board, this one takes 5v from USB and the charger chip boosts it to 12.6v to charge the 3 batteries in series : https://www.ebay.com/itm/363681759359?hash=item54ad1f407f:g:TJYAAOSwn8dhw-UQ

I looks like it's basically a step-up dc-dc converter configured for 12.6v  BUT a proper charger IC will monitor the voltage of the 3 batteries and if it's too low (ex batteries discharged down to less than 3v each, then the charger chip will slowly bring them up using less current and when they're above some threshold, they switch to charging as if they're normal batteries)

 

 

[Ploooopp]

6 minutes ago, mariushm said:

If you want to charge the batteries at 100%, you'll need a voltage higher than 12v. 

As I said .. the last few percent of a battery will be trickle charged with a voltage close to 4.2v, so the chip needs to output 3 x 4.2v = 12.6v to the chain of 3 batteries. 

In order to measure the voltage it sends to the batteries and regulate the voltage to that level, the chip contains some transistors inside and some resistors which cause a voltage drop, let's say at least 0.3v but probably closer to around 0.8v - 1v - it depends on the charger chip.

 

The BMS you linked doesn't do the charging - the chip on it is just a protection chip for the batteries - the one in the BMS link you posted is Ablic S-8254 : https://www.ablic.com/en/doc/datasheet/battery_protection/S8254A_E.pdf

 

Here's an example of a charger board, this one takes 5v from USB and the charger chip boosts it to 12.6v to charge the 3 batteries in series : https://www.ebay.com/itm/363681759359?hash=item54ad1f407f:g:TJYAAOSwn8dhw-UQ

I looks like it's basically a step-up dc-dc converter configured for 12.6v  BUT a proper charger IC will monitor the voltage of the 3 batteries and if it's too low (ex batteries discharged down to less than 3v each, then the charger chip will slowly bring them up using less current and when they're above some threshold, they switch to charging as if they're normal batteries)

 

 

So this item looks like the solution to all of my problems! (?) 

 

Also if I were to try it the quick way could I use a power bank pcb thing and wire its output to a step up at 12,6V and that to the bms for charging? Or should I bypass the bms and wire that to the batteries +/- leads? 

[mariushm]

The BMS protects the batteries - it's like a fuse, disconnecting the batteries if they're discharged too much, if you give too much voltage, and some protection chips also monitor the current taken from batteries and disconnect batteries if current is too high. 

The BMS allows you to basically make the charger simpler, the charger just has to send the voltage and check from time to time what voltage the batteries report back to estimate how much the batteries are charged. For example, the charger measures 10.5v so it knows from that each battery should be around 3.5v , so the batteries are not fully discharged so it can charge the batteries by giving at least 10.5v plus something, so it gives that voltage for some time, then switches back to measuring the voltage again. When it measures let's say around 4.10v x 3 then it can switch into "trickle charge" mode and keeps the voltage constant at 4.2v per cell and let's the batteries go to 100%. 

 

There's charger ICs which contain that battery protection and can balance batteries (making sure each battery in the series has same voltage) - if you use such charger, the BMS board isn't needed.

[Ploooopp]

9 minutes ago, mariushm said:

The BMS protects the batteries - it's like a fuse, disconnecting the batteries if they're discharged too much, if you give too much voltage, and some protection chips also monitor the current taken from batteries and disconnect batteries if current is too high. 

The BMS allows you to basically make the charger simpler, the charger just has to send the voltage and check from time to time what voltage the batteries report back to estimate how much the batteries are charged. For example, the charger measures 10.5v so it knows from that each battery should be around 3.5v , so the batteries are not fully discharged so it can charge the batteries by giving at least 10.5v plus something, so it gives that voltage for some time, then switches back to measuring the voltage again. When it measures let's say around 4.10v x 3 then it can switch into "trickle charge" mode and keeps the voltage constant at 4.2v per cell and let's the batteries go to 100%. 

 

There's charger ICs which contain that battery protection and can balance batteries (making sure each battery in the series has same voltage) - if you use such charger, the BMS board isn't needed.

Yo im learning so much, thank you! 

 

Okay so if I get this charger IC I won't need the BMS but if I opt to use the BMS I'd have to use step up and the power bank charger?