Help with Power Bank for guitar pedals with BMS 3s 25a. and 18650 lithium-ion Battery

[eduardo_gj1]

Hello, in advance I would appreciate all the help you can give me with this DIY project that I have in mind.

My problem is that when I go out to a gig I have to take various devices for my guitar and among those is my power supply for the guitar pedals.

I have several 18650 cells that were going to be discarded at work because they no longer charge, and it is only the bms or some cell that is damaged.

my doubts so far is regarding the BMS:
Lithium battery protection board 3S 11.1V 12.6V 25A PCB 18650 with scale
link:

Lithium Batterie Schutzplatine 3S 11,1 V 12,6 V 25 A PCB 18650 mit Waage: Amazon.de: Gewerbe, Industrie & Wissenschaft

Lithium Batterie Schutzplatine 3S 11,1 V 12,6 V 25 A PCB 18650 mit Waage: Amazon.de: Gewerbe, Industrie & Wissenschaft

www.amazon.de

I would connect 3s3p for about 9.6v and 15ah, I have that solved and how to select the batteries and charge and test them. now most of the pedals work with 9v and the amp hour when they are analog pedals does not exceed 0.3ah so it would have a good range of hours of use with a pedalboard of about 10 pedals. some pedals like the digital ones use more amp hours I think some have a consumption of 1ah (I'm not sure I should check)

Well now my doubt with the bms:
I am not very clear about the charging and discharging part, I mean in the same charge towards the batteries I could connect the modules: DC-DC XL4015 Adjustable Step-down Buck Converter 4~38V to 1.25-36v Voltage Regulator Module to lower the voltage to 9v (regular consumption of guitar pedals).
link:

https://www.amazon.de/gp/product/B09NY61SR8/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&th=1

And can I connect the battery charger while using the pedals, I mean use battery charge and discharge at the same time? I do not know if I explain myself very well

 

[eduardo_gj1]

i forgot to attach the battery type with https://www.18650batterystore.com/products/lg-f1l

 

[audioguru]

A missing spec for the buck voltage regulator is how much higher must its input voltage be.
Amazon does not know details of electronic modules. They sell mostly clothes and shoes.

You are playing your gig and the battery is fully charged at 12.6V and the buck converter is set to an output of 9V.
Then the battery voltage slowly drops to 10V and the buck has 1V across it but needs at least 2V across it (2V is the missing spec). Does the buck converter stop working?
Then your pedals suddenly stop working.

Your Lithium-Ion cells are 4.2V each when fully charged and are 3.0V or 3.2V when almost dead.

A battery charger for a Lithium battery must detect the charging current dropping when the battery has a full charge then the charger shuts off. It cannot do that when the charger has a battery plus load current, so the battery becomes over-charged and damaged.

 

[rjenkinsgb]

Both the battery protection board and the step down converter should be fine.

Note that the battery board is not a charge controller though, just protection and balance. You need a constant voltage, current limited supply to charge the battery.

This is the circuit I use with three cell packs, that allows simultaneous charge and use; it needs 15V in.
The battery charge is not affected by the load current. The battery only supplies power when the 15V PSU is not connected.

The voltage at the battery connections should be adjusted to 12.6V before connecting it, then checked again when it's fully charged, for the 3 cell pack. The charging current limit is set by R1, to whatever current gives about 0.6V across that. I use three 0.22 Ohm ceramic resistors in series, to give just under 1A max charge.

(I use similar protection + balance boards on my battery packs).

 

[Pommie]

There seems to be some confusion in power ratings. Batteries are rated in ah but other things are in Amps only. You can measure things in Watts and that will make more sense. For example your battery can deliver 9V and 15Ah which (multiplied together) gives 135Wh - 135W for 1 hour or 10W for 13.5 hours. If a pedal takes 9V at 1A then it uses 9W so will last approx 15 hours. Add up all the Watts used and use 135/Watts used to determine how long (in theory) the batteries will last.

Mike.

 

[audioguru]

1) A lithium-Ion battery cell is not fully charged when its voltage reaches 4,2V. It keeps charging then its charging current drops to a low amount then the charger should be disconnected from the battery to avoid overcharging which might cause a fire and/or explosion.

2) A lithium-Ion battery cell must never be trickle charged. If it haslo load then a cell can remain at the 3.7V storage and selling voltage for years.