BMS

[ionut_mtb]

Hello,

For powering my projects i usually use li-ion 18650 and 14500 (AA size) rechargeable batteries. i charge them separately every time, with TP 4056 module or other cheap charger. From what i saw charging current is aprox 1A. For 14500 (sanyo ur14500p 800mA) i lowered the charging current at 400mA (recommended datasheet current) which i think it is little high, but do the job.

I never used BMS and i want to try because i'm tired to remove every time the batteries from detector. My concern is the charging current. How is limited? Do i need to feed the bms constant voltage and constant current? For example if i want to charge 4S each one with 400mA i feed to bms max 1.6A?

[Carl-NC]

If you buy a pre-made battery pack it should include a circuit module in the pack that monitors each cell and limits the current. You simply provide it with a sufficient voltage. If you are going to build your own battery pack then you must design the module yourself. There are standard chips for doing this but I have never designed one myself.

[Skippy]

Carl:
Ready-built charge-balancing / protection circuits are easily available, at low prices. They're great for homemade packs, and seem available for packs from 2 cells to 6 cells ( 2S to 6S ). And obviously single-cell protection boards, too, without charge-balancing.
They presumably will come with some pidgin-English instructions, and they will have some maximum charging current they can handle. I think it would be wise to ensure any charger is current limited to a sensible level, and also limit the maximum voltage applied to the pack ( normally 4.2V per cell ). The protection board should stop the charging process at 4.2V per cell, but I'm not sure I would trust it.

An example 4S board:
https://directvoltage.com/shop/ardui...-16-8v-4-cell/

In theory, such a board means that just a DC power supply and a suitably chosen current-limiting resistor are all that's needed to charge the pack.

I've just done a search, and 7-cell boards are available, though they seem large, and have high current rating, a bit overkill for MD projects, though.

[Emersonpaz]

The BMS are wonderful after I started using them. I never made another type for the Polish pi. I had made a 3S pack that provided me with 12.4v fully charged. However after I finished the felezjoo pi I used the same pack replacing the 3S module with a 5S and adding 2 cells.

[Emersonpaz]

To charge 5S I use a 21v 2a power supply. Font and BMS purchased on Aliexpress

[F117]

This week in EDN there is an interesting article about a simple method to check the battery's capacitance: EDR = electrochemical dynamic response.


This method basically applies a short but heavy load pulse to the battery and checks the recovery from it.
Very much the same as we do in a PI detector.
In a PI, the MOSFET to apply the load pulse is already there, the slope evaluation is there too.
The only thing that gets in the way is the electrolytical buffer capacitor that is preventing the power supply from dropping.


https://www.edn.com/check-battery-ca...e-test-method/