I want to build a DIY power bank that can be powered using most types of laptop chargers. I do not have any background except personal interest and lots of videos and documents read online. I need someone with more experience to please have a look at my circuit and let me know if it is going to work or if I'm building a time bomb :)
I will include all the component specs and links for convenience.
I will use a 3S10P battery pack built from reclaimed li-ion cells from dead laptop batteries.
I am hoping to have sort of a 'plug n play' functionality to avoid using switches (plug in charger to automatically start charging the powerbank, or plug in phone and immediately start charging it).
I am planning to use a relay switch for this to avoid a simltaneous charging/discharging scenario where a charger is connected when a phone is charging.
The relay is connected such that the Normally Closed (NC) contact is connected to the output (phone QC converters), while the Normally Open (NO) terminal is connected to the step down buck converter output (used for charging the powerbank). The control circuit is powered by the input of the buck converter. This way (at least the i think it will work), when a charger is connected, the output is disconnected so that I can't use the powerbank to charge my phone when it is charging.
Component links & specs:
- NC temperature switch = 45 Celcius / 12v / 10A
- USB Quick Charge buck converters = 6-32v / 3.2A
- buck converter (12v output for charging battery) = 5-40V / 20A
- LCD battery meter = 100V / 10A
- BMS charger/balancer = 3S / 30A
- SPDT (5 pole) relay = 12V 20A
What i need help/guidance with:
I want to charge/discharge each cell at 1A max. Is there a chance that the the circuit may draw more than this? Don't want to be too harsh on the reclaimed cells.
Temperature switches trigger at 45 celcius. Is that safe for li-ion?
Is there need for a cooling fan for the buck converter used to charge the powerbank? Output will be 12.6V 10A and input will depend on charger used. Most laptop chargers i've seen output between 12-20V at 4-10Amps
What changes/additions or general suggestions would you recommend?