I dont see a protected output for 3s power.. or am i blind.. (good chance)
According to the specs it is for:
3.7 volts… single cell. Maybe you could charge the cells in parallel like in your diagram.
Duhh.. didnt even notice that when i was looking in a hurry.. well that but for 3s…
Would really like one with adjustable cutoff, some cutoff below 3v per cell.
I’ve not looked at DIY battery builds for a while as I decided I didn’t want the risks involved with a self-constructed powerbank pack from various modules… so take my advice with a grain of salt.
Uhh.. how low? What cells are you using? NMC or LiFePO4?
If NMC, any reason you want to go below 3V? Depending on the current draw, there’s often not much energy left in the cell below 3V.
I forgot to ask this earlier, but are your cells all identical or random harvested cells from battery packs?
Do you know about the importance of having matched strings of cells in series?
From a cursory Google search, Injoinic offer a number of ICs available in pre-built modules from AliExpress etc which accept (generally) 2S to 6S lithium cells and provide USB output.
Many (all?) don’t seem to offer cell balancing so you’d want a separate BMS between the battery terminals and the “charging module” which offers this. These boards take the supply from the BMS and apply various USB protocols for the USB outputs.
If you’ve modest 12V power requirements, theoretically you could draw from the USB C port on these type of boards by using a USB Trigger (assuming the board has correct charging protocol).
After you’ve found a board etc you’ll have to build a housing to protect the cell terminals and the circuit board etc. I suspect someone has 3D printed housing designs for the more popular boards.
What are your power requirements as this will dictate your BMS and power module.
3S cells supplying 100W, for example, will need a 35A(ish) BMS (and, obviously, cells capable of supplying this without overheating). If you’ve electronics to handle the 12V output, increasing the number of strings will reduce the current drawn from the battery.
Im saying some if not many cut off at or below 3v, seen a few even 2.5v for Li-ion..
Off of the 12v side im mainly wanting to run a small fan or light, no more than 1 amp .
But as Gravelmonkey mentioned. You will not gain very much by going below 3 volts. But you will reduce cycle life of the cells. I understand wanting to get as much energy out as possible. I thought the same. Until checking the difference in capacity when changing the cut-off voltage to 2.5 from 3 volts. it is usually in the rage of low single digits of percentage. Not worth the trade off for me. I still will match the data sheet numbers for cut-off voltage when doing capacity testing. But, that is only so my results are taken under the same conditions as the manufacturers tests. Other than that, 3 volts is fine as a compromise among capacity out cell wear, and safety.
Again im saying i DONT want my cells going below 3v…
I will be buying all the same cells, i know not to mix, and it will be in a box for protection..
My whole point is i didnt see any of the circuits that would charge with a type-c and have a pair of 5v usb power out slots.. that will shut power off when it gets low, AND have a protected full power output as well.. was figuring i would need to get a separate circuit to safely draw 3s power..
Sorry for any confusion, i have busted my back and they got me on pain meds till my surgery..
Paralyzed and in a wheelchair, got rods and screws in my back, popped the lower screws out and needing a big surgery again, my insurance has been d*cking me around and surgery is waiting for approval.. so not 100% thinking straight hahaha
In this case, are you looking for over current protection? It seems that you use terms in ways that make me unsure of your meaning. In a discussion like this it is always good to define the terms being used.
Very unfortunate about your back. I can only send best wishes your way. Hoping for the best outcome for you.
Again sorry for any confusion, im just now delving into the actual electronics and dont know actual terms, but ive been working on most all my own stuff and lots of RC cars, i know what a BMS does as in shuts power off if its too high or low, messed up an RC 3s battery once while running a fan as it didnt have any protection for low voltage..
Most of these diy circuits i see has a charge input that wont let it under/over charge, and if they have a output side for say a usb it has protection for low voltage cutoff, i would like to find one that has an adjustable low and or high cutoff value.. and needs to have a low voltage protection for the 3s output, just like the 5v usb output, just 3s instead of the low 5v..
This is all making sense in my head and reading it, just im confusing you guys as im talking redneck and you guys actually know what you are talking about..
Liitokala Lii-PD4 and Lii-PD2
Liitokala Lii-PD4 Lii-PD2