EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: rks96 on September 28, 2020, 02:55:39 pm
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I have 10 lithium cells! Each cell have a stand alone protection board uses DW01A (2 stand alone 8205A mosfet version) with discharge current protection of around 3a https://www.best-microcontroller-projects.com/dw01a.html (https://www.best-microcontroller-projects.com/dw01a.html). I want to create a battery pack 5c2p using separate multi cell BMS board https://www.aliexpress.com/item/32889959726.html (https://www.aliexpress.com/item/32889959726.html) uses bm3451 BMS chip.
5 cell BMS has discharging current: 25A and protection 60A (way too much for 2 of my cells in parallel)! If I use small single cell protection board on each separate cell my 5cell pack will be limited to around 2*3=6a max (2 cells in parallel) which is fine by me!
In short, it would work like this: I think!
Overcharge protection - > BIG 5 cell bms @ 4.23 - 4.28V! Single cell protection board would trigger only @4. 3V.
Single Cell over-discharge protect voltage - > BIG 5 cell bms @2.72 - 2.88V! Single cell protection board would trigger only @2.4V.
Over-discharge protect current -> protected by a single cell protection 3A a but I use 2s in parallel so 6A (if over current situation, then one of cell protection triggers first and then soon after other cell protection triggers since now all power has to come from only on cell). 5s BMS would trigger only @ 60A.
Each single cell has 10000mah capacity (5s2p --> 20000mah @ 21v).
Should I remove Single cell protection boards or leave them be? I am not planing on using more than 6a at any time anyways, but I still would like to have all protection and power possible! MYB each cell can handle more than 3a safely if I remove the single cell protection?
PS1: I didn't add single cell protection boards! Cells came with them already added! Also, I will not use included thin wires!
PS2: I will use CV-CC6A charging so these protection functions I don't care about!
PS3: Everything is from China so I don't know if I can trust any of these values!
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Thanks in advance!
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Leave them in place so you have lower current limit. 60A limit is too high for 2p of normal cells.
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The single cell built on board protection circuit will limit the total current of the series chain to 3A.
If I understood what you have said.
You will not be able to acheive higher current unless you remove the single cell protectiin circuits.
Make sure that cell voltages are within 0.01V when joining cells in parrallel or high balance current will flow when you join then together.
It is also best to make sure cell voltages are balanced when joining in series or you will have (series) unbalanced pack