CAPACITOR FAILURE ISSUE IN BMS BOARD -LI-ION 3.7 BATTERY OPERATED - Page 1
Forum section: electronics / projects

author: kashyapamit
author_rank: Newbie
timestamp: September 10, 2025, 11:26:48 am
content: Hello Everyone ,I have Design a circuit , which Application is to operate 3v - 1Amp LED Load through a current controle resistance from a Li-ion battery 3.7v 2600mAh , and same PCB i have given battery charging circuit also i charge battery from a 5V 1Amp dc charger through ic CL4056 (This is battery charge management ic ) which full charge the battery up to full and stop charging when its full ,,I am using two CHIP 0805 capacitor in this ckt ,, one on the battery and other on the charger side , circuit images attached below ,, LED Load current approximatly 900mAmp and charging current aprox 800mAmp ,,i am facing from the field after dispatch our products in field , Main issue is battery Dead, when i troubleshoot i found battery side capacitor faulty that was leaking cuurrent ,observed that capacitor get partially damaged which cousing leakage current that Leads to battery dead / Deep dischargei want to solution /or to exactly identify this phenomena why this is happening, this is not happening in all the pcs it is aprox in 20% pcs ..,, and fund probloms randomly ,,want to find Exactly route couse of this so that i can make Solid PCBThanks ..

author: mikerj
author_rank: Super Contributor
timestamp: September 10, 2025, 03:12:03 pm
content: MLCC capacitors can get cracked through stress from the PCB flexing which is why you have to be careful not to place then near mounting screws etc. When these capacitors crack they can form a leakage path or even dead short from the internal metal layers at the crack touching.

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: September 10, 2025, 03:52:32 pm
content: You have no overdischarge protection?

author: kashyapamit
author_rank: Newbie
timestamp: September 11, 2025, 05:52:42 am
content: Thanks for Reply , can i check this in house during Assembly Line , so that i can detect the probloms before dispatching in field , is there any device with which we can check the the partiall failure

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: September 12, 2025, 09:26:43 pm
content: Is the 4056 output a pulse? The cap might not be able to handle the ripple current. Otherwise, I also think cracking could be an issue.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 13, 2025, 02:37:55 pm
content: Try just not using that cap? Based on what you have drawn, it should not be necessary.

author: Niklas
author_rank: Frequent Contributor
timestamp: September 14, 2025, 10:22:22 am
content: I don't think there is a good method to test for this. We had a similar problem with a 1206 sized capacitor that was cracked during depanelization with V-cut. Other capacitors on the board of the same type were ok. Tried resistance and capacitance measurements, but nothing conclusive during production. On the returned field claims we measured a few ohms across the faulty capacitor, but no heat dissipation. Did some research and found investigations from NASA that pointed to similar results. No good way to detect it, instead try to avoid it. The mechanical cracks can occur in your assembly process, but the low impedance path takes so time to build up and depends on applied voltage for the material migration to occur.- close to the board edge where V-cut or mouse bites are used?- near screw holes?- is there any mechanical stress from the encapsulation?- manual soldering of capacitor or wires that could cause thermal expansion stress?