Investigating Affordable Large LiFePO4 Batteries: When Price Cuts Become Concerning?
In a recent video, tech YouTuber [Will Prowse] shared his findings on the safety concerns associated with using generic, unbranded LiFePO4 (LFP) batteries in off-grid and solar power applications.
The purchased battery, costing $125 for a 100 Ah capacity, was bought on Amazon without a recognizable manufacturer or brand name. Upon teardown, [Will] discovered potential quality issues, such as a row of missing cells and re-sleeved cells.
One of the key safety concerns revolves around the battery's Battery Management System (BMS). While the BMS includes over-temperature protection and under-temperature charge protection, it does not provide comprehensive safety features, potentially making it dangerous. The BMS allows a surge of up to 400 A, but lacks over-current protection.
Comparatively, another YouTuber's LFP battery had a lower capacity (88.9 Ah) and a different BMS, further highlighting the inconsistency in quality among these generic batteries.
LiFePO4 batteries are generally safer than other lithium-ion chemistries due to better chemical stability and lower thermal runaway risk. However, they still require an adequate BMS and physical disconnect mechanisms to prevent dangerous conditions like overcharge, overcurrent, and short circuits. Many generic batteries lack robust BMS or only rely on digital signals to control charging, which can cause inverter or charger malfunctions and safety faults.
Custom or cheap BMS implementations in generic packs can cause incorrect charge limits or sudden blocking of current, leading to confusing system alarms and potential system instability. Overcharging or charging at too high a C-rate not only degrades battery health but also risks thermal stress and internal damage that can compromise safety.
Moreover, although LFP cells are chemically more stable, lithium-ion batteries in general contain flammable electrolytes. Poor quality manufacturing or abuse conditions can still lead to electrolyte degradation, internal short circuits, and thermal events.
In light of these findings, [Will] does not outright advise against using these batteries but suggests caution. He recommends installing a fuse on the battery to provide some over-current protection and keeping a fire extinguisher at hand due to potential safety concerns. The batteries, if functioning well, could be advantageous for off-grid and solar-powered applications.
However, using batteries from recognized manufacturers with certified safety standards and well-integrated BMS and disconnect systems is advised to mitigate these risks. Vigilant charging control and system design aligning with manufacturer recommendations remain essential for safe operation.
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- Given the safety concerns discovered in unbranded LiFePO4 batteries, it's crucial to consider the advanced safety features often provided in batteries from recognized manufacturers and those that comply with standard safety certifications.
- While science has proven that LiFePO4 batteries are generally safer than other lithium-ion chemistries, the integration of technology such as robust Battery Management Systems (BMS) and physical disconnect mechanisms is essential for preventing dangerous conditions like overcharge, overcurrent, and short circuits in these batteries.
