A number of devices are available on the market to perform this task, with wide variations in quality, reliability and suitability for a marine installation. It needs to be built and engineered correctly. It is only a matter of time.īattery protection is therefore the first and most essential layer of any lithium system, because it implements all key safety functions and protects the asset. The human factor becomes embedded into the reliability of the scheme and momentary inattention or absence instantly results in zero protection.
Alarming is pointless for that matter: alarming relies on someone not only being present, but also understanding what is happening and knowing what to do. Also, due to the relative size of the battery and wiring, the risk is not so much towards the battery: something else is likely to melt or get destroyed first.Ī protection system must be able to act automatically at any time in case of detected issue, before a serious situation develops. Integrated short-circuit protection is also commonly found on small battery packs, but it is problematic to implement on larger banks, such as found on marine vessels, because the potential fault currents can exceed the interrupt rating of the disconnectors fusing must be used for this purpose. Give or take a few degrees at high sustained currents, a lithium bank on board should run at ambient temperature, at all times, no exception. Protection is simply a matter of keeping at all times each and every cell within its allowed operating voltage limits and ensuring nothing ever begins to warm up. Overcharging a lithium battery, or recharging it in a damaged state, can overheat it to the point where it can ignite and burn extremely hot.Excessive discharge causes severe and irreversible damage.Lithium cells are quickly destroyed by voltage excursions.Battery ProtectionĪn unprotected lithium battery can become a fire risk or an expensive fiasco: take care of the cells and the battery will take care of itselfĪ lithium battery cannot be responsibly operated without a layer of protection between itself and the electrical installation because: Using the right equipment considerably simplifies the task of building lithium battery systems. Battery protection must be seen as the basic subset of functions battery management is built upon: there is no management without protection, but at the lowest acceptable limit a lithium battery can be protected without being automatically managed.Ī 200Ah DIY lithium battery back for a yacht connected to a custom battery protection module.įrom left to right on the connector, the four cell voltage signals, the reference negative, the two power supply cores for the module itself and the cables from the temperature sensors. The first category represents acute needs which must covered by battery automated protection functions the second one pertains to battery management. Requirements to ensure a long operating life and an absence of issues over time.Requirements to be met to prevent dangerous developments, damage or the rapid destruction of some or all of the cells.The needs of lithium batteries fall into two categories: Battery Protection, Battery Management or Both? You are welcome to use it to build a system, but at your own risk and responsibility. It is certainly not sufficient or intended to turn a novice into an electrical engineer either. There is no guarantee that it will not change or grow over time. It reflects the knowledge I have accumulated building some of these systems. The information provided here is hopefully thorough and extensive. This article is aimed at guiding the process, but it is not a simple blind recipe for anyone to follow. DisclaimerĪ good understanding of DC electrical systems is needed to build and commission a lithium battery installation. Before a lithium battery can be put into service, it must be protected or the first adverse event to occur will damage or destroy it. A previous article detailed the design and assembly of such lithium battery banks. This article discusses the protection of lithium battery banks in the context of marine installations.
Dyi simple battery monitor for trolling motor battery series#
This article is part of a series dealing with building best-in-class lithium battery systems from bare cells, primarily for marine use, but a lot of this material finds relevance for low-voltage off-grid systems as well. Last Updated on 17 June 2018 by Eric Bretscher
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