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Lithium Battery & Thermal Runaways

by James Coomer 31 Mar 09:15 UTC
Lithium Battery & Thermal Runaways © James Coomer

A thermal runaway lithium battery fire is up there with uncontrolled gas fires, as one of the worstcase fire scenarios on a small vessel. While most fires have some form of management or fire control, a lithium thermal runaway battery fire does not.

Today's batteries, whether it be lead-acid, AGM or Lithium are all very safe as long as manufacturer guidelines are strictly complied with. Lead-acid and AGM batteries are well tried and tested, with most of their ventilation and fire challenges being well documented.

The challenge with lithium batteries is the myriad of cheaper lesser known lithium brands now coming on the market via social media to private buyers, bypassing reputable retailers.

We need to remind ourselves that reputable retailers have a lot to lose if their recommended batteries fail (including lawsuits from Insurance companies), so they have normally done their homework and carry reliable home-grown warranties.

Lithium batteries currently fall in the Class B fire category, which means that the standard ABC fire extinguisher can be used.

This, however, is no use if there is a 'thermal-runaway' situation within a lithium battery bank.

Thermal runaway fires are extremely difficult, if not impossible, to stop or extinguish.

A simple Google search about lithium thermal runaways will highlight the record so far in the aviation sector, where fires present a particular problem, their lithium cargo record being far from positive.

So what is a Thermal Runaway?

A thermal runaway is an unstoppable internal chain event, where a cell or part thereof very quickly reaches high temperatures. The causes are varied but include internal mechanical or thermal cell failure and short-circuiting deep inside the battery.

Due to the short-circuiting, heat is generated by this single defective cell. The enclosed heat source self-generates to much higher temperatures.

The very hot defective cell core becomes unstable, having no way to release heat except to the enclosed surrounding cells thermally inside the battery. The surrounding cells then join in the masquerade and the battery very quickly heats from the inside out, which they term a thermal runaway.

Meanwhile little can be seen at the battery surface. This all happens very quickly, taking minutes to self generate to a point where the battery becomes extremely hot.

Common cues and/or senses used in picking up most other fires include sight, sound, aural and touch (the latter normally being a result of the first three). With early signs of a thermal runaway situation, however, we only have the sense of touch.

With smaller portable devices, lithium thermal runaways/fires are easily remedied...toss it into the ocean.

Vessel lithium batteries used in house banks are normally tucked away somewhere in some very secure robust area. So when it's finally realised that there is a problem, and then questioning if it's battery-related, who would think of touching or even want to touch a battery to resolve a lithium battery fire problem? Thermal runaways happen quickly (as in minutes) and can get out of hand very quickly.

Recently chatting to someone who had built their own lithium battery bank from imported cells, we found them ill-prepared for a thermal runaway. Their cells had no protection.

So where does it leave a private person like you and me? Risk verse Reward. If an incident occurred, would the Insurer come to the party? I doubt it very much. There are incidents and aircraft hull losses caused by thermal runaways in freight loads of lithium batteries.

Technology today also have records of thermal runaways on smaller lithium powered portable devices such as mobile phones and laptops. So, it certainly does occur. It is, however, the lack of control of a thermal runaway that is raised in this article.

In particular, if you (a private individual) are the importer and are bypassing a professional supplier and/or installer. Check with your Insurance company, you may find your insurance is void by installing your own lithium. Surveyors will ask you too...we got asked.

So what can you do to ensure you've got a good lithium set up on your boat? The key to our system is a quality Battery Management System (BMS), quality being the operative word - for full details on the setup we use check out James Coomer's blog for his suggested tips.

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