LiPo Safe Disposal How To

LiPo Safe Disposal How To
Tony Arnold – StampedeProject.com
RC Car - October 2008

[img3.jpg], [img4.jpg] - SHOWING LIPOS IN ACTION ON CRAWLERS AND 1/8^TH SCALE APPLICATIONS

Inevitably, a LiPo pack will require disposal and luckily according to various environmental studies, LiPo packs have very little environmental impact compared to any other typical battery. During their useful life, Lipos have higher charge/discharge cycles counts and when disposed of properly leave almost no environmental footprint. Currently LiPo is one of the best options for both the power hungry and environmentally conscious.

[img6.jpg] – {CAPTION – Lipo packs should feel hard, if your pack suddenly develops a balloon-like spring to it, you should start disposal. The pack on the left if definitely bloated}

Houston , We Have a Problem

There are two basic situations where disposal is required. The first highly unlikely situation is where the pack self-destructs and you don’t have time to react. Maybe your cell balancing was so out of whack that one cell bottoms out a little to hard, or that hard tumble you took in turn #2 shorted or damaged the pack. Whatever the situation, the pack enters thermal runaway and swells so fast that it bursts into flames. Grab a fire extinguish and hopefully you can salvage your car. If this process happens inside, get the pack outside fast inside something that won’t burn.

Most commonly with age, cell imbalance, or pack damage, thermal runaway can start but can take days to start to puff a pack and typically won’t result in a fire. Our MaxAmps crawler pack was a more typical situation. The pack was run and over-discharged with the LiPo detection turned off on the ESC – Ops. On the next charging cycle it started puffing. Just to see what would happen I dropped it in a clay flower pot and safely observed it for three months with no further bloating or heat from the pack – it definitely gave me plenty of time to react. If you find a pack has puffed even slightly, consider it toast and start the disposal process.

[img7.jpg] – {CAPTION – A LiPo battery discharger is easy to make with a 12V auto/trailer light. Clip on the light and let it go until the light is out, then test with a voltage meter.}

LiPo Disposal

Disposal should be done outside, with adult supervision, heavy gloves, safety glasses, and a fire extinguisher. Keep the battery in a fireproof vessel like a clay flowerpot or in the dirt during the disposal process in case things get ugly.

[img8.jpg] – {CAPTION – Once the battery is discharged, clip off the battery leads and balancing taps, bag it and toss it - DONE.}

The goal is to discharge the pack with a low current draw to near zero volts. A motor is too much draw, but a 12V car bulb is perfect. I made a simple light bulb discharger with a 12V car/trailer light. Plug in the puffed pack and let it run until the light goes out, for big packs this could take a full day.

Once the light is out, grab a volt meter and assure the voltage reads less than .5V per cell – a 2S packs should be 1V or less. If the pack still has a voltage at or above .5V per cell, clip the light back on and let it sit for another couple hours and check it again. Our bloated 2S pack read less than .25V total after light bulb discharging.

Once the pack has been completely discharged and has a voltage of less than .5V per cell, the pack is harmless and cannot catch fire. The connectors can be clipped off and the pack dropped into a plastic bag and tossed in the trash. That’s it, no pack disassembly, no mess, no fuss.

What About the Saltwater Bath ?

The saltwater discharging method is now no longer recommended by manufacturers. Yes, lithium exposed to saltwater will discharge, however it can be very dangerous and extremely un-reliable. The problem with the method is that to work, the Lithium needs direct contact with the saltwater which means you need to cut a charged and potentially puffed pack underwater, flip it over and cut the other cell(s). You may see the potential dangers with this process and if done incorrectly will yield a LiPo pack on fire. The above light bulb discharge method is a better, safer, easier, and more effective means of fully discharging a battery to a state safe for disposal.

[img9.jpg] – {CAPTION – For those that have to see the insides of a LiPo pack, I’ll save you the trouble. Inside, sets of cells wired together just like a NiMh pack with layers of black gooey junk inside each cell.}

Need more info? Go to MaxAmps.com and order one of their LiPo safety CDs.

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SOURCES: MaxAmps – www.MaxAmps.com, StampedeProject.com