The introduction of Lithium Polymer batteries into the R/C hobby revolutionized the way we power our models. But as Spiderman’s uncle said “With great power comes great responsibility”…
What’s brought all this on then?
A new video came up on my YouTube feed today that got me thinking. Before we go any further I’ll let you watch it and see if it gets you thinking too. (In fact, you should click out to YouTube and also read the comments that follow the video).
To be honest, I don’t care what anyone says but unless you are actually Chuck Norris then everyone would have had the same reaction – “Oh crap, oh crap, oh crap, oh crap…” and so on. What concerns me is that the person who posted this video then promotes the actions of his “Navy trained” team as exactly the right thing to do in such an emergency – stomp on the exploding LiPo and kick it around the room a bit.
Anyway, the point of this article isn’t to point fingers. I think it is probably a good time though to look at what went wrong and what we can all learn from it…
I’m assuming that you already own a few LiPo batteries so I’m not going to go into a lecture about what a LiPo is…
What can we learn about LiPo safety from the video?
There are a couple of key points in the video that made me wince. I’m kind of hoping that they had the same effect on you and this is only going to jog your memory:
1. The battery was a DJI Phantom battery that was taken in from a customer and tested at 5 volts
Depending on the model, this LiPo was anything from $29 to $179 worth of battery. It wasn’t some cheap eBay battery. Even if you think you have the best LiPo’s on earth they are still vulnerable.
The battery was “taken in from a customer” so we can assume that despite some of the comments the people in the video had little or no information about this particular battery’s history. They don’t know if it had been thrashed, bashed, or crashed.
It was “tested at 5 volts”. This means it was terribly over-discharged for a 3-cell battery. One of the later comments scares the hell out me. “…we have dealt with many and they aren’t damaged. We can usually recover them and they are fine. We have and sell a bunch of them…” Listen carefully, I’m going to put this into a blockquote so it stands out:
NEVER TRY TO REVIVE AN OVER-DISCHARGED BATTERY. NEVER BUY A REVIVED BATTERY FROM SOME IDIOT WHO THINKS HE CAN SAFELY DO IT!
I know I said I wasn’t going to point fingers but I couldn’t help myself there.
2. It was simply sitting on the table
Given that we know LiPo’s can be dangerous it is never a good idea to leave them sitting around where they could get knocked, squashed, stabbed etc. etc. In the case of the video this is particularly pertinent as they knew this was an over-discharged battery that had obviously suffered some abuse and therefore may also have been damaged internally.
You can pick up LiPo safety bags easily enough online. These are great for transporting batteries to and from the field and also for charging. You can also pick up old metal “ammo” cases cheaply enough for bulk storage of batteries. I personally use a large steel “Rhino” box from Bunnings Warehouse.
3. Their first reaction was to throw it on the carpet and stomp on it
A LiPo battery fire is an out-of-control chemical reaction. Jumping up and down on it is not going to stop the reaction and in fact only spreads the “fuel” out allowing more air to come into contact with the chemical causing more flames – and possibly setting fire to your foot.
If you are going to have an area of the workshop set aside for inspecting and working on damaged (or even undamaged) cells it would be a good idea to make sure:
- You have a concrete or tiled floor
- You have a fire blanket available to contain the blaze
- You have a dry chemical fire extinguisher handy to put the fire out
It’s no good playing football with the fireball whilst someone runs to another part of the building to fetch the firefighting equipment. This is especially important if you are a commercial operation who is dealing with other people’s property.
What else should we be thinking about then when it comes to LiPo safety?
I guess the only other things to remember are those things that we should be doing on a daily basis:
- Always charge LiPo batteries in a safe area – outside or on a hard surface (concrete or tile). If it can go in a bag then all the better.
- Never leave batteries alone whilst charging – because you never know.
- Always use a dedicated charger – and double check the settings if it has multiple programs (I once charged a LiPo on a NiCad trickle charge)
- Always select your power system carefully – make sure your battery can handle the amps demanded by the motor/prop. Don’t push it either, make sure you have plenty of margin for error.
- Don’t over-discharge your batteries – use an appropriate ESC with voltage cutoff or an onboard battery monitor/alarm.
- Do dispose of old or damaged batteries correctly – see below.
Disposing of LiPo’s safely
When your LiPo reaches the end of its life (and they don’t live forever), it is important to give it a proper send-off.
The best way is to drop them into a bucket of salty water for a couple of days. This totally kills the chemistry in the cells rendering them safe for disposal. In fact, a totally dead LiPo is safe to go in the general household waste (but please do check with local laws before you do this).
If you want to take it one step further then this is a great guide on how to render a LiPo totally inert. Thanks to Kona R/C flyers for putting the effort into producing this.
So where are your LiPo’s sitting right at this moment? Still waiting to be charged on the bench after today’s flying session? Tucked in beside your Tx in your flight bag?
Or are they where they should be in a fireproof safety bag?
I’ll hold my hand up and say that I have probably broken most of these rules myself in the past week alone but that video made me stop and think – and I guess for that the guys at EZDrone should be commended.
Of course, we should never lose sight of the fact that Lithium Polymer batteries are what make everything we enjoy about electric flight possible. Just be safe and keep enjoying the power!