DRONE: Safe LiPo Charging

I've owned a few toys with Lithium Polymer batteries in the past and never really been aware of the risks associated with charging the things until recently. I've heard of LiPo fires and seen the YouTube videos but only ever associated the mishaps with improper use. It wasn't until I got in to racing quads and had my first big crash that I though of 'improper use' and that I could be putting myself and family unnecessarily at risk by charging them in the corner of my lounge room.

There are number of places you can read up on LiPo battery charging safety including safe storage, here are my favorites.

• The Drone Girl tips on LiPo charging safety
• Dronethusiast general battery safety guide
• RC Groups forum discussion on safe storage voltage

The main points:

1. ***Visually inspect batteries after a crash. DO NOT CHARGE DAMAGED CELLS***
2. Charge on a non combustible surface (concrete floor works well)
3. Charge LiPos in a fireproof container such as a LiPo storage bag or ammo tin
4. Stop charging after you batteries are fully charged
5. If you lipo catches fire make sure you don't breath the toxic fumes, so charge in a well ventilated area
6. Store LiPo batteries at safe storage voltage to prevent possible damage to cells

Really the most important thing to remember is not to charge damaged cells. This includes cells that have been punctured, dented or even batteries that have puffed up. This is the biggest thing you can do to prevent a LiPo fire.

To cover points 2 and 3 most American sites suggest an ammo tin as a good storage area but these are hard to come by in Australia, so I got creative and came up with my own solution:

Discharging LiPo batteries for safe storage

Charger mounted to outside of the charge box

I converted a cash box to charging/discharging box to hit points 2,3 and 6.

I haven't had a lipo fire (yet) so this solution isn't tested, but it goes a long way towards safety. 

Bill of Materials:

• Sandleford cash storage box ($20)
• Battery discharger (18USD)
• XT60 to Dean T plug adapter (2USD)
• Metal mount/heat sync for bulb mounting
• Power timer

Total spend was a little over $45

I now charge my batteries in the garage and use the power timer set to 4h to hit points 3 and 4. Although it's not a perfect setup to stop charging the batteries after they are full it's definitely going a long way towards safe charging of my LiPo batteries.

Update: 

I'm trying to come up with a way to use a power monitor that turns off the point once it sees a minimum power consumption coming from the socket. I'm experimenting with a Belkin WeMo Insight device that seems to look promising, although it's not the most cost effective device at $70 a pop. This should get me another step towards safe charging of my LiPo batteries.