Living with LiPo Batteries

Most RC vehicles now use either Lipo batteries, especially “hobby” RC’s vs “toy” RC’s, or they use NiMh. Ok sure, some entry level hobby RC’s, especially Ready To Run (RTR) ones may come with NiMh batteries with the option of upgrading (do it).

If you’ve been in the hobby for a while, you’ve seen the YouTube videos of LiPo’s bursting into a spectacular display of fire and smoke (I’ll add some below). Okay, yes, LiPo fires are a real possibility if you mistreat your batteries. So lets quickly go over some Do’s and Don’t’s. If you maintain and don’t mistreat your batteries, they should last you years.

Most LiPo batteries are paired in series of two or more and are labeled accordingly (2S, 3S, 4S, etc) and have a nominal voltage of 3.7v per cell. This is also known as the Storage charge. This is how they are shipped by the manufacturer and how you can safely store them for many months safely. Anything above that, or below that is a problem long-term. Heat is the enemy of LiPo batteries and where the problems come from so that’s important to keep in mind.

Lets start with low voltage (under 3.7v/cell). This can cause the chemicals in the battery to start reacting and over heating. Once this reaction starts, bad things happen. Some radio transmitters have low voltage warnings and cut-off’s to prevent totally draining the battery. Many drivers have watched their beloved RC vehicle go up in flames because the battery was drained to low. The reaction can occur quite quickly.

Overcharged (above 4.2v/cell). This can also cause overheating and will likely cause the battery to start swelling, or rupture. Once a rupture of a cell occurs, the chemicals react with the air and the flames start. Most modern, decent chargers will not let this happen. So when it comes to chargers, don’t buy a cheap one and make sure it has a protection system to prevent over charging. Once it reaches fully charged it will turn off and your battery is ready to use.

But what if you don’t use it? That’s bad also. It’s not going to over heat and start a fire but it will still cause damage to the cells if left in a charged state (higher than nominal voltage) for more than several days. I’ve even heard of cells becoming damaged in less than a week. So if you aren’t going to use the battery within a few days, use the Storage feature of your charger which will drain it back down to a safe level to store the battery long term.

Spektrum has come out with a line of “Smart” batteries that contain a microchip that will drain the battery automatically should you forget. Those batteries are generally more expensive but there is something to be said for that added piece of mind.

Abuse is another cause of fires. If a cell is ruptured and it starts reacting with the air, it’s game over. Now I know in the bashing and even the racing community, the vehicles get abused pretty darn hard and those shocks from crashing are transferred through the battery. Over time this will cause damage. It’s also important to note that while using the the RC vehicle, the battery will heat up and on really hot days, this could be enough for the battery to over heat. If you can’t hold your finger on it, it’s too hot. Give it a break to cool down.

As a rule, if you start noticing any swelling of the battery, it’s no longer safe to use. If you notice it starting to smoke or hiss…it’s game over for the battery. Get it unplugged and put it in a safe place to burn (ie. outside and away from any other flammable objects or material).

So what if you see that it is damaged, or swollen? Well obviously don’t use it but do NOT throw it in the garbage. It’s still volatile. You can drop it off at a chemilcal recycling depot in your area if you have one. Or check with your local RC race track. They may have someone who collects them. Failing that, you can submerge them in high concentration salt water. If you aren’t sure how much salt to add, just adding salt and stirring until you start seeing bubbles forming from the battery and/or connectors (make sure the whole thing is totally submerged including the wires and connectors). Once the bubbling completely stops, then it’s safe to toss it in the garbage.

Storing the batteries is fairly simple, unless you want to make it complicated. Always store your LiPo batteries in a LiPo pouch or bag. This way IF they fail, the bag will contain the flames (they won’t stop the smoke though and that stuff stinks and breathing it in would be harmful). You can also then store them in a ammo box (remove the rubber seal), fire proof safe, or some other metal box. There are also specialized LiPo storage boxes (the Bat Safe) on the market but they are quite expensive and only hold a few batteries. My personal choice is a 50cal ammo box with the rubber seal removed (if the seal is there and a fire starts in the box, the box could in theory burst causing other damage). I store my batteries in pouches and the pouches go in the ammo box.

Don’t store them in the fridge to abate any over heating concerns; room temperature is fine. And certainly don’t store them in the freezer. Condensation can occur on the cells and freeze and since ice expands, it could cause damage to the battery.

Pouches should also always be used while charging your batteries. Charging is generally considered the most dangerous time for LiPo’s so keeping them in a LiPo pouch is just good practice. NEVER leave charging LiPo batteries unattended!

Summary: Don’t over charge them. Don’t drain them. Don’t leave them charged for more than a few days. Don’t abuse or puncture them. Don’t let them over heat. If you observe hissing, smoke or swelling, don’t use it and discard it properly. Use a good charger. Store in LiPo pouches and also in a metal box (preferably not in the house but perhaps a garage or shed away from flammable objects).

If you take care of your Lipo batteries they should last a long time and provide hours and hours of RC enjoyment.

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