When you start a new hobby, you tend to learn some new and interesting things.
For instance, the new airplane I have flying has a battery technology that I had not worked with before. It is called lithium polymer batteries also known as LiPo.
I have worked with other rechargeable battery types, such as nickel cadmium (NiCd) or nickel metal hydride (NiMH). Most of my experience was with NiCd. 20 years ago that was about all you can get.
In the ’90s, after I was out of the hobby, nickel metal hydride showed up. It was an improvement over NiCd, mainly due to less toxic ingredients, and a greater amount of energy stored for the weight and size.
Moving on to today’s common batteries, Lithium Ion and Lithium Polymer. You know lithium ion batteries, because that is what is in your cell phone today and is the most common rechargeable battery in modern electronics.
Lithium polymer is the most common battery in radio control applications. It is what is used for drones, which has really expanded its use. The primary benefit of LiPo batteries is the amount of energy stored for the weight and size.
As a comparison, the NiCd batteries I used in the ’80s averaged about 1600 milliAmp hour capacity. The lipo battery that came with the plane has 3200 milliAmp hour capacity. They weigh about the same, with the NiCd being larger.
A benefit of LiPo batteries is that they can discharge at a much faster rate than the older style batteries. For instance the battery that came with my plane can discharge at 20C, which is 20 times it’s capacity. This equates to 64 amps of continuous discharge.
A side effect of that rapid discharge capability is that these batteries can be a little bit unstable. If there is a puncture or a strong impact, the battery will discharge everything in a very short amount of time. By that I mean they spontaneously combust or explode. You can set them off just by shorting the leads together.
A downside of LiPo batteries (besides being unstable) is that if you discharge them too far, they become damaged and it increases the possibility of fire when you try to charge them. The problem is the resistance in the battery is high enough that it can cause spontaneous combustion due to internal heating.
So how do I know this? I made the mistake of leaving the battery plugged into my airplane after my first day of flying (crashing). There was a slight draw of current to the radio, even though the radio was turned off. This over discharged the battery.
My charger is smart enough to not charge an overly discharged battery to avoid fire. That is a very smart move for Horizon Hobbies who made my plane and sell the battery the charger and everything as a kit. It limits their liability of causing a fire.
I bought a replacement battery so I can fly some more, but I hate that I only got one use out of the one that came with the plane. Is there some way I could bring this battery back to life?
It turns out there is a way, however it is absolutely not recommended. Common wisdom says you just throw these over discharged batteries in the trash and buy another one.
Me, being me, had to do some research, and I came across several YouTube videos (there is so much wisdom on YouTube) one of which is below.
If you decide to do this, do so at your own risk.
I ended up buying a new charger, one that can charge many different types of batteries. It would also allow me to do this little trick to get the dead LiPo back up and functioning again.
As per the video, I connected the battery to the charger and started charging it as a NiCd battery at .1 amps. The goal being to get the battery up to a charge voltage of about 9.6V, which is the lower safety threshold for these chargers running in LiPo mode.
The battery started with a charge voltage of about 2 volts, which I’d consider completely dead. I should probably have tossed it in the trash, per conventional wisdom. That is way too low and the battery sat in the state for several weeks. Most of the recommendations I saw on restoring these dead batteries said to start with a battery at about 6 volts.
It took 90 minutes to get to 9.6 volts.
I touched the battery about every 30 seconds to a minute, just to make sure it was not overheating. I really did not want a fire or explosion. It never got above ambient temperature.
Once it reached 9.6 volts, I turned off the charger. I connected the balance lead and set the charger to run in LiPo mode. I started the charge at 1 amp, which is low.
It took a little over 3 hours to charge the battery at 1 amp, which makes sense. This battery is 3200 milliAmp hour capacity, which is 3.2 amp hour capacity. 3.2 Amps divided by 1 Amp per hour charge rate = over 3 hours to charge. Then again, I’m sure I’ve got this wrong. I’ve not studied electronics as much as I have wanted to.
The end result is a battery that appears to have taken the charge and is ready to go flying once again. I’ll be marking it with a Sharpie or something to denote it’s unique status as a resurrected battery.
Good job. I will be watching to see how the battery performs now. Will it last as long as a new one? Will it take a regular charge next time? Idon’t have a clue as these are new to me as well. Good luck!