Storing Lipo batteries for faster charging times and longer lipo life

I just finished a quick flight at the park with my Trex 550e. What a fun bird to fly.

Trex 550e Upside down hover

That picture was taken last year on a nice summer morning. No pictures today but it’s the same heli.

Anyway, the point of this post is about lipo batteries. I just brought up the heli fly because I had such a great experience with it’s battery. Coincidentally, I was just talking today with someone about charging batteries and they wished they could charge 4 6S batteries in 20 minutes. You need a lot of Watts to do that. A 6S lipo is 22.2V nominal and the batteries for these helis are 5000mAh. So if W=A*V then 4 of these things take ~444W to charge in an hour. Triple that to do it in 20 minutes. The only charger I know of that can do close to that is the Powerlab 8. Given a big enough input power supply it can do 1344W output.

Step back a bit. When I first started flying RC airplanes and helis I wanted to fly all the time. Well, I still do but I was pretty gung ho from the beginning. I’d do like 3 or 4 flights per day if the weather wasn’t bad. Morning, evening, it was all good. We live by a park big enough to fly my small trainer so I’d just run out for a couple quick flights and then go back to doing whatever. I didn’t have time to charge my batteries before every flight so at the time I just charged them after the flights and left them charged all the time. It worked out pretty well except after a while I started learning that it might be best to not store them charged all the time. Apparently it breaks down the chemistry faster when they have a full charge. A day before you’re probably fine but charged all the time is going to wear them out much faster.

Ok, side note again. All my batteries that I did that with are still fine. I use them in planes and even an EDF still and as far as I can tell that early storing stuff didn’t do much harm to them. BUT… you know, the experts must have something they know so I better heed advice.

Fast forward a bit. I decide I should probably not store my batteries charged. I think this is the point I started flying less often. If I wanted to go fly something I had to take a moment and charge some batteries. You can see why someone would want to be able to charge their batteries FAST.

I got a better charger.

OK, so I have this charger that can charge faster than the original one I had but I have a lot of batteries by this time too. I hook them all up and charge most of them at the same time. It can take over an hour still. In the mean time, I keep learning and reading things and I find out that the experts are advocating not storing the batteries all the way discharged too. Apparently storing them discharged has a similar effect to when you store them charged. How much? I have no idea. My philosophy is that I’ll probably destroy the battery before I find out if the way I stored it has much effect. However, this is good news because 1) My fancy pants charger has “store” mode and 2) I get to fly faster if they are already charged a bit.

Store mode on these chargers puts the charge on the pack back to about 70% capacity. Somewhere around 3.85-3.9V/cell. So now I get to feel all dandy because I’m storing my batteries in such a way that the experts won’t complain AND, my charging time is cut in half. I just charge the packs before a flight, go fly, then stick the packs back on the charger for their storage charge and I’m good to go for next time.

Back to the heli flight today. I was smiling because I just stuck that one 6S 5000mAh pack on for a quick charge and 20 minutes later I was ready to go.

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