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.

Customize your laptop speed for temperature and performance

I while ago, I found a great article on Slashdot that shows how Windows XP manages variable speed CPUs. Well, at least it applies to Intel Speedstep technology. If you have an Intel processor (like the Core 2 Duo T7200 in my laptop), you can take full advantage of the different CPU frequency algorithms to get the desired performance from your machine.

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