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Monday, December 3, 2012

Charging The Lithium Polymer Beast

Generally I try to stay away from technical articles about electric chargers and such because this is not my area of expertise. Mostly I try to keep the blog just fun, but you do have to charge your batteries and you do need to know something about it. I came into electrics knowing absolutely nothing about how brushless power systems,  Li Po batteries and chargers worked, and it's been a bit of a learning experience. Mostly I didn't bother memorizing all the formulas and math, and simply tried to learn what works in the airplane and at the field, and the following is how I have learned to do it, so far, that is.

For years I have used the Thunder Power 610C AC/DC chargers, and those have served me really, really well. I can use either a 110V outlet, or even use my car battery to power this charger, so it is a very versatile unit.

 I also used the regular TP610C that was strictly a 12 volt unit. I still have two 610C AC/DC chargers, and I keep one under the seat of my car just in case I need it or one of my friends needs it. I've also got a second one I keep on the bench if I need to top a pack off real quick and don't want to go to the trouble of hooking up my more powerful system.
Both were reliable, hard working little chargers, but in the end they were still just that ....... comparatively little chargers without big power. For a lot of folks this is still just fine because the most common battery I see at the field is something like a 3s 2200 to 2700 mah. I can charge a 65C 2250 pack in about 12-15 minutes on a 610C, and this size battery is so inexpensive that you can almost have enough of them to fly all day anyway.

Where you need a lot of power is when you get up into charging something like a 6s 3850 pack. It takes my 610C about 1.5 hours to charge one of those, which is clearly too damm slow. I put up with that for about two days and decided it was time to get a fire breathing monster to charge those packs.

Having liked my 610Cs so much I wanted to stay with a Thunder Power charger (And so did Thunder Power!). I talked to my buddy Mark in service and he put me on to the Thunder Power TP820CD charger.


Now we are talking about a serious charger, but surprisingly the programming is very similar to the 610C, which itself is pretty easy to learn. As such, I was comfortable using this charger right away. I plugged it in without even opening the manual and understood it as soon as it lit up.
The primary difference, at least externally, is the TP820CD can charge two packs simultaneously. The difference internally is just how powerful this charger is, capable of feeding each battery a whopping 20 amps. Like this I can charge two 6s 3850 65C packs in 14-16 minutes, depending on how low the pack was beforehand. I can also charge my 4s 2700 65C packs in 12-14 minutes and 3s 2250 65C packs in about eight minutes! And remember, this is charging two packs at a time, and that includes charging different size and voltage packs at the same time.
Charging the packs fast like this means I don't need to take as many to the field, or even better I don't have to buy as many to begin with, which adds up when you are flying expensive 6s 3850 packs.  In fact, I now only need two of them instead of four. The difference would have more than paid for this charger.
Of course, there is a lot more to it than that because the charger does much more, and I am still discovering it. I just today played around with it a bit and figured out to use it to measure the internal resistance of the packs, and the good news there is that all they made it through the hot summer still in really good shape.
So, while I am still learning about this charger I am definitely loving it more and more.
The Solid Hobby Power Supply 
Initially I was powering my TP820Cd with a Feathermerchant 24 volt power supply, and it served me extremely well. It's a really good unit, though I have often wished it only needed one power outlet (instead of two) to operate. When I saw that Solid Hobby was manufacturing a Y-harness complete with on/off switch, I had to get one. I liked the unit a lot, except there was an awful lot of wire there. I suggested to Jeremy at Solid Hobby that the two cords coming out of the power supply be shortened, and then the switch could be velcroed to the top of the power supply. Jeremy swapped out my unit for the improved one at no charge, so I was pretty pleased with how I was treated. I believe all the switches now come this way.

Now I only needed to take up one outlet, and with the switch I wasn't having to unplug it every time I was finished. This new arrangement also tidied up all the wiring and made the whole thing much neater, which is exactly how I like things.
Later when talking to Jeremy via PM at RC Groups, he mentioned he would be manufacturing a 24 volt power supply, and incorporating a few improvements.  As pleased as I was with the other product, I knew I was going to want one of the The Power24+ supplies too.
Unpacking the The Power24+ today I was delighted to see how nice the thing is. Ok, I get it that no one goes to the field and says "Damm, you got a pretty power supply," but the truth is this thing looks real nice. It is a very well finished product. Initially I thought they had made an outer case, but later found out that each one is individually hand covered with black Ultrakote!
It did not take long to realize this charger was built for married men. My wife noticed right away the unit has little rubber feet on the bottom, and she remarked it's nice the thing won't scratch the kitchen counter! While that's practical enough, it is also nice this could keep the thing from sliding off the work bench. It also gets it up off the ground enough that it is much easier to get your hands around it to pick it up. This might seem insignificant until you get arthritis in your hands, and then it is a bit of a godsend.
Upon firing the unit up I could hear right away how much quieter it is. This will come in handy for guys who have to charge inside the house and don't dare disturb the Wifey's TV time. The fans also run at slower speed until more cooling is needed, and then they crank up.
Having been around racing and model airplane engines all my life, I have a bit of hearing loss. When there are too many noises everything seems to turn to mush, Around the field with the traffic and other noise, the cooling fans on a power supply make having a conversation around my pit very difficult for me. With this new unit I am sure that will become a lot easier.

As you can see, there are dual outputs, meaning you can use two chargers. In this picture, you will use the black outputs and the red outputs on the very left to run the power system as a 12 volt unit.

Here you can see the red jumper wire used to hook the two power units together and make a 24 volt supply. This is the way I will be running it with my TP820CD. Also note in the above pic the nice little shields over the cooling fan intakes. Every so often I accidentally stick one of my fingers in the fan on my other power supply while it is running, but you can't do that on this unit.

So far I have charged a few packs getting ready for tomorrow, but the real test for this power supply will be in the field. So far I am really pleased with it and look forward to seeing what she's got tomorrow.

Units will be going into production shortly. List price will be $110 for the power supply including the on/off switch + $15 for US shipping, so the total out of pocket will be $125.

 Also worth noting is that the Power24+ system comes with a one year replacement warranty, so you'll be making a safe investment in powering your models.


  1. hi how many chargers you can connect in 24v

    and in 12v how can i connect the charger


    i ask because just ordered 1

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