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How to Choose a Power Supply 28Apr09

Posted by tanker in Beginner, General Heli, Products.
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Integy Super Power Station

Integy Super Power Station

If you decide to fly electric helis one of the first things you are going to need after getting the heli ready to go is batteries. In order to use your batteries you are going to need a charger, and to be able to use a charger you are probably going to need a power supply. But which one to get? Ah, well read on…

First, the reason you might not need a power supply is because most chargers run off of DC current. This means you can hook them to your car battery (or an external car/marine battery). Depending on how large your packs are and how much you want to fly (and if you even have a car…) this may or may not be a practical option. Most fliers though are going to want a power supply so they can charge packs at home, run multiple chargers, charge multiple packs, charge larger packs, etc.

The first step in determining which power supply to get is to decide what battery packs you need to charge and how you want to charge them. Depending on your finances it is best to also think at least a year or two down the road. Remember that your power supply will most likely last you a lifetime so it will be money well spent. In addition, maybe your current heli just needs 3S packs but are you sure you are not going to move up to 5S or 6S or more later? If so, plan for what you think your largest needs will be. Once you have done all that it is just a question of watts.

Watts = Voltage x Amperage

So, assuming a 3S 2100 mAh pack that will be charged at 1C, that gives you: 4.2 (max volts per lipo cell) x 3 (number of cells) x 2.1 (amps at 1C) = 26.46 watts. So all you need is a power supply that can supply 26.46 watts. Well almost….

The charger itself draws power so you will always want to have a bit of extra power in there, so add in another 10-20 watts. In addition, are you going to want to charge more than one pack at a time? Are you going to want to run more than one charger at a time? If so, start adding up the watts. If you can charge two 3S packs at the same time on one charger and you want to run two chargers then you are going to need a power supply that can supply 106 watts minimum and probably more like 125 watts. Moreover, you will need to make sure the power supply outputs the proper voltage needed by your charger (normally between 10v and 15v) and will also supply enough amperage. Lastly, you will want to choose a power supply with the physical dimensions you may need (such as if you want to transport it) and that has good cooling (some cheaper power supplies do not have a fan or a use a poor quality fan).

Here is a real life example to illustrate another potential hurdle. I wanted to be able to run two chargers that were each going to charge a 6S 5000 mAh pack at 1C. Thus I needed a 252 watt minimum power supply.  I figured I would need 275 watts to be conservative. I chose the Team Integy Super Power Station 36A 12V Power Supply. That gave me 432 watts of power! In addition, the Power Station provides two 18A terminals with output jacks and one 36A terminal. This also seemed perfect as each charger only needed 11v and 5A so I could run one charger off of each of the 18A terminals. Well after getting everything hooked up and running the charge would quit after about a minute with a low voltage error on the chargers. How could this be? I tried hooking the chargers up in every way I could think of, one on the 18A, one on the 36A, etc, etc. No good. I contacted Integy and they basically replied saying, “Yeah it should work fine.” I was going to give up hope until one day I noticed on the back of the unit there was a metal tab marked “18A/36A.” It was set for 18A. I moved it to the 36A setting. This disabled the two 18A outputs but now the 36A output provided enough power to run the two chargers! So the moral of the story is that even if you have all the proper specs there may still be some oddity with the power supply you will have to figure out. Thus to save yourself some hassle it is best to use a charger that others recommend for your needs or that you will at least be able to return if it does not work out.

Team Checkpoint

Team Checkpoint

Of course not long after all of that trouble I discovered that others at my local flying club use the Team Checkpoint 12Volt 25Amp Racing DC Power Supply (300 watts) to run the same charging setup I was doing at half the price. Typical.

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