Power supply for big Eheli?

[Laurens]

I am thinking about slowly converting to Eheli's. Now at this moment I don't have a power supply, but I am looking for one. I've seen a 20A and a 30A power supply. I was wondering if the 20 A will do if I ever buy a 12S lipo heli.

[MinAirChris]

If you just want a supply to run battery chargers, yes. However if you want a supply to actually do the charging, then maybe not.

It's not so much the current that you need to look for so much as the ability to regulate voltage very closely under a heavy load. Generally speaking, what you want is a power supply that can regulate within 0.1 volt while supplying a load of at least 75% of it's rated value... a lab grade supply. Look to your local electronics surplus stores for these. Don't be surprised to spend several hundred dollars for a good used supply. Good supplies are made by Kepco, Hewlet Packard, and Sorenson just name a few.

I use a Kepco supply that can source 0 to 60 volts at 0 to 10 amps. I paid $250 for it used 12 years ago. It has worked well for me.

I also have a simple 13.8V fixed voltage supply that can source 20 amps for my chargers, this works just fine. I can charge two 5S4P packs at 4 amps each without overloading the supply. I think I paid $75 for that unit on EBAY.

Chris

[Laurens]

I made the mistake of looking at the wrong price for a IonX conversion kit, so I won't be buying a Ionx. I might stop at logo 14 max, so I'll buy a 20A supply.

[buster1]

Chris, I hear you can get a 25 or 50amp power supply from radio shack, I hear they work well. What do you think
Jeff

[Russ McC]

If you want to run two chargers, in my case two Astro 109s at there rated output you need 35 to 40 amps. I am using a Pyramid 35amp #PS-36KX, I got it off Ebay from a mew retailer, don’t remember who. This thing works great but its heavy so now I just use it at home. I now have two 23amp 13.8VDC Samlex America SEC 1223 supplies that are light and fit in the bottom of my tool box with the chargers. I bought them from a local Samlex dealer and got ripped off but they are great. A friend who works in a hobby shop said they had them for like 80 or $90 a piece I think, you don’t want to hear what I paid :arggg: So look around, prices my vary widely :glasses2:

[Russ McC]

I have friends who are using the Radio Shack supplies and they are working good last I heard, they are using two of the 25amp units, one for each charger just as I am using two of the Samlex supplies :cool:

[MinAirChris]

If all you want is a supply to run chargers, then pretty much any brand will do if it has the proper current capability. To determine your current needs:

Power in = power out + inefficiencies

So, if you want to charge a 5s4p battery at 1C (8 amps), at full voltage the charger has to put out 168 watts, which means it pulls a little better than 12 amps, (21V*8A)/13.8V=12.17amps. Figure at least 10% in heat losses (inefficiencies) and maybe another 10% for overhead and your up to 14.6 amps. If you want to use two chargers at once, then you need to double that to 29.2 amps. Now your up to a power supply that can source 403 watts...lots of copper and hence weight.

Some would try to sidestep this weight/cost and use a switching supply of the nature that is to be had from common computer power supplies. This can be done, but I would caution the individual to watch those first few charges as switchers tend to leave some ripple on their output which may lead to havok with the charger.

Chris

[skippy]

You don't need to buy a heavy power supply. Here is what I use and it works great. They have a 25amp and 45amp.

http://www.mfjenterprises.com/products.php?catid=18