Espritmodel.com Telemetry Radio
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Old Jan 30, 2013, 12:39 AM
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Victorville, CA
Joined Jun 2006
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Yeah, mine's bare-bones. No covering, feet or anything. No 12V connectors, only 24V with like I said, a Deans T-connector. I may stick some feet on it if that seems necessary when I get it to the field. I did make a Y-cord for the supply. I had a few power cords so I cut two of them and soldered into a Y. I didn't count that time in the hour since I did that after I posted. No extra fan grill either. Folks will have to keep their fingers out of there.
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Old Jan 31, 2013, 10:43 PM
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I read this entire thread and probably missed it, but what happens if DC ground is floated on both units in a 24volt configuration?
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Old Jan 31, 2013, 11:01 PM
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Victorville, CA
Joined Jun 2006
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Some seem to think it is a problem. I don't, however, being lazy, I only did the one. You don't have to open up the case if you don't float the ground.
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Old Jan 31, 2013, 11:08 PM
Stop scaring my donkey!
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Danger will Robinson!
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Old Jan 31, 2013, 11:10 PM
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Nonsense, have you tried it?
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Old Feb 01, 2013, 04:59 AM
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Isolating both power supply outputs will increase the possibility that high voltage can appear on the output should you have an internal fault in a power supply. In addition, if you connect your charger to your PC which may be grounded, the fact that the power supply output is floating may cause damage.
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Old Feb 01, 2013, 05:59 AM
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Melbourne, Australia
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Quote:
Originally Posted by feathermerchant View Post
Isolating both power supply outputs will increase the possibility that high voltage can appear on the output should you have an internal fault in a power supply.
Yes, possible. Multiple threads discussing this everywhere. Basically, if the numbers are correct, you're more likely to be hurt by an out-of-control RC bird.

Quote:
Originally Posted by feathermerchant View Post
In addition, if you connect your charger to your PC which may be grounded, the fact that the power supply output is floating may cause damage.
This is new to me. On the surface, the only way this can happen is somehow the zero entire unit builds up enough charge that the zero is in the low hundreds of volts potential diff with earth, that instantaneously zaps when connected to earth through your cable. Kinda like a static discharge.
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Old Feb 01, 2013, 07:47 AM
Use the 4S Luke
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Remember that there is a transformer in the power supply. It just operates at something like 20kHz instead of 60Hz. A transformer can short primary to secondary making for high voltage on the output side.
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Old Feb 01, 2013, 07:50 AM
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Danger.....
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Old Feb 01, 2013, 08:07 AM
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Ok, kinda thought it would be a bad idea, just wanted to make sure.
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Old Feb 01, 2013, 09:57 AM
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Victorville, CA
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Quote:
Originally Posted by feathermerchant View Post
Remember that there is a transformer in the power supply. It just operates at something like 20kHz instead of 60Hz. A transformer can short primary to secondary making for high voltage on the output side.
Have you ever seen this happen? Maybe if you were using a toroidal transformer and you somehow dropped it and was able to scuff the coated wires but I have never had a transformer short from the high side to the low side. Even if it did, having 120v on the output would still be there even if the grounds were connected. Nothing would happen unless you shorted them. All they would do is burn out your charger. The only time it might be a danger to you is if you grabbed both leads and even then I doubt the main fuse would pop unless you had it plugged into a ground fault circuit. Having the ground lifted in one of the units can still cause the scenario you worry about as that side could still do that.

Anyway, it is easier to just do one so it is probably a moot point.
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Old Feb 01, 2013, 10:11 AM
Stop scaring my donkey!
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Moot I reckon. Good pun!
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Old Feb 01, 2013, 05:36 PM
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Quote:
Originally Posted by feathermerchant View Post
Remember that there is a transformer in the power supply. It just operates at something like 20kHz instead of 60Hz. A transformer can short primary to secondary making for high voltage on the output side.
These are datacenter PSU's - on some of the most commonly used equipment in the world. 240/110V to output is bad news for these and we would surely hear a lot about them since this is a definite outage and data loss scenario.
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Old Feb 01, 2013, 06:12 PM
Stop scaring my donkey!
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Hi, I'm Reddi Killowatt, and I'm here to help you....
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Old Feb 01, 2013, 06:15 PM
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Victorville, CA
Joined Jun 2006
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Took my PSU to the field today to show off to my friends. One of the Pattern guys picks it up and says "Hey this is pretty light. My power supply weighs a lot more, how many amps is it?" I say it's 47 amp and he says "Oh mine is 70amp." I say, "How are you powering that, because mine uses up a 15 amp household circuit? He says it's not a problem so I ask how many volts are you putting out and he says 12V. Ah I say, mine is 25V. HE asks how that matters and I do the math for him. 12V*70A=840W. 25V*47A=1175W. Top that with the fact that your charger will run much cooler on the higher voltage since it doesn't have to work so hard to convert 25V to the 38V his 10S packs are using and he's like "Dude, build me one!". I tried to talk him into buying one from one of you guys who builds these things for sale but says he wants a bare bones one exactly like mine. Looks like I have to build another.

Blessings, Terry
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