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batteries plugged in backwards

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Old 10-24-2005, 01:56 PM
  #1
f4b4
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Default batteries plugged in backwards

hi guys,
I have a question about plugging a rx battery in backwards. On two occasions , i have plugged the battery in a rx backwards, not in the battery position possibly. The first time ,i saw smoke come from the rx,ipulled the plug and the pins of the rx came out and the wire burned in to my fingers ( ouch) .The second time ,I did it ,the battert burst into flames in my hands and i got rid of it fast. Ihave been flying for about 20 yrs. and work in the local hobby shop .The guys here say it can not hapeen.
What ,I want to know is have any of you ever had something like this happen.Bear in mind ,it could have been plugged into a channel .



thanks in advance Jerry b
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Old 10-24-2005, 02:19 PM
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2slow2matter
 
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Default RE: batteries plugged in backwards

On Rx's, there really doesn't need to be a dedicated slot for a battery. If fact, some receivers just use one of their "channel" slots for power. If you need that slot for an actual channel, then you can use a Y--one end to the battery, and one end to the servo. You could actually plug a battery into every slot on the RX if you wanted--just use Y's to hook the battery and servos to the channels together. You would still have 4.8 v (if all batteries were 4 cell), but you'd have a bunch of mah possible!

Back to the question--plugging a battery in backwards. If it is a dedicated battery slot (such as found on some rx), then it shouldn't hurt--because there should only be two prongs inside of the slot, and plugging the battery in backward wouldn't result in any current being pulled. However, if you plugged it into an operating channel, where there are three male prongs inside, then plugging it in backwards could have some negative consequences.

I believe most rx's have reverse polarity protection, but I could be wrong on this.
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Old 10-25-2005, 09:12 AM
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LesUyeda
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Default RE: batteries plugged in backwards

Depends on the radio. Most of the Futaba (and most of the current everyone else) has the positive lead on the center pin, ground on one of the outside pins, and signal on the other. Plugging that combination in backwards would result in postive being where it belonged, and no short would occur.

Most of the receivers that I am acquainted with have no reverse polarity protection.

Les
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Old 10-25-2005, 11:07 AM
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Default RE: batteries plugged in backwards

I can not speak for all models of the receivers but; the Futaba 127 will short out the battery if you plug it in backwards into the battery slot. If you plug it into any other slot, no harm--just won't work--but thelead that is normally the signal lead (in inside pin) is shorted directly to the center pin (the positive lead) by copper lands on the receiver printed circuit board on the battery slot only.
This results in a dead short accross the battery if you plug it in backwards resulting in lots of smoke and burned out wireing. If you doubt this, just remove the case and take a visual check.
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Old 10-26-2005, 09:09 AM
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LesUyeda
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Default RE: batteries plugged in backwards

With all of these "universal" connectors on things these days, if I had a 127, I would take my exacto knife and remove that connection, or better yet, cut off the pin that goes to that connection.

Les
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Old 10-27-2005, 08:14 PM
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Default RE: batteries plugged in backwards

I saw a buddy of mine burn up a battery. He uses Futaba almost exclusively. I assume it was a Futaba rx, but I don't know the model. I'm just glad he had the wing off the plane when he turned the switch on. If the wing had been bolted on, the whole plane probably would've burned. As it was, he just lost the battery and switch harness.
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Old 10-27-2005, 08:17 PM
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Default RE: batteries plugged in backwards

Quote:
ORIGINAL: LesUyeda

Depends on the radio. Most of the Futaba (and most of the current everyone else) has the positive lead on the center pin, ground on one of the outside pins, and signal on the other. Plugging that combination in backwards would result in postive being where it belonged, and no short would occur.

Most of the receivers that I am acquainted with have no reverse polarity protection.

Les
Futaba does, if you stick with their stuff. It's the little tab on the plug.
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Old 10-27-2005, 09:13 PM
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Default RE: batteries plugged in backwards

Boy you guys are nice!!! I bought a 2700maH NimH JR battery and hooked it up to my Futaba receiver and of course it was hooked up backwards. The pack got immediately warm (it was still in my hand), so I pulled it and switched it around. The way I can tell the correct polarity, is that the plug on either Futaba, JR, or Hitec all have bevels on the plug. Match the plug as per the wiring on what you're used to (IE match the bevel in the correct way it's plugged in).

I posted my backwards battery question on the battery forum and got grilled for not checking polarity with a volt meter!

MPB
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Old 10-31-2005, 06:08 PM
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Default RE: batteries plugged in backwards

Guys ,thanks for all the input, you anwsered my questions and I'm glad I didn't imagine this .Thanks for everything . F4B4
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Old 10-31-2005, 06:35 PM
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Default RE: batteries plugged in backwards

Just yesterday, I was helping a friend with his Futaba Receiver. Not sure the model, but it was a 7 channel full-size receiver. I plugged a battery directly into the battery slot without regard for polarity and smoke poured out from the wires to the battery. I do this all the time with my JR receivers and no trouble. The red wire is on the center pin, so plugging it in backwards puts the "hot" (red) wire in the same place but the ground (brown/black) ends up where the signal should be. This should cause no problem.

But it certainly did on this particular Futaba receiver. The receiver was not totally damaged becasue the pins inside the battery slot melted off. we just used the channel 7 slot for the battery from here on out.
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Old 11-01-2005, 12:36 PM
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Default RE: batteries plugged in backwards

Haven't done it the way you did, but I had everything in my G-202 in and plugged, and running the last wing bolt in, ran it through a wire somehow and it caused them to break and touch. It smoked very bad, and you can't imagine how long it took to get all the dumb wing bolts out. Melted all the wiring on the radio and the battery. Luckilly it didn't burst. Trashed 6 servos, 2 3 foot extextions, a battery and a brand new PCM Rx. Sent the RX in to be fixed and threw the rest away. Not a good move.
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Old 11-02-2005, 04:07 PM
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Default RE: batteries plugged in backwards

It sure would be nice to have some Futaba input on this topic. That is about the dumbest thing I have heard of in a long time. I would like to know what their reason is for shorting the unused pin on the battery slot to the hot lead in the center. That is just dumb!!
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