I recently had a few days were it looked like we were going to be able to go out and fly our foamy electric, but it alway got windy or something else came up. So, I had the 7.2v battery in the car quick-charger and everytime I went somewhere it would start out charging. It came up to full a couple times, but whenever I would turn the car off it would restart the cycle and act like it was taking more charge.
SO today we actually ALMOST flew, but immediately upon pluging it in, the thing in the picture fried and broke the circut. I thought maybe it was some diode that was a safety thing. (ie TOTALLY unneccesary) And since the battery tested at 8v (seemed a bit high) and we didn't have another, well... you guessed it. I removed it and promptly fried the reciever. *SIGH*

My question is... WHY? Is that .8v really enough to do damage? Is that even what casued it? What IS that stupid little thing, anyways?

Time to upgrade to a three channel.

PS - I am still wondering if anyone knows where to get small electric-motor type propellers.

nesail.com

That looks like a filtering capacitor but I may be mistaken....

It may have been providing a path to ground too, which you removed.


What you experience with the charger is normal. Don't agonize about the fact that the charger always wants to recharge the battery.

Usually when this happens you'll find that it will only continue for a few minutes before it thinks the battery is fully charged.


Diodes are NEVER "TOTALLY unnecessary"! Quite the opposte.

Always remember that the manufacturers NEVER EVER want to use more electronic components than they ABSOLUTELY have to, as this increases their costs.

They will always pare things down to the minimum required to get the job done and stay within specifications.

So don't assume that any electronic part is unneeded.

I guess I didn't make clear the fact that this was actually ON the battery packs negative lead. I'm starting to wonder if it's not some kind of fuse, actually, as I'm starting to think the reciever may actually be OK - it got hot enought to melt the foam, but one of the engines seems to be shorting out the works and the other works fine w/o heating up anything. Granted, it's been crashed many multiple times, once even in the water, so I shouldn't be surprised, but I am always painfully aware I know just enough about electronics to be dangerous. A smart man would have chucked the thing and bought a new one, but I just love to test and tinker. No wonder I like this hobby!

That is not a fuse.

It looks like a filtering capacitor as I mentioned.

It may have not been the cause or the source of the problem as you are suggesting, but it may have been the "recipient" of the current flow and heat.

I discovered that the reciever was fine, despite having gotten so hot. The one engines malfunction caused the little yellow component to burn out.
I accidentally discoverd that unlike some electric motors, these can't have the polarity reversed. So now I have two fried engines - Oh, well- I wanted to upgrade, anyways.

Yep, that's a cap. Capacitors perform very important functions within circuits and must be replaced. Because they resist changes in voltage they are often used in filtering but can have many other uses. Get a replacement and some 60/40 SnPb (Tin/Lead) rosin flux core solder. Use a low wattage iron and solder the new one in. Remember, heat the work and NOT the solder. This way the solder will stick. The joint should be shiny. If the joint is moved while setting, not heated enough, or otherwise contaminated it will be dull/discolored. Don't go overboard with the solder either, use just enough to fill the copper pad on the PCB.

REPLACE IT!!

If this is a capacitor, shouldn't it have a micro or pico farad rating? I ask because I took it to an electronics shop and the guy said it was a 7 amp (7A) micro-fuse. It did ACT like a fuse in that it cut off the battery's power when the enigine shorted the works.

If it is a capacitor, where would you recomend I find a replacment? I don't see any on the net. (But I don't see the micro-fuses, either.)

It's a cap. The guy's guessing. I bet I could find the exact part at Digikey if I took the time to do so.... but...

Discreet fuses are never placed on RC motors.... ( it's easier and cheaper to put in a fusible link if someone even thinks to use one... ).

Capacitors are all but mandatory.

They are used to lower the amount of RF noise generated by brushed motors

Look for replacement capacitors on Tower's site or any other that sells brushed RC motors.

It does have a capacitance rating, but it's almost never printed on the cap plain as day. It's be something like "103". And second the symbols on the cap look like they may be manufacturer specific. It's nothing I recognize.

If you go to Tower, they should have one (as mentioned) and if you knew the manufacturer and contacted them, they might give you the specs. In which case DigiKey of Jameco or you local supply house could get a replacement......

Any of the capacitors supplied with the 370, 400 or 500 brushed motors would work fine.

I think the same size is used on all of those motors.

It's a 7 amp fuse. The LF on the side is the manufacturers ID-Little Fuse. The 7A is the fuse rating of 7 Amps. I've used a bunch of this type here at work.
http://www.littelfuse.com/data/en/Da...ts/251_253.pdf is a data sheet for this fuse or one VERY close to it.

As to WHY it fried the RX? The fuse was protecting the circuit. Something (most likely the RX) was drawing too much power. By by-passing the fuse you removed the protection and allowed the bad RX to draw as much power as the battery could supply. That must have been over 7 amps or the fuse wouldn't have blown in the firt place. The RX had probably already failed. You finished it off and made any warranty worthless.[:@]

OK - that makes some sence, however, as I mentioned - the RX is seemingly fine. It appears as though the bad motor caused the fuse, which was on the battery pack itself, to go. And once I DID bypass it, the receiver got hot (which I was sure burned it out, but a nice heat sink may have save my bacon.).
All this comes off of the Estes Sky Rangers Blue Angles ROG Twin-Otter-looking airplane, which has seen a LOT of crashes (our 1st plane.) so it's not much of a surprise.

So my next question is - do most battery packs have these fuses? I'm tempted to start dissecting to find out, but hate to risk damaging them.

Now you found out why you should never bypass a fuse. They are there for a reason!

By now I'm a bit confused as to what went where, so I don't know if I'll be able to help much.

Sounds like the "system" started to pull too much current and began to heat up. After a bit of time the fuse finally blew and protected what was left. Then you bypassed the fuse and this allowed virtually unlimited current through the RX until it fried. The RX may have a built-in ESC for the motors and when one went bad is sucked too hard on the battery. Eventually it found the weak spot in the design and the RX gave up. Time for more money now.[:@] Sorry

Ahhhhh! I see CGR in the wings. Will post a picture soon of the SeaMaster 120.. Sorry I didn't have a coast guard decal to put on the side.