No spark resistor

[Boaterguy]

so today I canged out my 119 ohm resistor (4 sec charge time) for a smaller one, because it was heating up during charging. I went to the no spark calculator, and with 3350uF on 5S it told me to use 15 ohms.
I soldered up a 15 ohm resistor (brown, green, black, gold) and plugged it in. the resistor puffed up in smoke and I disconnected everything as quick as possible.
what happened? did I do something wrong? the resistor is pretty old (from my 50 yr old uncles university days) but doesn't look or work any different than a modern resistor, the previous one was just as old and worked fine.

[m4a1usr]

Do you know what wattage the 15 ohm was? You should probably using at least a 2 watt. As resistance values go down, surge current will increase.

John

[Boaterguy]

How do I figure out the wattage of a resistor?

[m4a1usr]

Resistors come in different wattage values( 1/8w, 1/4w, 1/2w, 1w etc) usually printed on them.

Read more: http://www.bcae1.com/resistrs.htm
John

[Boaterguy]

Thank you, I'll just go buy one instead of going through old ones.

[kookie_guy]

The wattage was way too low. If it looked like your average size resistor, then it was probably 1/4 or 1/2 watt. 2 watt is the minimum you should be using.

[m4a1usr]

Always remember to disconnect the anti spark circuit once the main battery/esc bullet has been connected. Leaving the anti spark resistor connected will only generate waste heat. Its not supposed to remain connected once the main bullets are attached.

John

[Flying Scotsman]

Thank you John for all your expert knowledge.....do you still have a torpedo kicking around in the basement?

Douggie

[Jacked1]

You will want a resistor that it's wattage is more than (V^2)/R. Power=(V^2)/R
V is your battery voltage and R is the resistance. :)
This will guarantee that you have no more resistor fires.

[Boaterguy]

okay, R at 15, voltage at 18.5. I get 22.5 watts, I don't know if I can find a 23 watt resistor anywhere.

[Jacked1]

A 10 Ohm 2watt will do for this. (That is what i have) I was thinking RMS on my other post , that would work for any application you would need a resistor for.

[Boaterguy]

will have to survive without one for tomorrow but when I get back I'll get around to getting one.

[m4a1usr]

Thank you John for all your expert knowledge.....do you still have a torpedo kicking around in the basement?

Douggie

Ha, ha. You ole' dog Douggie. Nah. While I tried to edge on the side of the markets and inflation, possesion of government hardware only garantees a lifetime membership in to a change in lifestyle choices. I prefer as an alternative to pick up cans along the road side as my retirement plan. Whats the worst that can happen? I become a Democrat and glue myazz to the "system"?

John

[norbique]

I use 18 ohm 2w resistors on my 6s setups. Work well. Resistors become slightly warm but nothing serious. I'm charging 5000uF total cap.

[drwayne]

I use 10ohm5W ceramic block ----[10R 5W ]----
on 6S for 8800uf
25cents
2second charge time.
cool as a cucumber ...

some think batts are not connected because click, click, click, no zap !

W