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Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
It works by Energy = (V^2 * C) / 2
It does not hurt the capacitors, they are made for it. What will hurt them is high temperatures(above 20 deg C will quickly reduce the lifetime of most capacitors) and excessive current.
Some capacitors also can take significant overvoltage for limited periods of time without taking too much damage. It is a cheap but not safe way to double your energy.
Registered Member #32
Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549
Cwazy wrote ...
ummm how does that work?? and doesnt constant charging of caps to their limit actually hurt the caps?
Going above in voltage gradually (or not so gradually) damages them. In pro applications, engineers leave a good safety margin to prolong life. Coilgunners don't care so much, as their caps don't get anything like so many working hours as, say, the caps in a power supply unit.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
24V is probably pushing the limit. Especially since those caps are used, I wouldn't go above 15V. It's the worst thing when you notice one of your capacitors it bulging, and even though it still works at the time you know its dying...
Registered Member #1106
Joined: Thu Nov 08 2007, 01:15AM
Location: Seattle, Washington
Posts: 25
ahh..haha so too much..what if i did the 2 banks in series (30v) and i charged that to 36v? would that be pushing too much as well?? the reason i would want to over charge is because when i use either 12v or 24v, i get close to 60j, but if i over charge it, i get close to 250j. thats a 4x imcrease in energy!
Registered Member #32
Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549
Overvolting caps is something I might do for a once-off project but not something I'd do for a project I'd use again and again.
Take seriously what Shaun is saying about bulging caps. Electrolytics don't pop, they go bang, and it's always surprising how big a bang a little cap can make.
Registered Member #1106
Joined: Thu Nov 08 2007, 01:15AM
Location: Seattle, Washington
Posts: 25
can i put the diode before the switch???
and also, how fast do the caps charge with the battery?? because i think i'll have 36v battery charging 30v caps, will i have enough time to turn off the charging curcuit before the voltage in the caps goes over??
and would this terminal strip work for my settup on my coils?? i plan to have breaks at 2 layers, 4 layers and 6 layers.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
You will probably not have enough time. An uncharged capacitor will act like a short circuit, drawing a huge amount of current to charge itself. Your batteries can probably handle that, but in order to slow charging enough for you to disconnect them at the right time, you would need to charge through a resistor so current is limited.
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New Coilgun plans..need feedback
