For those who tried the 1F tank!!! - Page 3

starfox · 01-08-2004, 02:24 AM

lol okay. agreed, i misread a few posts above.

i think we need more sticky threads, and maybe some more moderators on these boards to maintain the sticky threads. There's so many repeated posts asking the same questions over and over...

sorry about making the thread topic fork..

Ricky327 · 01-08-2004, 02:34 AM

Again I agree with you

This 1F come up so much and some are just fed up explaining so they dont bother. But newbies kept seeing this wonderfull looking dangerous 1F bomb (as you said) tank circuit and so they ask again.

To end it all...we can conclude that the battery is the one to go for if crank survival is needed for good or bad PSU design such as the inverters.

From "none" is saying a small capacitor is all that needed for a good PSU such as the sproggy design.

NOW someone make this thread sticky as recomemded by "starfox"

starfox · 01-08-2004, 02:37 AM

Might be better to write a FAQ, post it up in the newbie section then ask a moderator to make it sticky..

masch · 01-08-2004, 04:44 AM

1F capacitors? Why are they dangerous? I dont see any reason. Its just electronics right? What's a few mA can kill you is it?

Btw, if that's true that the sproggys 12V is derived from the 5V regulated stepped up, then why doesnt all the DC power supplies use this design?

starfox · 01-08-2004, 06:25 AM

1F cap is tens of amps or hundreds of volts! It's nothing to laugh at.
Normal capacitors are in the pico or microfarads.

I'd imagine that if you dropped a charged 1F cap from high enough, it would explode and leave a large crater in the ground, and you would smell a lot of ozone

Rob Withey · 01-08-2004, 07:04 AM

Quote: Originally Posted by starfox

1F cap is tens of amps or hundreds of volts! It's nothing to laugh at.

I wouldn't expect high voltages in a car application unless you are using some quite exotic charging circuitry, and lead acids are capable of supplying large quantities of current too.

Rob

Ricky327 · 01-08-2004, 09:10 AM

Yes capacitor is not a joke, just shorting them out when fully charge can give you a serious scare

I have shorted a 10,000uF at 30V once...bang flying molten metal, it actually melted my screw driver and the terminals

Its not the capacitor electric that will kill you its the build up pressure inside the capacitor when used wrongly. So much pressure will break the casing suddenly and acting like a bomb.

Well normally large capacitors do have some vent to allow excess pressure escape... but they can always fail.

Heres a link about big capacitors :

http://www.diyaudio.com/forums/showthread/t-755.html

Btw, if that's true that the sproggys 12V is derived from the 5V regulated stepped up, then why doesnt all the DC power supplies use this design?

Because its more expensive and awkward to make a step-up regulator.

Ricky327 · 01-08-2004, 09:11 AM

starfox, read your PM

starfox · 01-08-2004, 09:15 AM

Sorry Rob, forgot to say some more stuff.. i meant that 1F caps are also used in industry where they need to buffer large voltage spikes, that's where the hundreds of volts is from... should probably explain myself more..

choyak · 08-01-2004, 07:42 PM

A 1F cap is severely dangerous when the terminals are inadvertently shorted. The ESR is so low that a humongous current will flow to discharge the energy. This could be thousands of amps flowing

no1knows · 08-01-2004, 08:03 PM

I have a 1 Farad capacitor and a 150W inverter triggered by an ITPS, botht he inverter and capacitor are from maplin.co.uk. This setup survives the 1st crank, but if that fails and i crank a second time it may sometimes reboot. ITPS' as a rule do not survive crank due to their inbuilt voltage drops, so i can only think that the capacitor is keeping the voltage high enough for the ITPS to keep the relay triggered.

Never intended for the capacitor to do this but it does seem to work. I think ill be making a battery tank when i fiberglass in my goodies.

O, and btw, high voltage from a capacitor? The voltage in/out of a capacitor is the same, unless u wire it up to mains (which will blow an automotive capacitor) in which case you are going to see high voltages.

Regards

Ricky327 · 08-01-2004, 08:14 PM

Wow this thread is old, anyway...

The 150W inverter from maplin minimum operating voltage is about 10.5-11V from what i can remember.

It is possible that your battery goes just around that inverters minimum operating voltage during cranking and therefore survive the crank.

The relay should be able to hold itself much lower than 10V. Try it without the capacitor and see if it make any difference

stimps · 08-01-2004, 08:29 PM

im amazed so many people thought a 1F would be the go. Wiegh it up. On one hand you have a capacitor that costs a small bloody fortune, and discharges slowly as soon as it is needed. Hardly siutable for a "rock solid" power supply requirment. On the other hand you have a small Lead Acid sealed battery, which costs like, 10 dollars (you can use the really small ones i mean really no problems!) and it will keep the computer going for up to 5 minutes of cranking!!

No contest my freinds. Use a tank battery.

nzKAOSnz · 10-14-2004, 05:58 PM

hmmm. Huge amps etc - havent any of you played with a disposible camera flash...? A small cap, and F*** that hurts............

EDIT: oops. jst saw how old that was.......