2.6 kJ (~66000uf, 280v) Capacitor Bank - Page 1
Forum section: electronics / projects

author: AppliedVoltage
author_rank: Newbie
timestamp: March 11, 2013, 03:55:16 am
content: Thought you guys might like some high power stuff.This is a project I was working on before school started and the weather got cold. It's a decently sized capacitor bank, utilizing some big RIFA capacitors.The capacitors are 7290uf 280v RIFA brand. I haven't tested the actual capacitance of the bank, but I think it's probably rather close to the 66000uf mark.Here's the actual bank. The busbars are just some aluminum stock we had laying around. The wiring is some scrap 6 gauge, which handles the discharges with no problem.This was the switch I was using for the low voltage discharges (<42v). It started spouting sparks when I discharged it at 40v, so I abandoned it.These are the type of interconnects I'm using, to make things easier on myself. They're Anderson SB-50 600v rated quick connects, designed for the 6 gauge cable I'm using.Here was the 40 volt power supply... somehow a 12v transformer supply and a 12v battery charger put out 40v in series.Here's the charging resistor. 10 ohms when unheated, probably a bit more when 40 volts is put through it, and a lot more at 120v. It worked (and works) excellently. I also used these for discharging.I've changed the project quite a bit from when these pictures were taken. Nowadays I use a fused bridge rectifier straight off of the mains to charge it up to just under 170 volts. 3 series 100w light bulbs limit the current to a reasonable level. I also abandoned the switch in favor of just banging some battery clamps on each other. At some point I'll have some fresh pictures and maybe a video of the new bank.When I did a discharge test (shorting it out) at 100v, it vapourised some of the copper contact of my battery clamp. Anyone happen to know the formula or equation to figure the maximum amount of amps this thing can deliver? I'd imagine it's got to be in the realm ofridiculously highafter seeing that test.

author: Psi
author_rank: Super Contributor
timestamp: March 11, 2013, 04:15:17 am
content: Quote from: AppliedVoltage on March 11, 2013, 03:55:16 amYou first need to look up the capacitors series resistance from the datasheet and then work out the resistance of your busbars/wiring.Then V / Rtotal = I

author: M. András
author_rank: Super Contributor
timestamp: March 11, 2013, 09:42:41 am
content: hmm wondering about the sizes of those railgun cap banks which uncle sam uses on their prototype

author: mzzj
author_rank: Super Contributor
timestamp: March 11, 2013, 09:58:58 am
content: Quote from: AppliedVoltage on March 11, 2013, 03:55:16 am

author: AppliedVoltage
author_rank: Newbie
timestamp: March 13, 2013, 02:07:09 pm
content: Quote from: Psi on March 11, 2013, 04:15:17 amThanks! Now to actually find the datasheet...Quote from: mzzj on March 11, 2013, 09:58:58 amCap bank jealousy... description says over 100kj? That's some crazy stuff!

author: Neilm
author_rank: Super Contributor
timestamp: March 13, 2013, 08:37:31 pm
content: Quote from: AppliedVoltage on March 13, 2013, 02:07:09 pmI didn't find the datasheet for the actual devices, but I found one for a 8800uF cap in the same serieshere. The ESR for that was 15mOhms at 100Hz. Work out the resistance in your leads - I suspect they (including the connector) are the majority of the resistance.Neil