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Old 06-20-2018, 11:43 PM
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Aaron Aaron is offline
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Join Date: Feb 2007
Location: Washington State
Posts: 11,005
cap dump

Originally Posted by 2SeeMore View Post
I've been posting on the Beginners Handbook thread and remain very much a beginner, but now I want to add a cap discharge system so I can use my SG to rejuvenate car batteries - so here I am.

I couldn't find a photoflash type cap here in Costa Rica so I'll be ordering from the states and want to make sure I get it right.

Peter says photoflash caps are best but doesn't give details about ideal voltage or uF ranges. Though he shows an "example" cap of 15,000 uF and 80V, if I disconnect an output wire to my charge battery the neons come on, indicating the radiant spike is always over 100v so it seems like an 80v cap wouldn't be enough.

Any advice on the specs I should be looking for, and whether to get one or more caps?

Also, I'm thinking a simple cam activated switch is probably the easiest to start with, and I found these super cheap ones on Amazon -
Any feedback about whether they'll work?

Depending on the whole coil, the spikes can be hundreds of volts.

However, with 15k uf, the capacitance is large enough that you will never top the voltage. The goal is to dump the cap when it is ballpark several volts above the charging battery voltage at minimum. On Bedini's cap dump, it is common for it do dump when the voltage in the cap bank is twice the charging battery voltage and that is ok too.

John's cap dump has a comparitor to look at the charging batt voltage - probably too advanced at this point to try to do something like that, but you can do it by a timer - Peter provides a circuit in the book. You have to make sure to watch the charging battery so you can turn it off when the voltage is high enough.

80v 15k uf is the exact cap John uses in his larger cap dump circuits. 4 of them to be exact - in series and parallel.

Find the lowest ESR - effective series resistance - caps you can find. Those dump the fastest.

Anyway, the ones John used are from this company: United Chemi-Con | Aluminum Electrolytic Capacitors
Aaron Murakami

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