Need recom on capacitors for ripple filtering

[mbryner]

Got myself a new Midnight Solar Classic 200 charge controller for Xmas.   Now I don't have to use a rheostat to dial down the voltage to feed the Outback MX80 anymore.    The Outback can be dedicated to PV, and the new Classic 200 will be dedicated to Listeroid battery bank charging and future microhydro.

One of the guys on this forum is a employee of Midnight Solar and has been charging with his Listeroid via a Classic 200 also.   He has been using the VOC% mode set to 76% which loads down the 'roid good.    I had to set it to 61-63% VOC, which draws down the voltage from 160-170 peak DC to around 100 V.   That ends up around 2000+ watts (~40 amps).    I kept tripping the 60 amp DC breaker, so I had to switch to an 80 amp breaker.   Bear in mind that this is rectified single-phase 120 V AC, going through a large choke, into the charge controller.    I'm guessing the reason why the large amps through the breakers is that the charge controller is pulse charging w/ larger amperage (?).   I'm also guessing that the choke is not adequate for the purposes of smoothing ripple voltage at large amperage.

Do any of you have any suggestions of high capacity capacitors?   Where to get?  What size?   The forum member is using 5900MFD, 450VDC rated capacitors, but they are quite expensive on ebay and digikey is mind baffling.   Not going to try to make a tuned LC circuit because the amperage will be variable and I don't know much about the choke (it's just an old large transformer).   Probably just take out the choke and try w/ caps.

Thanks for any suggestions,
Marcus

mod:
P.S.  also, any recommendations on a momentary (few second) contact relay for the energize coil on my fuel solenoid?

[Jens]

Breakers generally rely on heating action and would average out the pulses of current going through but this is for AC breakers. I do not know if DC breakers are using a different tripping process.

As far as capacitors is concerned, I would suggest you try locating an electrician that does preventative maintenance on industrial lighting. I think it is HID lights that use a gigantic cap, 450V rated and about the size you ask for (but can be paralleled for greater capacitance). These capacitors are changed out at regular intervals and the old units go into the garbage. I can't say how much life would be left in them but considering that they would be free, a bit of effort would be well worth it.
The physical size is about 3" dia and about a foot long give or take.
I would try the cap after the choke (ie leave the choke in for now)

Re the momentary contact relay - try ebay or, if you are handy with basic electronics, set up a 555 timer circuit. Do not try to drive the energize coil with a low power relay, it will fry the contacts. Figure out the current draw and get the appropriate rated contactor for an inductive load and power that contactor with your timer or timer relay.
Correction .... you are talking FUEL solenoid - not sure why you want a momentary contact there, I thought you were talking about the run solenoid which controls your injector pump/s

[BruceM]

Hi Marcus,
The problem is likely either a defective breaker, or that there is a resonance going on between the pulsing midnight controller and the big inductive filter. 

If the midnight can handle the higher peak voltage and the variable voltage of straight rectified DC, then removing the inductor is OK, otherwise, some capacitance would do the trick.

It won't take much capacitance after the big inductor to disrupt the resonance, a motor run cap of even 22uF or 47uF might do the trick.  I don't recall what your output voltage is, but something just a bit over that would do for a rating if you leave the inductor.  There won't be much ripple, even an electrolytic would do.

Best Wishes,
Bruce

[mbryner]

thanks for the suggestions!