Alternate BCR - Verify Supercap Voltage Rating

The charger actually charges the supercap up to around 4.5 volts, you need a 5V rating.  And no, it's not an issue if the supercap voltage rating is more than the charge voltage, just if it's less.

Thanks John!  Does the resistance rating matter, I am looking at two from AVX at the digi-key site, one at 140 ohm and one at 180 ohm.

Also, how do I discern the + and - sides of the cap, and which leg gets connected to which wire of the 2 pin connector?

Thanks!

Dave

Milwaukee Road Dave posted:

Thanks John!  Does the resistance rating matter, I am looking at two from AVX at the digi-key site, one at 140 ohm and one at 180 ohm.

Also, how do I discern the + and - sides of the cap, and which leg gets connected to which wire of the 2 pin connector?

Thanks!

Dave

Don't worry about resistance.  The longer leg is +,  the wiring is Red is +, black is -

You may want to check Ebay,  China stock but cheaper than Mouser, Newark, or Digi-Key.

Milwaukee Road Dave posted:

Thanks John!  Does the resistance rating matter, I am looking at two from AVX at the digi-key site, one at 140 ohm and one at 180 ohm.

Are you talking about the ESR (Equivalent Series Resistance)?  If so, they have to be MUCH lower than that, in the milliohm region to work in this application.

Gary - Thanks for the input, much appreciated!

John - the Digi-key detail pages don't mention ESR, this is what they state:

2.5F (EDLC) Supercapacitor 5V Radial, Can 140mOhm @ 1kHz 2000 Hrs @ 65°C

2.5F (EDLC) Supercapacitor 5.5V Radial, Can 180mOhm @ 1kHz 2000 Hrs @ 65°C

Dave

180mOhm = milliohm

Why are you not using a single 5V package?  Easier to deal with, you just have to solder leads on.

John,

I didn't mean to infer I was using two caps, those are just the two individual caps I  am looking at.  In fact I think one of them I got from a post of yours from a few years ago.  Sounds like either one would work.  The cap you show in your last post is a 7.5F cap, which from what I have read would take longer to charge up at initial voltage introduction, but will hold the charge longer, do  I have that correct?

Dave

Milwaukee Road Dave posted:

Gary - Thanks for the input, much appreciated!

John - the Digi-key detail pages don't mention ESR, this is what they state:

2.5F (EDLC) Supercapacitor 5V Radial, Can 140mOhm @ 1kHz 2000 Hrs @ 65°C

2.5F (EDLC) Supercapacitor 5.5V Radial, Can 180mOhm @ 1kHz 2000 Hrs @ 65°C

Dave

Yeah, as others have stated, milli ohms as is .140 ohms.  Don't worry about it and you should get the one GRJ suggested, that's what I purchased. 

Does anyone have the part number/supplier for the 2 pin connector ?  I purchased the caps,  just need to add the connectors and I don't know the sizing arrangement for them.  My only other out is to order one of each close size to find the correct one.  Thanks,  JP

JPLOCO,

I intend to cut the 2 pin connector off the battery pack and use that.

Which cap did you order?

Dave

You can use the JST-PH connectors, they fit perfectly.

7.5F seems way to high.  I use 2.5 Digikey, which is plenty and seems to equate, in continuing sound time, to the battery.  I wonder if 7.5F would overload the charging circuit.

I think GRJ has dropped to 1.5F.

I use 1.5F caps, they've worked in all the places I've used them.  I prefer to minimize the load on the charging circuit, even though I'm not 100% sure that has an impact.  I know it can't hurt to have less of a surge load on it.

I'm not an electronics guys so this is an innocent question, above are components listed as having  a 65C temp rating.  For the Vintage consoles I play with, we typically use 105C rated CAPS etc.  Is 65C ok with our stuff, or would we be safer to use 85C or 105C rated components?  

If you go looking for EDLC (supercap) parts rated at higher temperatures, prepare to spend a lot more money on them.  Do you really think it gets to be 150F inside your locomotive or tender?

Gents,

Thank you to all for the input.  One last question, once installed, does the cap need to have air space around it's entirety, or can I lay it on a piece of foam tape?

Dave

No space needed, stick it anywhere it fits as long as it's not laid on some hot smoke unit or power regulator.

John, I agree, but it doesn't get to 65C on the frame of a Magnavox console either!  But 65C CAPs will die in short order.  The ambient condition is not a heat source in our case, but possibly the component usage might be, that's why I asked. I realize you've designed lots of circuits and so I have no intention of suggesting issues,  but I don't mind asking for my own understanding.  The 105C components are slightly higher in cost than 65C  but only a few cents usually.  Maybe if I go by high end stuff from Mouser... Dude, I'm happy to learn, store info away, it's all good