Bcr questions

Mike, the supercaps from Digikey pictured above contain 2 supercaps in series.  Obviously, no zener caps can be added, and they work fine.  Note we are not here talking about building a pack to replace the 8.4-volt battery, only the 2.4.

If you are building a 9V BCR with 4 individual caps, the diodes can prevent issues if a cap is not to spec with others.  For these 5V pairs no diode required.  The imbalance on just 2 caps is not a critical issue.  G

OK, thanks RJR, it's for the 2.4 v batteries. I guess if you use the 2 separate 2.7 v 3.3F SC's as detailed in Susan Deats' case for the 2.4v batteries then you need the zener diode across the leads.

I have some supercaps that are joined like the one shown in an earlier post; they are 5.5v 1.0F . Would 1.0F work OK?

thanks,

Mike

GGG spelled out the zener diode requirement. 

I cannot say if 1 F would suffice.  You want to have enough power to allow the loco to properly write data.  As GRJ pointed out to me, the 2.5 F are so cheap, why skimp?  The supercap also holds power for a considerable period of time after everything is shut down.  A larger supercap will more probably have power at hand when powering up in the future.    They are so much smaller than AA or AAA battery packs, space is not an issue.

OK, thanks everyone, getting to understand this. I gather that the higher the Farad number, the more charge (power?) it will hold, so 2.5F will hold a charge for longer than a 1.0F thus enabling better power up of the boards. I guess my stock (5) of double shrink wrapped 5.5v 1.0F KAMKAP capacitors might be iffy at times, better to go with the 2.5F ones.

Mike

As a wild guess, maybe, perhaps, you could tie 2 together in parallel?????

I guess in parallel you are not increasing the voltage which would remain at 5.5v but you would increase the Farads to 2.0  (1+1) ............ maybe?

Sounds reasonable, does it not?  Since I was doing 20+ locos and had no supercaps on the shelf, I just bought the 2.5's in bulk from Digikey.  If yu were doing a bunch of locos and had to order some anyway, I'd be inclined to just go with 2.5's.