Tír Na HiFi

Oh, one thing occurred to me that could be another gotcha in this charging scenario - if the caps start off with different levels of charge (voltage) before starting charging then the resistor may not balance properly - allowing the cap with a head start to stay ahead & overcharge by the end of ...

Very nice, jr - those 350F Maxwells are nice & what I use.
Nobody local bit on my supercap PS tour offer - ah well, I'll just have to tour it across the water

Yea, I have to play devil's advocate but your scheme will work fine running outputting lowish continuous current
A year proves it is working fine - what are you powering with it

Yes, this seems reasonable - digital circuits draw little current but what if you are not constantly charging the supercaps (when you go on holidays, for instance or when you just don;t want to be permanently charging the supercaps)? These are not like batteries that hold their charge with little to...

A useful description of the various techniques for balancing supercapacitors here - you can see that passive resistor balancing is dodgy & very slow (especially with 1K resistor) & leads to shortened supercap life - a 50ohm or lower is used in the paper Our technique of active balancing usin...

I've been using one of Ian Canada's UCPi boards set to 3.3V to power a Raspberry Pi DAC with good success. He has 2 325F-350F 2.7V Ultracaps in series with a 1K resistor across each which is supposed to keep them fairly balanced. I charge them together with a single 3.3V LT3042-based regulator that...

Rick
Quality of diode has no bearing - use a low dropout one to prevent too much heat & size it according to how much current you expect to pass

As you go up in Farads value the supercapacitor esr usually gets lower (in the same brand/model) The esr of the 350F supercaps Nige is getting are 3.2mOhm - two in series gives 175F & 6.4mOhm - very competitive, if not better than 26650 LiFePO4 batteries - it will be good to hear what you think ...

I hope the impedance mismatch is not too big an issue with a simple two element supply. Certainly with more elements this becomes far more ungainly. Then again, it might not make much difference at all. If Nigel's amps are still running properly with their original batteries that would seem to prov...

@Rick Yes, no need for DC-DC ISOLATED converter when using transformer with isolated secondaries but you probably need a diode on the neg (-) leg of each charger line to the (-) pole of each battery - this prevents reverse current from getting back into whatever regulator you are using - the DC-DC i...