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Slawman

Slawman

Deckline
9 Apr 2018
277
0
Sydney
Hi all,

I am putting some power buffers together for some of my short wheelbase locos.

Does anyone know how many amps a 1f, 25v array will drive? ie. if my loco draws 0.4 amps at top speed how long will it run after it loses power?

I am looking at these:

https://www.ebay.com.au/itm/1-6Pcs-10-26mm-2-7V-10F-Cylindrical-Ultra-Super-Farad-Capacitor-High-Power/322446788660?ssPageName=STRK:MEBIDX:IT&var=511421392774&_trksid=p2057872.m2749.l2649

These are pretty impressive but I am worried I will end up making a lightning strike.....:

https://www.ebay.com/itm/2x-100F-Farad-2-7V-DC-Super-Capacitor-EDLC-UltraCap-Solar-Power-Green-Enegry-USA-/161240113620
 
stockers

stockers

Trains, aircraft, models, walking, beer, travel
Staff member
GSC Moderator
24 Oct 2009
25,390
6
60
Nr. Ashford, Kent. England.
or you could make a trailing pick up truck.
Your not using digital, are you?
 
stockers

stockers

Trains, aircraft, models, walking, beer, travel
Staff member
GSC Moderator
24 Oct 2009
25,390
6
60
Nr. Ashford, Kent. England.
Have you checked the voltage on that first link - 2.7V,
 
Slawman

Slawman

Deckline
9 Apr 2018
277
0
Sydney
I am planning on putting them in series. 10 will give me 27v and 1f. I will put it on the DC side of my decoder. Does that sound right?
 
stockers

stockers

Trains, aircraft, models, walking, beer, travel
Staff member
GSC Moderator
24 Oct 2009
25,390
6
60
Nr. Ashford, Kent. England.
I am no expert here but I expect one will be along shortly - but.
1. I would use 35V caps
2. The output voltage is uncontrolled, your decoder will go pop. At a minimum, I think you need a voltage regulator between the cap and decoder. The cap will need feeding DC so a bridge rectifier will be needed - so how is your digital signal going to get through that.
Not as simple as it seems - perhaps its best to buy a Massoth unit despite the cost.
 
stockers

stockers

Trains, aircraft, models, walking, beer, travel
Staff member
GSC Moderator
24 Oct 2009
25,390
6
60
Nr. Ashford, Kent. England.
as an a side - thread drift already - will Caps work in series? I can see that they would just discharge in to each other.
 
gregh

gregh

electronics, computers and scratchbuilding
Hi all,

Does anyone know how many amps a 1f, 25v array will drive? ie. if my loco draws 0.4 amps at top speed how long will it run after it loses power?
Remember that as the current is taken from the capacitor its voltage will reduce.
Here's a simple approximation:

the drop in capacitor voltage in time T = current(amps) x T(sec) / capacitance (F)

so if you take 0.4 amps for 1 second and 1F capacitor, the capacitor voltage will drop by 0.4A x 1s / 1F = 0.4V

Note the approximation is only valid for voltage drops of less than about 1/3 of the original capacitor voltage.
 
Slawman

Slawman

Deckline
9 Apr 2018
277
0
Sydney
The DC output on the decoder boards I am planning to install on are regulated so the 27v should be OK.
 
John S

John S

Registered
5 Nov 2017
489
11
Exeter, Devon, UK
Last edited:
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Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
23,787
49
North West Norfolk
Hi all,

I am putting some power buffers together for some of my short wheelbase locos.

Does anyone know how many amps a 1f, 25v array will drive? ie. if my loco draws 0.4 amps at top speed how long will it run after it loses power?

I am looking at these:

https://www.ebay.com.au/itm/1-6Pcs-10-26mm-2-7V-10F-Cylindrical-Ultra-Super-Farad-Capacitor-High-Power/322446788660?ssPageName=STRK:MEBIDX:IT&var=511421392774&_trksid=p2057872.m2749.l2649

These are pretty impressive but I am worried I will end up making a lightning strike.....:

https://www.ebay.com/itm/2x-100F-Farad-2-7V-DC-Super-Capacitor-EDLC-UltraCap-Solar-Power-Green-Enegry-USA-/161240113620
I used to have a link to an online article for such an installation. I'm wondering if it was George Schreyer :think::think:
 
stockers

stockers

Trains, aircraft, models, walking, beer, travel
Staff member
GSC Moderator
24 Oct 2009
25,390
6
60
Nr. Ashford, Kent. England.
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
22,061
38
Tamworth, Staffs.
Do check the link above, for capacitors in series and parallel.. :nerd::nod::nod:

It is NOT the same as for resistors! :shake:
 
Slawman

Slawman

Deckline
9 Apr 2018
277
0
Sydney
Info available here: https://www.gscalecentral.net/resources/dcc-diy-stay-alive-voltage-buffers.55/

Here's one of a recently completed conversion of a Bachmann Lil Hauler with an LGB 55021 modified with the extra F2 function, stay alive and flickering oil effect lamps for the front and rear lights.

View attachment 238587

I am curious about the suggestion that the capacity be limited due to charge time. Massoth gold cap buffers carry a much greater capacity (I have one that uses a few of the 2.7v 10f cap).

Is the purpose of the resistor to allow programming capability to be maintained or is there another purpose beyond this?
 
Slawman

Slawman

Deckline
9 Apr 2018
277
0
Sydney
I used to have a link to an online article for such an installation. I'm wondering if it was George Schreyer :think::think:
That is an awesome link, thank you. There is nothing like seeing someone actually doing the mods and the detail around method and approach is great.