G Scale keep alive

[Slawman]

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-...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-Fa...ap-Solar-Power-Green-Enegry-USA-/161240113620

 

[stockers]

or you could make a trailing pick up truck.
Your not using digital, are you?

 

[stockers]

Have you checked the voltage on that first link - 2.7V,

 

[Slawman]

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]

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]

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]

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]

The DC output on the decoder boards I am planning to install on are regulated so the 27v should be OK.

 

[Slawman]

as an a side - thread drift already - will Caps work in series? I can see that they would just discharge in to each other.

https://www.kitronik.co.uk/blog/how-to-calculate-capacitors-in-series-and-parallel/

 

[Deleted member 4232]

Moved

 

[Rhinochugger]

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-Fa...ap-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

 

[idlemarvel]

Massoth have a wiki page on how to build your own keep alive, for small (one motor) locos.
http://wiki.massoth.de/tiki-index.php?page=Voltage+buffer+for+small+locos

 

[stockers]

Massoth have a wiki page on how to build your own keep alive, for small (one motor) locos.
http://wiki.massoth.de/tiki-index.php?page=Voltage+buffer+for+small+locos

Excellent - thanks.

 

[PhilP]

Do check the link above, for capacitors in series and parallel..

It is NOT the same as for resistors!

 

[Slawman]

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]

Is 3 ohm a reasonable allowance for the Buehler motor (30% efficiency)?

http://mustcalculate.com/electronic...ischarge.php?vfrom=35&vto=10&vs=0&c=.0022&r=3

 

[Slawman]

I used to have a link to an online article for such an installation. I'm wondering if it was George Schreyer

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.

 

[Greg Elmassian]

Slawman's calculations are correct for the caps he linked.

With that much capacity, a current limiting "inrush" resistor is a good idea...

Greg

 

[gregh]

Slawman's calculations are correct for the caps he linked.
Greg

Perhaps you mean my equation was correct - the other Greg = gregh

 

[Rhinochugger]

Eventually found the article I was looking for

Give Your Engines the Capacity to Ignore Ditry Track