Large Scale Central

R/C question - how much voltage is enough?

Electronics Power and Sound
#1

As a recent convert to the battery scene, my question is just how much voltage does one really need? I have no Aristo diesels, but it is quite likely one or two may be in the pipeline.

I normally operate modified Bachmann Annies at slow speed, so could probably get away with 14 volts. However, assuming sufficient amps available would 14 volts be sufficient to haul a reasonable length train up a reasonable grade? Also would a diesel from Aristo run comfortably on 14 volts or would around 18.5 volts be a reasonable compromise considering the dual need of both Bachmann and Aristocraft requirements?

Tony has already commented that excessive voltage is lost in heat dissipation. Also just how many amps does one need to run a reasonable length train (steam or diesel)? Is 2200mAh enough for a reasonable runtime (say two 2200mAh in parallel) or possibly one or two 5000mAh in parallel. Just how much capacity is overkill?

Is it desirable to use up one battery pack and then switch to another pack, or should one drain from both packs simultaneously?

#2

Tim.

When trying to give advice to battery R/C newcomers it is always helpful if we can get as much infromation as possible.

Determining battery voltage is quite simple really.

If you intend having the batteries on board the loco with the control system, then battery voltage becomes less of a one size fits all scenario. Primarily because there is very little chance of dissipating the heat from excessive battery voltage inside the loco.
Measure the voltage going to the track at what you would consider a top speed, add a couple of volts to allow for system overheads and that is what the maximum voltage you wil need for that particular loco.

If you intend to use trail car installs that will power many different locos, then you use the highest voltage you need for the fastest loco. Because trail cars are usually quite roomy and can be easily ventilated extra voltage is less of a problem.

Voltage determines speed, not hauling capability.
That is governed by the amperage capability of the controller and the ability of the batteries to deliver the amps you need.
The mah rating of the battery will determine how long the set up will run for. 2200 mah will give 2.2 amps for 1 hour.
How many amps you will require can be easily determined. measure the train running on track power without any lit coaches etc. You will be quite surprised how much amoerage you will require.

It is OK to run batteries in parallel provided you place diodes in the positive lines to prevent any backfeeding from one pack into the other. One diode drops about .7 of a volt depending on the diode type.
The draw will automatically take power from the highest charged battery. In situ charging with diodes in the packs will require special circuitry.
Another way is to use a DPDT switch to switch from one pack to the other.

If the batteries are on board they needed not be all that big a capacity.
I explained earlier in this topic that there is a very simple circuit available that permits the loco to run on internal batteries around a yard for example. Then, when an Auxilliary pack is plugged in, it disconnect the on board batteries.

If you haven’t done so already, might I suggest you read the beginners page for battery R/C at the RCS website.

#3

I run my Aristo RS3 on 14.4v batteries. It has plenty of speed. Aristo locomotives are not the power hogs…USAT tend to need more…but still, not a lot.

#4

Warren,
Do you know how many amps the RS3 draws? I’m going to be putting an RCS system into a friend’s RS3 and am in the process figuring out what size(mah) pack I need.
Thanks,
Dave

#5

The number of amps depends on the load placed on the locomotive. Stock locomotive with a half dozen cars on the flat will pull less than an amp. On the other hand load it down with a whole lot of cars and a grade and the amperage will climb like a baboon with it’s butt on fire.

#6
Warren Mumpower said:
... climb like a baboon with its butt on fire.
Ouch. That's an image I didn't need ;)
#7

He got into my pot of chili…:smiley:

#8
Warren Mumpower said:
He got into my pot of chili....:D
Ah, Mumpower's Hellfire Chili. Guaranteed to scare the sin out of you.
#9

I run my battery Annie on 18v. Its top speed seems reasonable.

I have 19.2 in my Mallet. I’ve never taken it to full speed, so it goes faster than I really need it to. It was 19.2 or 9.6, and I’ve heard that 9.6 won’t run the te very well. I’ve never measured the voltage at the nice slow lumber that’s appropriate for a Mallet.

#10

Tom, why 9v or 19.2v? What’s wrong with 14.4? That’s what I use and it runs the TE just fine.

#11

He had 9.6 volt packs, so he could use one or two… 9.6 or two times 9.6 = 19.2… it’s that new math thing!

I’d also guess they were cost-effective R/C packs.

Regards, Greg

#12

$16 for a 3800MAh 9.6v battery.

#13

I’m running 24 (two 12’s) volts in the battery cars and 14.4 volts in the tender equipped locos.
So far, not a problem.
The only drawback I can see is charging two batteries instead on one. And the extra expense of another battery pack…
But I have nothing but time on my hands…
jb

#14

Ya know guys…real trains stop for fuel too…I use Good ol fashioned Nicads…guess what…my three truck Shay runs n 9.6 V! I get about 90 minutes on a 1000mah battery pack. Thats about 90minutes on contiuous running, Pretty much all day during an ops session…is REALLY that big a deal to stop at the engine terminal and swap out a battery?

#15

Not at all! I have 2 of those 3800MAh batteries so I can swap and get going again. I usually put the one I took out on charge while I play.

#16

Most of what all of these guys above has told you is correct, however I use the Aristo 21 volt LI-ion almost exclusively. The reason is that these batteries are reasonably priced. If you search around you can usually pick them up for $40 to $45 a piece. I have been forced to pay over $60 a piece for 14.4 volt li-ion batteries. Also by using the same battery in all your locos you can swap them out easily. If heat insided the loco is an issue for you install a 12 volt fan.