Using a transformer to boost internal power

[bobgrosh]

Several years ago I tried charging my on-board batteries from track power. The problem was, I didn't have the sort of intelligent chargers available today, and I was trying to charge large batteries.
Chargers have gotten much better, and cheaper (I paid over 150.00 of one of mine back then). It seems to me that you could take one of those small chargers and remove the transformer. Use the electronics in the battery car or loco and get the AC from the rails.

That would make it easy to light coaches from the rails too.

I have a Phoenix sound card. Experimenting with it, I discovered it has a built in charger circuit that is really cool. It seems that the Phoenix card can demand some very high current spikes when making some sounds. The circuit limits how much current can be drawn from the rails (it's adjustable) and draws from the battery when the current requirement is high. Kind of neat ! Of course the main purpose is to keep the card supplied with voltage all the time. Unfortunately the Phoenix card only uses a 6 volt battery.

By the way, I've been using pairs of transistor batteries for years in some of my smaller locos. The DCC signal loss is not a problem. DCC is fully glitched just like better RC units. As long as the decoder has power it will control the loco just fine without the signal.

Anyhow. I thought that some of the new smart chargers might be small enough (once you remove the transformer) that combined with small batteries it could solve the space problems and provide unlimited run times.

B0B

[kstrong]

Chompers,

Never be afraid to ask questions. At some point in the early 1800s, someone asked if it were possible to travel faster than a horse, and look where we are today.

Bob,

Interesting thought. Are you thinking in terms of using the track power as a steady power source with an onboard throttle? The batteries would then act more as a UPS than anything else, but would certainly cover for dirty track, etc. You'd still run into trouble if you're using the rails to carry the DCC signal to the locomotive, but if everything's on board (receiver, encoder, etc.), and you're just using the rails to provide pure voltage, then you've got something there.

I know in the early years of battery power, folks toyed with the idea of using the track to charge batteries. They'd energize a passing siding, and as the battery car rolled onto the passing siding, it would tricle charge the battery. (This was in the days when gel-cells and lead-acid motorcycle headlight batteries were the norm.) With the advent of quick-charging NiCad and now NiMH batteries, this has become less of a concern.

I know some sound systems use a similar system of using track power to trickle charge the batteries that power their sound systems, so the concept isn't at all lost.

Later,

K

[Chompers]

OK well forget i even brought this topic up.

if people want i could get rid of it

[grandpopswalt]

Chompers,

As Kevin has said, it's a matter of available energy in the batteries. No matter how you arrange them, you can't get more power out than there is in them. If you did use that "voltage booster" to increase the voltage by a factor of 10, then you'd wind up drawing current at a rate 10 times faster than before . net result? - same amount of energy. An analogy of this law of physicis would be something like this: if you had enough gas (energy) in your car to travel 55 miles at 55 Miles-per-hour, then at 110 MPH you'd be able to travel the same 55 miles in 1/2 hour using the same amount of gas (ignoring wind resistence and increased friction losses) - that same amount of gas will only allow you to travel 55 miles - period.

Walt

[Chompers]

i was just using 1 amp because it made the math easier. i am just saying hook them up in parallel and you would have more amps then us a voltage booster to get the 20 volts.

[bobgrosh]

Why not just use two rechargeable 9 volt transistor batteries in series. They usually give you 8.2 volt each or 16.4 volts total. They will run a LGB loco for a couple of minutes. Then you could put a battery charger in the loco to keep them charged up. I would think that they would not run down on even the very worst dirty track, The loco should make it over a dozen feet of track even if the rails were completely dead.

B0B

[kstrong]

Won't work, because you're not creating energy, just changing how it's let out. The total power will always be the same.

Power = Current x Voltage

Let's look at a standard transformer: On the input (wall outlet) side, you've got 120 volts, on the output side 24 volts to go to your trains. If you've got a current draw of 1 amp at 24 volts, your total power output is 24 watts (24 volts x 1 amp). On the wall outlet side of the transformer, you've got 24 watts = 120 volts x 0.2 amps. Since the voltage is 5 times higher, the current draw is 5 times lower. The transformer is not creating energy, rather just changing it to be more useful.

Now, as cacole mentioned, transformers need a varying voltage to function--typically AC, but can also be modulated DC. There has to be a changing magnetic field for a transformer to work. You don't get that with batteries--their output is linear, so the magnetic field is constant.

Now, let's look at your battery scenario. You've got 8 cells, all rated at 1 amp/hour (meaning, they'll deliver one amp of power for a total of one hour, or 2 amps of power for 30 minutes, or 0.5 amps for 2 hours.) Now, if the cells are rated at 1.2 volts (common for NiCd or NiMH batteries), that gives you a total of 9.6 volts when hooked together in series. Now, let's say your motor draws 0.5 amps. The motor will run as fast as it will at 9.6 volts until the batteries die, which at 0.5 amps will be two hours.

Now, if you hook them up in parallel, you've got a 1.2 volt battery with a life of 8 amp/hours. Now, 1.2 volts isn't going to turn your motor, you need more voltage. Now, we've already established that a simple transformer won't work, but let's keep going on the premise of some kind of electronic mechanism which would allow you to increase the voltage. So, you take this battery and hook it up to this circuit so your output is 9.6 volts. (Keeps the math easy) The motor still draws 0.5 amps, so your total power is 4.8 watts. On the battery side, you've got 1.2 volts, so to get 4.8 watts from that 1.2 volts, you'll have to draw 4 amps from the battery. With the battery rated at 8 amp/hours, you'll run the batteries flat in the exact same 2 hours. If you wanted to get 20 volts out of that same battery, your battery life will be even less. If your motor draws the same 0.5 amps at 20 volts, you're using 10 watts of power. So, on the battery side, you're drawing 8.3 amps from the batteries. They'll go flat in just under one hour.

So, a straight transformer wouldn't work. There are electronic circuits which would allow you to increase a linear DC voltage, but you're not gaining anything by doing so. You actually lose a little energy in this process, so you're better off just hooking the batteries up in series. If you need more power, add more batteries. Today, they're certainly small enough where space is no longer the consideration it was just 5 years ago.

Later,

K

[cacole]

Transformers will work only with AC house current, not battery power. What you would need is a voltage doubler circuit used in electronics, which will work with DC Voltages. The problem you're going to encounter is finding a circuit with enough Amperage for what you want to do -- most voltage doublers are for low Amperage.

It would be far cheaper and more practical to just look for a battery with the Voltage and Amperage ratings you need for whatever it is you intend to do.

I operate all of my trains from 12 Volt Gel-Cell rechargeable batteries. These can be recharged using an automotive 12 Volt charger.

[Chompers]

[:D] i'm wondering instead of putting a bunch of batteries inceries, you could put a bunch of batts. in paralell then us an internal transformer to bost voltage.[8D] fo instead of having 8 1 amp batteries you would have 1 8amp[:p] battery then hook it up to a trans former to get 20 volts.


Would this work?[:)]

Just wondering

Chompers[:p]