Sorry if this a bit off topic, but I'm sure someone on this forum has an answer. I'm looking for a reasonably priced inverter to work with either a full set of locomotive batteries (72-75 VDC) or a half set (36 VDC or so), with an output of maybe 200 watts, 115 VAC.

This is for a holiday lighting application. I have found some VERY expensive military grade inverters online, with pure sine wave outputs, but they would be overkill for my purposes, both in price and specifications. Lights do not need 'clean' power.

I would imagine someone else has come up with a solution here, but so far my online search has not led me to anything cost effective. Any leads would be appreciated.

Quick Search turned up this....
https://www.amazon.com/BiXPower-110V-50 ... B0080YV0SY

and I'll qualify that we have a AIMS brand 36 volt 5000 watt modified sine wave inverter wired to one of the forklifts to provide 120v power in the remote reaches of the materials yard...

EDM, check your email.

Not sure how many and what type of lights you need to run, but here might be an easier option.

A few years ago I took a few strands of LED Christmas lights and plugged them into the class light plug on our SW9. Certain brands lit up and certain ones didn't. I would have to go back and check what brand I used. I had to modify the strings slightly because about every 3 ft the polarity reversed on the section of bulbs. I just had to cut, switch and reconnect the wires every 3 ft or so. Easy to do and it looked good when the locomotive ran past the loaded cars. Interestingly enough each role of lights was just the right length to run from step to step down the side of the locomotive.

I had thought of doing an experiment with LEDs, but the changing polarity issue might make it not too practical.

Another idea was a 24 volt inverter; some tractor trailers have 24 volt systems (or used to-). I have been looking at truck stops for a 24 volt unit. Tapping into three 8 volt locomotive batteries would work, but knowing my luck, the units I want to do this with will have the big 32 volt unit batteries, with no external jumpers.

Thanks for the suggestions, will keep looking. There has to be something reasonably priced out there.

"Tapping into three 8 volt locomotive batteries would work..."

While yes that would work, whatever current the inverter is drawing is going to cause the other 5 batteries to overcharge by that much. You really don't want to upset the load balance on the 8 batteries.

jb

I will also add to that. By tapping into your battery bank the way you describe, a low voltage ground will be created. We found that out on our Alco switcher a number of years ago. Also, when you order your voltage converter, make sure they understand that it must not be a grounded unit, or a low voltage ground will be created there, as will. I do not recall off hand what we used, but it was purchased from a local radio, communications outlet.
Leverett Fernald
Downeast Scenic Railroad

I had not thought about the charging imbalance between the batteries; kind of like keeping three phases of AC in balance, which I am more familiar with. And if the AC neutral is grounded, I can see where a low voltage ground condition could result. Still digging for something cost effective-

Since you already have 72 volt DC at the battery, why do you need to convert it to AC just to run lights? Instead, use LED lights that are expecting 12 or 24 volts DC and wire them in series to get to 72 volts.

For instance, I have 24 volt DC LED strips lighting parts of my shop. These particular LED strips come in 5 meter length, and 3 of the 24 VDC strips could be wired in series to get to 72 volts. In my case, I am using a 117 VAC power supply to convert to 24 VDC, but by wiring 3 strips in series for 72 volts DC one would not need any adapter/inverter at all.

FYI, these LED strips (as manufactured) already use series wiring in repeating segments of 6 LEDs to be able to accommodate the 24 volts running in the strips. These particular strips are "cuttable" between every 6 LEDs if 5 meters is longer than you want at a given location.

For my purposes, I used strips that are not "weatherproof", but most likely "waterproof" lights would be a better choice in your application. You could also feed the strips through clear plastic tubing if you wanted more mechanical strength. Or use so called "rope lights" in a 12 volt version.

Some example products:
https://www.ebay.com/itm/LED-Strip-RGB- ... ymCCPGgbOw

https://www.ebay.com/itm/Red-Incandesce ... SwSNZdGZMw

Those are just examples of available product, I am not endorsing any particular vendor. Also, if you were to choose 12 volt products, note that they would need to be wired in series of 6 LED strings to accommodate 72 volts, versus 3 series LED strings if 24 volts each.

36 or 72 volt systems are uncommon and there won't be many applications for what you are looking for. It would be better to step down the 36 or 72 volts into the more common 12V system (automotive systems). Then step up the 12 volts to 115VAC 200 watts. Both systems are cheap and easy to convert.

https://www.ebay.com/itm/DC-DC-Buck-Ste ... SwSYpbxVux

https://www.ebay.com/p/Pyle-PINV33-Plug ... 7675.l2644

You could try and contact Inverter Service Center in White House, TN. I would bet you could go buy one of those super quiet Honda generators cheaper than an inverter, and you could have more uses for it.

I appreciate the suggestion of using one of the Honda generators, but one goal is to get away from using several small gensets on the holiday train. There is a lot of electricity available on a diesel electric locomotive, just not the right frequency and voltage. The 75 VDC to 12 VDC to an inverter option, as also suggested, may not provide the wattage that we need.

Going back to small gas generators, we have been very happy with a WEN unit, used on another 'remote' and unrelated project. Probably a copy of one of the Hondas, it is rated at 2 kW, and cost something shy of $500, IIRC. We can run two angle grinders all day, stripping paint, and it will use surprisingly little fuel. In terms of initial cash outlay, one of these would be easier on the budget than one of the more expensive 75 VDC to 115 VAC inverters; I just don't want to go that route.

I've been very reluctant to even respond to this message because I don't know all the circumstances involved?

However, The solar/wind guys have been having various degrees of success with Reliable Electric inverters from China. They list 36 and 72 volt models. The label on top of the inverter suggest up to 110v DC input voltages are available. https://www.amazon.com/WZRELB-Reliable-Inverter-120VAC-Converter/dp/B014QJTBAU/ref=asc_df_B014QJTBAU/?tag=hyprod-20&linkCode=df0&hvadid=198107824285&hvpos=1o5&hvnetw=g&hvrand=6128841231549028613&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9009684&hvtargid=pla-348805312526&psc=1

The link is for the 12v model. One would have to contact Reliable Electric to make sure you get the voltage you need.

There are a lot of videos on youtube about the Reliable Electric inverter. Some good and some bad. For running just Christmas lights, I would imagine even a low end consumer grade inverter like these would be perfect. The smallest version I believe is the 1500w model.

I believe asking for a 36/72v inverter model on the wind and solar forums might yield even more results. The Field Lines being one such website.

One thing that concerns me though is HV spikes and nasty ripple off the DC generator that is charging the batteries. The inverter might need a large filter choke on the input cables to help filter some of the noise.

Robert

LEDs run on DC
Read the fine print on the power supply for lights like you want
You may find some that can run on 36 volts by getting rid of the AC supply
I have some LED under cabinet lights that include a power supply to convert 115 volt AC to 35 volt DC

I wouldn't expect that to work reliably.

LEDs are actually current-mode devices, not voltage-mode like incandescent bulbs. The LED strip or string lights are not simply a bunch of LEDs in series. They have driver chips which take the applied voltage and turn it into a constant-current drive. Yes, the individual LED elements, which have a forward voltage drop of about 2V each, may be wired in series strings, but at the end of that string is a switchmode power supply operating in constant-current (not constant-voltage) mode.

The old and dumb way to run LEDs for non-lighting purposes, such as indicators, from a constant-voltage source is to use a series resistor. This effectively sets up current that is almost constant because the supply voltage is so much higher than the LED forward voltage. But that is not used for lightning applications which demand high efficiency.

The end which is facing the user and expects 12VDC, 24VDC, 120VAC, 277VAC, etc. is simply the input to a switchmode supply, like a computer power supply. The problem with putting them in series is you don't necessarily get equalization of the voltage drops across the supply inputs. They may become unstable with some units switching on and some switching off in an oscillation.

You really need an LED driver module that is specifically designed for the input voltage desired, be it 32, 74, 600DC, etc. They aren't hard to find, but they aren't consumer-grade items generally.