Monorail 9V battery life?

[Big Sal]

Hi all. I'm displaying a MOC with a monorail at the Yorkshire Brick Show next weekend and was wondering if anyone here knows roughly how long a 9V battery will power the train for? Don't want to run out of batteries halfway through the first day because I didn't bring enough!

[Ashi Valkoinen]

Why don't you make some test runs? You buy two or three 9V batteries, and run your train at home. From two or three measurements you can estimate the exhibition battery needs. :)

[Big Sal]

That was my plan, but thought I'd ask first to save wasting batteries - I spent all my money on the model!

[AlmightyArjen]

Interesting to know. If you've tested it, please post here your findings...

[jtlan]

What kind of batteries did you buy? You can get a rough sense from the battery's capacity and the expected current draw of the motor.

Let's say the motor draws 200 milliamps (mA) at load. A typical 9V alkaline battery might have a capacity of 550 milliamp-hours (mAh). From this, you can expect to run the monorail for:

550mAh/200mA = 2.75 hours = 2 hours 45 minutes on a single battery.

Of course, I'm not sure what the current draw of the motor is; you might try measuring this with a multimeter if there's a wire you can splice in to. The 9V batteries you bought might have more or less battery too.

To circumvent the problem, you might consider buying a few rechargeable 9V batteries, which might be a good plan if you expect to run monorails a lot in the future.

[Big Sal]

Thanks to the above members for their help

My findings were that a single alkaline 9V battery lasted an entire day of the show (around 6 hours) but the train was seriously slowing down by the end. So the next day I used one battery for the morning and one for the afternoon and it worked great. Hope this helps anyone with my question in future!

If you'd like to see my model, it's here in the Sci-Fi forum.

[dr_spock]

Thank you for the doing the testing and providing the results.

Awesome job on your M-Tron display.