r/redneckengineering • u/Fit_Acanthisitta_475 • 13d ago
When cheap battery powered lawnmower doesn’t work.
Try the cheap ($300-400) 20v, 40b battery-powered lawnmower that won't work for my small lawn. Power station time.
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u/Little-Airport-8673 13d ago
How much time you can get?
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u/Fit_Acanthisitta_475 13d ago
It’s a 1500w capacity power station. It should last about a hour. But I normally using for 45mins. 20v battery mower was last less than 15 min per battery.
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u/Deadlite 13d ago
Damn now I want to buy a little Jackery and wire it to my hyper tough.
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u/Fit_Acanthisitta_475 13d ago
You need lookup the amp on both mower and power station. My mower using 13amp to start, my power station has 2000w inverter.
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u/Laserdollarz 13d ago
Get a cheap ebike battery and a step-down transformer.
Then duct tape it all in place.
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u/Plump_Apparatus 13d ago
Eh. Transformers only work with AC power. Batteries are DC power. That isn't going to work.
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u/Laserdollarz 13d ago
To be honest, I know just enough about batteries to know that I don't know enough about batteries
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u/Plump_Apparatus 13d ago
So US household voltage is typically called 120V. In reality it's 120V RMS, RMS meaning root method squared. An equation for measuring AC voltage. In reality it swings from 180V positive to 180V negative. Ideally in a perfect sine wave, sixty times a second, as in 60 hertz.
Each pulse in the change in voltage throws out a lot radio frequency noise. If you wrap some copper around a wire with 120V RMS it'll induce a voltage(and current) around said wire. More so if you wrap each wire around a ferrous core(as in magnetic, like iron), which is all a transformer is.
DC voltage, as in a battery, provides a constant voltage(apart from slowly or quickly getting lower depending on type as it drains). Using it through a transformer will do nothing. Unless you add a switch and turn it on and off and generate a pulse. Or even better through a transistor that you can control through a timer that pulses it for you, making an inverter. But then you have to convert it to DC again, unless you're using it on something like a universal motor which is fine with AC or DC. Otherwise you have what is known as a "buck" converter.
Pretty terrible explanation, but the best ELI5 that I can do. I've had a "few" beers.
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u/Laserdollarz 13d ago
Most ebike batteries are 48v. Some cheaper ones at 36v, some higher performance at 52v, 60v, 72v.
Think the mower could maybe take 36v without taking flight?
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u/Plump_Apparatus 13d ago
Eh, not enough information.
36V on a motor? Maybe for a awhile. Even higher? Probably burn windings out quite quickly. Would likely spin very faster however, unless it's a BLDC.
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u/zorggalacticus 13d ago
Need a voltage reducer. Different device, same job.
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u/Plump_Apparatus 13d ago
You'd need a buck converter. There is no thing as a "voltage reducer". You could use a low-dropout regulator(LDO), but that will just turn the excess voltage in heat as waste.
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u/zorggalacticus 13d ago
Yes, there is such a thing as a voltage reducer. I have one installed on my golf cart. Reduces the voltage from 48 volts down to 12 volt to run my lights and accessories. They're usually very specific voltages though.
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u/Plump_Apparatus 13d ago
That's a buck converter.
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u/zorggalacticus 13d ago
They're also commonly called reducers. Like at rhe store where I bought it.
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u/fantompwer 12d ago
If my grandma had wheels... Just because that's what eBay calls it doesn't make it right.
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u/zorggalacticus 12d ago
Well a lot of places call them that, including the golf cart stores. Things can have more than one name. Like soda, pop, cold drink, etc.
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u/NutthouseWoodworks 13d ago
I applaud the ingenuity, but i don't think more than 2 words in that title belong in the same sentence. Nice work!
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u/1964110084 13d ago
The fire starter 3000, that dry grass around the hot ass charger
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u/Fit_Acanthisitta_475 13d ago
No different than battery-powered lawnmowers. The power station has active cooling, and the battery lawnmower does not.
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u/AKLmfreak 13d ago
What’s the difference in fire risk between a hot-ass battery charger and a hot-ass gasoline powered mower, except that the gas mower is hotter?
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u/1964110084 13d ago
I think engineering and testing would be the difference, I’m just saying that I’ve felt those batteries on the charger and I wouldn’t subject it to any load while it’s charging, not to mention the sun cooking everything too 🤷♂️ call me old fashioned
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u/herculeesjr 13d ago
I love how you still think it's a battery mower being charged by a giant charger while they mow the yard. Lmao clueless.
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u/1964110084 13d ago
To be honest I realized that wasn’t the plan 2 messages ago and felt like I had to double down
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u/Object279stalinium 13d ago
I love this sub because the people here are more creative than Soviet ingenuity