Electric mower - AC to DC error

Hi everyone.

I’m hoping to get some assistance.
I’m in the process of setting up my electric mower to be a RC solar powered mower.

The mower is AC power in Australia, which is 240v. The mower is Ozito Model LMW 101 rated at 1100 watts continuous. I asked the mower company and they wrote back with “power factor is approx. 0.9 so that would mean the surge draw on startup would be approx. 2100W”
Mower works fine on AC mains. I’ve not modified it in any way (yet).
So, I’ve attached a car battery, fully charged to a 1500 watt continuous (3000 watt surge) DC to AC inverter. I originally got a Modified Sine Wave inverter. This one didn’t work, it seemed to start the motor spin, then stop, a second or so later, repeat. I thought that either the watts were full of crap (it works with less power hungry power tools) or that the modified sine wave was not working with the mower.
I now have a pure sine wave inverter (as I’m told), this one:
and again the same issue.

It’s got a pretty big capacitor in it, shown in photo CBB60 16 uf something to do with this?
I’m assuming it’s just there to provide the juice when the mower is under heavier load?

I don’t understand, am i doing something wrong? I don’t understand why it’s not powering this mower easily.

Any ideas or corrections on my logic/actions would be appreciated.


Read here for info on the capacitor.

Hi @Robin57159, thanks very much for that link, very enlightening.
It would seem, if I understand it correctly, that it is likely a “run capacitor”.

Is it possible that the run capacitor isn’t getting the full charge because my inverter isn’t a pure sine wave, only a modified sine wave inverter?

I’m probably showing all sorts of ignorances here, but I’m being very honest in order to learn where I’m going wrong.

Id like to see how it’s wired but it looks like a start capacitor. It would be in series with the motor start winding to cause a phase shift. Start capacitors and windings get disconnected by a centrifugal switch when the motor reaches approximately 75% of synchronous speed.

Also, forget about tyhe idea of them providing juice. Thats a DC system concept. In AC systems they’re used for phase shift for either getting the motor started or power factor correction.

Since the motor runs normally on mains power, the circuitry would appear to be fine. And as the motor spins up to speed on the DC to AC converters, then the capacitor is most likely a start capacitor, and functioning.

With that, then the converters are likely the problem. Either they are not running at 50Hz, or the “sine wave” output isn’t sinusoidal. Can you get some form of oscilloscope to look at the power coming from the converters?

I have a different thought.
1100 Watts at 240VAC would equate to around 92 Amps at 12VDC, assuming 100% efficiency.
(is my electronics theory correct here)

You would need a pretty good car battery to supply that much current continuously.

Inverters I looked at for specifications.
DC to AC 2000 Watts, 240Amp fuse on the DC side.
DC to AC 600 Watts, 60Amp fuse on the DC side.
DC to AC 150 Watts, 15Amp fuse on the DC side.

As a side note, a car battery is not designed to provide continuous current. And certainly not at its maximum capacity (assuming you are using a 12VDC 80 Amp Hour Battery). But, your local battery shop could advise you on a battery that would suit your situation.

This might not be the problem, but it is the first thought that came to mind


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I just read through your post again and on top of the battery issue above your inverter is underrated if it’s not specifically designed for running AC motors. A single phase motor pulls approximately 5 times its full load current on start-up. You’ll need an inverter with 10kW surge to be on the safe side. You may be able to get away with less but at reduced starting torque or as your finding it won’t start.

For the battery you should be using a deep cycle battery instead of a car battery. If you use the car battery you’ll get about 25-30% of the life you can expect from a deep cycle battery. You’ll also need to keep in mind that the car battery, as stated above, is designed for short bursts of high current. You’ll need to significantly reduce the rated current for continuous use.

Personally, I’d throw out the old mower and go and pick up a battery powered mower from the shop. You can charge the batteries using a solar powered inverter used for camping.

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Thank you to everyone for responding.
You’ve helped me learn a great deal.

In the end, I’ve decided to make the entire thing from scratch. It’s proving too difficult to mess with existing realities and far to power hungry.

So, I’m going to make the structure out of aluminium, mount 2 dc motors with whipper snipper blades, mount another 2 dc motors to control the wheels, hook it up with an arduino, solar panel controller, solar panel and SLA batteries.

If anyone is interested in the project, let me know and I’ll happily share.

Thanks again.

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