120V AC inverter?

[MechatronicsJoe]

I'm asking here because the Electric mower forum basically all just responded with "Get a Cordless mower" and I know I can do better.

Recently bought a house and with that comes all the projects of owning a house. I have 3x Ego 56V 4Ah Lithium Batteries that I want to use as that basis for a portable backpack inverter so I don't have to lug an extension cord everywhere. Basically, I want to run typically corded things: Leaf blowers, weed eaters, HVLP paint sprayers, and an electric lawn mower.

I'm focusing on the lawn mower right now as I think it has the highest current requirements of tools I will probably own.

What I've done so far:
It's a universal motor and feeding it straight 56VDC made it spin around 1/3 to half the RPM of what it normally does plugged in judging from the whine. Bought a cheap voltage doubler/boost module on amazon with a max output of 120VDC up to supposedly 900W (so 900W/120v ~7A) which led it to running around 80-90% max speed but getting bogged down quickly once I hit any grass..
Looked up some AC theory and it's saying that a 120v outlet circuit is in RMS and actually has a 170V wave peak, so my voltage may still not be high enough.

TLDR: Can anyone recommend an inverter for my application that can handle running a motor of this size?

 

[billvon]

>Can anyone recommend an inverter for my application that can handle running a motor of this size?

A 56V battery will usually run a 48V inverter. There are plenty of excellent inverters out there, like the Outback GFX1548 (1500 watts.) But it weighs 50 pounds. The Cotek line is a pretty cheap Chinese inverter but it's gotten reasonable reviews; there is a 1000 watt 48 volt version that will accept up to 60 volts. It weighs only 14 lbs.

 

[amberwolf]

Keep in mind that the startup inductive load of the motor could just blow the inverter up, even if it's nominal rating is higher than the motor specs indicate.

If the inverter has protection against that, at least it will shutdown the inverter before anything fails, but it still wont' be able to run the motor.

It's unlikely that inverters capable of running a large motor are going to be small/light. I have one from Harbor Freight that claims to be 3000w and is the size of three or four thick encyclopedia volumes (or a bigger small bag of dog food), and definitely weighs more, and I don't think it could run my B&D mower.



Since the motor is a brushed motor, you'd probably be better off to just run it right off your battery packs, though you'll need to series the three of them to get the voltage it needs to run at the proper speed.

Also, because the switch in the mower was designed for AC, it's possible it could weld stuck in the "on" position from the startup current / arcing, on DC. Not a big deal but something to keep in mind.

It's also possible that your battery packs might not handle the startup current and their BMS's might shutdown, too, in which case you'd either have to parallel another series set of them, or use the inverter plan with the 3 existing packs paralled at it's input.

The blowers and weed eaters are also probably brushed motors, and would also run off DC.

The sprayer is probably a solenoid requiring AC to do it's job, if it's one of those that vibrates and buzzes in operation. (similar to handheld hair/fur trimmers).

 

[dogman dan]

Well, does that pretty much take us back to get cordless?

For short duty work, I have taken a shine to the Ryobi stuff. I know it costs a lot to get it all, but I highly recommend you get a basic starter tool kit of the Ryobi 18v tools.

Get a drill, which comes fairly cheap with a charger and li battery, then get the string trimmer, also with batt and charger. This should run you about $200 if you catch the sales. Home Depot is the store that carries Ryobi, but you might find deals on ebay or amazon too.

Now you have at least two batteries, and can charge both at the same time. If you don't mean to blow the leaves in the yard for hours, the Ryobi cordless blower will be another good addition, but this time you don't need it with batteries. It will be fine for cleaning the walkways and porch.

If you have bikes, wheelbarrow, or just more than one car, add the tire pump, only twenty bucks.

If you will be doing remodeling, then at that time you can add more stuff, a sawsall, circular saw.

Now for the mower, keep hauling the damn cord, or run it on RC batteries. 5 ah size, but honestly, it might be cheaper in the long run to live with the cord this summer, and budget for a new cordless mower next season. Meanwhile, haunt the flea and garage sales, for a cheap deal on a 24v cordless mower that needs a battery.

If your yard is not large, then maybe consider the old school push mower, the reel type. Doing a 10x20 square with the push mower is easy. Each evening about sunset, go out and mow for 5 min. This should do a medium size yard twice a week. You do have to mow more often with a pusher. I can help you tune a push mower, so it does not suck like most will, even new.