# STX-38 Inverter



## jtdavies (2 mo ago)

I have my dad's old STX-38.And I've been thinking about power outages after a recent outage in my neighborhood.

We have generators to take care of my family. (Too many generators)

I was wondering about a low cost solution to provide power for my neighbors' fridges/freezers in the event of an outage. Backup to the backup to the backup.

Could a small inverter, say 500 watts, be powered from my tractor?


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## sixbales (May 18, 2011)

Howdy JT, welcome to the tractor forum.

Your old STX38 doesn't have a PTO shaft, so from a practical standpoint there's no way to drive a generator. Besides that, 500W isn't much power, may not be capable of starting refrigerators / freezers.


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## Bob Driver (Nov 1, 2017)

Sure .... It's a fairly simple process to turn that STX-38 into another portable generator. Sell the STX on Craigslist, throw in another $500, and head to Lowes. That's way easier than the engineering required to turn that STX into a portable generator powerful enough to run a refrigerator/freezer..... Not trying to be a smart ass, just giving you the dose of reality you requested, welcome to the Forum......


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## FredM (Nov 18, 2015)

I thought an inverter was the electronic device that attached to a 12 volt battery and converted the DC to AC volts to power household goods, like sixbales says, "500 watts isn't much power" and I can assure you, that amount would be pushing to start a refridgerator, 110 volts your system would give approximately 4.54 amps recurring decimal point, I have used a 1KVA gen set to power a single door fridge and a small box type freezer, but you had to start the fridge first and let settle down before the freezer could be started, so you may get away with a 500watt inverter..

And I agree with jtdavies about having too many gen sets, I have 3 and they are a pain in the butt, if they aren't run at least monthly, you will have problems when they are needed to run.

I didn't mean to take over your post, tell us what or how you planned to use an inverter with the STX-38,


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## jtdavies (2 mo ago)

That's what I was thinking, but I obviously wasn't too clear. An inverter attached to the STX-38 battery. 

I can see a 500 watt won't be enough. But a 1000 watt? Could the STX motor keep the battery charged to run a fridge or freezer?

I know this isn't a long term solution. But just about everyone on my street has a riding mower. If I could lend out an inverter long enough to get their fridge or freezer back to cold that would be a good thing.

Alternately, I could do the same thing with my car. But the mower would be easier to get in tighter quarters.



FredM said:


> I thought an inverter was the electronic device that attached to a 12 volt battery and converted the DC to AC volts to power household goods, like sixbales says, "500 watts isn't much power" and I can assure you, that amount would be pushing to start a refridgerator, 110 volts your system would give approximately 4.54 amps recurring decimal point, I have used a 1KVA gen set to power a single door fridge and a small box type freezer, but you had to start the fridge first and let settle down before the freezer could be started, so you may get away with a 500watt inverter..
> 
> And I agree with jtdavies about having too many gen sets, I have 3 and they are a pain in the butt, if they aren't run at least monthly, you will have problems when they are needed to run.
> 
> I didn't mean to take over your post, tell us what or how you planned to use an inverter with the STX-38,





FredM said:


> I thought an inverter was the electronic device that attached to a 12 volt battery and converted the DC to AC volts to power household goods, like sixbales says, "500 watts isn't much power" and I can assure you, that amount would be pushing to start a refridgerator, 110 volts your system would give approximately 4.54 amps recurring decimal point, I have used a 1KVA gen set to power a single door fridge and a small box type freezer, but you had to start the fridge first and let settle down before the freezer could be started, so you may get away with a 500watt inverter..
> 
> And I agree with jtdavies about having too many gen sets, I have 3 and they are a pain in the butt, if they aren't run at least monthly, you will have problems when they are needed to run.
> 
> I didn't mean to take over your post, tell us what or how you planned to use an inverter with the STX-38,


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## FredM (Nov 18, 2015)

jtdavies said:


> That's what I was thinking, but I obviously wasn't too clear. An inverter attached to the STX-38 battery.
> 
> I can see a 500 watt won't be enough. But a 1000 watt? Could the STX motor keep the battery charged to run a fridge or freezer?
> 
> ...


The inverter was produced to power smaller items like computers and the esky type fridge/freezers, you would have to look at the household fridge/freezer power draw, then there is the battery in the STX, most likely 200CCA, then there is the charging system on the STX, in the end, something on the STX would fail from overload, now if the engine on the STX was a horizontal shaft, then look at somehow at belt driving a generator from an engine pulley and that way, you would be utilizing the engine power fully, this wont happen because the engine is a vertical shaft.


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## unsquidly (Jul 13, 2021)

jtdavies said:


> That's what I was thinking, but I obviously wasn't too clear. An inverter attached to the STX-38 battery.
> 
> I can see a 500 watt won't be enough. But a 1000 watt? Could the STX motor keep the battery charged to run a fridge or freezer?
> 
> ...



Here is a simple way to find out what an inverter will power.......Use the simple formula for Power.........P(Power measured in Watts)=I is the current (measured in amps) and I is the voltage ( measured in volts). So, a 500 watt inverted will have an output of about 4.16 amps (500 Watts divided by 120 volts). Not going to run a whole hell of a lot with less then 5 amps of 120 volt AC power......


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## unsquidly (Jul 13, 2021)

FredM said:


> I thought an inverter was the electronic device that attached to a 12 volt battery and converted the DC to AC volts to power household goods, like sixbales says, "500 watts isn't much power" and I can assure you, that amount would be pushing to start a refridgerator, 110 volts your system would give approximately 4.54 amps recurring decimal point, I have used a 1KVA gen set to power a single door fridge and a small box type freezer, but you had to start the fridge first and let settle down before the freezer could be started, so you may get away with a 500watt inverter..
> 
> And I agree with jtdavies about having too many gen sets, I have 3 and they are a pain in the butt, if they aren't run at least monthly, you will have problems when they are needed to run.
> 
> I didn't mean to take over your post, tell us what or how you planned to use an inverter with the STX-38,


You are correct Fred and a converter converts AC to DC......


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## FredM (Nov 18, 2015)

unsquidly said:


> Here is a simple way to find out what an inverter will power.......Use the simple formula for Power.........P(Power measured in Watts)=I is the current (measured in amps) and I is the voltage ( measured in volts). So, a 500 watt inverted will have an output of about 4.16 amps (500 Watts divided by 120 volts). Not going to run a whole hell of a lot with less then 5 amps of 120 volt AC power......


Arrh!! 10 volts out in my conversion


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## unsquidly (Jul 13, 2021)

FredM said:


> Arrh!! 10 volts out in my conversion



LOL.......Y'all are on the 220 volt the same as the rest of Europe, right?


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## FredM (Nov 18, 2015)

unsquidly said:


> LOL.......Y'all are on the 220 volt the same as the rest of Europe, right?


WE run 240 volts household and 415 volts commercial unsquidly.


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## Rolex (11 mo ago)

I run a 240v 120lt bar fridge with a small freezer off a 1200w inverter at my farm (rolex)

It is 100% sloar powered, 1000w struggled while the 1200w has a little excess power to supply some of my other needs. 

Running the fridge is not the problem, replenishing the battery may be, you will need to know the spare capacity of the tractors charging system. 

When I invert from dc to ac at 240v I loose about 10% of the power I don't know if 110v is similar


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## westbay6 (Oct 10, 2020)

TractorData lists the yellow deck JD STX-38 as having a 15A charging system. That means the tractor should be able to put out 13V x 15A = 195W of power continuously, minus whatever the ignition system draws. So, maybe ~150W.

This site here  lists the average power consumption of a modern fridge at 46W - 69W, though older fridges might be up to 115W. If that figure is accurate, then you could probably power a fridge continuously with this lawn tractor, given a high enough amp hour battery and a large enough inverter to handle the inrush current of the fridge. 

Most inverters will cut the output if the input voltage drops too low. Even if you're starting with a warm-ish fridge that will run longer than usual at first until it cools down, the inverter will likely cycle the output enough to let the charging system keep up. 

Check the power requirements of the fridge you want to run and get an inverter rated to handle it and I think you'll be fine.


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