DIY Cheap Inverter With Junk Parts

Intro: DIY Cheap Inverter With Junk Parts

If you stay in South Africa you would know that our beloved country is currently being run down by our government, But lets not get political :-)

ESKOM dubbed Eksdom is the sole power company in South Africa and is doing a real bad job at delivering power to its consumers and probably the only company asking consumers not to buy power from them , Weird hey!

So ESKOM has invented what they call load shedding, where by on a regualr basis power gets shut in areas right across the whole country , Except off coarse where the directors of ESKOM stays (Ok Just kidding , or wait is it true?) dont know but I dont doubt.

In my area loadshedding usually happens on Wednesdays at around 20:00 to 22:00.

I needed a solution that will allow me to watch TV and have internet during those hours. I found a couple of a old broke PC upses, the actual inverters were still fine just the 7ah internal batteries were dead.

Before I started I checked the voltage its using to charge the battery and it was charging at 13.54 volts, which was perfect because usually SLA (Solid Lead Acid) batteries usually start to gas at 14V and up also I noticed this charger maintains the battery by clicking a relay every now and again to top it up.

See the youtube video how i built it

PARTS USED

1 X 102 A/h Deep Cycle Battery

1 X Broke UPS rated 460Watt

Soldering Iron to extend the UPS battery leads and some soldering wire.

Battery Clips

Heavy gauge wiring kit

STEP 1:

STEP 2: Take the UPS Apart

Open the UPS, In my case the UPS enclosure only had 4 screws holding it together and the front face just clipped off and I could remove a cable plug to separate the front button from the circuit board.

WARNING

Immediatelyremove the battery terminals to prevent a potential lethal shock!

STEP 3: Remove the Battery

Remove the battery, In this step's picture you can see the battery is swollen and its casing is cracked.

After removing it chuck it into the dustbin ( hehe only joking make sure you dispose of it correctly)

STEP 4: Remove the Power Outage Buzzer.

Most UPSes have a buzzer to indicate its running on battery, this will drive you totally nuts and it will be very distracting.

the UPS is used also dims the front LED when its buzzing so I still have an indication to see when its running on battery as opposed to mains.

Not that it matters because I never have a load on this unless its load shedding, because when I'm at work and the power goes out during the day I dont want the UPS to power the TV, Internet or Decoder whilst not using it.

STEP 5: Extend the Battery Terminals and Drill Holes in the Enclosure.

You need to extend the battery terminals so that you can hook it up to a bigger battery outside of the now dedicated inverter.

I stripped all the leads and extensions then twisted them tight and also soldered it, I went wild on the soldering, Note if the wires are to thin it will become hot and potentially be a fire hazard, be careful!

After that I drilled some holes and used grommets to fit the wires through.

And you are done with the inverter you can close it up.

STEP 6: Build a Male Kettle Cord Lead

I used an old ordinary extension lead, cut off the 3 prong plug and soldered on a male kettle cord lead.

Usually this is the lead you plug into the PC and the other side into the UPS.

STEP 7: Set It Up

I emptied one side of my TV cupboard then neatly stacked my battery and inverter next to each other, in the picture i'm only using one of the inverters seen in the picture, dont use 2 inverters off the battery.

Remember a battery also has a limit, just because it says it can deliver 100 Amps in an hour it doesnt mean you should or can draw that much, you will destroy your battery if you draw too much amps from it and will die quickly, Die not as in goes flat quick, die as in die buy a new one.

In this step I also show you how the max volts used to charge the battery,

STEP 8: Important Notes

Make sure the inverter is double the wattage you are intending to run.
So add up everything you will be running from it then times that by 2.

For safety sakes, don't permanently use it as backup only plug things into it when you are there and need it.

Im drawing 110watts from this 102a/h battery and it will last 3 hours, if i draw around 200watts the battery leads become hot, BAD BAD BAD, So again for safety sakes dont run more than total 110watt appliances per 102a/h battery and you will be fine.

I would advise to check up on the battery water levels once every 3 or so months.

For crying out loud! DO NOT ACCIDENTALLY SWITCH THE POLARITY unless you like fireworks, mark the cables properly with Black and red , I used black insulation tape on the negative terminal.

If you have suggestions and notes to make let me know then I update this list.

Comments

[irjayjay]

Thanks for the tutorial. I'm quite puzzled. I bought a Mecer 720W UPS inverter and a 150ah deep cycle gel battery. Wiring them up was easy and the inverter came with cables. The first few cycles it would last about 3.5 hours on a load of about 200W - just my laptop. After about 10 cycles the battery only lasts 1.25 hours. This is after having it for a month. Only does 50% discharge max and there were maybe 3 times I got close to that. The battery is rated for 700 cycles if you discharge to 50%.

This is the second new battery I've used, so I sent the UPS back.
I'm really scared to buy another one now in case it ruins more batteries.

What am I doing wrong?

[saadland]

Hello, I really hope you are still visiting this able, and you will give me some answer.
I recently did the same project, Computer Backup UPS + Bigger Battery, unfortunatly with no success. Even the UPS, I used is rated 850W, so I guess, it is supposed to be able to charge those battery above 100A.
Also, how did you manage to find at what voltage, your UPS is charging a battery?? The UPS I used is not turning on if there is no battery connected to it. And when I connect a battery to it, and check the voltage, I am reading the internal voltage of the battery, not the voltage supplied by the UPS itself.
Thx.

[mviljoen2]

I just measured the voltage whilst the battery is connected. Probably not the best way to do it. But I figured if the battery is full it doesn't really pose much of a load.

Back then When I built this it worked fine until I realized the charger is reducing the battery life from about hours to only 30 minutes. even after having it on charge for days.

No wonder the original battery packed up they way it did in the photos. I then bough a ctek charger to charge the batter whilst not connected to the Inverter. When i need it I just connect it to the inverter using battery clips. The Ctek charger increased the batery life again to normal.

Dont trust these small el-cheapo inverters with an expensive battery ;-) Besides they are not meant to charge a 100Ah battery when it was designed to only charge a 7Ah

Probably not what you wanted to hear but I hope it helps.

[goofykl9]

Hi, nice project, the battery cables may need to be bigger to deal with the load, on my project I used automobile battery cables.

[mviljoen2]

Yep, I dont have this setup anymore except for the battery..
I changed it a bit, its now charging from Ctek charcher and I also build a little cart to move it around. Works great run a 75W fan for about 4 hours, can run much longer never needed to run it for longer than 4 hours.

[jompon2547]

can i run big motor with this?

(it use 120v to run)

[Winston 8]

Viljoen! Load shedding this is a South African instructable #very proud

[JJ Slabbert]

Baie kreatief. I'm also South African, but went the route of buying an pure sine-wave inverter at for a very large amount of money. This system is an good example of diy creativity. If you are interested you can surge for my solar management and monitor system that will enable you to remotely manage and monitor inverters via internet.

[MikB]

"also I noticed this charger maintains the battery by clicking a relay every now and again to top it up."

It's possible: I don't know your particular UPS. But ... I suspect though that the battery is constantly trickle charged, at a slightly elevated voltage, to give a compromise between BULK charging (which if done forever would kill the battery fast), and trickle charging (which takes forever to bring the battery back up).

This is why your original battery cracked and died. They usually do.

The clicking you hear MAY be a relay that operates to buck/boost the mains voltage, so that small under or over voltages are corrected without disturbing the battery. Both of the types of consumer UPS I have do this. (AVR - automatic voltage regulation).

Bigger battery is a good idea (7Ah is tiny, currently running 18Ah externals, and have used 25Ah's in the past). Better to use a big battery and not flatten in, than a small one run into the ground.

[hlevine]

'n boer maak 'n plan. Very nice.

[slo5oh]

I did not see where you mention what type of battery you are using. It's very important for people to understand NOT to use a normal car battery inside your home. When a normal lead acid battery is charged it release oxygen and hydrogen a very combustible combo.

[jbotha4]

I did exactly the same thing. my unit last about 6 hours. currently your unit only runs for 3 hours because the ups cuts when the batteries reach 50%. if you utilise a deep cycle battery you can easily drain the battery to 10%. nevertheless I would recommend it to be done the same way if you are a dit guy

[mviljoen2]

I did mention its perfect for an SLA battery, agree its not totally clear though :-) everyone i'm using an SLA, batteries tend to gas over 14v this is charging @ 13.54v

[johng652]

Brilliant! Short of moving next door to one of the board of directors or emigration, maybe find a solar charger for when the load shedding lasts more than a couple of hours.

The last thing you want to hear is, "We're for the government, we're here to help".