Let's design our own UPS

[Tomtomtom]

Lately I was thinking what it would take to build a pure sine wave inverter from scratch... should be cheaper than what is on the market?

I doubt it. Except for specialised stuff, mass-produced is always going to be cheaper than buying parts at low volume. The MOSFETs alone will probably come to nearly a grand before you even think about how you drive them.

Then there's safety. I'm not keen to try even the simplest modified-sine design because I'm not qualified to play with the kind of voltage you find on the output of an inverter, nevermind the currents which could easily start a fire.

 

[RaptorSA]

Just sharing pics of my current build... I've started to really enjoy getting into this stuff.

My mom is in her 70's and needed something to keep a few things running etc.
Took me ages to finally decide on what I needed to do, since I decided to make modularity, longevity and quality a priority instead of trying to save a few bucks just have issues again in a few years. What started out as a good idea turned unit the system I've depended on in the past 3+ years. So here we are.... Full Circle....

What started as me looking into the usual Mecer etc. trolley crap has turned into this, a 5kWh LFP 48V battery that'll be paired with a 3000W Growatt capable of taking a decent sized solar array in future, if things were to get too bad.

I've ordered all the extras like bigger and better sized battery cables to keep it as clean as possible, a decent battery fuse for added safety and AC trip switch etc,.

Cannot wait to get my hands on the inverter and the rest of the parts soon so I can finish this beast.
It'll probably take less than 2 hours to assemble.

What I wanted:



How it's going:



The idea is of course to mount the inverter above the battery like the example below... but since it's collapsable if I can find a good way to mount the inverter in front of the battery it'll be a killer "littler" system that can either stand vertically or horizontally.

 

[Düber]

Just sharing pics of my current build... I've started to really enjoy getting into this stuff.

My mom is in her 70's and needed something to keep a few things running etc.
Took me ages to finally decide on what I need to do, since I decided to make modularity, longevity and quality a priority instead of trying to save a few bucks just have issues again in a few years.

What started as me looking into the usual Mecer etc. trolley crap has turned into this, a 5kWh LFP 48V battery that'll be paired with a 3000W Growatt capable of taking a decent sized solar array in future, if things were to get too bad.

I've ordered all the extras like bigger and better sized battery cables to keep it as clean as possible, a decent battery fuse for added safety and AC trip switch etc,.

Cannot wait to get my hands on the inverter and the rest of the parts soon so I can finish this beast.
It'll probably take less than 2 hours to assemble.

What I wanted:

View attachment 1464951

How it's going:

View attachment 1464953View attachment 1464955

The idea is of course to mount the inverter above the battery like the example below... but since it's collapsable if I can find a good way to mount the inverter in front of the battery it'll be a killer "littler" system that can either stand vertically or horizontally.

View attachment 1464993

View attachment 1464991

That is an excellent idea, please keep us posted with it.
I have two elderly aunts that are sitting in the dark currently but have two left thumbs. So this looks like just the thing for them.

 

[RaptorSA]

Just sharing pics of my current build... I've started to really enjoy getting into this stuff.

My mom is in her 70's and needed something to keep a few things running etc.
Took me ages to finally decide on what I needed to do, since I decided to make modularity, longevity and quality a priority instead of trying to save a few bucks just have issues again in a few years. What started out as a good idea turned unit the system I've depended on in the past 3+ years. So here we are.... Full Circle....

What started as me looking into the usual Mecer etc. trolley crap has turned into this, a 5kWh LFP 48V battery that'll be paired with a 3000W Growatt capable of taking a decent sized solar array in future, if things were to get too bad.

I've ordered all the extras like bigger and better sized battery cables to keep it as clean as possible, a decent battery fuse for added safety and AC trip switch etc,.

Cannot wait to get my hands on the inverter and the rest of the parts soon so I can finish this beast.
It'll probably take less than 2 hours to assemble.

What I wanted:

View attachment 1464951

How it's going:

View attachment 1464953View attachment 1464955

The idea is of course to mount the inverter above the battery like the example below... but since it's collapsable if I can find a good way to mount the inverter in front of the battery it'll be a killer "littler" system that can either stand vertically or horizontally.

View attachment 1464993

View attachment 1464991

@Düber

Jirre I have the worst post Valentines hangover ever but I finally just got my inverter delivered after a month's delay.
The stock sizing of components for this thing couldn't be more perfect.... it looks like I'll actually be able to mount it to the trolley frame without having to mount wood or aluminium slats first, just straight up drill and bolt.

Can't wait to start the final build this weekend.

 

[leutwein]

I custom build and sell these if anyone would be interested head over to https://www.facebook.com/JuiceBoxSA/

 

[Park@82]

I custom build and sell these if anyone would be interested head over to https://www.facebook.com/JuiceBoxSA/

High amp chargers are damn expensive. How much do your charge for the 640wh one on your fb page?

 

[leutwein]

High amp chargers are damn expensive. How much do your charge for the 640wh one on your fb page?

Using a Victron 7 amp charger. Price is R8750

 

[wingnut771]

Using a Victron 7 amp charger.

So it doesn't cover the loads and charge?

 

[leutwein]

No it's not a UPS, so whatever runs from the inverter gets power from the battery. The idea was to build something that is still portable and light, UPS inverters are bigger and more costly
if the load is less than 7amps say 80w or less you can leave it plugged in permanently

 

[Park@82]

Using a Victron 7 amp charger. Price is R8750

Yeah I saw that. 7a seems kinda slow. But I can understand that you are trying to cut costs. I can imagine that your cost ex labour is close to 8K. Inverters, LFP batteries and LFP chargers are insanely expensive now.

A small pure sine inverter build in LFP charger would have been ideal for your build but I only see them without pure sine and only support for lead acid. e.g. this one https://leroymerlin.co.za/800w-inve...64&sfdr_hash=653c61a14bd5e2747653a47f1c7a0c0c

 

[Jarrod]

No it's not a UPS, so whatever runs from the inverter gets power from the battery. The idea was to build something that is still portable and light, UPS inverters are bigger and more costly
if the load is less than 7amps say 80w or less you can leave it plugged in permanently

Throw in one of these and it can function as a ups

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It will impact cost tho. I kinda have the same small setup but with a victron inverter. So i can set at what volts the inverter must switch off to prolong battery life.

 

[Pineapple Smurf]

Getting there on my project
Free salvaged 18650's
My 7S100P is almost complete
Taken over 3 months to test each cell
Average 2200mA each
This will be a 24v array (4.2v x 7 = 29.4 volts actually)
1540 amps @4.2volts
= busload
But the curve drops quickly to settle at 3.7v nominal so on this number we can calculate my power wall will be 5698Wh on average

Basically a 5killowatt battery bank

 

[wingnut771]

Getting there on my project
Free salvaged 18650's
My 7S100P is almost complete
Taken over 3 months to test each cell
Average 2200mA each
This will be a 24v array (4.2v x 7 = 29.4 volts actually)
1540 amps @4.2volts
= busload
But the curve drops quickly to settle at 3.7v nominal so on this number we can calculate my power wall will be 5698Wh on average

Basically a 5killowatt battery bank

View attachment 1476677

How did you manage the free part?

 

[Park@82]

Throw in one of these and it can function as a ups

Takealot.com: Online Shopping | SA's leading online store

South Africa's leading online store. Fast, reliable delivery to your door. Many ways to pay. Shop anything you can imagine: TVs, laptops, cellphones, kitchen appliances, toys, books, beauty & more. Shop the mobile app anytime, anywhere.

www.takealot.com

It will impact cost tho. I kinda have the same small setup but with a victron inverter. So i can set at what volts the inverter must switch off to prolong battery life.

That's perry cool. I didn't know you get onses that can switch automatically.

 

[Park@82]

Getting there on my project
Free salvaged 18650's
My 7S100P is almost complete
Taken over 3 months to test each cell
Average 2200mA each
This will be a 24v array (4.2v x 7 = 29.4 volts actually)
1540 amps @4.2volts
= busload
But the curve drops quickly to settle at 3.7v nominal so on this number we can calculate my power wall will be 5698Wh on average

Basically a 5killowatt battery bank

How do you test them?

 

[Pineapple Smurf]

How did you manage the free part?

They were destined to eWaste

 

[Pineapple Smurf]

How do you test them?

With my Opus BT-C3100 charger
I measured the mA value
As well as the resistance, the lower the number the better, mine averages out at around 120 milli ohms

 

[Park@82]

With my Opus BT-C3100 charger
I measured the mA value
As well as the resistance, the lower the number the better, mine averages out at around 120 milli ohms

Nice. I didn't see them locally when I looked about 2 years ago. I have a Liitokala Lii-500.

 

[Pineapple Smurf]

Nice. I didn't see them locally when I looked about 2 years ago. I have a Liitokala Lii-500.

Bought mine here, not the best reviews on the power forums but at least it gives you a guideline
And that's all I needed
Are the cells good or phucked?

Opus BT-C3100 4Slots Smart Intelligent Universal Battery Charger

Opus BT-C3100 4Slots Smart Intelligent Universal Battery Charger (10001310) Specifications:Brand: Opus Model: BT-C3100 V2.2 Rechargeable Battery Qty: 4 Input Voltage: AC 100~240V 50/60HZ Output Voltage: DC 12V, 3.0A LCD Screen: YES Auto Circuit Detection: YES Built-in Protected Circuit: YES...

www.electromannsa.com

 

[wingnut771]

Bought mine here, not the best reviews on the power forums but at least it gives you a guideline
And that's all I needed
Are the cells good or phucked?

Opus BT-C3100 4Slots Smart Intelligent Universal Battery Charger

Opus BT-C3100 4Slots Smart Intelligent Universal Battery Charger (10001310) Specifications:Brand: Opus Model: BT-C3100 V2.2 Rechargeable Battery Qty: 4 Input Voltage: AC 100~240V 50/60HZ Output Voltage: DC 12V, 3.0A LCD Screen: YES Auto Circuit Detection: YES Built-in Protected Circuit: YES...

www.electromannsa.com

How long does 2200mAh take?