Let's design our own UPS

Thor

Honorary Master
Joined
Jun 5, 2014
Messages
44,262
Hello Guys,

This is a continuation from this:


The ratel is VERY good value for money, @ginggs we are nerds, you know that. We want more, simply because more is possible so why not?

I am busy studying electronics again, but it will require too much time so whilst I study I would like to pay an electrical engineer to create a PCB for me.

I would then want to create a 3D sketch for a housing unit for it, again, just not enough time to make this work in Fusion 360, and will need the PCB first so looking to pay someone for this part as well.

My questions, do any of you know an electrical engineer that I can speak to?

I want to build a bigger version of the Ratel.

Or maybe through sheer luck, we can come up with a solution between all of us.

This is what I want to achieve:

Always-On / Loadshed Olifant (top-end model)

Input
1 x 12V/24V DC-jack Brick or AC cable and then the rectifier is inside the PCB

Output
2 x 9V 1A DC
2 x 12V 2A DC
1 x 24V 2A DC (mikrotiks, normally 700mA, but 24 volt)
3 x USB 5V 1A DC

  • Lithium-ion cell: 18 X 65 mm Cylindrical
  • Cell Capacity: 2200 mAh
  • Cell(s) in Series: 3
  • Cell(s) in Parallel: 5
  • Circuitry: Safety Circuit / Smart Battery System
  • Battery Voltage: 11.1 V
  • Battery Capacity: 11000 mAh
  • Battery Energy: 122.1 Wh
It needs to draw from AC when AC is available and only draw from them batteries when the AC drops and it should not overcharge the batteries.

Then for the "Loadshed Rooikat"

Input
1 x 12V/24V DC-jack Brick or AC cable and then the rectifier is inside the PCB

Output
3 x 9V 1A DC
1 x 12V 1A DC
4 x USB 5V 1A DC

  • Lithium-ion cell: 18 X 65 mm Cylindrical
  • Cell Capacity: 2200 mAh
  • Cell(s) in Series: 2
  • Cell(s) in Parallel: 5
  • Circuitry: Safety Circuit / Smart Battery System
  • Battery Voltage: 7.4 V
  • Battery Capacity: 11000 mAh
  • Battery Energy: 81.4 Wh
It also needs to draw from AC when AC is available and only draw from them batteries when the AC drops and it should not overcharge the batteries.

My personal requirements:

2 x Mikrotik
1 x Fiber Ont
1 x Tenda Router
2 x Raspberry Pi

The idea being, if whoever asks me what can I get to keep my internet on, forever, whilst eskom is down. I can just send them one of these units.

In essence, there are good UPSes on the market, but we can do better and some of us might have niche requirements or just want more batteries because we can.

The idea here is to see if we can crowdsource a bit of knowledge and create a POC UPS, an opensource UPS if you will...

The DC UPS must take AC in and then have the selection of outputs (discussed here: https://mybroadband.co.za/forum/threads/lets-design-our-own-ups.1120162/#post-26783490) and only use the battery when the power goes out.

3D printers and components are very affordable actually and Eskom is not going away so if you are a nerd like me & you want to always have your internet and raspberry pi with pi-hole on during load shedding, but you want a bit more than what the market has to offer then this is the thread.
 
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If you search around you can find all those circuit diagrams online. Just need to put them together in one design.
 
Question is always, what do you want to power...
You want a pi, someone else wants their random ONT... Someone else wants their TV...

As soon as you go AC the losses are so huge it makes it a different product in my mind.

Ps: but still, I'm interested...
 
Question is always, what do you want to power...
You want a pi, someone else wants their random ONT... Someone else wants their TV...

As soon as you go AC the losses are so huge it makes it a different product in my mind.

Ps: but still, I'm interested...

100% correct.

Perhaps we should come up with a output list and just take it from there. something that can cover 100% of DC powered needs & then we leave the AC for another device.

So something like:


Output
4 x 9V 1A DC
4 x 12V 1A DC
5 x USB Type A 5V 1A DC
2 x USB Type C 5 1A DC
1 x USB Type C (PD) 20V <- unsure if this is practical. ?

Any other output needed?
 
100% correct.

Perhaps we should come up with a output list and just take it from there. something that can cover 100% of DC powered needs & then we leave the AC for another device.

So something like:


Output
4 x 9V 1A DC
4 x 12V 1A DC
5 x USB Type A 5V 1A DC
2 x USB Type C 5 1A DC
1 x USB Type C (PD) 20V <- unsure if this is practical. ?

Any other output needed?

24V and 48V for PoE
 
Output
4 x 9V 1A DC
4 x 12V 1A DC
5 x USB Type A 5V 1A DC <-- feels like overkill?
2 x USB Type C 5 1A DC <-- dont know about you, but 1a phone charger is too slow... Qc3 better...
1 x USB Type C (PD) 20V <- unsure if this is practical. ?

Any other output needed?
Something that I keep feeling a need for :
19V DC for monitor... (Think 3a?)
19.5V DC for Dell Laptop... (Many Amps!)

Wonder what other common DC items there are?
How many TVs are DC with a ac/dc right there?
 
/subs

I probably have the skills to do this (masters in electronic engineering) but my wife is due to have a baby any day now and my actual day job takes the rest of my time.

But I'd be keen to contribute somehow at some point.

If you want to produce just a few it'll be expensive, but not ludicrously so. Like any hobby.
If you mass-produce, it can end up pretty cheap per unit, but then there would need to be enough demand to justify that. I'm talking hundreds of thousands of units. If someone has a contact with a manufacturer in China somewhere, perhaps. I know there is a facility somewhere in Jo'burg that can assemble such products, so that may be an avenue, I forget the name of it now.
 
100% correct.

Perhaps we should come up with a output list and just take it from there. something that can cover 100% of DC powered needs & then we leave the AC for another device.

So something like:


Output
4 x 9V 1A DC
4 x 12V 1A DC
5 x USB Type A 5V 1A DC
2 x USB Type C 5 1A DC
1 x USB Type C (PD) 20V <- unsure if this is practical. ?

Any other output needed?
If you have the battery storage of the UPS as 6 cell lithium based, then Vmax = 25.2 V, Vmin ~= 18.6 V.

You can have USB C PD output using a boost/buck PD controller like this (https://www.usbgear.com/CGL-CCG3PAv3.html)

The rest of the barrel or banana outputs can be high efficiency buck controllers - they're cheap (like R50 each with a display https://www.communica.co.za/products/bmt-adj-dc-dc-module-3a-display)

You can have an XT-60 output on the box if you need to connect an additional pure sine inverter for things like TVs or dumb chargers for laptops / computers
 
I think everyone is trivialising these outputs. You can't just output a bunch of variable DV voltages on independent rails from without spending a bit. We're talking expensive here IMO.
That said, I'm a fan of simplicity with high efficiency, low heat converters like these:
Independent buck circuit for each output. Everything shares common ground
 
Independent buck circuit for each output. Everything shares common ground
So outputs:
19v 3A
2x 12v 1A
1x 5v 2.5A
1x 5v 1A

In theory, what kind of battery (and charge circuit) do you envisage is required for something like that to be able to run for 2 hours?
 
So outputs:
19v 3A
2x 12v 1A
1x 5v 2.5A
1x 5v 1A

In theory, what kind of battery (and charge circuit) do you envisage is required for something like that to be able to run for 2 hours?
Do you want all those outputs to be able to run at max draw at the same time? Or will there be some kind of overall limit? Both are options, but the beefier option will obviously be more costly.

The other thing that I'd suggest is, make it 4-5 hours rather, because certain municipalities use 4-hour load-shedding blocks (Jo'burg). Also, Cape Town's blocks are 4 hours from stage 5 upwards (though we pray that we will seldom need to use this).

As to what the battery would look like, it would almost certainly be made up of 18650 cells. It can be almost an arbitrary number in series, I forget whether buck or boost converters are more efficient, some research would need to be one around that. But probably something like 3s4p (i.e. 12 cells) would buy you quite a bit of capacity. Cost for just the cells would be close to a grand at normal market rates.
 
Can we please add a cheap PWM solar charge controller, but a good branded one, like Victron for example built into this UPS? This way we can add a solar panel to it to help charge it during load shedding

20amps should be good

 
/subs

I probably have the skills to do this (masters in electronic engineering) but my wife is due to have a baby any day now and my actual day job takes the rest of my time.

But I'd be keen to contribute somehow at some point.

If you want to produce just a few it'll be expensive, but not ludicrously so. Like any hobby.
If you mass-produce, it can end up pretty cheap per unit, but then there would need to be enough demand to justify that. I'm talking hundreds of thousands of units. If someone has a contact with a manufacturer in China somewhere, perhaps. I know there is a facility somewhere in Jo'burg that can assemble such products, so that may be an avenue, I forget the name of it now.
I have the contacts, I can get us the PCBs mass produced if needed (Shenzen factory we used before)

And in Stellenbosch is a moulding business wou can create the case if we give them a 3D printed prototype.

I still think it would be expensive, but it doesn't matter as it will be the UPS we want, the one that has no compromises, I'll pay for that.
 
If you have the battery storage of the UPS as 6 cell lithium based, then Vmax = 25.2 V, Vmin ~= 18.6 V.

You can have USB C PD output using a boost/buck PD controller like this (https://www.usbgear.com/CGL-CCG3PAv3.html)

The rest of the barrel or banana outputs can be high efficiency buck controllers - they're cheap (like R50 each with a display https://www.communica.co.za/products/bmt-adj-dc-dc-module-3a-display)

You can have an XT-60 output on the box if you need to connect an additional pure sine inverter for things like TVs or dumb chargers for laptops / computers
Maybe.... One of the ports is a variable one, so the guy can tweak the buck boost to the exact voltage he needs. (on port then that essentially becomes the joker card)
 
Do you want all those outputs to be able to run at max draw at the same time? Or will there be some kind of overall limit? Both are options, but the beefier option will obviously be more costly.

The other thing that I'd suggest is, make it 4-5 hours rather, because certain municipalities use 4-hour load-shedding blocks (Jo'burg). Also, Cape Town's blocks are 4 hours from stage 5 upwards (though we pray that we will seldom need to use this).

As to what the battery would look like, it would almost certainly be made up of 18650 cells. It can be almost an arbitrary number in series, I forget whether buck or boost converters are more efficient, some research would need to be one around that. But probably something like 3s4p (i.e. 12 cells) would buy you quite a bit of capacity. Cost for just the cells would be close to a grand at normal market rates.
I think we should aim for more rather than less. In terms of run time. 8h - 12h maybe, just enough that we never need to worry about it.

The batteries are dirst cheap, I can get the 18650 2200mAh for R80 each and that is without bulk discounts.
 
I think we should aim for more rather than less. In terms of run time. 8h - 12h maybe, just enough that we never need to worry about it.

The batteries are dirst cheap, I can get the 18650 2200mAh for R80 each and that is without bulk discounts.
I generally try and get the Samsung 3500mAh cells, which are a bit more pricy, they tend to have more charge cycles as well. But if we over-provision by enough then that shouldn't be an issue.
 
12 x 2200 mAh @ 3.7V = 97.68Wh @ 100 DoD.
If the batteries cost R80 each then that is R960 for the batteries.
Why not rather use a BlueNova BN13V-8-104Wh which provides 104Wh, has a built in BMS and costs R999 on Takealot? Then add a decent LiFePO4 charger like a Victron Blue Smart IP65 12/5 charger for R1293 and then the batteries, BMS and charge circuitry is done. That is my plan.

One needs to find cheap 2000 mAh+ 18650 batteries for say R40 each before the addition of BMS, battery holders, etc. starts to make sense. Easier to justify if one has access to old discarded laptops.
 
12 x 2200 mAh @ 3.7V = 97.68Wh @ 100 DoD.
If the batteries cost R80 each then that is R960 for the batteries.
Why not rather use a BlueNova BN13V-8-104Wh which provides 104Wh, has a built in BMS and costs R999 on Takealot? Then add a decent LiFePO4 charger like a Victron Blue Smart IP65 12/5 charger for R1293 and then the batteries, BMS and charge circuitry is done. That is my plan.

One needs to find cheap 2000 mAh+ 18650 batteries for say R40 each before the addition of BMS, battery holders, etc. starts to make sense. Easier to justify if one has access to old discarded laptops.
My understanding is that LiFePO4 has less energy density.

I suppose size isn't a massive factor here, but LiFePO4 will be bigger than the 18650 brick, I think?

I see on the Blue Nova website it says it is a drop-in replacement for lead-acid... I wonder if I should then in the meantime until we figure this UPS out, buy a normal 650watt UPS from meccer, but then remove the 7ah alarm battery it has in the side and replace it with this: https://www.bluenova.co.za/wp-content/uploads/2020/01/BN13V-11-140Wh.pdf because 1400 Wh = 107Ah.

My network rank plus the Synology pulls about 3 Amps if my calculations are correct. So this means I could run the rack for 30+ hours.

If I do the same and buy another 650watt UPS and add this Blue Nova battery then I can run my Samsung Q70T TV and Soundbar for 20 hours.

Mmmm...

Am I missing something or can that actually work?

I think Blue Nova made a typo. 1400Wh is alot.

2021-01-20_12-42-16.jpg
 
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