Let's ideate on making a Level1 UPS that doesn't suck

Disclaimer: I’m lazy but I didn’t read through all 101 comments, only around 25 or so.

Don’t use lead-acid cells, the relative capacity is horrible and they emit not-so-healthy gases when they charge.
LiFePo could be a better option, they’re basically fireproof Li-Ion/Po

Well I feel like we need to get a few dimensions on the ups. Maybe a few sizes for different applications. Then we can sort what commercially available batteries would fit and sort of build on top of that.

If it is capable of handling lead-acid it can fit all the kinds of li-ion batteries because of their bigger capacity everything can fit in the footprint of lead-acid.

I thought it was expected of us to make the whole UPS and I don’t have time right now however if it’s only for the batteries I can recommend them right now @Wendell LiFePO4 is the best chemistry for a long lasting battery. They have a minimum of 2000 cycles life before degradation compared to LiCoO (the high capacity ones that catch on fire) which have at leat 500 and lead-acid which have between 200 and 400. The only problem of LiFePO is the nominal output of current however tommorow I will make a table for comparison.

How should the AC filtering work?
I thought that some UPSs continuously charge and drain the battery simultaneously to filter the output through the battery.
Could that, or shouldn’t that be an option here?

To my knowledge, batterys tend to slightly drop in voltage after having finished charging.
And on bad chargers i think that sometimes causes another charge to start again and again and again.
Is that what you guys mean with “overcharging” ?
And Should / could that be avoided in this case?

To me, overcharging means going above the supposed voltage of a cell.
On LiPo RC Hobby cells you can technically go up to 4.5V without that much of a risk of explosion etc.
But degradation is pretty high so it’d be some crazily good cell to survive that more then 10 times max.
You’d do that where you need that 5% extra for a few times only of cause.

Back to the UPS unit itself, i’d like to see a modular approach with maybe inspiration from the open compute (OCP) design philosophies and hopefully available schematics and boardviews for those like me who want to be able to repair their stuff when the time comes. #RightToRepair.
At this point, please mark all power-rails + their expected voltage on the pcbs and mark and break out enable and "everything OK " pins. That would be much appreciated.

  • the obvious additional things…

Thanks. Gona start saving for this one.

It may also be useful to add on some USB ports for charging phones and such

1 Like

If this will be dedicated for PCs… isn’t it much more efficient to have the DC power from the battery DC going to the motherboard?
…instead of DC --> AC --> DC ( e.g. ups battery --> inverter --> pc power supply)

4 Likes

Problem is PC’s have several rails on different voltages… 3, 5 , 12 V etc. Keeping Power from battery DC to DC is more effective when its the same but that’s tnot the problem.

buck converters should be more efficient get the other voltages you’ll need for the motherboard.
Its how the DC to DC picoPSUs work…

not to mention… how do you think normal atx PSUs work… they only take in one voltage and spit out the several voltages… they likely use mosfets or other types of voltage regulators to get the other voltages.

Im old school they tap the transformers at the required winds for the voltages. It’s not my field so maybe AC to DC has moved on.

I dont mind being schooled its hard to keep up with everything.

the battery voltage will likely be from 12V-24V so no boosting will be required so the only thing is too step down the voltage which is easy enough with modern components. Most of your power draw will likely come from the 12V rail so you dont need todo much conversion so you get a higher efficiency.

2 Likes

Probably do not want to start reinventing the PC side of things. Not sure if we collectively want to but maybe pick 3 battery choices and or a few of the modular components that are overall wanted. Then we can move the idea forward to something we can start fine tuning. I may be jumping the gun just thinking get things dialed in here.

3 Likes

In defense of lithium ion batteries, we use them for motorcycle OEM replacements as they are much lighter and they can actually last over the winter without having the have a trickle charger attached to it. The only problem is the first time you try to turn on your bike for the new season is that it might not crank right away. This is mostly because of the temperature outside where the bike is and so you might not have that issue with a UPS that’s meant to be in a house the entire time.

I’m an electrical engineer, and this thread piqued my interest.

A typical laptop battery might be around 100Wh, so a 250Wh UPS using lithium isn’t crazy. Battery working life can be extended by not charging above 80% and not discharging below 20%. If you treat the batteries well they should easily last 10 years.

The other complication with lithium is that you end up with lots of individual cells rather than one or two big lead acid ones. So you have to design the system with that in mind, and ideally make it able to cope with individual dead cells.

Beyond the batteries and a charging system you will need an AC converter that can handle say 1000W, and a system to automatically switch over when the mains fails. That’s not easy to design, there are a lot of safety issues to consider and you have to assume your UPS is going to get hit with all sorts of nasty spikes.

Someone should make a UPS that lets you use recycled batteries. I’d buy that.

4 Likes

YES!
shipping battery’s is expensive aswell.
And everyone can get small motorcycle battery’s or giant truck battery’s according to their needs.

Also recycling big plus! easy on nature and your savings.

1 Like

my thought is to make a smart UPS that uses an Arduino or similar for the brains so that you can control the charging circuit with it so that you can change out the battery setup as new tech comes out or just have the flexibility for it to be modular so that if the price point of a NIMH solution is cheaper in country y and a LiFe option is better in country x it just becomes a dropdown and variable input solution and the UPS can use both.

1 Like

Yes, you are right that some laptops do have 100Wh batteries, but the reason they exist in laptops is because the laptops themselves aren’t pulling too much current from the battery. The higher the current pull, the larger the battery needs to be (plus, may also need a different battery chemistry, which results in different battery sizes, higher price, etc etc etc).

It would be nice if the battery had some sort of safe disconnect to minimize chance of shock when changing batteries.

2 Likes

should reach out to Johnny Guru for his input on people to talk to about the UPS.

if you have mechanical switches on the out side of the case that breaks the connection. then it is easy to make it a lot safer when removing batteries as you can remove the connectors from a lever instead of by hand.

Something as such would work. I know APC uses a little flap that bridges to prongs.

Just something that makes it an open circuit while you plug and pull batteries, that way it doesn’t arc trying to equalize the voltage between the battery and the rest of the UPS.

1 Like