Car battery charging below float voltage?

[Paul]

Power outages, have statistics.

Here, a power outage is 1 second. Or a power outage is 2+ hours. In fact, the long power outages have been lengthening in time, in the last decade. One lasted a day. The last one was two days plus. The power company is on a safety kick, where power repair trucks sit idle on the street, with staff sitting on their hands.

As such, a single leisure battery and three 80 ampere loads, that's a huge load. And the 130 Ah leisure battery, you're not really supposed to be running those flat. This means you have well-less than an hour of capacity. How many BOINC units can you do in half an hour ? Is it worth XXX pounds currency, for the privilege of doing so few units ?

With a UPS, the objective is to allow clean shutdown of all computers. You could buy a consumer UPS for each 1kW supply. Maybe this would give you 8 minutes holdup time, or 4 minutes holdup time. You would need to send the shutdown signal, to all the computers, so they would begin shutting down.

You cannot buy the lowest tier of UPS either, if you really plan on handling a full kW load. There are some really awful UPS that will smoke if you do that.

A commercial UPS, a double conversion rack mount, might have the power rating to run your entire computer room. But, you will be charged a commercial rate for such a beast. In your IT days, you might have had such rackmount UPS in the server room. They seem to be quite common. As double conversion, they have a cooling fan that runs constantly (unlike a consumer SPS which runs cool until it flips to battery).

Buying three UPS, would be an intermediate solution, compared to buying a Tesla Powerwall (price has gone up 2x since introduction), or some of the less well thought out consumer "battery bank" thingies. There is one product, which does not even work as well as a double conversion UPS, which would be cheaper than a powerwall, and they're about 1kWh each.

*******

The video card uses 3.3V and 12V

The motherboard uses 3.3,5,12,-12,+5VSB.

The leisure battery only has one voltage, not six or seven voltages.

You need to pick the logically correct point for backup powering this mess.

Your plan right now, is just plain wrong.

Paul

[Rod Speed]

Or you could get real radical and get a generator for the longer times without power and use the car battery to give you time to start it and switch over to it.

A UPS and generator would do that fine with the car battery supplying the very high 12V demand with his unusual config.

Not if he never get long power failures.

[Commander Kinsey]

Do you live in India? I can't remember my last power outage. This battery is not for power outages.

The computers are not powered by that battery. They run directly off the mains. They do nothing in a power outage.

I have one for the computer in here, plus the screen, stereo, internet router, and lights for the whole house. That runs off two of those batteries. The pathetic little batteries inside UPSs are useless, I bought a 2nd hand one without batteries and connected the leisure batteries to it. Lasts 20 times longer.

My parents bought a 720W UPS which will power a 15W LED standard lamp for 8 hours, or that plus two fridges for 2 hours. Pathetic. I'm trying to persuade my dad to let me connect a couple of leisure batteries to it. The original intention was to power the pumps for the oil boiler but they changed their mind and said they can just use the fireplace. For some reason he doesn't trust me connecting stuff to his fusebox.

My APC 1kW UPS can power a 1kW vacuum cleaner, even though motors at the full load rating are not supposed to be connected to a UPS (they draw 5 times the current at startup).

Nah, I'd get a 5kW solar invertor, and add lots of leisure batteries which are dirt cheap. A 240V powered relay will easily switch the load between that and the mains instantly.

Actually most of the load could run straight off the battery as it's 12V.

If the doom sayers are correct and we end up with mass power shortages, I may end up with the whole house on UPS.

We did, it held the (on wheels) server cabinet very steady!

No, ours did not make any noise. If there was a fan it was totally silent when not under load.

Those are a stupid idea. Lithium Ion batteries?!? Way too expansive. Li Ion is for when you need light weight, otherwise lead acid is far cheaper.

No it does not, my video cards run entirely off 12V.

A very small amount of current. The CPU is 12V for example.

You might care to read what I'm doing first.

[Joe]

Not just the fuse, but the type and quality of fuseholder. I occasionally deal with portable 25Ah battery boxes, fused at 10A, and I've seen a couple of cases of part-melted fuseholders. The spring contact of the panel-mount fuseholder just isn't up to maintaining a low resistance with a high-ish current over long periods.

You'll want a high rupturing capacity fuse, and a fuseholder that grips around the fuse end caps fairly tightly. Don't be tempted to buy the cheapest.

[charles]

A great many years ago, we had problems with a low voltage power supply not delivering the right voltage. It was eventually traced to a 5A glass enclosed fuse which had a resistance of 1 Ohm. A whole bad batch!

[Commander Kinsey]

I used a Henley fuse, the ones they put on incoming feeds to houses in the UK. No holder, hoseclipped on, like this:

[Commander Kinsey]

Surprised that didn't melt and therefore blow.

[The Natural Philosopher]

When I designed a radio receiver hifi amplifier i got called to the production line where all the radios suddenly developed 0.25% distortion And yet on my test bed, thy were all 0.05%.

The test line was using the same connector that was in the original radio. Designed to be plugged in once, and that was it, the silver plating was now covered in silver oxide, making a first class - well now, about a tenth rate - rectifier...

[Paul]

Here is the original question.

I have now deleted all of your misconceptions about electricity and wiring. As they are irrrelevant to properly running 8 computers with a total of

15 graphics cards.

*******

List the assets.

In each column, you fill with the number of units needed for the load to the right of it.

Mains CCT UPS column ATX supply --- mobo --- 2 graphics cards

Mains CCT UPS column ATX supply --- mobo --- 2 graphics cards

UPS column ATX supply --- mobo --- 2 graphics cards

ATX supply --- mobo --- 2 graphics cards

ATX supply --- mobo --- 2 graphics cards

ATX supply --- mobo --- 2 graphics cards

ATX supply --- mobo --- 2 graphics cards

ATX supply --- mobo --- 1 graphics cards

On each ATX supply, you total up the electrical loads, and buy the next largest supply. A 1000W supply can power a 600W system, and have 400W of unallocated margin left over. The real draw from the wall is 600W, not 1000W. It is the actual load that determines the billable consumption.

Each ATX supply is independent of the other ATX supplies. There are no bus bars, copper plates, dangling wire assemblies going all over the place. Each of these, is assigned room on your rack shelving. No misconceptions about electricity are required, if you do it like the gamers and scrotes do it. The money wasted on a leisure battery, could have bought you three cheap ATX supplies instead, until you have the eight independent supplies needed. There should be excess supplies on Ebay, from coin miners going out of business.

+--------------------------------------------------+ \ ATX supply --- mobo --- 2 graphics cards \___ Neat and tidy packaging / +--------------------------------------------------+

You total up the real consumption of each system, if fitting UPS boxes.

You pick UPS boxes (if you really want or need UPS) according to the real load of the PCs. The PCs can each have a 1kW supply, but the UPS is gauged by the 600W load (or whatever). You follow the rules for loading a UPS.

A Kill-O-Watt meter can make measurements on each system, and making actual measurements on each motherboard plus 2 graphics cards, allows you to do a better fit of UPS boxes to loads. The meter measures in W as well as VA, and you can compare those numbers to the W and VA limits of the prospective UPS.

You might not need eight UPS boxes (of the cheap tier). Maybe fewer boxes will be needed, for the systems that have the weak past generation graphics cards. You can't fool us into believing the fifteen graphics cards are 4090. They aren't.

You allocate the UPS boxes to mains circuits, according to the breaker ratings in the panel and associated outlets. Using the real/measured 600W value or whatever the measurement shows, in each case. If you run Prime95 and Furmark on a system or a similar kind of max_load, you can get a better idea of what the max_load really is.

Summary: If you do stuff like normal people do it, there won't be any leisure batteries or bus bars or other crap in the picture. The wiring will be neat and tidy. Your fire insurance person will be well pleased and you will continue to have fire insurance.

Paul

[Hul Tytus]

Your guess agrees with the results here. The first voltage/current recorded was, from memory, 12.5 volts at .25 amps. This was about 6 or 7 days ago. A couple of days ago I weighed the battery and in the process wiggled it a bit. Next day the voltage & current were noticably higher. Due to the wiggling?

Hul

[Animal]

whoosh

[chop]

You never could bullshit your way out of a wet paper bag.

[Commander Kinsey]

So I can't see them and refute your reasoning for dismissing them.

I assume CCT means circuit? The free dictionary shows 132 possibilities. I'll take it to mean a 13A 240V plug.

Ugh, I guess I need to change to fixed width text for this....

You've made too many assumptions. The above is nothing like what I have. The GPUs are not spread evenly through the MBs. I don't use UPSs.

No no no. The computers themselves - the MB, RAM, CPU, SSD run off normal PC power supplies.

Stupid way of doing things. With my current setup, I can add a GPU anywhere on the shelving and connect it to any computer. And I get a rock solid voltage of whatever I set the PSUs to(they're variable from about 10 to 15 volts. The PCI Express specs say 11.4 to 12.6V, so I've set it to 12.6V, which means even if there's any voltage drops on wires, it has plenty of room, but it will never go over the specs when unloaded. It also means less ucrrent going into the input side of the VRMs on the GPUs.

Those things do not have a stable voltage output, and are often a fair bit below 12V.

I'm not interesting in neatness, I'm interested in stability and ease of adding parts, swapping parts, testing parts.

I use an amp clamp on the 12V buses.

Old ones use the same electrical power, they just do less work. The designers tend to get limited by the heat they can dissipate in the size of a video cassette.

Fuse.

Nah. 30A 240V going to the garage. Three 13A sockets. If something gets warm I shift a load.

I use Milkyway at Home to fully load them.

The whole point of the bus bars was to get rid of the clutter of many ATX supplies loading individual cards with cables everywhere. It actually looks about 3 times tidier than before. With bud bars tacked along the shelving, there's only a 6 inch cable from each PSU to that bar, and another 6 inch cable to each GPU.

I don't have fire insurance.

[Commander Kinsey]

It's surprising when the battery is 12V open circuit, an extra half volt only supplies 0.25 amps. I guess we need to think about the chemistry of the battery to know why it's so low. It must be more than a simple resistance, otherwise giving it 14.5 volts would only charge it at 1.25 amps.

[Jasen Betts]

the voltage is too low for a 6 cell lead-acid battery, and too high for a 5 cell battery. maybe try supercapacitors instead.

[legg]

Get serious. Battery terminal clamps are not expensive. Niether are CNL or ANL automotive/marine fuses.

Fuses that interrupt DC are different animals.

Your illustrated clamp has obviously not run at more than few tens of amps. At 100A you'd be able to measure the voltage drop and probably be able to smell it.

Whatever happened to 50% derating on power sources?

Distributed computing through BOINC is supposed to employ unused computing resources. It's not intended to tip the ballance of global climate, or to mine bitcoin.

I expect you find your winter heating bills are unaffected, but summer must be pretty intollerable in that room.

RL

[Hul Tytus]

Keep in mind that charging current is limitited both by the battery & the charger. The data I stated was from a charger with a max current due to a 12v transformer rated at 2 or 3 amps.

Hul

[Rod Speed]

He's in the wilds of Scotland, it never gets that warm there in summer.

[Commander Kinsey]

Hose clips are precisely what you see in a car to attach a battery for the purpose of a few hundred amp starter motor etc.

Bollocks. The voltage matters, and I'm giving it way less then the 240V it's rated at.

The clamp isn't carrying the current.

WTF are you talking about? The power source is rated to x, it can do x. Unless it's Chinese, then you divide by two.

Why would it matter if they're unused resources or ones bought for that purpose? They use the same power.

I'm an atheist, I realise climate change is f****ng baloney.

Who mentioned bitcoins?

The room has windows duh.

[legg]

Look again. The aim of a battery connector is to provide maximum air-free contact to the round terminal's surface.

Read more. The I^2t rating of a fuse is good only in it's rated application. AC current is self-interupting, by source reversal. DC isn't and will arc, potentially with explosive results.

With such modest terminal contact, the iron clamp will be developing the same (increasing) voltage drop as the terminal contact degrades. Measure it.

<snip>

As long as the battery's no actually doing anything, as your app describes, you'll not have to worry about it.

Happy number crunching (WCG since Y2K on 3+ machines)

RL