PC Battery power...

The_Great_Sephiroth

The_Great_Sephiroth

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Let me begin by saying that yes, I know this is a game and not something trying to simulate real life. The zombies I meet in real life are NOTHING like the ones here, for example.

That said, let's talk about electrical power. Unless you're running a big diesel like me, most pickups and cars have 12V DC batteries with 300~500 amps of starting power in them. I used to do electrical work and I have brought my own home up to code (I bought an old house that had cotton insulating wires!), so I know something about power. I decided to figure out what the real-world wattage should be using the toys given to us in-game. What I found out after doing the math was insane.

The formula to figure out DC watts using only voltage and amps is "amps multiplied by voltage equals watts". So let's take a pristine car battery in 7 Days and see how many watts it has. Assume a 500amp battery. 12 volts times 500 amps equals 6,000 watts, or 6 kilowatts! Our battery boxes have six of these. That is 36,000 watts (36kW) per battery box! Based on this, I got curious as to what a "perfect" battery in 7 Days was.

Each battery (level 6/purple) produces 50W of power. The formula for finding amps is "watts divided by voltage equals amps". So we take 50 watts and divide it by 12 volts to get roughly 4.1 amps. That's right, the amount in two (sometimes one) double-a (AA) battery. In the real world, each cell in the battery produces around 2.2v of power, and most modern batteries have six cells. This is why a peaked battery is actually 13.2v if there is no draw on it, not 12v. Also why your car is good if at idle you're around 13.8v on the dash. In fact, 13.8~14.8 volts is normal for a car.

So for giggles, if these were motorcycle batteries for smaller engines (not Harleys!) and were 100 watt batteries, they'd still produce 1,200 watts (1.2kW). I would love to see these numbers in-game along with more power-hungry, advanced tech. Maybe a high-end electric fence that eats 100W per post, but deals lethal to human (heavy damage to zed) types of damage. We could also use real-world power consumption for lighting. Just a fun thought, but I figured that those who don't know electricity would get a kick out of knowing how much power six REAL batteries would produce. Now imagine the carnage and have fun!

 
Yeah, but then you'd need to deal with power inverters as well, because someone else will come along and complain about that.

Then we'd need step-up transformers to power the electric fences. Then you'll need to sit and calculate RMS and how much loss and all kinds of other things requiring much Trigonometry that we all hate. 

I've got the background too and I don't want to deal with that in a zombie apocalypse game.

As far as the electric fence, remember it only takes 10mW across your heart to kill you.

 
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The_Great_Sephiroth said:
Assume a 500amp battery. 12 volts times 500 amps equals 6,000 watts, or 6 kilowatts!
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Yup, the ingame ones are relatively weaksauce in that regard. But a real car battery only has somewhere in the neighborhood of 50 Amp hours, if you were to draw that 500 amps constantly, you'd get about 6 minutes of use from one. In-game minutes are about 2 secs each, so 15 seconds of trap use.

Not that I'd mind the idea of betterer traps and more veried electric systems in the game :)

 
Krougal said:
Yeah, but then you'd need to deal with power inverters as well, because someone else will come along and complain about that.

Then we'd need step-up transformers to power the electric fences. Then you'll need to sit and calculate RMS and how much loss and all kinds of other things requiring much Trigonometry that we all hate. 

I've got the background too and I don't want to deal with that in a zombie apocalypse game.

As far as the electric fence, remember it only takes 10mW across your heart to kill you.
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Zombie hearts don't beat, do they? I assumed their systems had all shut down during the "zombification" process. I assumed our goal would be to fry them to a crisp so they cannot move.

theFlu said:
Yup, the ingame ones are relatively weaksauce in that regard. But a real car battery only has somewhere in the neighborhood of 50 Amp hours, if you were to draw that 500 amps constantly, you'd get about 6 minutes of use from one. In-game minutes are about 2 secs each, so 15 seconds of trap use.

Not that I'd mind the idea of betterer traps and more veried electric systems in the game :)
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You are NOT wrong. A car starter draws a LOT of power. Heck, most modern vehicles, including my work truck, are basically rolling computers, and they draw a lot just sitting still! Think of the infotainment systems these things have. Now, couple that with a CAN bus that connects PCM, TCM, and dozens of other systems, each being a small computer system. Lots of power to sit there doing nothing!

 
The_Great_Sephiroth said:
Zombie hearts don't beat, do they? I assumed their systems had all shut down during the "zombification" process. I assumed our goal would be to fry them to a crisp so they cannot move.
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That's a very good question. I mean they still eat. They bleed. So many things to not think about for suspension of disbelief.

The closest to anything plausible was the fungus thing in, I already forget the name of the game HBO made into a series.

Nobody but the devs really know the rules of the 7DTD world.

Oh, and then there is the burnt zombie, so no, I don't think burning them to a crisp would work either.

 
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Krougal said:
Oh, and then there is the burnt zombie, so no, I don't think burning them to a crisp would work either.
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But molotovs and flaming arrows/bolts do work. Maybe the burnt zombies just needed to be cooked a little longer.

The OP's explanation was interesting. Yet, the image (model) for a battery bank shows all the car batteries to be wired in series (increasing voltage, not amperage). So somewhere in all this there's some wires crossed. Not that it matters 'cause its a game, not a simulator.

 
Melange said:
But molotovs and flaming arrows/bolts do work. Maybe the burnt zombies just needed to be cooked a little longer.

The OP's explanation was interesting. Yet, the image (model) for a battery bank shows all the car batteries to be wired in series (increasing voltage, not amperage). So somewhere in all this there's some wires crossed. Not that it matters 'cause its a game, not a simulator.
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Yeah. This is a pretty silly game when you get right down to it.

Try not to look at the things you aren't supposed to look at lol!

 
The_Great_Sephiroth said:
The formula to figure out DC watts using only voltage and amps is "amps multiplied by voltage equals watts". So let's take a pristine car battery in 7 Days and see how many watts it has. Assume a 500amp battery. 12 volts times 500 amps equals 6,000 watts, or 6 kilowatts! Our battery boxes have six of these. That is 36,000 watts (36kW) per battery box! Based on this, I got curious as to what a "perfect" battery in 7 Days was.
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IIRC, the stated 500 amps only needs to be available for 30 seconds at 7.2 volts (at a specific temperature) to meet the standard. 

Perhaps looking at the power (or energy) capacity would be clearer?

If an average vehicle battery is rated for 55 Amp/hours then that equates to 660 Watt/hours.  That is approximately 660 watts for 1 hour or 66 watts for 10 hours (or whatever ratio in between).  In that context a 50 watt (presuming the game really means watt/hour) output for a Tier 6 battery seems reasonable and fairly realistic.

 
8_Hussars said:
IIRC, the stated 500 amps only needs to be available for 30 seconds at 7.2 volts (at a specific temperature) to meet the standard. 

Perhaps looking at the power (or energy) capacity would be clearer?

If an average vehicle battery is rated for 55 Amp/hours then that equates to 660 Watt/hours.  That is approximately 660 watts for 1 hour or 66 watts for 10 hours (or whatever ratio in between).  In that context a 50 watt (presuming the game really means watt/hour) output for a Tier 6 battery seems reasonable and fairly realistic.
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Ever been trawling in the south? We used a 700amp battery with a 90 amp motor. Lasts about seven hours, depending on how much trawling to fishing we did. It was an old truck battery, not a deep-cycle marine battery. It came out of my Dakota when I swapped in a 950amp beast. Either way, you are partially correct in that, at full draw, it will only last an hour or less, but at a partial draw it could last days.

As for temps, you are also correct. Cold temps tend to weaken battery power while hot temps (to an extent) do not. I suppose extreme heat as would be found in southern Navezgane would possibly cause trouble.

 
Well first off: there are different types of batteries : Alkaline, NiMh, Lithium. And those have subtypes. They all share same metrics, but as are made for different purposes perform drastically different under different circumstances. Example: I would not suggest degrading your alkaline batteries lower than 40% as it does damage their capacity in quite a short run. Then comes the voltage -> there are 1,2V...2,4...12V, 24V, 48V batteries and a wide variety of capacity. Yes most regular cars have 55A/h 12V (660W) batteries, but the ones equipped with start/stop function would have a larger battery (60-75A/h) and different type (EFC/AGM) that handle way more cycles charge/discharge, and don't forget we've got Teslas and other completely electric vehicles! Those carry battery packs up to 70 kW! And that is a freaking beast!

From personal observations: last year due to blackouts.... y'all know why we had them... had to buy myself a few batteries to support my workdesk. So a 34" monitor and my Mac consumed a 100 A/h 12V battery in approximately 8 hours.  1 optical-LAN router + 1 LAN switch + 1 Asus Wifi router consumed 2 linked 60A/h batteries in aprox 25Hrs. So it is not that much!

About our batteryBank and inverters -> we may actually assume it already has an inverter! It is a wall mounted/floor based (it is up to you )))) case for batteries with lets say 20A inverter.

Sorry... its is a bit late, and I lost my thought. I'll try to come back tomorrow and finish what I wanted to explain ))))

 
First off, different types are irrelevant. 99% of the cars out there use lead-acid. Only EVs use different types. Some of us bikers run LiPo or LiFe or others to lighten the limited load on our bikes, but the batteries in-game are lead-acid. Also, alkalines don't recharge so who cares if they go below 40%? Run them dead and replace them. As for NiMH, I had two AA batteries I bought in 2004 that finally died. NiMH Energizer, 2500mA. They stopped charging last week. Nearly 20 years old. Regularly brought to nearly empty.

You are also talking about DC to AC conversion. There is no AC power in the game. Everything is DC power. No phases to worry about or anything. It's all simple DC, so there is no conversion lost via a chopper circuit or anything. You lose a bit on the conversion.

Finally, sounds like you have weak batteries or just a poor UPS. I have a 2U on my gaming rig and monitor and another 2U on my NAS, router, cable modem, PoE switch, and SimpliSafe alarm. The gaming rig runs about three or four hours on my battery with the battery powering my 24" G-Sync monitor and the rig (i9-11900k, RTX 3080 Ti, 750W PSU, 64GB RAM, four HDDs in RAID10, four SSDs in RAID10 a single HDD for the OS, and four PCIE NVME sticks) so something is up. The other one runs my equipment for at least sixteen hours. More if I allow the NAS drives to sleep (I do not). For reference, my UPS model is PR100LCDRT2U and has very good AVR.

 
The_Great_Sephiroth said:
First off, different types are irrelevant. 99% of the cars out there use lead-acid. Only EVs use different types. Some of us bikers run LiPo or LiFe or others to lighten the limited load on our bikes, but the batteries in-game are lead-acid. Also, alkalines don't recharge so who cares if they go below 40%? Run them dead and replace them. As for NiMH, I had two AA batteries I bought in 2004 that finally died. NiMH Energizer, 2500mA. They stopped charging last week. Nearly 20 years old. Regularly brought to nearly empty.

You are also talking about DC to AC conversion. There is no AC power in the game. Everything is DC power. No phases to worry about or anything. It's all simple DC, so there is no conversion lost via a chopper circuit or anything. You lose a bit on the conversion.

Finally, sounds like you have weak batteries or just a poor UPS. I have a 2U on my gaming rig and monitor and another 2U on my NAS, router, cable modem, PoE switch, and SimpliSafe alarm. The gaming rig runs about three or four hours on my battery with the battery powering my 24" G-Sync monitor and the rig (i9-11900k, RTX 3080 Ti, 750W PSU, 64GB RAM, four HDDs in RAID10, four SSDs in RAID10 a single HDD for the OS, and four PCIE NVME sticks) so something is up. The other one runs my equipment for at least sixteen hours. More if I allow the NAS drives to sleep (I do not). For reference, my UPS model is PR100LCDRT2U and has very good AVR.
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that's neat!

Unfortunately we had no option of buying such stuff when they started nuking our power grid...

Here are some pictures of my "handmade" setup:

the first one feeds power-hungry Asus WiFi router (do not remember the exact model but it is huge thing from 2016)

second one feeds optical-lan + router

third thing feeds 34" Dell monitor and a MacBook

camphoto_684387517.JPG

camphoto_1804928587.JPG

IMG_6811.JPG

 
Nuking your grid? Are you in Europe? These batteries are from 2012. When the internal four die or get weak, I just replace them. Yes, eight batteries for TWO UPS devices with AVR. It isn't cheap, but it protects my stuff!

I do like the way you wired those BIG batteries into the UPS devices though. Very clever, and they offer WAY more amps than the tiny batteries that came in them!

 
Bah, you guys have never tried to scrape together a working system from old batteries and it shows!

Firstly, you all seem to have missed Peukerts law. The amp hour rating of a lead acid battery is at a 20 hour draw rate (by tradition). If you draw any faster than that, you will not get the full capacity of the battery. How much you have to de-rate the battery depends on whether it was designed as a cranking battery or a deep cycle battery. If it's putting out 500A and found in a car, it's a cranking battery.

Secondly, lead acid batteries sulphate fast if not kept charged. This reduces both the peak voltage and the capacity.  How long has it been since those cars we're salvaging from has been run?

If we're talking "realistic", we'd be lucky if any of the batteries worked even at half their original spec if the apocalypse was a year ago. Those would be near new batteries when the apocalypse occured, in mild temperatures (neither hot nor cold) and a car with virtually no quiescent load. After 3 years, the only way to salvage them would be to pour out the acid and replace it with fresh ones and hope the lead sulphate crystals haven't caused an internal short.

Then again, this is just a game, right?

 
Batteries are rated far higher than 20AH now. The two in my diesel pickup are 80 or 90AH ratings. The one in my F-150 when I had it was 60AH from the factory but I replaced it with a 70AH battery. The F-150 had a BMS in it and no setting for a 70AH battery, so I disabled the BMS and the truck ran like my diesel does, basic charging system. I had to program the BMS to tell it I put in a new battery too, so it would learn the charging characteristics, but Ford's database in the BMS only consisted of their batteries, hence the need to disable the BMS. I digress!

 
The_Great_Sephiroth said:
Nuking your grid? Are you in Europe? These batteries are from 2012. When the internal four die or get weak, I just replace them. Yes, eight batteries for TWO UPS devices with AVR. It isn't cheap, but it protects my stuff!

I do like the way you wired those BIG batteries into the UPS devices though. Very clever, and they offer WAY more amps than the tiny batteries that came in them!
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Yep, in Europe, pictures are from my home in Ukraine.

Yep, the original batteries in those UPS were 9Ah tiny moto batteries, the charger in UPS only has 0.25 Ah potency so the car charger used to charge lead doesn't even notice its presence :D

 
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