Using car battery to run your PC?

[Chiyawa]

Crazy idea: Can you use a car battery to run a desktop PC? I mean, well, like just plug in the positive terminal and negative terminal of the car battery, design some buck converters for 12V, 3.3V, 5V, and the rest?

 

I have a big car battery (12V 68A rating from my 4 wheel drive truck), which is still okay (just maybe to weak to start the truck even at full charge) and I'm wondering, could it be turn to like UPS where it can still give me better time to shut down the system? Or can it be plug in to some old inline UPS and use it (I know most UPS only use 7.2V, I just need to buck the voltage down? Also, their battery sucks!)?

 

Anyway, just a little crazy idea I had, but it'll be good. I can save lots by buying a 1500VA UPS that only last for 5 minutes.

[Rohith_Kumar_Sp]

you can, my friend does with an inverter and he even uses a bike battery, just don't expect crazy brackup, at the end of the day they're all just batteries. 

[LWM723]

I was thinking of this but I thought the UPS batteries were 12v.

[Guest]

You mean 680 CCA?

Automotive batteries are designed for constant charge and big fast discharge. Aside from the fact that they are dangerous..... Yes, could work as a UPS battery. 

But for the proper type of battery, you want a marine or Deep cycle battery. Then you can run equipment for an expended period of time before voltage drop off. Good to about only 30% SOC. A starting battery is meant to stay above 80% SOC.

[Chiyawa]

7 minutes ago, Rohith_Kumar_Sp said:

you can, my friend does with an inverter and he even uses a bike battery, just don't expect crazy brackup, at the end of the day they're all just batteries. 

Hmm... Okay, I'll check and see.

 

I need a backup for about 2 hours. My area is constantly facing black out due to construction work.

[Chiyawa]

11 minutes ago, LWM723 said:

I was thinking of this but I thought the UPS batteries were 12v.

Most consumer UPS has 7.2V battery. Some industrial UPS has 48V battery (although the size is similar to 7.2V battery), and the mega UPS (we are talking 30kVA) uses 20 12V batteries in series, making the battery terminal of 480V.

[Chiyawa]

20 minutes ago, ShrimpBrime said:

You mean 680 CCA?

Not sure what is CCA, but my battery type is automotive battery found in diesel/gasoline engine type cars and trucks. The battery brand is Panasonic, has 17 plates, and with capacity of 68A. That's all I know about the battery. I just change the battery as it is getting weak and couldn't start my truck, but I think it still can serve for other purposes. Battery health is at 60%.

 

20 minutes ago, ShrimpBrime said:

But for the proper type of battery, you want a marine or Deep cycle battery.

Hmm... I wonder where you can get this type of battery... Anyway, I live in Malaysia, so this type of battery is not commonly available.

[BlueChinchillaEatingDorito]

33 minutes ago, Chiyawa said:

Crazy idea: Can you use a car battery to run a desktop PC? I mean, well, like just plug in the positive terminal and negative terminal of the car battery, design some buck converters for 12V, 3.3V, 5V, and the rest?

 

I have a big car battery (12V 68A rating from my 4 wheel drive truck), which is still okay (just maybe to weak to start the truck even at full charge) and I'm wondering, could it be turn to like UPS where it can still give me better time to shut down the system? Or can it be plug in to some old inline UPS and use it (I know most UPS only use 7.2V, I just need to buck the voltage down? Also, their battery sucks!)?

 

Anyway, just a little crazy idea I had, but it'll be good. I can save lots by buying a 1500VA UPS that only last for 5 minutes.

It works... but not brilliant if you forget to charge the battery back up when you prior to putting it back into the car. 

[Guest]

5 minutes ago, Chiyawa said:

Not sure what is CCA, but my battery type is automotive battery found in diesel/gasoline engine type cars and trucks. The battery brand is Panasonic, has 17 plates, and with capacity of 68A. That's all I know about the battery.

 

Hmm... I wonder where you can get this type of battery... Anyway, I live in Malaysia, so this type of battery is not commonly available.

Your country makes batteries.... All kinds of different types including Lithium. lol?

 

So it's 68 Amp hours. 

 

CCA stands for Cold Cranking Amps, something common to the cold climates in the mid west where I live.

That means under 0c, that's the rated current in a given load. (engine starter)

 

[GhostRoadieBL]

30 minutes ago, Chiyawa said:

design some buck converters for 12V, 3.3V, 5V, and the rest

so you mean replace the PSU with a car battery and add circuits to step down the voltage to each desired plug?

...  technically yes but it won't run well and you will 99% chance fry a CPU and GPU

one of the biggest hurdles is conditioning the power output, batteries (all batteries) don't put out stable voltage due to the chemical reaction being nearly but not exactly identical every second or millisecond. In theory you can have enough circuitry and capacitors to take up fluctuations in the CPU, GPU, RAM, SSD, etc's loads which your battery won't keep up with. Reactive loads are why PSUs and motherboards have dozens of capacitors and resistors on the boards to instantly supply amperage when required, batteries are comparably extremely slow to react. 

you can do this with a normal PSU and an inverter or even a 12V PSU for an ultra low power system up to like 400watts. then the smoothing is done inside the PSU and not the addon voltage regulators. 

 

very cool idea though, I'd love to see how long you could run a PC on just a deep cycle battery. An Alternator would also run havoc on the system with fluctuating voltages based on what the engine is doing. 

[Chiyawa]

1 minute ago, BlueChinchillaEatingDorito said:

It works... but not brilliant if you forget to charge the battery back up when you prior to putting it back into the car. 

The battery will not be put into the car as it is an old battery (3 years old) and couldn't start the engine. Still, it can be use for a wide variety of devices. I have a 12V truck fan and I modify its wiring so it clips to the battery terminal and works.

[WereCatf]

25 minutes ago, Chiyawa said:

Most consumer UPS has 7.2V battery.

I've never seen a UPS with 7.2V battery. I have four UPSes myself and every single one uses a 12V gel-battery.

[Chiyawa]

13 minutes ago, ShrimpBrime said:

Your country makes batteries.... All kinds of different types including Lithium. lol?

Well, yes, we produce quite many batteries, but all will be exported and we only have cheap China batteries available for purchase. Even we have Samsung brand products, but often, it is a second grade one. So it's no surprise Samsung products reject rate is high. Welcome to Malaysia.

 

15 minutes ago, ShrimpBrime said:

CCA stands for Cold Cranking Amps, something common to the cold climates in the mid west where I live.

That means under 0c, that's the rated current in a given load. (engine starter)

I see. So that's what CCA stands for. I live in hot climate country so I'm not aware of this. Thanks for the info.

[Chiyawa]

1 minute ago, WereCatf said:

I've never seen a UPS with 7.2V battery. I have four UPSes myself and every single one uses a 12V gel-battery.

Hmm, strange. Mine one uses 7.2V sealed Lead Acid battery.

[LWM723]

I use an old car battery and small inverter to power a light, radio, cell phone, etc... in a power outage. You can get a deep-cycle battery at a boat dealer or RV dealer as well as any shop that sells car batteries.

[WereCatf]

57 minutes ago, Chiyawa said:

I mean, well, like just plug in the positive terminal and negative terminal of the car battery, design some buck converters for 12V, 3.3V, 5V, and the rest?

I forgot to reply to this part: those already exist, like e.g. https://www.ebay.com/itm/DC-12V-300W-PSU-PC-ATX-Power-Supplies-Module-for-HTPC-Mini-ITX-Car-Power-Supply/192971973834

 

Just don't believe the wattage-rating, it's 150W at best. It may handle 300W for like a second or two, but never, ever trust the wattage-rating on these kinds of items from China.

[Chiyawa]

18 minutes ago, GhostRoadieBL said:

so you mean replace the PSU with a car battery and add circuits to step down the voltage to each desired plug?

Initially yes. That's why it's crazy idea. But thanks for correcting me and warn me of the potential dangers. I knew it is dangerous to just replace the PSU entirely. Your explanation gives me more insight why it is a bad idea.

[Guest]

1 minute ago, Chiyawa said:

Well, yes, we produce quite many batteries, but all will be exported and we only have cheap China batteries available for purchase. Even we have Samsung brand products, but often, it is a second grade one. So it's no surprise Samsung products reject rate is high. Welcome to Malaysia.

 

I see. So that's what CCA stands for. I live in hot climate country so I'm not aware of this. Thanks for the info.

Well most batteries are all the same. Lead Acid batteries have been around a very long time. 

My point was the application the battery is designed for, I still think a deep cycle (if you can find one) would better suit your needs.

 

And quite well I might add. While the power goes out, the Deep cycle will likely handle the PC, lighting, a power strip and charge your phone for an extended period of time. 

 

The issue with starting batteries is they drop voltage on a steep curve. Deep cycle, you can think of, is like a lithium battery. You can pull current and it will sustain a voltage down to empty SOC. But the Deep Cycle drops between 20-30% SOC. (SOC stands for State of Charge) 

A 12v starting battery at 80% SOC will be under 12v output. The deep cycle battery will sustain the 12v for most of it's duty cycles.

[Chiyawa]

3 minutes ago, WereCatf said:

I forgot to reply to this part: those already exist, like e.g. https://www.ebay.com/itm/DC-12V-300W-PSU-PC-ATX-Power-Supplies-Module-for-HTPC-Mini-ITX-Car-Power-Supply/192971973834

 

Just don't believe the wattage-rating, it's 150W at best. It may handle 300W for like a second or two, but never, ever trust the wattage-rating on these kinds of items from China.

Hmm... They do indeed have this part. But yeah, the number are pretty sceptical.

[Chiyawa]

5 minutes ago, LWM723 said:

You can get a deep-cycle battery at a boat dealer or RV dealer as well as any shop that sells car batteries.

I don't see a deep cycle battery in car repair shop. Looks like I need to broaden my search.

[Chiyawa]

3 minutes ago, ShrimpBrime said:

Well most batteries are all the same. Lead Acid batteries have been around a very long time. 

My point was the application the battery is designed for, I still think a deep cycle (if you can find one) would better suit your needs.

 

And quite well I might add. While the power goes out, the Deep cycle will likely handle the PC, lighting, a power strip and charge your phone for an extended period of time. 

 

The issue with starting batteries is they drop voltage on a steep curve. Deep cycle, you can think of, is like a lithium battery. You can pull current and it will sustain a voltage down to empty SOC. But the Deep Cycle drops between 20-30% SOC. (SOC stands for State of Charge) 

A 12v starting battery at 80% SOC will be under 12v output. The deep cycle battery will sustain the 12v for most of it's duty cycles.

Interesting. Thanks for your suggestion.

[WereCatf]

4 minutes ago, Chiyawa said:

Hmm... They do indeed have this part. But yeah, the number are pretty sceptical.

Mini-box is more trustworthy and they also offer a bunch of different kinds of DC-DC PSUs. Take a look at https://www.mini-box.com/DC-DC

[LWM723]

7.2 volts may be Malaysia specific. What brand is your UPS?

[Chiyawa]

2 hours ago, LWM723 said:

7.2 volts may be Malaysia specific. What brand is your UPS?

K.O.S.S. and APC...

 

Oh my goodness, that 7.2 is Ampere, not Voltage. Oh my. Sorry about that. I mixed up a lot of things lately.

[Chiyawa]

2 hours ago, WereCatf said:

Mini-box is more trustworthy and they also offer a bunch of different kinds of DC-DC PSUs. Take a look at https://www.mini-box.com/DC-DC

Okay. I'll be checking it.