Hi everyone,
I have an LG G3 that I want to use as a stationary device and leave it hooked up permanently.
I prefer not to do it with a battery for various understandable reasons.
My questions are:
What parts do I need to convert USB 5V to 3.8V?
What other factors (like currant) should be considered and how to deal with them?

Thanks!

 

Welcome to AAC!

Have you tried simply powering the phone with no battery installed to see if it will power on? If it doesn't, you can stop there.

 

Welcome to AAC!

Have you tried simply powering the phone with no battery installed to see if it will power on? If it doesn't, you can stop there.

It won't. I want to hook it up to the battery terminals, but I don't want to give it more power than it needs and built for.
I didn't understand your answer, why not to try power it in this way?

 

Can the phone be used when it is connected to the charger (with a battery in it). If so, then just do that. The battery will likely last indefinitely since, even as it ages, it never has to actually deliver any power. The charger will handle any issues associated with not overcharging the battery.

 

Can the phone be used when it is connected to the charger (with a battery in it). If so, then just do that. The battery will likely last indefinitely since, even as it ages, it never has to actually deliver any power. The charger will handle any issues associated with not overcharging the battery.

The battery is a part of the charging circuit, so although it will work, I prefer not doing it this way.

 

My questions are:
What parts do I need to convert USB 5V to 3.8V?
What other factors (like currant) should be considered and how to deal with them?

Your phone converts the 5 volt USB to charge the battery and the battery is likely a smart battery in a phone with a smart charging system. The phone will not work at all less a battery and trying to "fake" the phone into believing there is a battery in it will likely prove more challenging than it is worth. There is no converting 5 volts to 3.8 volts. Even if you had a DC to DC converter it still would not power the phone to where it would work. Current is not a factor. When the phone draws power it demands what it needs and no more. When the phone battery charges it determines how much current to draw (fast charge or slow) based on the source and what is available. The entire system is "smart".

My phone, a Samsung Galaxy 7 will not even function unless a dead battery has a chance to build a small charge. Smart battery with a smart charging system. My phone will not operate less a battery and even then the battery needs a certain percentage of charge before the phone will operate. Since the phone has a smart battery and charge system I can leave it sitting on the charger a week and it matters not. Yours is likely the same.

Ron

 

The battery is a part of the charging circuit, so although it will work, I prefer not doing it this way.

Why not? What is it that you are trying to accomplish? Your initial post only said that you prefer to do it without the battery for "various understandable reasons." So help us understand what those reasons are.

 

various understandable reasons.

Not to me. What are they?

ak

 

he general deal is that the battery can supply a larger current than the TYPICAL USB charger. Without "handshaking", you can only get 100 mA out of the USB port.

At one time I tried to charge the battery and tethered the phone at the same time or at least I thought I was charging the battery, but the phone eventually quit. I had a Razer phone that worked fine.

I even tried a USB isolator so that the laptop was connected to USB and the phone got it's power from an external source.

I too must have like a 5% charge for the phone to function. If I have the charger plugged in and talk while the phone is at a low charge, the phone will eventually drop the call.

The only thing I can think of to try is to replace the battery with a super capacitor. The battery could have "smarts", but my phone battery has 4 terminals. one + and one - and the two middle terminals are a thermister.
That you will have to substitute. Be sure to get the battery polarity right. Some batteries are not marked.

The voltage of the supercap might actually have to be larger than the battery voltage. 5.5 V rated super caps are easy to come by.

I loved the Razor because it had a built in FAX modem, but you needed your carrier to enable CSD csd data for it to work, otherwise when you called a modem, it would immediately hang up.

I did modify a PPP driver for Mac OS9 for the Razer phone so I had dial-up Internet when I called my ISP.
It was one of my unusual projects.

I do have an external charger, so I can charge the battery outside the phone, The charger is smart enough not to care what the polarity is.

 

Why not? What is it that you are trying to accomplish? Your initial post only said that you prefer to do it without the battery for "various understandable reasons." So help us understand what those reasons are.

Not to me. What are they?

ak

The battery is quite old and might stop working or, although rare, explode.
By using USB I eliminate these possibilities.

he general deal is that the battery can supply a larger current than the TYPICAL USB charger. Without "handshaking", you can only get 100 mA out of the USB port.
At one time I tried to charge the battery and tethered the phone at the same time or at least I thought I was charging the battery, but the phone eventually quit. I had a Razer phone that worked fine.

I even tried a USB isolator so that the laptop was connected to USB and the phone got it's power from an external source.

I too must have like a 5% charge for the phone to function. If I have the charger plugged in and talk while the phone is at a low charge, the phone will eventually drop the call.

The only thing I can think of to try is to replace the battery with a super capacitor. The battery could have "smarts", but my phone battery has 4 terminals. one + and one - and the two middle terminals are a thermister.
That you will have to substitute. Be sure to get the battery polarity right. Some batteries are not marked.

The voltage of the supercap might actually have to be larger than the battery voltage. 5.5 V rated super caps are easy to come by.

I loved the Razor because it had a built in FAX modem, but you needed your carrier to enable CSD csd data for it to work, otherwise when you called a modem, it would immediately hang up.

I did modify a PPP driver for Mac OS9 for the Razer phone so I had dial-up Internet when I called my ISP.
It was one of my unusual projects.

I do have an external charger, so I can charge the battery outside the phone, The charger is smart enough not to care what the polarity is.

I meant an USB charger, not a PC port.
Those can provide 2.1A or even 4A like Oneplus DASH CHARGING.

Anyway, I see that it's not very practical and probably waste of money trying to do it.
Thank you for you answers