automatic switching on power loss solution

[thDel]

hi, i have a project that im working on which is a never failing phone charger. with this idea i have a dc input form mains power and another from a power bank and of the mains power input fails the usb output will automatically switch to being powered by the battery. the issue is the wall charger has a 3a output and the battery has only 1a output so if i just have the charger hooked up to the battery which is constantly being charged by the dc input i will only get 1a even when power is on.

 

is there a way i can have the input charge the battery and the phone simultaneously then as the power goes out have the source switch to the battery

 

thanks, del

[Eigenvektor]

Sounds like a solution in search of a problem. How often does your mains go out that it is an actual concern to keep your phone charging during that time?

 

In theory you could attach two power sources in parallel, if their output voltage was exactly the same. Since power output of a charger typically changes based on how full the battery currently is, this would be a bad idea.

 

You could probably build a more elaborate setup with a small circuit that switches power sources based on whether mains is available or not. Similar to how an emergency light switches on when mains is gone…

 

~edit: Just to be clear, solutions like this exist (e.g. UPS) for critical systems like servers that should keep running or at least be switched off in a controlled manner during a power outage, but that seems oversized for charging a phone.

[jaslion]

15 minutes ago, Eigenvektor said:

Sounds like a solution in search of a problem. How often does your mains go out that it is an actual concern to keep your phone charging during that time?

 

In theory you could attach two power sources in parallel, if their output voltage was exactly the same. Since power output of a charger typically changes based on how full the battery currently is, this would be a bad idea.

 

You could probably build a more elaborate setup with a small circuit that switches power sources based on whether mains is available or not. Similar to how an emergency light switches on when mains is gone…

 

~edit: Just to be clear, solutions like this exist (e.g. UPS) for critical systems like servers that should keep running or at least be switched off in a controlled manner during a power outage, but that seems oversized for charging a phone.

Could also just have a battery bank charging the phone and the battery bank being charged too. Basically a mini phone ups so to say.

[Needfuldoer]

Why not just use an AC adapter to keep the battery bank charged, and always charge the phone from that?

 

[ AC Power Adapter ] --> [ Battery pack ] --> [ Phone ]

 

Even a modestly sized battery pack will fully charge a phone a couple times, so that should be plenty of buffer.

 

If you wanted a huge bucket of reserve power, you could get a deep cycle 12v battery, charge it with a bulk/float AC wall charger, and hook up a couple automotive USB chargers. That would give you several weeks of phone charges worth of offline reserve. (But that's "solar powered cabin in the woods" territory.)

[Eigenvektor]

10 minutes ago, jaslion said:

Could also just have a battery bank charging the phone and the battery bank being charged too. Basically a mini phone ups so to say.

8 minutes ago, Needfuldoer said:

Why not just use an AC adapter to keep the battery bank charged, and always charge the phone from that?

OP addressed this point in their original post. The power bank is limited to 1A, while the regular charger can provide 3A. That's why they want to switch.

[Needfuldoer]

Just now, Eigenvektor said:

OP addressed this point in their original post. The power bank is limited to 1A, while the regular charger can provide 3A. That's why they want to switch.

The easiest (and maybe least expensive) solution would be to get a new battery pack with more power output. If the power goes out they'd be down to 5 watts of charging on their proposed rig anyway.

[jaslion]

2 minutes ago, Eigenvektor said:

OP addressed this point in their original post. The power bank is limited to 1A, while the regular charger can provide 3A. That's why they want to switch.

A different power bank is the solution here then.

[Eigenvektor]

7 minutes ago, jaslion said:

A different power bank is the solution here then.

Agreed, but I felt bad for pointing out the obvious route, so I decided not to