need info about batteries

[SDWdidi]

Hey there,
 

  So I got to 6th grade of a technical school and we have to find something out to make as a project (doesn't have to be anything very complicated). The idea of my project group was, making some kind of a plug to USB to allow you  charge your phones battery during all night but avoiding the battery to get worn off. Basically the plug would let electricity go through until the battery is 100% full then the plug wouldn't allow electricity to go through. As I said this is mainly to avoid the problem that you can't charge the phone all night and avoiding it getting worn off.

Now my question are various: 

1. Why do batteries ware off after a while ? (You see that batteries after a while work less and less better then when they're being used)

 

2. What happens with the battery if you keep it charging while it's 100%? (Internally)

 

3. What are the factors of the deterioration of the battery? Is the charger one of them??

[W-L]

13 minutes ago, SDWdidi said:

-SNIP-

Batteries don't keep charging when they are full in smart phones and devices, they drop the current to a very small amount and trickle charge it which is not recommended. The battery can degrade faster if you use higher amperage chargers that heats the battery up more so than lower amperage chargers, so it's a trade off by quickly charging your device. 

[SilicateWielder]

2 hours ago, W-L said:

Batteries don't keep charging when they are full in smart phones and devices, they drop the current to a very small amount and trickle charge it which is not recommended. The battery can degrade faster if you use higher amperage chargers that heats the battery up more so than lower amperage chargers, so it's a trade off by quickly charging your device. 

Yes, in order to prevent over charging, you need to use a BMS, these are also used in battery packs as well.

 

They're nowhere near as good as hobby chargers though.

[SDWdidi]

14 hours ago, W-L said:

Batteries don't keep charging when they are full in smart phones and devices, they drop the current to a very small amount and trickle charge it which is not recommended. The battery can degrade faster if you use higher amperage chargers that heats the battery up more so than lower amperage chargers, so it's a trade off by quickly charging your device. 

 

well the idea I had is a plug with some sort of a timer to exactly prevent that (the degradation of the battery). Basically what It would do is check how fully charged the battery is and stop giving current to the battery to prevent the degradation(yes I know that the battery degrade over time but the lessen the speed onto it)

 

[Mira Yurizaki]

50 minutes ago, SDWdidi said:

well the idea I had is a plug with some sort of a timer to exactly prevent that (the degradation of the battery). Basically what It would do is check how fully charged the battery is and stop giving current to the battery to prevent the degradation(yes I know that the battery degrade over time but the lessen the speed onto it)

 

Just as an FYI, you need to have a current counter to check the battery charge accurately. Voltage readings do not accurately tell how much is left in the battery because batteries can retain almost near open-circuit voltage even when "dead".

[mariushm]

Your phone has that circuitry already built in, there's a chip that takes care of charging the battery.

The battery itself (replaceable or not) has a tiny protection chip which prevents the phone from overcharging it or from taking too much energy from it (to discharge it below safe levels for lithium, like 3.2v or something like that)

Also, some phones will actually have circuitry that - after the battery is charged - will automatically switch the phone to running straight from usb instead of the internal battery and automatically fall back to battery when the usb connector is unplugged. Basically, it's as if the phone has a built in UPS. But this would make it hard to design some gadget that would monitor the current and voltage in the usb port in order to figure out when the battery is fully charged.

See here some good documentation about charging batteries

 

see page 5 figure 6 for lithium-polymer : http://www.richtek.com/en/Design Support/Technical Document/~/media/AN PDF/AN023_EN.ashx

some more details about rechargeable batteries : http://www.ti.com/lit/an/snva533/snva533.pdf

and some notes about how to extend battery life, how to make them last longer by not charging them to much etc (but thse things are already doe internally by phones) : http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/portable_power_management/battery_charger_ics/804PET22li-ion-battery-life.pdf

 

[W-L]

1 hour ago, SDWdidi said:

well the idea I had is a plug with some sort of a timer to exactly prevent that (the degradation of the battery). Basically what It would do is check how fully charged the battery is and stop giving current to the battery to prevent the degradation(yes I know that the battery degrade over time but the lessen the speed onto it)

 

That's very doable if you have a current sensor once it drops below a certain level it can basically cut off any type of charging until say a user unplugged and replugged the cable.Some chargers I have seen have that capability and cut off until it battery drops a significant amount before charging again, but in general battery degeneration isn't terrible these days most are able to have a good number of charging cycles without loosing a large amount of it's original capacity. 

[SDWdidi]

10 minutes ago, W-L said:

That's very doable if you have a current sensor once it drops below a certain level it can basically cut off any type of charging until say a user unplugged and replugged the cable.Some chargers I have seen have that capability and cut off until it battery drops a significant amount before charging again, but in general battery degeneration isn't terrible these days most are able to have a good number of charging cycles without loosing a large amount of it's original capacity. 

 

yeah all though it would be better to have that extra bit of life in the battery in my opinion

[SDWdidi]

45 minutes ago, mariushm said:

Your phone has that circuitry already built in, there's a chip that takes care of charging the battery.

The battery itself (replaceable or not) has a tiny protection chip which prevents the phone from overcharging it or from taking too much energy from it (to discharge it below safe levels for lithium, like 3.2v or something like that)

Also, some phones will actually have circuitry that - after the battery is charged - will automatically switch the phone to running straight from usb instead of the internal battery and automatically fall back to battery when the usb connector is unplugged. Basically, it's as if the phone has a built in UPS. But this would make it hard to design some gadget that would monitor the current and voltage in the usb port in order to figure out when the battery is fully charged.

See here some good documentation about charging batteries

 

see page 5 figure 6 for lithium-polymer : http://www.richtek.com/en/Design Support/Technical Document/~/media/AN PDF/AN023_EN.ashx

some more details about rechargeable batteries : http://www.ti.com/lit/an/snva533/snva533.pdf

and some notes about how to extend battery life, how to make them last longer by not charging them to much etc (but thse things are already doe internally by phones) : http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/portable_power_management/battery_charger_ics/804PET22li-ion-battery-life.pdf

 

 

thanks man will take a look into all this later on

 

just to know do you have by any chance another idea in that (in my school we learn to be a electromechanical technician)

[SDWdidi]

Just now, SDWdidi said:

thanks man will take a look into all this later on

 

just to know do you have by any chance another idea in that (in my school we learn to be a electromechanical technician)

 

what I meant any other project we could try to do (at the moment we are just trying to brainstorm ideas)