USB LiIon/LiPoly charger, charging calculation

[danidub]

Hello, a quick question, if I apply 4 volts to the DCIN input at 0.6A, what would be the time for charging a 1000mAh LiPo battery? Is there any equation? or calculation for me to use with other LiPo capacity?
Thank you,

Daniel P

[wildtang3nt]

The Adafruit chargers charge at a maximum rate of 500mA without modification, so a safe guess would be a couple hours.

[danidub]

Hey! thank you for the reply,
I have made wrong my question, I have a little generator capable to provide 4 volts aprox and a current of 0.6 A aprox.

This is a Thermoelectric generator that will provide 4.3 V and 0.6 A working in the "best conditions".

How much current the charger will draw from my generator? for charging at 500mA (as factory default)

Or, using this setup, is there a way to calculate or estimate time for charging a 1 mAh LiPo battery?

Thank you again,
Daniel P

[john444]

Hi Danidub,

if I apply 4 volts to the DCIN input at 0.6A, what would be the time for charging a 1000mAh LiPo battery?

According to the datasheet, the USB LiPo charger (Id: 280) requires a minimum of 4.5-V for operation. I would speculate that only the idle current would be drawn from
your 4-V thermionic generator or about 17-mA.
The generator will not put any charge into the attached LiPo until the generator's output exceeds the LiPo voltage + 0.3-V. If the LiPo is low you may get some charge but it will taper off as the LiPo voltage increases. The result is: it will never reach full charge and even partial charging times will become excessive.

It is necessary to exceed the charging voltage as well as the operating voltage of the internal circuitry.
The internal circuitry needs about 0.3-V more than the charging voltage of 4.2-V (or 4.5-V).

When operating properly, the charging current varies during the charge cycle.
You might refer to the data-sheet and tutorials for the details.
http://www.microchip.com/wwwproducts/De ... e=en020210
http://learn.adafruit.com/usb-dc-and-so ... ly-charger

[danidub]

Hello john444!

According to the datasheet, the USB LiPo charger (Id: 280) requires a minimum of 4.5-V for operation. I would speculate that only the idle current would be drawn from your 4-V thermionic generator or about 17-mA.
The generator will not put any charge into the attached LiPo until the generator's output exceeds the LiPo voltage + 0.3-V. If the LiPo is low you may get some charge but it will taper off as the LiPo voltage increases. The result is: it will never reach full charge and even partial charging times will become excessive.

It is necessary to exceed the charging voltage as well as the operating voltage of the internal circuitry.
The internal circuitry needs about 0.3-V more than the charging voltage of 4.2-V (or 4.5-V).

When operating properly, the charging current varies during the charge cycle.
You might refer to the data-sheet and tutorials for the details.
http://www.microchip.com/wwwproducts/De ... e=en020210
http://learn.adafruit.com/usb-dc-and-so ... ly-charger

John, thank you for your answer, maybe it was my mistake, but I'm not using the charger id 280, I'm usning id 259 (https://www.adafruit.com/products/259) and in the datasheet is written Vmin 3.75 — Vmax 6. According to this data, it goes again my question:

I have a little generator capable to provide 4 volts aprox and a current of 0.6 A aprox.
This is a Thermoelectric generator that will provide 4.3 V and 0.6 A working in the "best conditions".
How much current the charger (https://www.adafruit.com/products/259) will draw from my generator? for charging at 500mA (as factory default)

Or, using this setup, is there a way to calculate or estimate time for charging a 1 mAh LiPo battery?

Thank you again,
Daniel P

[timi]

is there a 1mAh battery ?

for example if you charge a battery that is 1000mAh with 500mA then it would take 2h to charge in ideal condition, usualy the efficiency loss is ~10-30% so expect more than 2h ...

[adafruit_support_mike]

is there a 1mAh battery ?

I sincerely doubt it. Even the smallest hearing aid batteries are good for 60-80mA/hr.

For power levels that low, you're getting into capacitor territory. A 1F capacitor will supply 1A of current for 1s, so it will supply 1mA for 1000 seconds. There are 3600 seconds in an hour, so a 3.6F supercap would do the job. It would also have the virtue of almost unlimited discharge/recharge cycles, and would charge to full power in a fraction of a second.

[john444]

Danidub,

First, it is not very good to post in multiple places.
It is confusing and becomes difficult for others to follow the discussion.

I'm not using the charger id 280, I'm usning id 259 (https://www.adafruit.com/products/259) and in the datasheet is written Vmin 3.75 — Vmax 6. According to this data, it goes again my question:

The answer is still the same:

The generator will not put any charge into the attached LiPo until the generator's output exceeds the LiPo voltage + 0.3-V.

in the datasheet is written Vmin 3.75 — Vmax 6

True. but, that is for charging. Just below the 3.75-V value is the note:
"Vreg(Typical)+0.3V" which I take to mean the charger requires 0.3-V over the battery voltage.
So... Again, to fully charge a LiPo to 4.2-V you must input at least 4.5-V.
This charger is not able to boost the input voltage.

How much current the charger (https://www.adafruit.com/products/259) will draw from my generator? for charging at 500mA

The data-sheet indicates that the charging current accuracy is about 10% plus the status LEDs. I do not have this model of LiPo charger and I don't have a schematic viewer on his computer. I will guess that the LEDs are pulling about 10-mA each. Only two can be on at a time so the total is about 520-mA +/-10%.

using this setup, is there a way to calculate or estimate time for charging a 1 mAh LiPo battery?

The generator will not put any charge into the attached LiPo until the generator's output exceeds the LiPo voltage + 0.3-V. If the LiPo is low you may get some charge but it will taper off as the LiPo voltage increases. The result is: it will never reach full charge and even partial charging times will become excessive.

This is regardless of the LiPo capacity.
Also, I will presume that you intended to express 1-Ahr cell instead of 1-mAhr because you mentioned having a 1,000-mAhr cell in your first post. So... If you are able to supply the 259 with 500-mA it will take slightly over 2-hr. In normal use it will probably be less since it is unlikely that you will start with a fully discharged LiPo.
Good Luck,
and try to keep related topics in a single forum thread.
John

[danidub]

Hello timi!

is there a 1mAh battery ?

for example if you charge a battery that is 1000mAh with 500mA then it would take 2h to charge in ideal condition, usualy the efficiency loss is ~10-30% so expect more than 2h ...

I'm sorry, it was a 1000mAh battery not a 1mAh, thank you for the calculation, that was something I need!
Thank you!