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[on:]

I couldn't find any details to what amperage I should recharge a 3.7v 165mAh LiPo battery, so I'm currently charging it at 106mA.  I was shooting for 100mA, but 106mA was the closest I could get with the resistors I have.  What is the max amperage can I charge the LiPo battery safely, 500mA?

[Reply #1 on:]

I don't think you can safely or reliably recharge LiPos without a dedicated LiPo charger circuit. The charger has to monitor when the cell is full and stop the charge to prevent damage.

Someone more familiar with charging ICs may be able to recommend something.

[Reply #2 on:]

I understand, but I think I can estimate how full the battery is by determining how bright it can light an led compared to the brightness of an led using usb pc power.  This is a cheap battery I don't care if I destroy it.  Just wondering how much current people suggest I should load in general for such a battery.

[Reply #3 on:]

I couldn't find any details to what amperage I should recharge a 3.7v 165mAh LiPo battery, so I'm currently charging it at 106mA.  I was shooting for 100mA, but 106mA was the closest I could get with the resistors I have.  What is the max amperage can I charge the LiPo battery safely, 500mA?

Most LiPo cells can be safely charged at up to their 1C rating or 165ma in your case, less is no problem just takes a little longer. There are special Li-Po cells that can be charged at significantly higher then their 1C rating but cost more and one should always check the datasheet for details about these higher charging and discharging rated cells for conditions and warnings to use them in high current discharge and recharging modes.

 And by all means one really should use a purpose designed Li-Po charger chip to charge cells, they perform several checks before actually starting the charge and change from constant current to constant voltage late in the charge cycle.

Here is a link to a datasheet of a lipo cell charger. You set the max charge rate by the selection of one programming resistor. It's a good read on what all is involved for properly charging a single cell lipo. Series connected lipo charges can get even more complex as there is great benefit to having the ability to detect an unbalanced pack condition and correct it during a charging cycle.
http://www.sparkfun.com/datasheets/Prototyping/Batteries/MCP73831T.pdf

Lefty

[Reply #4 on:]

LiPo charging is something that you want to make sure you do properly. None of this "I think the method is close enough".

[Reply #5 on:]

You can put together a simple circuit using something like this:

http://ww1.microchip.com/downloads/en/DeviceDoc/21984e.pdf

[Reply #6 on:]

Maxim's MAX1811 is nice little LiPo charging chip.
Can charge at 100 or 500mA, and 4.1 or 4.2V.

http://www.maximintegrated.com/datasheet/index.mvp/id/2536?ver=C&utm_expid=50713806-2&utm_referrer=http%3A%2F%2Fwww.maximintegrated.com%2Fpst%2Frun.mvp%3Fq%3Dmax1811

[Reply #7 on:]

I'd buy the Maxim's MAX1811 integrated circuit.  Is it easy to setup?  Is there a sketch that goes along with it for monitoring?  I still don't know what to do with the 5 pins.  Any videos of the charge circuit in use?

[Reply #8 on:]

I just set it up like the datasheet shows.
I have a 1000mAH battery, and queried the supplier about it: use 500mA, 4.2V
So I set those 2 pins accordingly, and have an LED as shown to show when it is charging.
I have a 5V supply that I connect it to. Been in use a year+ now, no problems so far.

[Reply #9 on:]

On the BATT output, is that a capacitor in the design?  If so, what size?  I understand the GND of the LiPo battery just gets tied to GND.  The CHG line will output a HIGH or LOW to light the LED?  What goes to LED "To In" line as shown on right?  SELV, EN, SELI are simply set by either sending HIGH or LOW on line?  Also when I look up this IC on ebay I see 8 pins.  Why am I only seeing 7 pins in the circuit diagram (schematic)?

[Reply #10 on:]

Here's how mine is set up in my remote control.

[Reply #11 on:]

what is the small box under the lipo battery represent?  How did you know what size capacitors to use?

[Reply #12 on:]

Small box is just a connector.
Cap values are from the datasheet.
I believe it says "use >= some value" and those were values I had on hand.

[Reply #13 on:]

Have a look at this.
http://www.ebay.nl/itm/3-7V-Lithium-ion-battery-charge-5V-1-5A-USB-out-all-in-one-PCB-charge-iPhone-/121017503840?pt=Battery_Chargers&hash=item1c2d349060

for the price I cant make it myselve.

Paco

[Reply #14 on:]

Wow, inexpensive.