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Topic: Lithium battery (Read 4913 times) previous topic - next topic

raschemmel

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"but it doesn't stop the discharge"
the componement do not stop the discharge of the battery at 3v but when it's dead at 2.5v
As mentioned, the atmega will reset at 2.6V due to the default brownout threshold.
The 3.0 V comparator is a good idea. As I said earlier, the "best way" (as you put it) , is to have two sets of batteries and a DPDT relay that switches batteries when the one in use gets low and has a 680 uF cap to maintain the processor voltage during the 50 mS the relay is switching. That way you are always charging one while the other is in use. One half of the relay is to switch the arduino battery and the other half is to switch the battery charger from one battery to the other.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

guillaume55

As mentioned, the atmega will reset at 2.6V due to the default brownout threshold.
The 3.0 V comparator is a good idea. As I said earlier, the "best way" (as you put it) , is to have two sets of batteries and a DPDT relay that switches batteries when the one in use gets low and has a 680 uF cap to maintain the processor voltage during the 50 mS the relay is switching. That way you are always charging one while the other is in use. One half of the relay is to switch the arduino battery and the other half is to switch the battery charger from one battery to the other.
I have not enouth space for 2 batteries (and I prefer to use popular battery if I muss to replace the battery it will be easier)
I didn't say the relay was not a good solution but if think the comparator and the LTC3335 use less space
Can I replace LTC3335 by NCP1402 ? I don't need more than 100 mA

"At this point, however, you won't have 3.3V to run your Linduino.  From the block diagram you posted, I'm not sure how the TP4056 will get turned back on to recharge your dead battery."
Yes, CE can stay enabled?
Thank you

raschemmel

Read the datasheets.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

guillaume55

thanks
I've already read the datasheets
Could anyone check my shematic? I not sure if I had to add as far as capacitors or if I can divid the number of capacitor znd if I can ground all the shematic at the same ground
(made with KiCad, so I attach a screenshot too)
Thank you

BigBobby

Can I replace LTC3335 by NCP1402?
The NCP1402 is a step-up regulator only.  It can only make output voltages that are higher than the battery voltage input.

You said you need to convert a battery between 3V-4.2V to a constant 3.3V output?  In that case you need to step down most of the time, and only step up when the battery is betwwen 3V-3.3V.

raschemmel

You have to choose one or the other. Either you input voltage is <3.3V and you need a STEP UP or it is > 3.3V and you need a STEP DOWN. You can't have your cake and eat it too... ;D
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

BigBobby

The LTC3335 can.  It's a buck-boost.  You pay a little bit in efficiency, but you can have your cake and eat it too.

raschemmel

Quote
The LTC3335 can.  It's a buck-boost.  You pay a little bit in efficiency, but you can have your cake and eat it too. 
After thinking about it on the way to work , I realized that even if you only had one of each type you could still do it by putting the stepup first and step the voltage up to 6V, then use the stepdown to step it down to 3.3V.

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

BigBobby

After thinking about it on the way to work , I realized that even if you only had one of each type you could still do it by putting the stepup first and step the voltage up to 6V, then use the stepdown to step it down to 3.3V.
That's one way to make a buck-boost.  That way makes it easy to visualize the efficiency hit too.

The LTC3335 explains how its buck-boost works on page 14 of its datasheet.

raschemmel

Quote
That's one way to make a buck-boost.
(go down , then up...)(using separate devices)

or a boost-buck (go up, then down)(using separate devices)
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

guillaume55

Thank you for your help
This time I have a buck boost regulator (I will use a LTC3531-3.3 because I want to reduce the size and the LTC3335 is a little bit big) but one line makes me affraid :
"If the die temperature reaches approximately 150°C, the part will go into thermal shutdown and all switches will be turned off"
Ok it will be turned off but 150°C is good ... for the cake but not for the gps (who is heat sensitive.
The datasheet don't give a temperature vs V in curve... maybe it's can vary but reach 150°C
An other question : when the battery charge, the wire who is connected to bat + become - because the charge process invert the chemical reaction ?

BigBobby

#26
Apr 21, 2016, 07:21 pm Last Edit: Apr 21, 2016, 07:21 pm by BigBobby
Thank you for your help
This time I have a buck boost regulator (I will use a LTC3531-3.3 because I want to reduce the size and the LTC3335 is a little bit big) but one line makes me affraid :
"If the die temperature reaches approximately 150°C, the part will go into thermal shutdown and all switches will be turned off"
Ok it will be turned off but 150°C is good ... for the cake but not for the gps (who is heat sensitive.
The datasheet don't give a temperature vs V in curve... maybe it's can vary but reach 150°C
The 150°C die temp will be much hotter than the PCB where the IC is attached.  The GPS will not see temperatures anywhere close to the die temp of the voltage regulator IC.

Quote
An other question : when the battery charge, the wire who is connected to bat + become - because the charge process invert the chemical reaction ?
I'm not sure what you mean by this.  In your diagram the TP4056 will make a voltage that is slightly higher than your battery voltage so that current will be forced into it.   You will never see a negative voltage at your battery terminal, although you will see "negative" current flow into it if you defined "positive" current as flowing out of the battery into the LTC3351.



guillaume55

I didn't know how the battery charges, thanks a lot for your help  :)

guillaume55

I have just a last question :
I searched in the mic834 datasheet the resistor values but I can't understand one thing
"Programming the Threshold"
I've understand there is a voltage divider for the threshold but my input voltage will vary between 4.20 and 2.9v also the threshold input voltage will vary too?
Thanks you

BigBobby

I have just a last question :
I searched in the mic834 datasheet the resistor values but I can't understand one thing
"Programming the Threshold"
I've understand there is a voltage divider for the threshold but my input voltage will vary between 4.20 and 2.9v also the threshold input voltage will vary too?
Thanks you
You will used a fixed voltage divider at your trip point.  You want 2.9V to be your minimum battery voltage?  Then use the equations from page 5 -> http://www.micrel.com/_PDF/mic834.pdf

Equation 1:    2.9V = 1.240V * (R1+R2) / R2
Equation 2:    R1 + R2 = 1MΩ

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