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How do i adjust the charger circuit to charge 1.5V AA NiMH battery with solar panel ?

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tengyy

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The minimum sense voltage for the TL431 is 2.5 volts. What else component can I use ?
 

dick_freebird

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What kind of solar panel?

Even if it's (say) a 900mAH cell, a C/10 rate is mighty
low for single string - 90mA vs your usual 4" cell I
recall giving 500mA or so, might be better now.

So I guess my point is maybe you want to forego
all the circuit fiddling and get a string of 4 right-
sized (current) cells, which will probably be pretty
compact. Maybe you want to charge at a higher
rate. I think sundown will serve for charge termination.
 

tengyy

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I change the AC to DC input to be like the solar panel input current.

My solar panel is within 5V output with the table light
 

Audioguru

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A Ni-MH cell has a voltage as high as 1.5V only when it is overcharging at a current that is too high for it. Look at www.batteryuniversity.com or at the applications manual from www.energizer.com .
A battery charger IC detects the small drop in voltage when a Ni-MH cell becomes fully charged then stops the charging to prevent overcharging.
My solar garden lights overcharge and cook the Ni-MH battery cells in the sunshine all day long and the cells still work after a couple of years.
 

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Vbase

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R2 is for limiting the charge current.
You can use LM317L as a sensor for 1.2V. R4 and R6 changed. The way it works; when voltage between the output of LM317L and adjust is higher than 1.2V the regulator stops current through it and LED2 goes off and so T1. 4 x 1N4001 are to give enough voltage for LED2 and LM317L. It will work down to 5V from the solar panel.

 
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Audioguru

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You should not use a Lithium charger circuit for a Ni-MH battery because a Lithium battery needs to have its voltage limited and the current is sensed to drop low but the Ni-MH battery does not. The Ni-MH battery needs to have its voltage sensed for a small drop that occurs when it is fully charged.
 

tengyy

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You should not use a Lithium charger circuit for a Ni-MH battery because a Lithium battery needs to have its voltage limited and the current is sensed to drop low but the Ni-MH battery does not. The Ni-MH battery needs to have its voltage sensed for a small drop that occurs when it is fully charged.

How to the let voltage sensed for small drop that occurs when it is fully charged? have suggestion mah?
 

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How to the let voltage sensed for small drop that occurs when it is fully charged?
That is what is recommended by battery manufacturers like Energizer in their online Ni-MH Applications Manual and at www.batteryuniversity.com . Battery charger ICs detect the small voltage drop.

have suggestion mah?
The datasheet from the manufacturer of your battery will show its rated mAh. Most rechargeable batteries have their rated mAh printed on them. The mAh of a battery drops when it has many charge and discharge cycles.
 

tengyy

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R2 is for limiting the charge current.
You can use LM317L as a sensor for 1.2V. R4 and R6 changed. The way it works; when voltage between the output of LM317L and adjust is higher than 1.2V the regulator stops current through it and LED2 goes off and so T1. 4 x 1N4001 are to give enough voltage for LED2 and LM317L. It will work down to 5V from the solar panel.



THank for your recommendation, but in this circuit... The green LED will light up but red dint light up when it is excess certain voltage
 

Vbase

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The red LED lights up when the charge current is over 500mA. 500mA through R2 turns T2 on. It isn't likely that your solar panel will source more than 500mA. If you want to see red LED on connect to your circuit external power supply that can source more than 500mA.
 

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