Making or buying a protective circuit board for charging a 9v battery

Hello every one. Ive been trying to figure out how to make a circuit or even find a company that makes a small compact circuit that would allow me to charge a 9V battery with a micro usb input. I want to be able to charge a 9V battery with either a car charger or wall charger that plugs into the system with a micro usb.

Basicly what this board does but for a 9V battery.

https://dx.com/p/charge-discharge-p...ion-batteries-17-4mm-1-9mm-26112#.UwOOIGePKUk

Ive been reading articles like this (see below) that talk about how you need to protect batteries from over charging and other things

https://voltaicsystems.com/blog/solar-charger-tutorial-part-4-battery-protection/

Also would I need a voltage regulator I found this one that would work.
**broken link removed**

I would be very great full for any help thank you all.

You linked to a "protection circuit" for a Lithium cell which is not a charger circuit.

You have a 9V battery but you did not say what is its chemistry (Ni-Cad, Ni-MH or Lithium) and did not say if it has 6 cells (7.2V) or has 7 cells (8.4V).
Also its datasheet (you did not post it) will say the recommended charging current.

You linked to an Ebay voltage regulator but the ad is mixed up. It says +9V but the part number 7909 is for NEGATIVE 9V. Maybe it is actually a 7808 +9V regulator, who knows? Western manufacturers do not make a 9V regulator so maybe it is made by a poor quality manufacturer over there in ebay land. Its MINIMUM input will be 11V so it cannot be used with a 9V battery.
I found a Chinese datasheet written in Chinese, not English. I recommend using a device made by a Western manufacturer that has an English datasheet.

audioguru said:

You linked to a "protection circuit" for a Lithium cell which is not a charger circuit.

You have a 9V battery but you did not say what is its chemistry (Ni-Cad, Ni-MH or Lithium) and did not say if it has 6 cells (7.2V) or has 7 cells (8.4V).
Also its datasheet (you did not post it) will say the recommended charging current.

You linked to an Ebay voltage regulator but the ad is mixed up. It says +9V but the part number 7909 is for NEGATIVE 9V. Maybe it is actually a 7808 +9V regulator, who knows? Western manufacturers do not make a 9V regulator so maybe it is made by a poor quality manufacturer over there in ebay land. Its MINIMUM input will be 11V so it cannot be used with a 9V battery.
I found a Chinese datasheet written in Chinese, not English. I recommend using a device made by a Western manufacturer that has an English datasheet.

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Very sry about that looks as though I need more help than I thought.

Which of the two battery options has the highest capacity? The (8.2V) or the (7.2V) I assume its the 8.2V but I could be wrong. I need the option with the highest capacity.

What im trying to do is make a charging circuit for an EL inverter that is protected which uses a 9V battery. I want it to be able to charge the battery with out worrying about it over charging or damaging the controller or the battery. I am also looking to make it chargeable with a car phone charger if possible. Any articles or sites are helpful. Forgive me If I seem needy not trying to have any one do all the work for me just trying to learn and accomplish the goal. Thanks

Thank you for the education on it.

Sheldon Williamson said:

Which of the two battery options has the highest capacity? The (8.2V) or the (7.2V) I assume its the 8.2V but I could be wrong. I need the option with the highest capacity.

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Simply look them up.
A 9V rechargeable battery with 6 cells is only 7.2V and has larger cells (higher capacity) than a 9V battery with 7 cells that is 8.4V.
Ni-Cad was used many years ago. Its capacity was low. They were all 6 cells and are not made anymore.
Ni-MH is new and some 9V batteries have 6 cells for a higher capacity but are only 7.2V. Other Ni-MH 9V batteries have 7 cells and are 8.4V to match the voltage of 9V alkaline batteries.
Some Oriental batteries purchased on e-bay have capacity claims that are lies.

What im trying to do is make a charging circuit for an EL inverter that is protected which uses a 9V battery. I want it to be able to charge the battery with out worrying about it over charging or damaging the controller or the battery. I am also looking to make it chargeable with a car phone charger if possible. Any articles or sites are helpful. Forgive me If I seem needy not trying to have any one do all the work for me just trying to learn and accomplish the goal.

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There are charger ICs available. They show a block diagram on their datasheet.
There are many charger circuits on the internet. Some work and others don't.
I downloaded the Ni-Cad and Ni-MH Battery Manuals that are full of charging and discharging rules from www.energizer.com click on Technical Info at the bottom of the home page then select the battery. Also look at their datasheets.
Go to www.batteryuniversity.com to learn about batteries.

Wow thanks a lot that a lot of good information.

Ive been searching and searching and cant find any charging circuits I keep finding tons of diy projects where people use 9V to charge their phones but not the battery. What key words do you use?

How do you know which work and which don't have you learned this from trial and error or searching online.

Now will it be a problem finding a IC with a 5V input (micro usb charger output) and a 9V output? All the ones Ive found are very close in voltage like 6V input 4.2V out put
What key words would I use to find some thing like this? is there a lingo I need to know? I always end up with a ton of crap like alibaba and places like that not actual suppliers.

Im not very good at searching things on the internet I find some stuff but its usually very generic

Thanks for the help. Please forgive my ignorance.

We know about charging batteries and converting 5V to a voltage suitable for a 9V battery charger because we are geeks and learned about electronics in university.

For feeding micro USB 5VDC from a computer to the charger circuit you need a voltage boost converter that boosts 5VDC to 9VDC. It is easier to take 12VDC from a computer's printer output and feed it to an LM317 adjustable voltage regulator set to 9V.

In addition to having an input from micro USB 5VDC for the charger you said you also want the charger to have an input from a 12VDC car battery or from a wall charger that already has enough voltage to charge a 9V battery. Then a voltage boost converter is not needed.

You said the EL Inverter is protected which is odd. Usually a Lithium battery is protected, not an inverter circuit. A good charger circuit will protect a 9V battery from overcharge and another circuit will protect it from over-discharge.

Isn't the EL inverter normally powered from a 9V alkaline battery that does not use a voltage regulator? A 9V regulator can reduce the 12V from a car to 9V for the inverter circuit. A voltage boost converter and a wall charger do not need a voltage regulator.

Nice that is sweet so you just add resistors to adjust the voltage of it im reading. That's awesome.

Im sry I must have stated that wrong. The inverter is not protected but needs to be. Where do I find these protection circuit or what key words do I need to search to find them?

Most of the batteries I have found don't come with protective circuits' at least the traditional 9V batteries that are rechargeable don't.

For the car aspect of the project, I assumed all phone chargers had an output of 5V in a car and from a computer so I assumed using a car phone charger would still only put out 5V but the charger would have the 12V input not my circuit from what I understand.

Yes the inverter is normally powered from an alkaline 9V So it already has a voltage regulator?

Thanks again im learning a ton. Very exciting.

Sheldon Williamson said:

Nice that is sweet so you just add resistors to adjust the voltage of it im reading. That's awesome.

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Like a 7809 0r 7909 voltage regulator, the input of an LM317 adjustable regulator must be at least 2V higher than its output.

Im sry I must have stated that wrong. The inverter is not protected but needs to be. Where do I find these protection circuit or what key words do I need to search to find them?
Most of the batteries I have found don't come with protective circuits' at least the traditional 9V batteries that are rechargeable don't.

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The protection circuit you found is used on a Lithium battery to prevent it from EXPLODING or CATCHING ON FIRE. An inverter circuit or a Ni-MH battery doesn't.
The article you found talks about a prevention circuit that prevents overcharging or over-discharging a Ni-MH battery to make it last longer.

For the car aspect of the project, I assumed all phone chargers had an output of 5V in a car and from a computer so I assumed using a car phone charger would still only put out 5V but the charger would have the 12V input not my circuit from what I understand.

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You do not want a phone charger. You want a 9V battery charger that maybe you can buy or you can make one.

Yes the inverter is normally powered from an alkaline 9V So it already has a voltage regulator?

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I don't think an EL inverter has a voltage regulator. The 9V alkaline battery is about 9.5V when brand new and its voltage quickly drops to 7.2V as it is used then slowly drops to 6V. The EL light will simply get a little dimmer that you might not notice.
A car battery is 14.4V when the car is first started then it drops quickly to 13.8V. When the engine stops the voltage slowly drops to 12.6V. A simple series resistor can reduce the voltage to 7V to 9V.
A "8.4V" Ni-MH rechargeable battery is about 9.8V when fully charged that quickly drops to 7.6V then it slowly drops to 7V when it should have its load disconnected.

audioguru said:

Like a 7809 0r 7909 voltage regulator, the input of an LM317 adjustable regulator must be at least 2V higher than its output.


The protection circuit you found is used on a Lithium battery to prevent it from EXPLODING or CATCHING ON FIRE. An inverter circuit or a Ni-MH battery doesn't.
The article you found talks about a prevention circuit that prevents overcharging or over-discharging a Ni-MH battery to make it last longer.


You do not want a phone charger. You want a 9V battery charger that maybe you can buy or you can make one.


I don't think an EL inverter has a voltage regulator. The 9V alkaline battery is about 9.5V when brand new and its voltage quickly drops to 7.2V as it is used then slowly drops to 6V. The EL light will simply get a little dimmer that you might not notice.
A car battery is 14.4V when the car is first started then it drops quickly to 13.8V. When the engine stops the voltage slowly drops to 12.6V. A simple series resistor can reduce the voltage to 7V to 9V.
A "8.4V" Ni-MH rechargeable battery is about 9.8V when fully charged that quickly drops to 7.6V then it slowly drops to 7V when it should have its load disconnected.

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Will I need any kind of protection circuit then? I know you said a good circuit would not need one but im a little fuzzy on what exactly the good charging circuit is. Is it the circuit where I go 9V charger to the battery with a voltage regulator, is that all it consists of ?

What stops the charger from over charging?

basically what im trying to do is take this inverter put in a rechargeable 9V and splice in a charging port into the existing battery wires then fill the battery compartment with potting so that nothing can get corroded from moisture. So I don't have to replace the battery I just charge the unit.

Forgive me if im frustrating you

If I do find a charger that charges a 9V then do I need to do anything at all to the inverter besides at a charging port? No protective circuit not any thing.

I think you are right just finding a charger with a 9v out put would be better than building it all inside the inverter. I just need to know what I need to put in the inverter now.

When you say it should have it load disconnected does that men if left on it could ruin the battery or cause issues?

Also ive seen where people have made circuits where they use capacitors and regulators in combination when the voltage is above 9V they store it in a capacitor and whe its below the capacitor helps out to equalize. Is that some thing that's hard to do and would it work in my application?
Thanks a lot this is really helpful.

Sheldon Williamson said:

Will I need any kind of protection circuit then? I know you said a good circuit would not need one but im a little fuzzy on what exactly the good charging circuit is. Is it the circuit where I go 9V charger to the battery with a voltage regulator, is that all it consists of ?

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A voltage regulator is not a charger circuit.

What stops the charger from over charging?

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I gave you links to battery tutorals that talk about all the things a good battery charger circuit does. There are battery charger ICs available that do even more things.

basically what im trying to do is take this inverter put in a rechargeable 9V and splice in a charging port into the existing battery wires then fill the battery compartment with potting so that nothing can get corroded from moisture. So I don't have to replace the battery I just charge the unit.

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DO NOT pot a battery.
Many years ago I potted a battery with some blinking lights. The first one blew up because the battery produced gas that had high pressure beneath the potting. Luckily nobody was killed and the damage was minor.

If I do find a charger that charges a 9V then do I need to do anything at all to the inverter besides at a charging port? No protective circuit not any thing.

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I do not think so.
Simply read the minimum and maximum supply voltages on the datasheet for the EL inverter.

When you say it should have it load disconnected does that men if left on it could ruin the battery or cause issues?

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A circuit must disconnect the load when the discharging battery voltage is less than about 7V. Maybe you will see that the EL light is dim and then you will turn it off.
The Battery University tutorial I linked talks about what happens if the battery voltage gets too low while it is still powering a circuit. The weakest cell goes dead then becomes charged in reverse by the remaining discharging cells that destroys the cell. Then the second weakest cell gets charged in reverse and is destroyed. Then the third etc.

Also ive seen where people have made circuits where they use capacitors and regulators in combination when the voltage is above 9V they store it in a capacitor and whe its below the capacitor helps out to equalize. Is that some thing that's hard to do and would it work in my application?

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It does not make sense. There are many people who do not understand electronics so they add capacitors and regulators all over the place.

One thing to add to what has been said, is to make sure you are using rechargeable batteries. The typical 9V alkaline batteries you buy at the supermarket are NOT rechargeable.

Also, be aware that a rechargeable version of any given cell size will almost always have lower capacity than the non-rechargeable part.