SMART battery Charger help needed

[Frosty_47]

Dear Comrades,

I am once again seeking your help in yet another project design. I am struggling to come up with a design for a universal battery charger that will automatically shut it self down when the battery has been charged. The problem I am facing is that this "universal battery charger" is designed to charge many different types of electrolytic batteries ranging from 3V - 24V and all having different Ampere/hour ratings. What methods are there to solve this problem?

Thank you for your time and interest !

 

[audioguru]

There are a few types of rechargable batteries that are very different from each other. Lead-acid, Ni-Cad/Ni-MH and Lithium-Ion/Lithium-Poly.

You forgot to say which type you want to charge.

 

[Krumlink]

3-24V sounds like lead-acid. He even says ampre hour ratings.

one thing that would simplify the circuit is to have a rotary switch, so that you could select the voltage and Amp rating. That would make it easy. Then you have a zener diode rated to the voltage (also selected by the rotary switch, say through a high amp MOSFET) and amp rating and you could have a working charger!

I HAVE NOT TESTED THIS, PROCEED AT YOUR OWN RISK.

WARNING: If the batteries explode, I want you to know that ALL YOUR BASE ARE BELONG TO US.

 

[Gayan Soyza]

The problem I am facing is that this "universal battery charger" is designed to charge many different types of electrolytic batteries ranging from 3V - 24V and all having different Ampere/hour ratings. What methods are there to solve this problem?

There is no method.I have different charges for different type batteries.
*For NIMH I have a separate charger built by me.
*For SLA I have another charger built by me.
*For Li-ION I have very sensitive charge control charger.
*For NICD I don't have a charger because NICD not available in my place & they are replaced by NIMH.

 

[Frosty_47]

Thanks

Sorry I forgot to mention that this charger is for Lead-Acid batteries only. I already build the charger and it uses the rotary switch to select the voltage and a separate potentiometer attached to LM317 (in current regulating mode) to control the output current. This is not the issue though. My question is how do I make the charge shut off after the battery has been charged? Is there some kind of "voltage sensing circuit" that can shut the charger off when the voltage across the battery terminals increases to it's "charged potential" ? Or perhaps I can figure out the approximate time it takes to charge a lead acid battery based on it's Ampere/Hours rating. Since the charging is designed to charge the battery at 10% of its ratted ampere/hour rating, perhaps I can design timing circuit that will automatically set the charging time based on the charging current.
For instance: If a 3Ampere/hour battery requires 8 hours of charging at a constant current of 300mA, than I can adjust the timer circuit to that charging time when the initial current through the battery is at 300mA. I am not sure how I will go about designing such a “timer circuit”.

Does anyone else have better ideas (I mean besides shooting myself).

Thanks

 

[Krumlink]

Good to see my little idea working!

I dont know what circuit you would use for a battery sensing circuit, but they are out there!

 

[Sceadwian]

A lead-acid battery only charger isn't exactly universal. Read the wikipedia entry and research on a google a bit more, the topic is covered ad nauseum elsewhere.

 

[Hero999]

3-24V sounds like lead-acid. He even says ampre hour ratings.

You can't get 3V lead acid batteries, the smallest cell voltage is 2V.

The charger needs to be programmable and have different profiles for different battery chemistries. You might be able to detect the kind of battery chemestry and state of charge by measuring its impedance and how it responds to charge but I wouldn't count on it being acurate.

 

[Krumlink]

Sorry I forgot to mention that this charger is for Lead-Acid batteries only. I already build the charger and it uses the rotary switch to select the voltage and a separate potentiometer attached to LM317 (in current regulating mode) to control the output current. This is not the issue though. My question is how do I make the charge shut off after the battery has been charged? Is there some kind of "voltage sensing circuit" that can shut the charger off when the voltage across the battery terminals increases to it's "charged potential" ? Or perhaps I can figure out the approximate time it takes to charge a lead acid battery based on it's Ampere/Hours rating. Since the charging is designed to charge the battery at 10% of its ratted ampere/hour rating, perhaps I can design timing circuit that will automatically set the charging time based on the charging current.
For instance: If a 3Ampere/hour battery requires 8 hours of charging at a constant current of 300mA, than I can adjust the timer circuit to that charging time when the initial current through the battery is at 300mA. I am not sure how I will go about designing such a “timer circuit”.

Does anyone else have better ideas (I mean besides shooting myself).

Thanks

Uh hero, did you read this?

 

[Frosty_47]

Thanks you all for the information. Why not create independent circuits appropriate for different battery type and let the user manually select the type of battery? Anyways, I still can't find the answer to my original question, that is: What type of circuit can monitor the charging process and shut off the charger when the it feels that the battery has been charged?

Thanks

P.S. by "Universal Charger" I meant Universal SLA charger...

 

[bryan1]

Eh Frosty ya might want to checkout the silicanchip website they have done 2 smart battery chargers and i've made the second version. It charges just about every battery bar the lipoly ones as they werent around when the circuit was designed. If you can still get a kit it wont be cheap off memory I paid $190 for the kit. albiet pricey I reckon you wouldn't find something similar on the market for anywhere near that price.

Cheers Bryan

Edit:- Here's the link to the above charger I mentioned. https://www.siliconchip.com.au/cms/A_101728/article.html

Dont go paying for the article if this does interest you I can PM you the schematic.

 

[Frosty_47]

Thanks Bryan

Eh Frosty ya might want to checkout the silicanchip website they have done 2 smart battery chargers and i've made the second version. It charges just about every battery bar the lipoly ones as they werent around when the circuit was designed. If you can still get a kit it wont be cheap off memory I paid $190 for the kit. albiet pricey I reckon you wouldn't find something similar on the market for anywhere near that price.

Cheers Bryan

Edit:- Here's the link to the above charger I mentioned. https://www.siliconchip.com.au/cms/A_101728/article.html

Dont go paying for the article if this does interest you I can PM you the schematic.

Thank you Sir for providing this information. I am not interested in purchasing a premade charger. I would very like to design one myself. I am sure the schematic of this charger could clear up some questions in my head..

Ones again, thank you for your time and help !