Adding Nicad Battery pack to 5v circuit that is constantly charging

[kimbear]

Ok, so I am looking to make something portable, that was originally designed to be desk top locked. It has a 12v Wall-Wart power supply, and the circuit runs off of a 5vdc and a 3v dc regulator. Its actual running current is quite low, on both voltages, So I would like to free it up, and add NiCads that constantly charge whenever the Wall Wart is plugged in, and also runs off the Wall Wart. Anyone have a nice simple schematic for me to do this.
(Ps I know that this is a clumsy explanation, but bear with me, Im not very bright)
Thank you in advance

 

[Nigel Goodwin]

Just trickle charge the NiCD's - however, they will most likely fail in a few years.

 

[kimbear]

Thats ok, 7 Nicads arnt that expensive. Do you have a good circuit for this, and can I run the circuit off of the NiCads while they are trickle charging Nigel?

 

[simonbramble]

you want this device:
https://www.maximintegrated.com/en/products/power/battery-management/MAX713.html

Personally I would use NiMH batteries. Their capacity is slightly lower but they last a lot longer and are easier to deal with. You need to terminate the charge when the voltage just starts to plateau. NiCad batteries have a slight negative dip. NiMH batteries have a flat plateau and the '713 handles all of that

With this circuit, the current sense resistor is in the battery path, but not in the load path, so you are just sensing the current charging the battery and it does not get upset by the load current.

Ideally you should charge the batteries at a rate of "C" since this gives better charge termination so you might want to consider just charging the battery when it has decayed below a certain voltage and not keeping it in constant trickle charge mode

 

[audioguru]

Do any stores sell antique Ni-Cad batteries anymore? Even very cheap solar garden lights use Ni-MH cells that are sold everywhere now.
Duracell and Energizer in North America have not made Ni-Cads for many years.
Google says that the EU has banned Ni-Cad batteries because they produce toxic waste.

 

[kimbear]

Whatcha think about something like this, Im lazy lately with my operation that I had:

21V 1A AC/DC US Adapter Charger For 5S Lithium Li-ion LiPo 18650 Battery Packs | eBay

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[kimbear]

Do any stores sell antique Ni-Cad batteries anymore? Even very cheap solar garden lights use Ni-MH cells that are sold everywhere now.
Duracell and Energizer in North America have not made Ni-Cads for many years.
Google says that the EU has banned Ni-Cad batteries because they produce toxic waste.

Thank you Audio Guru, you are knowledgeable as always.
To be honest, I spend quite a bit of time every Spring replacing dead nicads on solar lites of my Mate. I dont have a problem buying nicads, hell they even sell them in the Dollar Stores. I am careful to take the old ones to be properly recycled. I think I will go the Li-Ion way....I use them in my Drones, and I dont know why my mind went to NiCads for Backup...its my age I think.

 

[audioguru]

Personally I would use NiMH batteries. Their capacity is slightly lower but they last a lot longer and are easier to deal with.

No. The capacity of a Ni-MH cell is much higher than a Ni-Cad.

 

[kimbear]

Thank you guys I will use a NiMH pack...now for the charger. Im sorta looking at a premade module on ebay...whatcha think.

 

[Visitor]

Do any stores sell antique Ni-Cad batteries anymore? Even very cheap solar garden lights use Ni-MH cells that are sold everywhere now.
Duracell and Energizer in North America have not made Ni-Cads for many years.
Google says that the EU has banned Ni-Cad batteries because they produce toxic waste.

Why always with the "how can you be so stupid" attitude?

 

[audioguru]

The 21V battery with five Li-Ion cells is not much use powering your 5V and 3V things.

 

[kimbear]

Why always with the "how can you be so stupid" attitude?

Because in this topic, I dont have the mad skills that you guys have

 

[Visitor]

Because in this topic, I dont have the mad skills that you guys have

No, it's not you. Audioguru always answers that way.

 

[audioguru]

I always answer with facts. If people cry who are corrected with my facts then that is their problem, not mine.
My problem is that there are too many NOOBS here.

 

[Visitor]

My problem is that there are too many NOOBS here.

Thanks for doing your part to make them feel unwelcome.

 

[audioguru]

I am not a teacher and never wanted to be one. I come here to talk to my peers about new and improving circuits, not about the basics.

 

[Buk]

I am not a teacher and never wanted to be one. I come here to talk to my peers about new and improving circuits, not about the basics.

Then why not just say nothing in threads that are beneath you?

 

[Tony Stewart]

AG is correct to give the straight facts. Chinese imported NiCads should be illegal as they are very toxic to the environment (ground water). Get a grip on your low self-esteem and learn from the experts. Just face it. we all started as Noobs. But now you guys have something called internet search engines. use them wiser. A better answer comes from a better question.

 

[Buk]

Chinese imported NiCads should be illegal as they are very toxic to the environment (ground water).

Hm. So, it would be okay to import NiCds from Yausa or Panasonic in Japan?
How about NX(enix) in the UK?
Or Varta in Germany
Or ArtsEnergy(Saft) in France; and Sunnyvale California?

 

[Visitor]

					AG is correct to give the straight facts. Chinese imported NiCads should be illegal as they are very toxic to the environment (ground water). Get a grip on your low self-esteem and learn from the experts. Just face it. we all started as Noobs. But now you guys have something called internet search engines. use them wiser. A better answer comes from a better question. Facts are awesome. Facts presented with an opener of "How can you be so stupid?!?" are not useful. Yes, people need to post better questions, starting with a subect with more than "I need help urgently!" Most posts here are asking for help. Providing a clue to the help needed with help knowledgeable people read it. This forum is largely comprised of grumpy old men. Attracting new members is kind of vital to keeping it alive. People asking honest questions should be guided along. Sure, many of the questions posted here can be easily answered by Google....if a person knows what to search for. Sometimes, questions are asked as a reality check. Just because "the perfect solution" shows up in a search doesn't mean it's the best solution for a particular problem, or sadly, it may not be a workable solution at all.