Previous in Forum: Delay "Off" Timer on Fridge Light   Next in Forum: Billion Tons of Rare Earths
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
15 comments
Rate this Comments: Nested
Anonymous Poster #1

Charging a Nickel-Cadmium Battery

02/05/2024 4:24 PM

Hi,

What will happen if a 7.2 V (6 cells in series ), 800 mAh battery is connected to a 5.0 V, 2,000 mA source (Cellphone charger)?

Thanks,

Job
Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
SolarEagle
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33180
Good Answers: 1806
#1

Re: Charging ni-cad battery

02/05/2024 5:17 PM

You need a proper designed-for-purpose charging system for batteries...

$12 cheap

https://batteryuniversity.com/article/bu-407-charging-nickel-cadmium

__________________
 All living things seek to control their own destiny....this is the purpose of life
Reply Score 1 for Good Answer
Go to Next "Almost" Good Answer
thankan
Commentator

Join Date: Apr 2009
Posts: 91
Good Answers: 1
#3
In reply to #1

Re: Charging ni-cad battery

02/05/2024 8:39 PM

Thank you Guru;

Regards,
Reply
3
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32008
Good Answers: 838
#2

Re: Charging ni-cad battery

02/05/2024 5:24 PM

It will charge to <...5V...> and no further, in about <...800...>/<...2000...> = 25 minutes or so.

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply Good Answer (Score 3)
Go to Next Good Answer
thankan
Commentator

Join Date: Apr 2009
Posts: 91
Good Answers: 1
#4
In reply to #2

Re: Charging ni-cad battery

02/05/2024 8:40 PM

Thank you Guru;

Regards,

Job
Reply
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32008
Good Answers: 838
#6
In reply to #2

Re: Charging ni-cad battery

02/06/2024 5:09 AM

Either that or it will go BLAT! depending on which way round it is connected.

Please make sure all other CR4 readers are out of the room before so doing.

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32008
Good Answers: 838
#8
In reply to #6

Re: Charging ni-cad battery

02/06/2024 7:27 AM

See #7⇓

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
dkwarner
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 6175
Good Answers: 247
#5

Re: Charging ni-cad battery

02/05/2024 11:37 PM

If your thread title is correct, you shouldn't bother charging it at all! Ni-Cad batteries don't hold a charge well, and to my knowledge haven't been used in new equipment for a decade or two. Recycle it properly!

About 12 or 13 years ago, I investigated getting a replacement Ni-Cad battery for a very nice Makita hand drill. It was cheaper to buy a new drill with a more modern battery than to buy a replacement Ni-Cad battery. The batteries (Li-ion) of the M12 Milwaukee that I bought as a replacement still hold a good charge and do an amazing amount of work.

__________________
 Teaching is a great experience, but there is no better teacher than experience.
Reply
2
Randall
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 5786
Good Answers: 314
#7

Re: Charging a Nickel-Cadmium Battery

02/06/2024 7:25 AM

A NiCad is considered to be fully discharged at 1.1V, so the no load voltage of the battery of 6 cells will be greater than 6.6V. So, nothing will happen.

I'm assuming that the charger won't force discharge the battery down to 5V.

Why are you asking?

__________________
 We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Reply Good Answer (Score 2)
Go to Next Good Answer
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32008
Good Answers: 838
#10
In reply to #7

Re: Charging a Nickel-Cadmium Battery

02/06/2024 7:32 AM

<...Why...asking?...>

Perhaps the temptation to play and discover the wonders of the universe has been overtaken by the desire to involve CR4 readers instead; who knows (rhetorical question - NNTR)?

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32008
Good Answers: 838
#9

Re: Charging a Nickel-Cadmium Battery

02/06/2024 7:30 AM

If the voltage at the terminals of the <...7.2 V...800mAh battery...> exceeds the <...5.0 V...> at the <...Cellphone charger...> then nothing will happen other than the development of a learning exercise.

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32008
Good Answers: 838
#11

Re: Charging a Nickel-Cadmium Battery

02/06/2024 7:33 AM

Is there a prize for the first correct answer?

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
Randall
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 5786
Good Answers: 314
#12

Re: Charging a Nickel-Cadmium Battery

02/06/2024 7:49 AM

These posts which describe replacing a 7.2 V NiCad battery with two Lithium Ion cells might be relevant.

https://cr4.globalspec.com/comment/1304174/Re-The-Future-of-the-Battery

https://cr4.globalspec.com/comment/1304187/Re-The-Future-of-the-Battery

__________________
 We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Reply
2
DownEasta
Participant

Join Date: Nov 2009
Posts: 3
Good Answers: 1
#13

Re: Charging a Nickel-Cadmium Battery

02/06/2024 11:51 PM

If the Ni-Cd pack is deeply over-discharged so that it's series voltage is below 5v then they would at least come up to 5v then stop charging. However, if monitored carefully for voltage and heating, you would be able to charge 3 cells at a time using your 5v supply. You would simply stop charging each set of 3 when they reach 3.75v or begin to get quite warm to the touch. Of course, don't leave them charging unattended. A better plan would be to charge the 3-packs through a 1 ohm 1 watt resistor to lower to current to the 1C rate and protect them better.
Reply Good Answer (Score 2)
No more Good Answers. Go to first "Almost" Good Answer
Randall
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 5786
Good Answers: 314
#14
In reply to #13

Re: Charging a Nickel-Cadmium Battery

02/07/2024 3:15 AM

GA

How about two blocks of three using two diodes and a resistor in series. That way you could dispense with the monitoring.

__________________
 We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Reply Score 1 for Good Answer
No more "Almost" Good Answers.
67model
Guru

Join Date: Dec 2010
Posts: 1686
Good Answers: 116
#15

Re: Charging a Nickel-Cadmium Battery

02/17/2024 7:06 AM

NiCd batteries have a nominal discharge voltage per cell of 1.4, 6 cells series is 8.4V.

If you connect a 5V/ 2 amp cellphone charger, that is probably a 5V constant regulated source with an electronic 5 amp overcurrent limit.

If the battery is charged, it will discharge to 5V when connected to 5V charger, 1.0 volts/cell is discharged for NiCd.

The small, torch battery sized, NiCd do not keep charge well. However, being part or fully discharged for long time does not damage them like lead-acid.

5 volts on 3 cells is ~1.66 v/cell @ 25 Celsius. Once 80% charged, cells will gas at that voltage, with 2 amps available they will overpressure, blow the seals and leak out corrosive potassium hydroxide. No more than 0.1C current when gassing is recommended. Hot cell has lower gassing voltage, a positive feedback to damage.

5V is too low to charge 3 cells safely - the 1 ohm series resistor is too low to limit gassing current. 10 volt charger with 68 ohm series resistor would keep below 80 mA - charging time would be 16 hours.

5 V open circuit with 80 mA current limit would work for 3 cells, but if you want fast you would need a complicated current limit.
Reply
Reply to Forum Thread 15 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

67model (1); dkwarner (1); DownEasta (1); PWSlack (6); Randall (3); SolarEagle (1); thankan (2)

Previous in Forum: Delay "Off" Timer on Fridge Light   Next in Forum: Billion Tons of Rare Earths

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
General Discussion:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (86 right now)
Show Members
Advertisement