nicad battery charger

[iditu]

good day
please i want you to give me schematic diagram and an analysis of nicad battery charger.the transformer should have a secondary rating of 12v and primary of 220v.thank you

 

[Thunderchild]

after the 12v transformer put a single diode and then a capacitor (1000 uF will do) in this way u have a simple DC power supply then conect a resistor from the capacitor to the positive of the battery to charge and the negative of the battery to the negative of the power supply. the resistor should be calculated so that the current will charge the battery in no less that 5 hrs and make sure it is of the right wattage
note that if u need a lot of power u can use instead of the single diode a full wave bridge rectifier of 4 diodes that can be found all in one chip. tell me if u want me to draw a diagram

 

[mstechca]

good day
please i want you to give me schematic diagram and an analysis of nicad battery charger.the transformer should have a secondary rating of 12v and primary of 220v.thank you

Buy a charger, and buy a digital multimeter. then you can analyze the voltage, resistance and amperage changes with a battery charger. You might need to take some screws apart.

 

[Thunderchild]

how unimaginative cmon its two seconds math to calculate the values. if we all did it your way what would be the point in doing our own stuff hehe first u buy it then u pay for the components to rebuild it

 

[chiba]

I think we'd need more info to calculate anything, what does he want us to do with this 12v? step it up or down, does he want to float, trickle or a fast charge, is he happy with a timer or does he want peak or temp detect or all of the above?
btw, I typed "nicad charger circuit" into google and got 52,600 results.

This may help:
**broken link removed**

 

[Futterama]

A NiCD (nicad) charger can be a simple voltage supply and a power resistor as Thunderchild mentions.

But there are things to consider:

NiCD (and NiMH for that matter) is most happy to be charged in about 1 hour. If the battery to be charged is rated 2000mAh, then the charger should output 2000mA of charging current.

The charge termination (when to stop charging) is a very important matter to consider. This can be done in several ways:

- The user terminates the charge by removing the battery either after the 1 hour charge period or when the battery becomes warm to the touch.
- A timer terminates the charge after 1 hour.
- A temperature sensor terminates charge when the battery temperature is around 40˚C.
- A deltaV peak detector terminates charge (when a NiXX battery is fully charged, then voltage drops 10-20mv per cell, this can be detected and used to stop the charging).
- A deltaT detector terminates charge (the battery temperature rises when the battery is fully charged and when the temperature rises 1-2˚C per minute, the charge should be terminated).

Some usefull links on battery charging:

http://www.batteryuniversity.com/
**broken link removed**
**broken link removed**

Proper battery charging is not easily archieved :roll:

I hope this helps :wink:


Regards,
Futterama

 

[audioguru]

NiCD (and NiMH for that matter) is most happy to be charged in about 1 hour. If the battery to be charged is rated 2000mAh, then the charger should output 2000mA of charging current.

All Ni-Cad and Ni-MH battery cells I have seen say to charge them at 1/10th their A/hr rating for 14 hours. The 40% extra makes up for charging losses.
If the cells are separate, it is best to discharge them before charging so that a timer won't overcharge them. :lol:

 

[Futterama]

Quote from **broken link removed** : "the fast charger fills a pack in about one hour. Fast charging is preferred because of reduced crystalline formation (memory)"

When you buy new batteries, they should be charged at a rate of 0.1C (1/10 of the capacity per hour) but this is only to "align" the cells with each other. After that, the charge rate should be 1C (one hour charging) as suggested by www.batteryuniversity.com. The info is from www.buchmann.ca <- the author is the founder of Cadex Electronics Inc. and they produce battery analyzers, so I think they know what they are talking about :wink:


Regards,
Futterama

 

[Thunderchild]

i tyink that chsrging in 1 hour is not recomended. think about the generation of heat. i charge 2.3A NiMH cells with my 1A charger and they get very hot - imagine at 2.3A i think frankly they would burst. this was particullarily when they were new now they let off less heat although it could be that i have gooten used to the "alarming" temp increase.
as for so and so recomending 1 hour charge time how come my 1.9A batteries say to charge at 525 mA max. i should think that the producer should know what he is making no ?. As for temperature sensing i think it is more precise to sense a 3 degree difference from room temperature as different room temperatures will generate a different battery temperature so 40° is dangerouse (imagine an escimo waiting for his battery to get to 40°C i think he would be the first Escimese Kamicaza)

 

[audioguru]

Hi Thunderchild,
According to Energizer, who don't make Ni-Cad's anymore:
1) Ni-Cad's begin heating only when they are nearing full charge. Ni-MH's heat continuously when charging, with their temp increasing very quickly when they are nearing full charge.
2) Heat ruins the life of a Ni-Cad or Ni-MH cell.
3) Ni-Cad's and Ni-MH's do not accept a charge when cold. Energizer's limit is 15 degrees C for their Ni-MH's.
Their website www.energizer.com has very detailed battery applications manuals.

If a polar bear tried to charge a cold Ni-Cad or Ni-MH battery, nothing would happen. If anyone tried to over-charge a battery at a high current and high temperature, it wouldn't explode. Battery manufacturers don't want a law-suit so they have an over-pressure vent on each cell. What comes out of the vent is something very valuable and the vent might not reseal. A cell that has vented is doomed to early failure.

 

[Futterama]

Thunderbird, my statement of 40˚C was based on an ambient temperature of room temperature (in technical terms, when nothing else is mentioned, ambient temp is assumed to be room temperature: 20-25˚C).

It sounds like your cells are either cheap or in bad condition. NiCD is indothermic meaning they absorb heat when charging, but when fully charged, the energy the charger tries to put into them, is converted to heat.
NiMH is exothermic, meaning they produce heat during charge. The heat should not be dramatically at a charge rate of 1C.

Look at this document from panasonic about charging NiMH batteries:

https://www.actec.dk/NiMH-charge.pdf

They state that the recommended charge rate for fast charge is 0.5C to 1C.

I would certainly use 1C but if the battery becomes too hot, I would use 0.5C since (as audioguru says) heat is bad for NiCD and NiMH cells.

Another solution for the heat problem could be ventilation from a fan.