NICd battery charger

[ulot]

hello i got this circuit from electronics-lab but i just started getting errors lately with post.
I just want to know if i can change the series connection of the batteries to a parallel one so i don't have to use the swithc cos' i can't seam to lay my hands on a switch right now.

also with a 7805 it appears that the maximum current i can get is 500mA (i hope i'm right) can i change this to a 7808 so i derive more current at least a max of 800mA?

 

[Nigel Goodwin]

No, you shouldn't charge the batteries in parallel.

As for the regulator, a 7805 is 5V (hence the 05) at 1A maximum, a 7808 is 8V (08) at 1A maximum, so changing it wouldn't make any difference.

 

[Edmond]

hello i got this circuit from electronics-lab but i just started getting errors lately with post.
I just want to know if i can change the series connection of the batteries to a parallel one so i don't have to use the swithc cos' i can't seam to lay my hands on a switch right now.

also with a 7805 it appears that the maximum current i can get is 500mA (i hope i'm right) can i change this to a 7808 so i derive more current at least a max of 800mA?

Hi I recommend to you, to use an LM317 and not 7805. The 7805 have hot too high power loss. The charging current for LM317 can be simple calculated: I=1,25/R (R is the resistance between the adj. and out pin). The last two numbers (78xx) refers to the output voltage. This type of regulators supports 1-1,5A. I suggest you to read some documentation about the battery charging concepts! If you are unfamiliar with the main electronic components, with this simple circuit and the battery charging concept, is better to buy one in the shop.

Edmond

 

[ulot]

how about this one?
i agree i don't know about the details of the working of the 78series or any IC for that matter but i do know the basics of electronics
the batteries are in parallel right? so what's the diffrence between the two of them?

 

[Nigel Goodwin]

but i do know the basics of electronics
the batteries are in parallel right? so what's the diffrence between the two of them?

NO! - those batteries are NOT in parallel, they are being charged independently, each having it's own current source.

 

[ulot]

can i then arrange the batteries in the first circuit like they are in the second? what i want is for them to be charged with each having a different current source which i desire to be variable.

 

[Nigel Goodwin]

can i then arrange the batteries in the first circuit like they are in the second? what i want is for them to be charged with each having a different current source which i desire to be variable.

Yes, duplicate the 7805 section from the original circuit for each battery you want to charge, this will give you independent current control to each battery.