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can MAX712 be used for charging NiCd?

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joozwa

joozwa

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max712

Hello everybody :D
I have a question as in the topic. Has anybody tried charging NiCd cells with MAX712, which is basically designed for NiMH? I've read a lot (including application note) but found no answer. MAX713 terminates fast charge by detecting negative voltage slope (cell voltage beginns falling), and MAX712 - by detecting zero voltage slope (cell voltage stops raising). So I think there's no danger of overloading NiCd by MAX712, which detects full charge more precisely, am I right?

Thanks in advance
Łukasz
 

max712 charger

I used only 713 but I read app notes. I agree with you.
Anyway you can make the pcb and solder a socket. If you need substitute 712 with a 713 you can do it as soon as you get it.
 

    joozwa

    joozwa

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max 713 charger pcb

look at the vharging characteristic of battery, you'll fing the solution
 

    joozwa

    joozwa

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max713 pcb

Hi, thanks for your answers :D
trapoe said:
I used only 713 but I read app notes. I agree with you.
Anyway you can make the pcb and solder a socket. If you need substitute 712 with a 713 you can do it as soon as you get it.
Click to expand...
I've already got both 712/713, but the second one in a SMD package and you know what it means for beginner :D... That's why I wonder if I can use one MAX712 based charger for both NiCd and NiMH cells.

e_eja said:
look at the vharging characteristic of battery, you'll fing the solution
Click to expand...
I've done so, and my answer is "yes", but I'm not quite sure, because it's stated that MAX713 is for NiCd and NiMH and nothing like that is written about MAX712. I guess MAX712 can terminate NiCd fast charge just a little bit too early, but nothing wrong should happen besides.
Please help
Łukasz
 

If this is a prototype and you're a beginner I suggest to use DIP package.
I just checked Maxim site and you can get few samples of MAX713CPE+, C means "commercial" i.e. 0-70 °C, and P means Plastic dip 16 pins.
Anyway waiting for 713 you can use 712.
 

    joozwa

    joozwa

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Thanks, I'll try :D
As far as I know Maxim does not send samples to Poland any more. I bought mine from a guy who'd got them from Maxim some time earlier :| But, in fact that was almost the only chance for me to get them :( And, wasn't it for such people, Maxim would surely continue sampling to Poland...
So, I understand I can replace MAX713 with MAX712 for Nickel-Cadmium cells and nothing wrong should happen.

Regards
Łukasz
 

Today I made the first attempt to charge NiCd with MAX712. I use old GPs 1000mAh and fast charge current is 500mA. The charger (which is simplest linear application circiut) switches to trickle charge after about 20 minutes each time :( So my guess was correct, the device terminates charge too fast. The batteries don't even get warm. Voltage across sensing resistor is correct (250mV) so fast charge of 500mA is not a problem even for old cells. I' not sure if I should try also at 750mA or 1A :| Seems like it's better to use MAX713 (or only NiMH cells :D ), or another charger.

I think topic can be closed.
Thanks,
Łukasz
 

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