NiMH battery charger - need some explanation

EDAboard.com Forum Index -> Analog Circuit Design -> NiMH battery charger - need some explanation

Author

Message

BABESH

Joined: 27 Sep 2005
Posts: 118
Helped: 10

27 Apr 2009 6:02 NiMH battery cahrger

Hi,
I saw from datasheet of battery manufacturer that NiMH battery can be left
un terminated with charge rate of C/20, for ever.

Will this current charge the battery pack?

After what time will the battery be fully charged?

thanks in advance.
--Babesh

BABESH

Joined: 27 Sep 2005
Posts: 118
Helped: 10

27 Apr 2009 15:36 NiMH battery cahrger

can any battery expert through some light on to this.

--thx.

Audioguru

Joined: 19 Jan 2008
Posts: 1152
Helped: 95
Location: Toronto area of Canada

28 Apr 2009 1:33 NiMH battery cahrger

If the battery is completely discharged then at C/20 it will take 20 hours plus 40% more for losses. The total time to make the battery fully charged is 28 hours.

BABESH

Joined: 27 Sep 2005
Posts: 118
Helped: 10

28 Apr 2009 2:43 NiMH battery cahrger

Guru,
Thanks a lot, it gave some hope for me abt this method of charging.

If battery Capacity is say 4200mAH, then c/20 is 210mAmp.

so (4200/210)*1.4=28Hours, is this equation holds good?

Then few sites are giving that factor as 1.6.
why is that factor...

thx
Babesh

Google
AdSense
Google Adsense

28 Apr 2009 2:43 Ads

Audioguru

Joined: 19 Jan 2008
Posts: 1152
Helped: 95
Location: Toronto area of Canada

28 Apr 2009 3:04 Re: NiMH battery cahrger

Energizer shows that a high current charge at a C rate makes a Ni-MH cell fully charged at 110% of its capacity.
A C/10 rate makes a cell fully charged at 140% of its capacity.
Maybe C/20 needs 150%.

Sorry, but you need login in to view this attachment

BABESH

Joined: 27 Sep 2005
Posts: 118
Helped: 10

28 Apr 2009 6:14 Re: NiMH battery cahrger

Guru,
Your data is supporting to equation.
Thanks a lot for proving me with data,
Now i will try waiting for 33 hours to charge the batteries.

Thanks
--Babesh.