NiMh charging method

[Rob Horton]

Hi,

I'm thinking of adding a battery backup system to a project of mine. I will
be using a NiMh battery pack of 7.2v with a capacity of 1.8Ah.

To keep things simple and cheap, I was thinking of leaving the battery
permanently connected to a trickle charge of about 18mA (1.8A / 100).

What I would like to know is:

(1) If the battery is in an initial discharged state, will the trickle
charge eventualy fully charge the battery?

(2) Can I really leave the battery permanently connected to the trickle
charge?

Thanks.

Rob Horton.

 

[James Beck]

In article <vn58g7pco12ja5@corp.supernews.com>, yahoo.com@mr_horton
says...

Hi,

I'm thinking of adding a battery backup system to a project of mine. I will
be using a NiMh battery pack of 7.2v with a capacity of 1.8Ah.

To keep things simple and cheap, I was thinking of leaving the battery
permanently connected to a trickle charge of about 18mA (1.8A / 100).

What I would like to know is:

(1) If the battery is in an initial discharged state, will the trickle
charge eventualy fully charge the battery?

(2) Can I really leave the battery permanently connected to the trickle
charge?

Thanks.

Rob Horton.




The quick answer is IT DEPENDS.

I doubt very seriously that .01C is going to bother the battery as a
trickle charge. Now, if the system drain or self discharge rate is
greater than the trickle rate then the battery will eventually go dead
or never charge. I would say, try it and see. At that rate I can's see
you hurting it.

Jim

 

[JeB]

On Thu, 25 Sep 2003 09:06:33 +0100, "Rob Horton" <yahoo.com@mr_horton>
wrote:

Hi,

I'm thinking of adding a battery backup system to a project of mine. I will
be using a NiMh battery pack of 7.2v with a capacity of 1.8Ah.

To keep things simple and cheap, I was thinking of leaving the battery
permanently connected to a trickle charge of about 18mA (1.8A / 100).

What I would like to know is:

(1) If the battery is in an initial discharged state, will the trickle
charge eventualy fully charge the battery?

(2) Can I really leave the battery permanently connected to the trickle
charge?

I'm guessing you can find an IC "smart charger" that will handle the
details for you.

 

[R. Steve Walz]

Rob Horton wrote:

Hi,

I'm thinking of adding a battery backup system to a project of mine. I will
be using a NiMh battery pack of 7.2v with a capacity of 1.8Ah.

To keep things simple and cheap, I was thinking of leaving the battery
permanently connected to a trickle charge of about 18mA (1.8A / 100).

What I would like to know is:

(1) If the battery is in an initial discharged state, will the trickle
charge eventualy fully charge the battery?
--------------

Yes.

(2) Can I really leave the battery permanently connected to the trickle
charge?

Thanks.

Rob Horton.
---------------

No, it will experience voltage depression that will drastically
reduce its capacity over time.

-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public

 

[John Fields]

On Thu, 25 Sep 2003 09:06:33 +0100, "Rob Horton" <yahoo.com@mr_horton>
wrote:

Hi,

I'm thinking of adding a battery backup system to a project of mine. I will
be using a NiMh battery pack of 7.2v with a capacity of 1.8Ah.

To keep things simple and cheap, I was thinking of leaving the battery
permanently connected to a trickle charge of about 18mA (1.8A / 100).

What I would like to know is:

(1) If the battery is in an initial discharged state, will the trickle
charge eventualy fully charge the battery?

(2) Can I really leave the battery permanently connected to the trickle
charge?
---

Note from:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_NiMH_ChargeMethods.pdf

that trickle charge is _not_ recommended.

Since the chemistries will be similar regardless of manufacturer, I
suspect the charging characteristics will also be similar. To be sure
though, you need to find out from the manufacturer of the cells.

--
John Fields