Jump to content

Welcome to Geeks to Go - Register now for FREE

Geeks To Go is a helpful hub, where thousands of volunteer geeks quickly serve friendly answers and support. Check out the forums and get free advice from the experts. Register now to gain access to all of our features, it's FREE and only takes one minute. Once registered and logged in, you will be able to create topics, post replies to existing threads, give reputation to your fellow members, get your own private messenger, post status updates, manage your profile and so much more.

Create Account How it Works
Photo

NiMH charging.


  • Please log in to reply

#1
samplerdave

samplerdave

    Member

  • Member
  • PipPip
  • 27 posts

Hello Geeks.

 

I'm not sure which section to present this, so any mod please feel free to move it if required.

 

While passing a skip I noticed a cordless battery that was looking for a new home.

 

Closer examination shower a hole had been burnt in the side where the battery attaches to the drill.

 

But I thought it would be interesting to play around with this thing.

 

It is a DeWALT 18 Volt 2.6 Ah battery and is comprised of 14 cells.

 

The next bit is supposition on my part, so don't hesitate to tell me if my reasoning is wrong.

 

I am assuming that each cell is 18/14 = 1.286 volt nominal.

 

And that each cell can supply 2600 mA/14 =185.7 mAhr.

 

The test so far.

 

One cell was scrap, burnt.

 

The others measured 0.083 Volt (no load).

 

I attached each cell across my variable power supply and slowly raised the voltage.

 

At about 1.5 volt the amp meter kicked into life and slowly fell back to around zero.

 

The cells then measured about 0.953 Volt.

 

I am now charging each cell via my SC-608 Smart Charger at 300 mA. On the NiMH/CD setting, of course.

 

The charger is indicating 1.4V at 0.3 Amp.

 

(waiting for this cell to complete)

 

Stopped charging after 37.39 minutes.

 

Indicates 182 mAh and 246 mWh.

 

Cell  now showing 1.337 Volt (no load)

 

 

 

Looking at the recommended charge rate it seems to be 0.4C. Where C is the capacity in mAh.

 

This would give me a charge rate of 74.28 mA if the capacity is as I have calculated.

 

My question is, am I approaching this right ?

 

Dave.


Edited by samplerdave, Today, 01:42 PM.

  • 0

Advertisements







Similar Topics

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

As Featured On:

Microsoft Yahoo BBC MSN PC Magazine Washington Post HP