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Charging "nonrechargable" batteries

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ragnar

Tue Feb 28 2006, 01:26PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Sometimes after a battery is fully discharged (depending on the chemistry), it's almost guaranteed to leak, especially if left connected to something that'll draw current from it.

Even just leaving it discharged on your desk, there are reactions going on inside, and there's a small chance of it bubbling and fizzing I'm sure.

I'm not sure if 9V batteries have vents as opposed to most AAA, AA, C, D cells which have a pressure seal under/around the nipple end. Could there have been pressure buildup...?

Bored Chemist

Tue Feb 28 2006, 05:59PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Afrotec thinks that you get acid from leaking alkaline cells (the clue is in the name). Bjorn says that, at least sometimes, the cells really do explode.
I have seen Bjorn talking a lot of sense in the past too. Guess what I'm not planning to do without a blast shield?

Wolfram

Tue Feb 28 2006, 10:21PM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

I've had a cell taken from a 9V battery explode once too. I was making a small LED flashlight and these cells seemed nice for the job. I was holding an almost discharged cell in my hand and connected it to the circuit (joule thief) and the cell exploded, spreading zink powder gunk everywhere. The end cap hit my thumb and it hurt for a few hours. The bang made my ears ring. These cells seem to be completely sealed (as stated earlier in this thread). I guess this cell had a lot of pressure inside, just below bursting pressure, and when I started drawing current from it the additional gas buildup caused the pressure to rise just enough for it to explode. I think it was from a duracell battery, but I don't remember anymore, as it was over a year ago.

Anders M.

cjk2

Wed Mar 01 2006, 01:27AM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

For anyone interested, here is a copy of my abstract and research plan.

Abstract

The purpose of this project was to see if batteries being sold as â€œnon-rechargeableâ€ could actually be recharged after they were considered â€œdeadâ€. All batteries were drained to the same voltage, and then charged in one of three chargers. Each battery was only tested once and the cells were tested in pairs. Final data showed that the batteries can be recharged, but tend to lose some of their charge over time. The lost charge was relatively small in relation to the original voltage of the battery, so the project was still successful in replacing some of the lost energy due to use of the cell. This experiment is useful because it could prove to be a good way to reuse batteries and lower the amount of wasted money and resources in manufacturing disposable batteries. Even if standard batteries could be reused only once, the price consumers pay for batteries would be reduced by 50%.

Research Plan

Project Title:
â€œCharging the Unchargeableâ€

Question/Problem:
Can standard â€œnon-rechargeableâ€ batteries be recharged?

Hypothesis:
Yes, standard batteries can be recharged.

Engineering Goals:
Use several different chargers of different types to prove or disprove the myth that common household batteries can not be recharged.

Method and Procedures:
Discharge all tested batteries to a voltage at which they would be considered dead. Attempt to use three different charging methods to bring the batteries back to their original condition. Test the batteries in pairs of two, and only test each battery once. Test three different brands of batteries to see which (if any) will perform the best when recharged. Batteries will be tested on the following types of charges: one commercial unit, and two custom units. Custom chargers will use a pulse-charging method and a constant-current charging method.

Bibliography:

Glencoe/McGraw-Hill, Physical Science, pgs. 202-207

I hope the research and abstract sound ok because they are due tomorrow and I really can't change them at this point...

A picture of my chargers(both on one board):

...

Wed Mar 01 2006, 01:37AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

no afrotech

Reminds me of my 7th grade science project based around the effectiveness of a radiant barrier with/without a layer of fiberglass at insulating your house. Got first place

As to your project, a few suggestions (which may or may not matter depending on your school)
1. try each battery >1 time. Perhaps just a few trials, so that you can refer to the possibilities of using batteries >2times...
2. set some criteria before the experiment, like consider a battery that is <1.2v at 100ma dead for high current applications and 1.2v@2ma for low current applications. You might also consider (especially if doing >2 trials) specifying what capacity a charged battery needs to be considered still working. I believe the normal speck for that is once the battery has reached 1/2 of its original capacity...

Good luck!

Wed Mar 01 2006, 07:29PM

Registered Member #256 Joined:
Location:
Posts: 124

my friend was trying to explede AAs with a short circuit across the ends, wasnt succesful and i guess i know why now lol i guess there is a pressure release seal.

Sulaiman

Wed Mar 01 2006, 08:35PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I think that the first thing you need for this project
is a battery discharger/monitor,
to give quantitative answers to your question.

For a few runs I just use
a suitable power resistor
my digital multimeter
a clock with a seconds hand/digits,
and Excel spreadsheet.

After 4 or 5 runs you will appreciate the value of an automated system.

thom

Fri Mar 03 2006, 06:14AM

Registered Member #239 Joined: Thu Feb 23 2006, 03:15AM
Location: canada
Posts: 23

Sulaiman wrote ...

I think that the first thing you need for this project
is a battery discharger/monitor,
to give quantitative answers to your question.

Good point

Has anyone built one?

Chargers/discharges can be extremely complicated and expensive. But a pure discharge circuit that measures the mAH and displays a stat or two on a LCD shouldnt be too bad.

The only problem is if your using Li-ion or similar, you would need some way to set a cutoff voltage, or it would damage the battery.

Vaxian

Wed Apr 11 2007, 11:14AM

Registered Member #635 Joined: Tue Apr 10 2007, 01:56AM
Location:
Posts: 85

I have had allot of success charging alcaline batteries with a cheap NIMH charger.
You simply need to monitor the voltage of the cells over time and not let them go over 1.8V
I never had one explode, had some leak on me and corrode the contacts of the charger.

This would be a simple solution, if you need to use a pulse charger then discard above info.

Dan

Steve Conner

Wed Apr 11 2007, 12:48PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

You do realise almost all of the many threads you're replying to have been dead for over a year, right? Anyway, welcome to the board.

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