Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Ever tried recharging ordinary alkaline batteries?

Status
Not open for further replies.

Hero999

Banned
I've heard about it before but I've never tried it and after seeing this website I decided to have a go myself.
**broken link removed**

I used an ordinary slow NiCad battery charger, it's pretty old so I'm not bothered if the battery leaks and makes a mess.


I tried a 9V alkaline battery that I was using to power a multimeter, it wasn't completely dead as it read 7.4V but it was weak enough for the battery warning symbol to show.

The charger uses half wave rectified DC and the name plate says it puts out 20mA. I tested the peak open circuit by connecting a capacitor to the output and measuring it with a DVM, to my surprise it measured in excess of 30V!

I connected the battery and left it to charge for 8 hours in a safe place. When I took it off charge it measured 11.4V, I was surprised it hadn't leaked. I left it for a day to settle down and it still measured 10V.

Now here's where the fun really started, I put it in my multimeter and it worked well but it displayed the battery warning symbol when I activated the backlight and it was very dim. I thought "oh well it's obviously gone high impedance" but after playing around with it for a few miniutes I noticed I could get the back light to turn on at full brightness without the battery warning symbol displaying. I turned the meter off and on and I noticed the same thing again, at first the low battery warning symbol would come on when I activated the backlight but after several activations the black light would work at full brightness without the battery warning symbol.


I thought "this is wierd" and I decided to investigate further by measuring the battery voltage with another meter whilst it was turned on. It turns out that when there wasn't much load on the battery it would read 9.6V, then when I turned the backlight on it would drop to <4V but I noticed that after a few activations the voltage under load would creap up to about 8.6V when the light is on, then after turning the meter on and off this would happen again. I tried short circuiting the battery with a screw driver tip and the same thing happened again.

What do you think is causing this?

Perhaps the battery is somehow over voltaging itself and the excess voltage must be drained from the battery before it will carry a load; it could be just one of the cells that's causing this but it doesn't make much sense.

Maybe if I had limited the charge voltage to 9.6V this would have never had happend.
 
I've only ever heard of being able to "refresh" them a couple times by throwing them on a charger where they never reach near their fully capacity. But frankly, I don't use alkalines for anything so I've never tried it.
 
Recharging (refreshing) alkaline batteries.

Use high end batteries! I use the “copper top”. Cheep “radio shack” batteries will not work well.

Do not run the battery down all the way! It will not recharge well.

In a wireless microphone application (church) we replaced 9 volt batteries every 4 weeks. I think each week we use 1/4 to 1/6 of the battery. I built a trickle charger. I do not remember what current level it charged at but I know it was small. (maybe 1/4 power per day) We had all week to recharge. The voltage was limited to 9.75 volts. We now replace the batteries after one year. They are still good but starting to be week.

My friend used a copper top D battery. He used 10% of the battery in one hour and then for the next 23 hours recharged at 1% per hour. He did this 200 times and the battery tested new.

Bottom line: the top 10% to 20% of a high quality battery can be replaced many times. The bottom 10% of the battery cannot be replaced.

Limit the current. Charge slow. Limit the voltage. Do not over charge.
 
"Re-charging" will not replenish used chemicals. I think it just charges the capacitance of the battery. The charge fades away if the re-charged battery is not used immediately.
 
AudioGuru, I did not test if the “charge” lasts over time. We stored the batteries on the trickle charger, used the battery, then returned it back to the trickle charger. In the case of the wireless microphone; 6 days charging, 1 hour waiting, 1 hour use, back to the charger.

I think that I can (to a limited extent) replenish the chemicals. If only a small amount of the battery was used. If 80% of the battery is used; then the battery can not be ‘restored’.
 
There used to be 'recharegeable alkaline' batteries available. They had to be recharged often and were limited with the number of recharges they could take. They were prone to chemical leakage.

Their advantage over normal rechargeables was low leakage of charge.

The **broken link removed** is for charging standard alkali cells.
 
Recharging doesn't replenish the chemicals, it simply reverses the chemical reaction that occurred when the battery was discharged.

This battery has worked so well I think I'm going to go back to using alkalines for my multimeters and recharge them often.

I'm going to build a charger (I don't see the point in spending money on an overpriced charger) that will limit the current to 10mA and the voltage to something like 9.9V. I'll do more research first to find out what current and voltage levels are the best.

Recharging alkalines makes sense to me, you get the advantage of a rechargable but with the low leakage of a single use battery.
 
wouldn't they blow up?????
 
I've exploded button cells before but that's only because I used excessive amounts of current but 20mA into a 9V battery shouldn't blow it up, in my experiance it didn't even get warm.

The button cells were interesting, I used a 9V battery and they didn't explode when I was passing the current though them, they exploded awhile later.
 
If you “refresh” your batteries with a NiCad 1 hour charger they will leek! A 4 hour changer will do the same thing soon. I think I recharged at a 1 day or less rate.
Limit the voltage. Limit the current. Do not let them get hot or even warm.
 
I didn't use a 1 hour charger, I used a cheap 16 hour NiCad charger.
 
I think using any charger designed for NiCads is pushing your luck. I think building a custom charging circuit with a current limit of 10 or 20mA would be the better route.
 
The charge I used is very basic, it doesn't do any voltage sensing or anything fancy. It's just a transformer which a half wave rectifier and a resistor connected in series with the battery.

You're right though, it would be better if I built my own charger which I'm going to do.
 
http://www.p2pays.org/ref/14/13394.htm

Why re-invent the wheel? I'm not sure if these things are around (notice last update date of 2002 at the end of the page) But Rayovac tried this idea years ago, didn't catch on because secondary cells are significantly more re-useable than trying to recharge a primary cell, the chemistry just doesn't work right on a primary cell, too many biproducts are created in the charge/discharge cycles to allow many charging cycles, probably one of the reasons lead-acid cells are still used extensivly, no other better cheapear easeier sollution exists. Lipoly tech is getting there but it'll never beat throwing a hunk of lead into a tub of sulfuric acid with a few wires connected as a cheap easy and safe sollution (if waste products are recycled)
 
I've seen chargers on the market but they're too expensive and probably not as complected as the marketing hype says.

I agree that alkaline batteries probably don't charge well but even if I can only get three uses out of the same battery it's still saved me enough money to make it worthwhile.
 
Just do constant current at 1/10th or 1/20th C for an hour longer than the best guestimate of the state of charge says should fill the cell.
9 volts are probably not a very good idea because they're actually batteries not cells like AA/AAA etc... 9 volts really need to be banished. Modern lithium primary cells have all but completly replaced them, at least in inteligent designs, for things like memory backup and emergency use they're perfect. If it's a shorter term (a year or two) backup sollution alkaline cells are fine, anything that needs recharging every few days/weeks or months really should be designed around secondary cells.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top