Charging Alkaline Batteries

[raptor1956]

About 25 years ago give or take there were a number of companies that were selling battery chargers designed to charge alkaline batteries.  I seem to remember they were not around for very long and that although you could in fact add capacity to an alkaline battery the actual increase in capacity even after several recharges was not great and there was the risk of the batteries leaking.

OK, so how does my memory of this jive with reality?  What was/is the actual recharge potential for alkaline batteries (cells) and what risks are there.  For me, the only battery type that I might have interest in boosting the charge a bit is 9V batteries as most everything else I have is either 18650 LiIon or Eneloop NiMH AA's.  With a smart PS such as the Rigol DP832 you can accurately control charge current and voltage limits so if anything were able to charge an alkaline then these newer PS's should be the ticket.


Brian

[madires]

There are rechargable alkaline cells called RAM. They can be recharged about 30 to 50 times and got a quite low self-discharge.

[edavid]

About 25 years ago give or take there were a number of companies that were selling battery chargers designed to charge alkaline batteries.  I seem to remember they were not around for very long and that although you could in fact add capacity to an alkaline battery the actual increase in capacity even after several recharges was not great and there was the risk of the batteries leaking.

OK, so how does my memory of this jive with reality?

You forgot that these chargers were only for special cells like the Rayovac Renewal.  They were not intended to be used to charge standard alkaline cells, which can't be recharged, period.

[raptor1956]

About 25 years ago give or take there were a number of companies that were selling battery chargers designed to charge alkaline batteries.  I seem to remember they were not around for very long and that although you could in fact add capacity to an alkaline battery the actual increase in capacity even after several recharges was not great and there was the risk of the batteries leaking.

OK, so how does my memory of this jive with reality?

You forgot that these chargers were only for special cells like the Rayovac Renewal.  They were not intended to be used to charge standard alkaline cells, which can't be recharged, period.

Oh yes, the Rayovac Renewal -- I do remember them.

So, what was the difference in these special alkaline cells versus the standard ones -- there doesn't seem to be a Wikipedia source for info on them?


Brian

[Fungus]

About 25 years ago give or take there were a number of companies that were selling battery chargers designed to charge alkaline batteries.  I seem to remember they were not around for very long and that although you could in fact add capacity to an alkaline battery the actual increase in capacity even after several recharges was not great and there was the risk of the batteries leaking.

It's true!

But you'll be disappointed in how much extra capacity you can get. And the risk of leaks is high.

There's plenty of information in google.

[MosherIV]

Hi

Do not know if it was that long ago, I rekon it was 20 years agao, I graduated around that time and I remember meeting up with someone from my Elec Eng course and he told me he worked for one of those companies making an alkaline re-charger. That is normal alkaline not the Rayovac.

I do not remember anything about adding extra capacity, if anything the capacity dropped. So badly in fact that they adverised "recharge alkaline batteries upto 6 times!"

In reality it is not that hard, charging generates gas. While NiCad and NiMhd can recombine eventually, alkaline will vent, so the trick with alkaline is to charge for a very short period and then stop and wait for the gas to combine. Some chargers did some fancy timing or charge counting but the basic principle is pulse and wait.

[amyk]

Yes it is possible and has been done with limited success: https://en.wikipedia.org/wiki/Recharging_alkaline_batteries

In theory any battery chemistry can be recharged; in practice, side-reactions that produce undesirable byproducts make it problematic.

[IanB]

OK, so how does my memory of this jive with reality?  What was/is the actual recharge potential for alkaline batteries (cells) and what risks are there?

The way to know if a battery can be recharged is to consider what happens to the internal state of the battery after a discharge-charge round trip cycle. An ideal rechargeable battery will end up in exactly the same state that it started in.

Very few actual battery designs are successfully able to do this, which is why there are only a limited number of rechargeable battery types in common use.

It is extremely difficult to design a special alkaline battery that behaves this way, and regular disposable alkaline batteries certainly do not. So the recharge potential of alkaline batteries is limited at best. Rechargeable alkaline batteries have therefore not been commercially successful.

[raptor1956]

OK, appreciate the feedback...

It is mostly as I remembered it and it appears the risks outweigh the rewards so probably not a good idea to do.  For me, the only alkaline batteries I use are the 9V types like what my Fluke meters have and it's mostly for my Fluke meters that I asked.  But, why risk leaking stuff into a several hundred dollar meter to save a few dollars a year.

Apparently the best method for charging, as per the Wikipedia article on "Recharging alkaline batteries" (https://en.wikipedia.org/wiki/Recharging_alkaline_batteries), is to use pulse charging with 80% DC and low current.  They gave no specifics on just what the current should be or what the terminal voltage should be, but given the generally low number of recharge cycles and the rapidly declining capacity with each recharge there is too little benefit for the great risk of leakage.  The idea of recharging is tempting, particularly given the cost/WHr of a 9V battery, but thankfully my Flukes are not particularly power hungry so a battery can often last a few years.


Brian

[helius]

In addition, alkaline cells are sold with a warning not to recharge them and this voids their warranty. Some consumer devices also carry warnings not to use recharged alkalines.

[Audioguru]

My Fluke multimeter turns itself off if I forget to. Then its cheap 9V alkaline battery lasts for years. Duracell batteries leak, Energizer batteries do not and are guaranteed not to leak.

[edavid]

My Fluke multimeter turns itself off if I forget to. Then its cheap 9V alkaline battery lasts for years. Duracell batteries leak, Energizer batteries do not and are guaranteed not to leak.

Energizer batteries leak sometimes.

Duracell batteries have the same guarantee as Energizer.

[setq]

My nan used to put her batteries in the oven for a bit. That worked!

(A bit...)

[Matthames]

This is something that I had to look into once for a product. To be honest there is no advantage in recharging alkaline batteries as the most you would get from it is 10 cycles before the batteries become unusable. Unless you have a specific reason for recharging them other than saving a few quid/bucks you are better off replacing with new batteries. Even then you are probably better off using rechargeable batteries.

[Fungus]

you are probably better off using rechargeable batteries.

This.

Recharging alkalines will never be more than an interesting experiment. You can buy rechargeable 9V batteries.

[BradC]

When I was in high school (back in the late 80's) I built a charger for alkaline a cells. It worked a treat if you charged them up before they got down to about 50%. I had a load of fun recharging batteries for months until I had a couple eject hot electrolyte with some force. I gave up after that. A leak, I could cope with but this made a hell of a mess. Destructive investigation showed some serious degradation of the cell casing, so I guess each cycle just eats away at the case a bit more until they unload.

Mine were just generic alkaline cells I picked up in bulk on a trip to the States. The charger was a pulse charger with short but high current pulses. Charge cycle terminated when the cell held above 1.5v. It was a naive attempt, but worked long enough for me to learn a bit more about primary cells.

[edavid]

Recharging alkalines will never be more than an interesting experiment. You can buy rechargeable 9V batteries.

Yes, looks like there are some good ones now (LSD NiMH or Li-ion):

http://www.metaefficient.com/rechargeable-batteries/rechargeable-lithium-batteries-9v.html

[raptor1956]

Recharging alkalines will never be more than an interesting experiment. You can buy rechargeable 9V batteries.

Yes, looks like there are some good ones now (LSD NiMH or Li-ion):

http://www.metaefficient.com/rechargeable-batteries/rechargeable-lithium-batteries-9v.html

Good info ...

The Li-ion batteries would seem the most interesting given the greater capacity, but the operating voltage topping off at about 8.4V and running down to about 6V might be an issue.  About what voltage will a typical Fluke DMM shutoff?  To be more specific, at what voltage will a Fluke 27 (30 years old) and a Fluke 85 (25 years old) shutoff or fail to operate correctly?  If the shutoff point or the point where operating is out of spec is, say, 7.5V then you might only get half or less usable capacity.  OTH, even at half capacity they should still last longer than the NiMH versions as they too might shutoff before reaching minimum cell/pack voltage.

What would be interesting is the possibility of a single cell Li-ion battery with integrated boost converter to provide 9V all the way down to cell shutoff at 3.2Vish and for the converter to shutoff at that point to protect the cell.  I would think the loss of package volume necessitated by the inclusion of the boost converter would be somewhat offset by being able to run a single cell. 

Of course, such a device to be practical would obviously have very limited current/power output capabilities, but that might not be a problem for a DMM.  Given a nominal 4.4WHr capacity of an alkaline 9V battery and a 1000 hour operating time of a typical DMM the average power requirement is on the order of 4.4mW though it's likely that would be higher when the DMM is sourcing current as it would doing resistance or capacitance measurements.  But, a very high frequency boost converter with a power limit of, say, 12mW, might be small enough to be built into the 9V can.  Or, the 9V battery clip might have the boost converter and the whole volume of the 9V can could be filled with Li-ion chemicals.


Brian

[IanB]

The Li-ion batteries would seem the most interesting given the greater capacity, but the operating voltage topping off at about 8.4V and running down to about 6V might be an issue.

Bear in mind that alkaline batteries are rated to deliver their full capacity when discharged down to about 1 V per cell (even 0.9 V if you want to extract every last drop of energy). So a 9 V alkaline battery will start out fully charged at 9.5 V or so, and will be fully depleted at about 6 V or so.

This is really not much different from the lithium battery. If the meter has been well designed, it will not have a problem.

[Fungus]

The Li-ion batteries would seem the most interesting given the greater capacity, but the operating voltage topping off at about 8.4V and running down to about 6V might be an issue.

6V is a perfectly normal cutoff voltage for a PP9.

They generally have 6 small 1.5V batteries inside them (AAAA size).



The cheaper ones have a stack of 6 1.5V chemical cells inside:



A well designed device will have no problem with 6V.

[Fungus]

What would be interesting is the possibility of a single cell Li-ion battery with integrated boost converter to provide 9V all the way down to cell shutoff at 3.2Vish and for the converter to shutoff at that point to protect the cell.  I would think the loss of package volume necessitated by the inclusion of the boost converter would be somewhat offset by being able to run a single cell. 

Sounds like a job for Batteroo.

[Zero999]

My nan used to put her batteries in the oven for a bit. That worked!

(A bit...)

Yes, heating the battery will help to increase the voltage and enable more energy to be extracted from it but it doesn't recharge it.

[setq]

Also makes your sausages taste funny afterwards 

[Gyro]

The Li-ion batteries would seem the most interesting given the greater capacity, but the operating voltage topping off at about 8.4V and running down to about 6V might be an issue.

Bear in mind that alkaline batteries are rated to deliver their full capacity when discharged down to about 1 V per cell (even 0.9 V if you want to extract every last drop of energy). So a 9 V alkaline battery will start out fully charged at 9.5 V or so, and will be fully depleted at about 6 V or so.

This is really not much different from the lithium battery. If the meter has been well designed, it will not have a problem.

Actually Duracell specifies an end voltage of 4.8V for the standard MN1604 9V Alkaline battery, although there is only about 10% remaining capacity between 6V and 4.8V (depending on load current).