NiCd Batteries

[maltaron]

Why can we not get Nicad batteries any longer? The NMH type are next to useless - they will not hold a charge when not in use.

 

[ericmark]

The technical data tells the reverse story it's the NiCad which losses charge and the NiMH which are advertised as maintaining 90% after 1 year shelf life.

However something has changed with charging systems. New camera stipulates "DO NOT USE NiCad" but can use NiMH and as far as I can tell it's something to do with recharging.

If one looks at the humble AA battery the capacity has changed dramatically I have batteries marked from 600mAH to 2100mAH all same physical size and this means very easy to get them mixed in a single item.

In the old days all my chargers for AA cells charged them as pairs so with mixtures of mAH it was a problem in that batteries were not fully charged or reverse charged when put in items and used in series. The charger I use now has 10 individual bays so each cell is charged on it's own merit. Since using it I have found in general batteries lasting a lot longer.

Main use for my AA cells is to power a flash gun for camera. The primary cells although larger capacity can't deliver the power quick enough and so I have to use rechargeable. With the old 600mAH NiCad I carried a pocket full of spares as I would get between 10 and 15 flashes before the re-charge time for flash gun became to long. The batteries would still work but took to long. Put the newer NiMH and I get 50 flashes before I need to change them.

So I wonder if you have swapped to to NiMH from NiCad without changing the charger being use?

 

[ericmark]

Found the answer here it says:-

Nickel Cadmium or NiCd rechargeable batteries are now restricted to medical and military use in Europe because of the heavy metal used in their construction. They also suffered from low capacity and a memory effect. Their replacement NiMH rechargeable batteries do not suffer from these drawbacks.

The details for Nickel–metal hydride battery and Nickel–cadmium battery are on Wikipedia and the problems in charging the Nickel–metal hydride battery is highlighted.

The charging voltage is in the range of 1.4–1.6 V/cell. In general, a constant-voltage charging method cannot be used for automatic charging. When fast-charging, it is advisable to charge the NiMH cells with a smart battery charger to avoid overcharging, which can damage cells and even be dangerous. A NiCd charger should not be used as an automatic substitute for a NiMH charger.

Seems I was not too far out with my off cuff answer.

 

[ericmark]

Until maltaron asked the question I never even considered if my chargers were suitable for NiMH batteries. Reading on the subject I found this:-

Delta V Charging.

The best method of charging both NiCd and NiMH batteries is the so called delta-V (change in voltage) method. If one plots the terminal voltage of the cell during a charge with a constant current, it will continue to rise slowly as charging progresses. At the point of full charge, the cell voltage will drop in a fairly short time. The amount of drop is small, about 10 mV/cell for NiCd (lower for NiMH), but is distinctive. DV charging is nearly always allied with temperature measurement as a backup (and for the truly paranoid really high capacity chargers for big batteries usually incorporate fail safe timers as well).

My main charger

it seems uses this method and is OK for NiMH and also my second charger

will also charge NiMH batteries however it does not seem from the details to be anywhere near as good at the first. It does switch off after 9 hours but has not got the DV charging used with first type.

What now worries me is the host of items like two way radios which use standard AA cells and have built in chargers. Including telephones and I know I have replaced the batteries in my mothers and my telephones and did not even think until you raised the subject if they were suitable to be charged in the items.

I would guess the charge rate is so low that there is no danger but to guess is dangerous so I now have a task going around all the old stuff checking if NiMH are fitted and if so is the charger suitable.

I have already had problems with exploding batteries.

Mouse 4

• ericmark
• 11 Dec 2009
• 5

I think this one was mistakenly re-charged when it was a primary cell but it was in the mouse for a good 24 hours before it exploded.

It would be interesting to hear from others as to use of AA cells and chargers used. With things like battery drills we use a battery pack which came with drill with charger which came with drill so all are matched. It's the PP3, AAA, AA, C, and D cells which are likely to be a problem.

So thank you for raising my awareness to this problem.

 

[electronicsuk]

If you want rechargeable batteries with an extremely low self-disacharge rate, look at Sanyo Eneloop. I won't buy anything else any more. They'll happily sit for a year and more and still be good to go when you need them.

 

[maltaron]

Thanks for all your replies and info. However, regarding chargers, The first time I noticed the problem was a new Hitachi drill - the NMH batteries supplied were useless until charged about 12 times - now they are acceptable but only when taken straight off the charger into use. The nicads in my old drill will sit in the van till required and work fine. I have also just taken some cordless phones out of use and switched them off - after 24 hours the NMH batteries were flat.

 

[ericmark]

If you read the history on batteries you will see over time they have improved. The problem is I can look at the writing on cells bought from Lidi which are claimed to have a long shelf life and also some much older cells and there is nothing to tell me which is which except for:-
"Manufactured in 2011/06" and "Ready to Use battery".

As far as I can tell it's the "Ready to Use battery" or the "Charge before use 7 hours" that lets us work out if they are the newer design which hold their charge or older design that will not.

With a 14 hour charge there is not a real problem except you have to wait 14 hours. In the past nearly every battery would say charge for X number of hours before use. And many warned the battery could be damaged if not charged for that time before first use.

I know the problem on site you plug in the charger only to find it unplugged and something else plugged in instead. I have also seen where people refuse to charge the items at home. So there is no way they will every get a 16 hour charge.

In the main when I have looked at a battery which does not hold it's charge I find a faulty cell. Where a battery is an odd shape I have changed cells and tried to solder. This silly lead free solder needs to be hotter and does not flow as well as the lead stuff so easy to damage the cell when replacing it.

Buying a Hitachi drill or any other make one has little or no indication as to how old it is. I when answering this when to look at my old cordless phones. Discontinued line but many still being sold as new. And you don't tend to look at the box to find out date manufactured. I have a few time bought drills to use as screwdrivers and they don't need to be top of range for that use. And I have found cheaper to replace whole drill than to buy a new battery.

So it's not that NiMH are not as good. It's just some old NiMH are not as good and the problem is identifying new or old NiMH and as far as I can tell it's the "Ready for Use" that we want and we must reject those that say "Charge before Use".

 

[maltaron]

Many thanks Eric for interesting info. At present I am looking at AA and AAA types for camera and remotes etc. So as long as I buy fresh NMH I should be OK.

 

[big-all]

nicads and low use are very inefficiant as more power leaks than is used
nicads are great for high power uses but must be fully cycled before recharging
where as li-ions and nmh can be charged at any opportunity regardless off charge held
you can also short charge where around 45-60% charged in 15 mins

 

[ericmark]

I also have problems with the move from NiCad to NiMH where used with my ICOM U16 Ex PMR radio. The old batteries are about US so I need to change the cells. However the charger is a Delta Voltage type. I have started a new post to see what others think.

However where battery and charger are bought together not really a problem it's where the equipment is expensive like with these 70cm two way radios and as a result it is worth going to the trouble to re-cell the batteries.

It is the change in the voltage curve to trigger the delta voltage charger that is the problem. 16 hour chargers are not a problem neither those using temperature to work out when charge is complete. It's the voltage curve types that present a problem as although with a cell it will still work will it work with a battery of cells?

I set my charger with 3 cells to just top up and 3 cells to discharge first when using old NiCad battery with idea that batteries would on average be cycled every other charge. However with the new NiMH cells the settings are not so clear cut. I did not like the flatten before re-charge as if un-plugged even for few seconds it would discharge all my batteries again. Using with an inverter in the car this happened every time I started the engine.

So your question has generated even more questions on how to up-grade.