My sister recently bought a camcorder and wants some extra batteries. Her old batteries were NiCad, but the new one is NiMH. She wants the new batteries to be NiMH, but I can’t remember if she can charge them on a NiCad charger. I searched here, but none of the threads I found addressed this particular issue.
If it’s an old charger then it probably won’t charge NiMH batteries. Modern chargers usually charge both NiCad and NiMH.
You may have to buy a new charger. It is worth doing so, NiMH batteries are far better/longer-lasting than NiCad (they even last longer than Alkaline batteries)
Old chargers will charge NiMH batteries but it will take longer. An old charger will take 12-16 hours while a new one would take 1-2 hours.
andy_fl what about chargers that were around before NiMH batteries were invented?
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- I posted a thread about this recently; everything I saw said not to mix different rechargable batteries and chargers. The NiMH charger I ended up buying also can charge NiCd’s, there’s a switch on it.
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- I posted a thread about this recently; everything I saw said not to mix different rechargable batteries and chargers. The NiMH charger I ended up buying also can charge NiCd’s, there’s a switch on it.
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If it was a trickle charger without autoshutoff then it would work but charging times will be really really long, about 3-4x the NiCd where the NiCd would take 8-16 hrs to start with.
This cannot be answered with a yes or a no but I’ll give you some general information.
A cell has a certain rated capacity C expressed in mAh. This number is essential in determining the charge and discharge rates. You should be able to charge and discharge at C/10 with no problem or special precaution. That means you discharge at C/10 and the battery should last 10 hrs and then you recharge at C/10 for about 14 hrs and the battery is fully recharged. Note that NiMH batteries of the same size have 50 - 100% more capacity than NiCads. This method is the simplest and the best for the life of the battery. After the battery is charged NiCads should be removed or switched to a trickle charge of C/50 or they will be damaged. NiMH batteries can withstand C/10 indefinitely without damage. Always use slow charging if you are not in a hurry. I charge my 1300 mAh AA NiMh batteries by just driving about 100 mA through them and I do not worry about how long they have been charging. Just leave them a day or less, depending on the discharge. In general a slow charger designed for NiCads should work fine with NiMh; it will just take longer due to the higher capacity of the NiMhs.
Fast Charging: Fast charging is trickier. The faster you charge the more things you need to take into account. Batteries can be charged at C/5 or more but the higher the current the more you have to watch the voltage (so you know when to cut off the fast charge) and the temperature. Trying to determine the state of charge by measuring the voltage is very tricky because it depends on the temperature. You will notice battery packs have four terminals. Two are the battery and the other two are the temperature sensor. Regular chargers for AAs will generally not have temperature sensor.
So, fast chargers are supposed to charge at a high rate while watching temperature and voltage and then switch to a trickle rate. It is easy for them to overcharge the batteries and damage them unless they are very well designed and built.
This is the way I chrge my NiMhs: I built a charger with a regular battery holder, a wall adapter and a couple of resistors. One resistor will allow about 100 mA through the pack and this is what I normally use. The other will allow about 400 mA and I will only use this for a short while when I need a fast recharge. Actually I hardly ever use this setting as I have two sets of batteries for the camera and I just change over.
My advice is to have two or three sets of batteries so that you can slow charge them. They will last longer.
This is bad, and possibly dangerous, advice. I strongly urge people to use chargers only with the type of batteries they are intended to be used with.
Well, not really. The main difference between an AA Nicad and an AA NIMH is that the NiMH has more capacity. So it is true that the Nicads charger should charge the NiMH but just take longer in proportion to the capacity which would be twice as much at the most (not 8 times).
The most important thing is to understand the process. If you are not willing to take a moment to understand it then the safest thing is to get a slow charger. Fast chargers come in all sorts and what may be good for one battery may be bad for another. With fast chargers you are taking your chances and relying on luck.
Thanks for the information everyone. Looks like she will have to shell out for a new charger when she gets the NiMH batteries. Seems the safest thing to do right now.
Lok