NimH or Nicad

ShipsWoofy

ShipsWoofy

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Anyone know which is better for a torch. Looking to buy rechargeables for a torch and I know there are differences in the way each deliver power, but which would anyone recommend for a mag light. 3 x D required.

Torch is used fairly often and recharging on board not a problem.

Thoughts?
 
NimH.

However, for torches I generally use dry cells as they last for ages. Whilst I frequently use the torch it's usually only on for a short time. The advantage of dry cells is that they fade slowly. With rechargables you've got light one moment, the next you're in darkness!
 
Thank you for that, but I thought that was one of the differences between nicads and NimH, the nicads more closely resembled alkalines with respect to output.

Can't find any data online to support, only shops selling the things.....

Found a great deal on NiMh by the way, 4x 2500 mAh or 2x D 2300mAh for £3.99.
 
NiMH without question.
Reason - they deliver the power required and can be recharged at any time without creating a "memory" effect unlike NiCd which will develop a memory and hence loose capacity very quickly if not fully discharged between recharges. meaning when you need the torch the batteries may not be fully charged or at full capacity /forums/images/graemlins/frown.gif
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"Artificial intelligence is no match for natural stupidity"
 
AFAIK Nicad and NimH are not very different, but the real advantage of the later is that they don't suffer from the memory effect.

I doubt if the AA's will be 2500mAH, if the D's are 2300mAH, but that's a good price. It's not Aldi is it? Lidl had a similar deal a short while ago so I bought a whole pile of batteries.
 
That will have postage added, but what is that about VAT free if the order is under £18? I wonder if C&E will agree?
 
Dry cell vs NiMH vs NiCD

Dry cell is open voltage 1.5 .... under load often less than 1.2 and low ampage. The discharge curve is a steady decline from moment you start to use the cell. Light will decrease as use .... with momentary recovery when left off for period.

NiMH open voltage is 1.2 ~ 1.3 ..... under load minimal reduction with capability to high ampage when shorted. Discharge curve is flat line till very near end and then a rapid drop to near zero. Literally no warning of light failing.

NiCD open voltage is 1.15 ~ 1.25 .... under load minimal reduction and capable of very high ampage if shorted. Similar discharge characteristic to NiMH .... little warning of light failing.

Me ... I would have a set of Dry-Cells as back up and use NiMH wherever possible. NiCD's are old technology and superceded by better NiMH and LiION .....


Of course you now have opened the door to all the arguments about memory effects of NiCD's ... a fact that Mallory Duracell Technician confirmed to me years ago ....
 
I think that you should go for NiMh as they dont suffer so much from memory effect and generally having higher capacity. NiCads I believe are better for really high current discharge, which for a torch should not be a problem.

Ian
 
Generally agree with the others. NiMH better than Nicad, little memory effect, and have a higher capacity. However for a torch, unless it can be kept on charge or at least charged regularly I prefer alkaline cells. They hold their charge for years if not used and have a much higher capacity. Neither Nicads or NiMH like being left discharged and neither retain their charge for as long as dry cells.

If you must use rechargeables then at least keep a set of alkaline batteries as back up because as sure as eggs are eggs one day you'll find the rechargeables have gone flat.

You will have more than one torch on board won't you!
 
[ QUOTE ]
However for a torch, unless it can be kept on charge or at least charged regularly I prefer alkaline cells. They hold their charge for years if not used and have a much higher capacity. Neither Nicads or NiMH like being left discharged and neither retain their charge for as long as dry cells.

[/ QUOTE ]My HH VHF has NiMH batteries and they hold their charge for over 6 months between charges.
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"Artificial intelligence is no match for natural stupidity"
 
Thank you for the replies, I have ordered some of the NiMh cells. I use NiMh for camera's, VHF, h/h GPS etc etc. I had never used them in a torch though and was not sure if they would be ok in a 'bigger' torch.

Have a 12v charger for all batteries on board and fed up of buying D cells for the torch. We have two other 'emergency' torches in each of the aft cabins which are pretty much never used. But the mag light is in constant use in lockers or engine rooms etc.

Memory effect is not one of the reasons I was questioning the type to use, it was as above, I thought nicads more closely resembled dry cells which do have some benefits, like going dim not just shutting down. I will be keeping dry cells in the Lifebuoy Lights.
 
Can't find any data online to support

Panasonic (and others) have a lot of good data on their site for the various battery chemistries - current link is http://www.panasonic.com/industrial/battery/oem/, but if that changes go to panasonic.com, industrial, batteries and select the OEM option.

NiCd's also show immediate sharp drop of of voltage at discharge (in a torch its brightness will decay from bright white to orange very suddenly) so with either NiCd's or NiMH's is best to keep a spare charged set of batteries on hand - I have used 2 off 3 cell Maglites with NiCd's for many years, one in use and the other charged, unused. NiMH is fine, NiCd's have the advantage of lower internal resistance so are good for high discharge applications such as handheld radio transmitters.

Depite what people persist in saying (sort of like how some relish propagating fears about necromanical bacteria, etc /forums/images/graemlins/smile.gif), NiMH's suffer EXACTLY the same problem as NiCd's. That is they can suffer from crystallisation of the Ni electrode which reduces its effective area and thus the battery's capacity - what many, (incorrectly) refer to as "memory" effect. Should it occur it is reversible by a deep discharge (but never to or close to complete discharge) and a full charge.

So, your NiMH's should be treated just like one would treat NiCd's. Which poses a difficulty in torches as we tend to use them 'til brightness lost (same habit with battery powered drills, run them 'til they don't turn anymore) by which time they are almost dead flat and running the risk of pushing a cell into reverse charge and permanently damaging it. I ALWAYS swap torches or replace the batteries the moment the torch I am using starts to dull in output and recharge the batteries as soon as possible so not sitting discharged.

John
 
sorry, but this supposed memory effect was decades ago with the early nicads. With modern batteries, you can forget it. Nicads are usually cheaper and more robust, ie tolerant of overcharging, overdischarging, and fast charging. Their big drawback, as has been mentioned , is that while they keep a constant discharge rate pretty well(which is a big plus in many applications), they then rapidly drop off. For some applications this might be an issue, but that really depends on your battery management. With a good fast charger you can recharge a pack of nicads in 15 minutes. Not bad, id argue!
 
We use NiMh batteries in a torch, and have done for a couple of years now. That's used every day at home throughout the winter. We use a torch that take four AA batteries - same as GPS and camera. This was a cheap experiment (£3.99 torch, existing batteries) but has worked out better than purpose-made rechargeable lanterns.

Tony S
 
I have a \'beam-gun\' .....

It has a sealed lead-acid battery inside and its unbelievable !! Cost me 6 quid and it honest shines a search-light style beam that you can see going up into the sky.
It recharges via mains or car ciggy lighter in about 2 hrs.

The handles are not fixed and it can be set to any angle etc. to sit on floor / table etc. while leaving hands free to work ... amazing tool.

Oh yes - its a chinese cheapie an 'all !!
 
[ QUOTE ]
NiMH's suffer EXACTLY the same problem as NiCd's.

[/ QUOTE ]BS
[ QUOTE ]
That is they can suffer from crystallisation of the Ni electrode which reduces its effective area and thus the battery's capacity - what many, (incorrectly) refer to as "memory" effect. Should it occur it is reversible by a deep discharge (but never to or close to complete discharge) and a full charge.

[/ QUOTE ]BS
[ QUOTE ]
So, your NiMH's should be treated just like one would treat NiCd's.
John

[/ QUOTE ]Battery Care and Maintenance



What is the difference between NiCad, NiMH and Lithium Ion batteries?

Batteries in portable consumer devices such as a laptop, camcorder, cellular phone, etc., are typically made using either Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH) or Lithium Ion (Li-Ion) battery cell chemistry. Each type of rechargeable battery chemistry has its own unique characteristics:

NiCad and NiMH:

The main difference between the two is that NiMH battery (the newer technology of the two) offers higher energy density than NiCads. In other words, the capacity of a NiMH is approximately twice the capacity of its NiCad counterpart. What this means is for you is increased run-time from the battery with no additional bulk or weight. NiMH also offers another major advantage: <font color="red">NiCad batteries tend to suffer from what is called the "memory effect". NiMH batteries are less prone to develop this problem and thus require less maintenance and conditioning. </font> NiMH batteries are also environmentally friendlier than NiCad batteries since they do not contain heavy metals (which present serious landfill problems). Note: Not all devices can accept both NiCad or NiMH batteries.

Lithium Ion

Lithium-Ion (Li-Ion) has become the new standard for portable power in consumer devices. Li-Ion batteries produce the same energy as NiMH battery but weighs approximately 20%35% less. This is can make a noticeable difference in devices such as cellular phones, camcorders or notebook computers where the battery makes up a significant portion of the total weight. Another reason Li-Ion batteries have become so popular is that they do not suffer from the "memory effect" at all. They are also environmentally friendly because they don't contain toxic materials such as Cadmium or Mercury.



The Do’s and Don’ts of Battery Use

Battery Do's:

Fully charge/discharge battery up to 4 cycles before achieving full capacity of a new battery

Fully discharge and then fully charge the battery every two to three weeks for battery conditions.

Run the device under the battery's power until it shuts down or until you get a low battery warning. Then recharge the battery as instructed in the user's manual.

Remove from the device and stored in a cool, dry, clean place if the battery will not be in use for a month or longer,

Recharge the battery after a storage period

Ensure maximum performance of the battery by optimizing the device's power management features. Refer to the manual for further instructions.

Battery Don'ts:

Do not short-circuit. A short-circuit may cause severe damage to the battery.

Do not drop, hit or otherwise abuse the battery as this may result in the exposure of the cell contents, which are corrosive.

Do not expose the battery to moisture or rain.

Keep battery away from fire or other sources of extreme heat. Do not incinerate. Exposure of battery to extreme heat may result in an explosion.
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"Artificial intelligence is no match for natural stupidity"
 
[ QUOTE ]
Fully discharge and then fully charge the battery every two to three weeks for battery conditions.

[/ QUOTE ]

Wow, I don't think the writer appreciates how many AA, PP3 and now D cells I have /forums/images/graemlins/grin.gif... It would be a full time job!

Anyway, thank you for that post cliff, I have saved it as it has some good points. Luckily one of my mains chargers has a charge - discharge cycle which is worth its weight in gold IMHO.

I am also aware of the non toxic properties of NiMh cells, it does make a difference to me anyway!
 
I know what you mean - some of these folk live in ivory towers wrapped up in their own little technically correct worlds.

A few years ago a company i was involved with changed over all battery packs to NiMH from NiCd because the equipment was never discharged fully before recharging and with NiCd the charge capacity was reduced to ~20% within 4 months but the NiMH cells were still going strong after 18months with little if any sign of "memory effect" - these were powering lamps, transceivers and other opto-electronic equipment and were recharged once or twice per day as they could not afford any piece of equipment to run the batteries flat.

Do a google on NiMH batteries or NiCd batteries - there is a wealth of information available which contradicts some of the posts here. /forums/images/graemlins/wink.gif
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"Artificial intelligence is no match for natural stupidity"
 
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