NiCD or NiMH?

[timmy]

After using both now for some time, my preference is actually NiCD (battery size AAA-D).

The self discharge rate is much lower than NiMH, they seem to charge more easily using solar, although I do realize that is in part some to the lower mah rating.  I also wonder if some of the mah rating for NiMH is slighty "exaggerated"?

An example would be my radio, generally operates very close to 12+ hrs a day, rated at 1 watt (4.5v input), in reality it consumes greatly less.  A 2.88w pack (4.8v at 600mah NiCD) lasts about 9-10 hrs.  I have ran some cheapie Powerizer 2500mah NiMH batteries (4.8v at 2500mah) and show a voltage of generally 1.21v to 1.23v after usage.  (12w)

I used the radio the last couple nights (at least 12 hrs) via some 1000mah NiCD batteries (4.8w), although they are new which I am sure has alot of effect on retaining voltage, they are running about 1.17+ or so volt after usage. (4.8w)

What is your preference and why?

[scottsAI]

Hello timmy,

I stopped using small NiCD. Power tools are NiCD.

Replaced with NiMH, bought some cheap 2500mahr.

First time I used them they were bottomless!

Second half that, each use they held less and less.

3 years later still use in LED flashlights. Better than NiCD worked for me.

Shortly after above, bought some name brand, 2000mahr at three times the cost.

They never seamed like a bottomless battery but have worked for as long and still going.

Stopped using the CD player, so do not have a big load any longer to see how they work.

A charged battery holds the charge for a few weeks, then dies off.

As they get older the NiMH do not get the fuzzes like the NiCD did.

Have fun,

Scott.

[Bruce S]

timmy;

    I prefer to use NiCds. Several reasons

1. ) I get the Sub-Cs free.:-) Sure they're in packs that are either 5x3 or 4x4 and used, but free is free. For info on these Nothing To Lose is the guru of re-wiring these :-)
   
2. ) Even with the theory that NiCds have a lower limit of density than NiMh they are constantly showing up in the Amp Hour ratings and getting denser all the time. They are now available in 5Ah in the "D" size and even bigger in "F" size.
   
3. ) Larger temperature swing usage levels.
   
4. ) Completely recyclable.
   
5. ) More cycles that NiMh. 1000 cycles versus 500 or less.
   
   

One thing that is very bothersome is that the Cadmium is VERY harmful is they are opened. I don't do this so I make sure the completely spent ones are turned into an approved recycler.

Up in my files/diaries should be a velomobile or pictures of a battery bank that built a used NiCd banks that powers a 600 watt motor that is used to go to and from work for our company.

Hope this helps

Bruce S

[ghurd]

I will defer to Bruce on all such matters.

I made a solar controller for various configurations, then found micro-solar will add a lot (enough to keep up) though not enough to reach overcharged for batteries being regularly switched out. It was hard to maintain double the allowed float current for very long per day.  We don't run out of AAs, but they never reach 'over voltage'.

It could be the nimh just are not completely and fully charged.

G-