Re: How quickly should rechargables drain?

On 9 May, 13:26, ASAAR <cau...@xxxxxx> wrote:
On 9 May 2007 04:41:08 -0700, Seán O'Leathlóbhair wrote:

But I have noticed that NiMH do seem to self-discharge quite quickly
when not in use. In this way they are worse than the older NiCd. So,
I top them up before an important shoot and I carry some alkaline
batteries in my kit bag for emergency use. If you are a dedicated
rechargeable user you could try NiCd as a backup. Heavier, less
capacity, but they don't seem to self-discharge so fast. Or look for
suitable Li-ion batteries but they may be expensive.

You won't find suitable Li-ion AA batteries, as their voltage is
more than double that of NiCD, NiMH, alkaline or lithium AA
batteries. NiCd isn't a good backup solution since it also has a
fairly high self discharge rate. But there is a good alternative,
and it retains its capacity longer than even Li-ion batteries.
Several manufacturers now make NiMH batteries that have extremely
low self discharge rates. A minor drawback is that their capacities
are less than standard NiMH batteries (2000 and 2100 mAh for AA
cells) but this is much higher than any NiCD you can find. If you
charge them and then store them unused, they'll retain most of their
capacity a year later. Unfortunately, they don't have standard
names. Sanyo calls them Eneloop batteries. RayOVac calls them
Hybrid batteries. Radio Shack sells their overpriced version and
doesn't really identify them. Uniross may have their own version,
but that's not a brand readily found in the USA. These batteries
can be identified though, because unlike traditional NiCD and NiMH
batteries which have to be charged before using them the first time,
these new types are precharged and can be removed from their package
and used immediately.

Thanks.

I guess that explains why general purpose Li-ion batteries don't
exist. What is their voltage? If it is about 3V then some devices
could accept them paired with dummies. Probably dangerous since some
people would get it wrong, put two real ones in and blow up their
devices.

I hadn't heard of the slow self-discharge NiMH, I will look out for
some. NiCd discharge much quicker than alkaline but I find them
better than regular NiMH. Certainly not a good back-up though. If
you can't find the NiMH that you mention, use alkaline.

Nothing special about Uniross, they just happen to be the last brand
that I bought.

--
Seán O'Leathlóbhair

.

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