On 06/07/10 3:17 PM, Robert Sneddon wrote:
In , SMS
writes
On 06/07/10 6:21 AM, Robert Sneddon wrote:

The Sanyo Eneloop low-discharge NiMH battery technology is being
licenced more widely nowadays.

Is it being licensed or are other companies just building their
batteries in a similar manner?

AFAIK Sanyo has patents on the methods of making the electrodes and
internal support structures that reduce the self-discharge rate
significantly. Unless the other manufacturers have arranged licencing
then they are open to lawsuits for infringement or they have twiddled
their designs sufficiently to avoid the legal problems. I've not heard
anything one way or another.

What Sanyo did with the eneloop product is not rocket science--the
technology for reducing self-discharge in Nickel based batteries is not
new.

Patent lifespan is 19 years as I recall -- I don't remember seeing low
-discharge-rate Ni-chemistry cells on the market before much before
2005.

The problem is that same design changes that reduce self-discharge also
reduce capacity, and we were seeing something similar to megapixel wars
with mAH wars. People just got fed up enough with self-discharge that
they were willing to go with eneloop AA cells at 2000mAH versus regular
NiMH AA cells which have up to 50% greater capacity.

I've used high-capacity Ni-chemistry cells in the past but I noticed
that their self-discharge tended to obviate the claimed extra capacity
unless I was incredibly diligent about charging them immediately before
use. In addition the increased capacity never seemed to survive more
than a dozen or two dozen recharge cycles. I used (and still use) simple
Ni-battery chargers with limited intelligence which probably didn't
help. The charge retention of the Eneloops and their successors are a
great convenience and I make up for the more limited capacity by
carrying a spare set of similar low-discharge cells along with me. Maybe
higher-capacity versions of the 1st-gen technology will appear in the
future, who knows?

While the eneloop, and other low self-discharge cells, solve one of the
major problems with NiMH cells, they still have most of the drawbacks
of AA cells in general, and NiMH cells in particular.

Still better than Li-chemistry cells with their high self-discharge
rate,

Li-Ion and Li-Po packs are only a little worse than eneloops in terms of
self-discharge. I.e. in 100 days, the eneloop cells will be around 90%
and the Li-Ion will be at around 80%. ANiMH would be at around 10%.

The lifespan of a Li-Ion pack is a little less in terms of time, but you
get far more cycles from each cell. The charging is more complex, but
the complexity is taken care of for you in the charger and the
protection circuit, temp sensor (and sometimes the micro-controller) in
the battery pack.

The list of advantages and disadvantages is as follows:

20 Advantages of Li-Ion Batteries over NiMH Batteries

1. Much lower self-discharge rate (except for newer Hybrio and eneloop
NiMH cells, which trade low self-discharge for lower capacity)
2. More charge/discharge cycles
3. Usage pattern and charge regimen is better suited to digital cameras
(and other devices where the usual pattern is partial discharge/full charge)
4. Self-Discharge rate is constant during the life of the battery (NiMH
batteries steadily increase in self-discharge over the life of the battery)
5. Greater energy density by weight
6. Greater energy density by volume (AA batteries are not practical for
sub-compact and ultra-compact cameras because of size, and AAA batteries
are not practical because of capacity)
7. Greater number of shots per WH
8. Faster shot to shot times, especially when using flash
9. More convenient to swap and charge than AA cells (no fumbling with
multiple cells, and keeping track of which battery is in which set)*
10. Far better cold weather performance
11. Far better performance at high temperatures
12. Devices using Li-Ion batteries are more reliable than devices using
AA batteries (unlikely to have a battery door flip open and have the
batteries scatter all over)*
13. Li-Ion batteries can be left in devices that are not used for long
periods of time
14. Li-Ion batteries have protection circuitry built into the pack and
do not rely on the charger for this protection
15. Accurate charge level gauge is included in most Li-Ion powered
cameras, but is not possible in NiMH powered cameras (low-battery
indicator only)
16. Li-Ion batteries do not suffer from polarity reversal
17. Li-Ion batteries do not suffer from the "dud" cell problem
18. No need to "Battery Match" cells of similar capacity
19. Rechargeable battery and charger come with the camera, versus buying
a charger and batteries for an AA powered camera
20. Smaller and lighter chargers

* This advantage is over AA batteries in general, not specifically NiMH
AA batteries. The advantage applies to AA batteries of other types as
well (Alkaline, Lithium, etc.).

8 Advantages of NiMH Batteries over Li-Ion Batteries

1. Li-Ion packs are proprietary, you can't substitute disposable AA
cells if your battery goes dead in the middle of nowhere, and you have
no spare battery, and no AC or DC power for charging*
2. Longer shelf life*
3. Faster charging (though high-rate charging significantly reduces
battery life)
4. AA cells will always be available, while less popular Li-Ion packs
may be discontinued*
5. Multiple devices that use AA or AAA cells can share batteries and
chargers (though there are Li-Ion chargers that can charge many
different battery types by the use of adapter plates)*
6. NiMH AA cells can be charged from a 5 volt USB port, while larger
Li-Ion packs (7.4V) cannot.
7. You can buy NiMH batteries at a good price from stores like Wal-Mart
and Fry's but for Li-Ion you must order the battery packs from an
on-line retailer that specializes in batteries in order to obtain good
quality packs at good prices.
8. Hot Shoe Flash and Camera Can Use the Same Type of Battery

generally limited operating lifespan and their finicky charging
and temperature requirements. They also don't store well -- I bought a
laptop once, surplus but still sealed in its box and unopened. The
brand-new Li battery pack was dead on arrival, failing to take a charge.
The battery pack had a date code on the case indicating it had been
built only two years before.

Two years of unused storage is an eternity for a Li-Ion battery, and
also for a NiMH battery. I have some non eneloop NiMH cells that I
bought and was not religious about keeping charged. I tried to use them
last month. They are all now bad. They were in storage for about two
years. My fault. I have an AA trickle charger that I built and I didn't
have the batteries on it.

More information is available at "http://batterydata.com/".

That's your vanity website, yes?

No. Every statement on that site has been fact-checked nine ways to
Sunday. Early-on there were a few corrections that I made after people
e-mailed me, but no one has found any errors in the site for more than a
year. Some of the costs may have changed a bit, but that's about it.