Just heard an Art Bell ad - Tonight's subject: Unified Field Theory

On 9/23/08, Apptech <apptech@paradise.net.nz> wrote:
>> Russel,
>> why so big deal?
>> The NiMH are so cheap now that it doesn't care if life time is 1 or
>> 0.5 it was specified.
>> 4x2100mAh NiMh can be as low as euro 4 ($6.6), austrian price (not
>> australian)
>
> I'm not going to go into enough detail to fully answer the question due to
> commercial considerations - my client may not take kindly to such of his
> business arguments as I'm aware of  appearing in detail on the internet :-).
>
> In a single cell solar charged device that has a substantial charge rate
> (say much better than C/10) the battery can be subject to massive overcharge
> on a sunny day. This is not a vast problem with a typical "path light" where
> the PV panel capacity is low, the battery of no great quality and the
> manufacturer's expectation is that in many cases the product will in many
> cases not last more than a season. Such products also are usually of
> marginal capability in the first place with total energy storage being less
> than that required to keep a LED running at low level all night. And the
> customer has usually not invested so much in the product that they are going
> to get too upset at a one season lifetime. And they may not even know where
> they bought the light or what brand it was- if it had one. If about none of
> these assumptions apply then things may be different.
>
> If instead however you have a brand relevant product that has a much higher
> PV energy output and which aims at a quality customer experience and a
> longer than pathlight lifetime, then issues such as 'boiling the battery
> dry' start to matter. The conventional battery charging solutions and end
> point termination measures prove relatively useless due to limited charge
> energy supply, very wide ambient temeprature changes and need for a low cost
> solution. When your ambient temperature can exceed the usual
> terminate-on-temperature endpoint then temperature termination may not be
> easy to implement. When energy input varies widely and unpredictably and
> possibly rapidly then delta V or delta t termination becomes problematic. If
> you sell a million (maybe not yet :-) ) then a 10 cent saving is $100,000.
> The absolute amount starts to matter, even if the percentage is small. If
> the product still needs to be built to a price then the percentage may not
> be so small as to be able to be ignored. Ideally the cost of the protection
> will be approximately zero. Operating on a single battery supply has its own
> challenges. I was going to say that practicality and price do not allow any
> ICs in the solution, but in fact there is one there. The 2 or 3 lead package
> tends to hide the fact that it is one.
>
> Does all that sound like a big enough deal? :-) :-) :-)
>
>
>   Russell
>
>
>
>
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