Apptech wrote:
>> Nicads are so 20th century anyway -
>> why anyone would design with them is
>> beyond me.
>>     
>
> I'm surprised. I thought you were aware of the requirements 
> for cost effective solutions :-).
>
> And you may not then know quite as much about alleged 
> alternatives as I thought you may have.
> Let me educate you a little.
>
> While I made no mention of actually using NiCds, in fact the 
> product line that I "inherited" does in fact use NiCds in 
> one product. Said product is meant to be both as low cost 
> and as high quality as possible. For much the same reasons 
> as NiCd's are still used in all COMSATs it makes reasonable 
> sense to use them in this product.
>
> NiCds are reasonably robust and if suitable care is taken to 
> avoid their problems (such as whiskering if improperly over 
> discharged) then they will give good $ oper capacity, good 
> cycle life, excellent resistance to over charge subject to 
> certain conditions being met, generally good availability 
> (so far) compared to alternatives, and low absolute cost. In 
> this application most of those factors are relevant.
>
> The product is intended for use in deepest Africa in all the 
> usual meanings of the term. It is a solar rechargeable 
> product which will be exposed to recharging outdoors all day 
> every day (literally) and substantial use essentially every 
> night. Few "domestic" products are subject to such extreme 
> environmental challenges.
>
> The current darling of the battery world, Lithium Ion, in 
> its many many flavours is a superb battery chemistry in many 
> applications, but not in all. As well as a rather poor deep 
> cycle lifetime it has a finite calendar life (nominally 
> about 2 years) due to ongoing internal oxidation once 
> initiated, unless you choose some of the newer chemistries, 
> but these so far offer longer calendar life for very 
> substantially reduced capacity. Any device which need 
> internal electronic protection to prevent it behaving like a 
> piece of lowish energy ordnance, and which sometimes manages 
> to bypass said protection, is not a good starter for use in 
> ultra rugged field use by untrained users. Add the fact that 
> it reaches 2/3 capacity at a good current rate but then is 
> able to use current at an ever decreasing rate as charge 
> state progresses makes it a bad match to solar panels which 
> need to be able to use all their output when it is available 
> if the battery is less than fully charged. Add to that zero 
> tolerance to overcharge (unless you go to eg Spinal 
> chemistries which eliminate all metallic Lithium from the 
> active cell at full charge but suffer lowered capacity in 
> exchange. Add all that up and your 21st centrury wonder 
> (also born in the 20th century) starts to look like a Gen X 
> or Gen Y young person to whom all truth is relative and who 
> takes no thought for tomorrow
>
> NimH has most of the relative advantages of NiCd and a 
> somewhat higher energy mass and volumetric density but a 
> higher self discharge rate except in very recent versions 
> which command such a price premium as to even further price 
> them off the market. They are not so ROHS hag bound but in 
> Europe still suffer from the mandatory disposal directive.
>
> Lead acid, which is still currently NOT subject to ROHS 
> restraints, thanks to the lobbying abilities of its 
> proponents and the lack of an economically sensible 
> alternative in larger energy capacities, is essentially not 
> a sensible alternative in systems with AA sized cells.
>
> What 21sty century solution are you then going to propose, 
> and how does it achieve its magical superior environmental 
> footprint?
>
>   
>> And it's probably next to impossible to get non-Chinese
>> nicads,
>>     
>
> Your point?
> Assuming that it is not a racist one I'll note that if your 
> supplier has demoinstrated, as they have, a consistent 
> capability to produce NiCd cells that exceed their industry 
> competitive specification, then why would you have problems 
> with their being Chinese sourced?
>
>   
>> making it even more bizarre why it would bother anyone
>> that nicads are being aggressively phased out.
>>     
>
> Obviously, given the above, as new meaning of the word 
> bizarre that I have never previously encountered.
>
>   
>> And as a customer, I would never buy anything
>> with a nicad battery in it,
>>     
>
> Is this a philosophical choice?
> If so, you presumably don't use phone circuits that use 
> satellite links, as all COMSATS rely totally on their Nicd 
> batteries.
>
> And, presumably, if this is a philosophical objection you do 
> not use lead acid batteries in your car, UPS and more?
>
> Or, if it is a soundly based engineering decision, what [art 
> of the above points do you disagree with.
>
> Where a product MUST be priced to, literally,  be affordable 
> in African villages and 3 x 800 mAh NiCd batteries are a 
> good energy fit to the requirement, would you still really 
> avoid their use?
>
> I will in fact be looking at alternatives. eg 2 x NimH at 
> higher capacity per cell will still operate a boost 
> converter and, as the product will use a boost converter 
> that could be acceptable. However, this raises issues with 
> solar panel matching and minimum startup voltage and boost 
> efficiency. As I am currently getting 90%+ in my boost 
> converter at 3V I'd like to avoid losing efficiency if 
> avoidable.
>
>   
>> my thoughts would run something like "Nicads!
>> What, is this thing designed in New Zealand or
>> something?
>>     
>
> Assuming that's not a (failed) attempt ata  personal slur or 
> a racist comment I'll reply.
>
>         "With pride".
>
> I'd intended to leave this a wee bit longer for good enough 
> reasons, but:
>
>             www.bogolite.com
>
> I didn't design that, but I'm redesigning it.
>
> While the existing light is not designed in NZ, as much as I 
> can manage to cause it to be so, the new one will be. There 
> are issues with that, but at the end see how you like it. 
> How many of your products are designed to be exposed to the 
> equivalent of outdoors Africa all day every day, rain shine 
> and Hippopotomai and have a target lifetime in the 10 to 20 
> years range?
>
>   
>> Sorry, I want quality goods, I'm looking elsewhere".
>>     
>
> Assuming that you are amenable to reason, please (re)read 
> the above technical comments. APART from its ROHS status the 
> NiCd battery is an excellent match to the engineering and 
> economic requirement. Can you explain where your idea that 
> they are essentially "low quality" comes from. They have 
> engineering issues which must be overcome. in the case of 
> NiCd  the significant issues can be overcome with good 
> engineering at little or zero cost. Unlike eg LiIon which 
> has such fatal flaws in this application that they are 
> unable to be overcome without inventing a whole new battery 
> type (eg finite calendar life regardless of use due to 
> internal oxidation).
>
> Also, if you are thinking of suggesting AAA cells in any 
> chemistry please beat yourself thoroughly and continually 
> and come back only after you have recanted.
>
>   
>> Now that I've offended the Chinese nicad manufacturers and 
>> the New
>> Zealand engineers on the list, I'll go back to my LiIon and 
>> LiPo corner...
>>     
>
> The wise only take offence, if then, when a superior opinion 
> points out errors which they wish to cling to. And not when 
> an inferior argument is used against a position of merit. 
> So, both the Chinese manufacturers that my client uses, and 
> I, are not offended. I can't speak for Jinx or Brent or some 
> others, so you'd best hope that they too are wise.
>
>   
>> Oh, and by the way, ... what cadmium did to a certain 
>> river, ...
>>     
>
> There is no doubt that the elimination of cadmium from 
> products in general is a desirable aim. But, like all 
> desirable environmental aims it needs to be balanced against 
> all relevant factors. The unavailability of the stunningly 
> effective anti-mosquito insecticide DDT for use in 
> intelligent and low and non-mobile ways against malaria 
> carrying mosquitos is one of the great tragedies of this 
> age. Tens of millions of people die because of this PC and 
> unscience based decision. Total unavailability of NiCd 
> batteries doesn't rank in quite the same class, but they, 
> like many things, have a place in the world where they are 
> the most reasonable solution.
>
>   
I was forced to a similar conclusion as well. While researching some 
info about
NiMH I found out that NiCad cells have a much lower impedance than NiMH
and also are easier to charge fully because the "knee" is more prominant.
We dropped LiIon and LiPO when they were seen as being safety liabilities
(although once China decides to enforce safety laws, this issue might go 
away).
>> There are reasons for environmental laws, dude.
>>     
>
> I'd be interested in knowing what the addition of "dude" 
> there, in the mind of the writer, was intended to convey.
>
> As a NZer (and proud) I can totally understand the rest of 
> the sentence up to there.
>
>   
>> And just because there are compromises made
>> in them, it doesn't mean that what protections they
>> do offer are bad.
>>     
>
> Non sequitur / Straw man.
>
>   
>> I'll go back to my LiIon and LiPo corner...
>>     
>
> As per much of the above.
> LiIon and LiPo (the same at heart) have an important place 
> in the order of things. But if you are suggesting that they 
> are a good solution in all (or even a majority ) of portable 
> solar charged products then you have more to learn about 
> battery chemistries than I would have expected. And /or are 
> happy with the product having short lives, custom and 
> expensive batteries. (A major plus for some manufacturers).
>
> If I do have to move the product away from NiCd, and in 
> Europe it's essentially a necessity, it will certainly not 
> be into low calendar life, non available-sun-energy 
> accepting Lithium chemistry alternatives. Small solar 
> operated products that use Lithium recahrgeable batteries 
> have probably been designed by US engineers or not designed 
> at all. [[ I'm new at this - is that the proper way to do 
> say it ? :-) ]].
>   

I think these products (sidewalk LED lights) use supercaps, not 
batteries, to obtain
a reasonable "battery" life expectancy. I own a small one than 
illuminates my house
number for about 4 hrs after dark. It seems to pulse the LED to 
increase  "battery" life.
> FWIW for thos who get this far, if you want to increase the 
> life of Li chemistry rechargeables, charge them to 2/3 
> capacity. On the more common 3 hour chargers that's after 1 
> hour. On LiPo with fast charge it will need to be 
> established. Very new li variants may not have this 
> limitation but with std liIon the WORSt lifetime storage 
> point is at full charge.
>
>   

We decided on NiMH when it was determined that it represented the future for
the Nickel technologies, especially as long-life versions are soon being 
introduced.

--Bob A
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