low internal resistance of rechargables a problem?

[JonSidneyB]

I know that some lights do not like rechagables due to the low internal resistance. I am wondering if this problem with low internal resistance can cause problems with other items. Does anyone know if electronic items can be damaged by this quality that rechargable batteries have. I am thinking about switching to rechargables for maybe 80% of my at home battery applications but I want to be careful not to ruin things.

 

[snakebite]

only a problem with luxeon lights that dd and depend on the internal resistance of alks.dont worry about it in other apps.

 

[evan9162]

Some cheap cameras depend on the internal resistance of alkaline batteries to limit current in their flash recharge circuits. Using rechargables have literally resulted in a meltdown of the recharge circuit - there have been accounts of such things told here in the past.

 

[JSWrightOC]

That sounds like a poorly designed circuit. Sadly, it wouldn't cost that much more to build it better, ya know...

 

[Doug Owen]

[ QUOTE ]
JSWrightOC said:
That sounds like a poorly designed circuit. Sadly, it wouldn't cost that much more to build it better, ya know...

[/ QUOTE ]

I guess that would be my take as well. Is low internal resistance a problem? No way, it's a *feature*! Makers work very hard to keep it low (and for good reasons), some marginal circuits, however.....

Doug Owen

 

[JonSidneyB]

they might manufacture it with low resistence, but If they are supposed to be a perfect replacement for other batteries, should not its affect on products be considered. The only reason I even knew there was a potential for a problem what some lights that are already pusing the power envelope using batteries that have more resistance, then you start using batteries that have less resistance and fry the light.

Would there not be other battery using items pusing the edge and then when you switch to something with less resistance, you then puch the item over the edge?

 

[Doug Owen]

You know, when you build a product, you have to accept the commonly available technology in the real world. A firearm, for instance, must work not only with the ammunition it's designed for, but for any realistic round that might be chambered. If I build a flashlight that takes AA cells, *and there are already AA cells out there with lower internal resistance or other "problems" for my product*, the responsibility to mitigate those problems rests with me. Right? I need to use a different battery, mechanically lock out the 'dangerous' types if possible, or *fix* my design.

Shoddy design is the route to this trouble. No 'worst case' analysis done here, and that's for sure. There are any number of ways these days to protect against this sort of problem, but often they take an increase in skills, resources or increased cost. Often a combination of these.

So that's my early morning opinion on the subject at hand. Sure there are marginal products out, and no doubt more to come. But in a case like this, that's all they are, marginal. It's irresponsible to provide a product that is vulnerable to improvements in cell technology. If Duracell could lower their internal resistance on average (what 'everyone' would see as an improvement), I would think they'd rush to production, wouldn't you? Maybe with a quick stop at the patient office to prevent all the other makers from doing the same..... It's irresponsible to provide a product that can be destroyed with commonly available things an owner might mistake. To the vast majority of citizens the cells are the same, except one you have to throw away. Most folks haven't a clue how electricity works, nor need to. That's why the cell has different ends mechanically. And the 9 Volt battery snap connector is 'gender keyed'. Little old Ladies in tennis shoes, the one's we work very hard to get to change their 'disposable' life style, simply cannot be expected to comprehend the difference, nor should they.

When stopped by the cops, 'I didn't know this car could go that fast' has never worked for me. "That battery shouldn't provide so much power" shouldn't work here, either.

It is the *maker of the end product* that has the responsibility to deal with this. He needs to have learned how to do it correctly (skills), found a way to get the materials or process to use otherwise well understood technology (resources) or not been so cheap (cost). Possible exceptions might be made for things like 'non electronic' products like the Reactor III with (the uncommon) Li AA cells. Serious warning about the problem, like we do with putting (very common) 20 gauge shells in the more common 12 gauge gun (sticks in the bore, destroys the gun with the next 12 guage shell) when you buy it, and in the aftermarked community. But for an electronic flash, and a 'high end one' at that? Shame on the flash maker.

Doug Owen

 

[Tomas]

Re: low internal resistance of rechargables a prob

The most any designer/engineer/manufacturer should be able to expect from an "AA" battery, for example, is a source voltage within a certain range, a physical layout that meets the AA spec, the ability to provide at least "X" amount of current, and the ability to function in the expected range of environments.

Other design features, such as the cell being able to supply greater current than the "average" or "low end" design or being re-chargable, or using a technology that makes it capable of providing, oh, 6AH of continuous power, or the ability to function in a temperature range of -80 to +400 C are normally outside the design criteria for a product, unless one of these extraordinary features is required by the product.

(One can demand more from a cell than normal, for example, and control the type used because of that, but demanding less than what can be expected from already available and common cells is incredibly poor engineering. You product MUST be able to survive commonly available, conforming cells. This is from me, an engineer ... )

Putting a 2V or 3V AA sized cell into a product designed for 0.9 - 1.7 volt cells would normally be unacceptable since the AA spec does not allow for those voltages. There is nothing in the AA spec, however, that limits the ability of the cell to provide large amounts of surge current ...

So, if a 'better technology' or even just 'better quality' AA cell that meets the nominal AA specs has very low internal resistance it's just the way that cell happens to be.

If a product designer depends on the internal resistance of a cell to protect his product from damage, he is leaving his product wide open to damage from advancement and or improvement in the way the cells are made.

As a quick example, if a product were designed to require the performance limitations of the carbon-zinc ("heavy duty") AA cell that was common a few years back, an alkaline cell could easily destroy it ...

Uh, let me put that another way ... "What Doug said." /ubbthreads/images/graemlins/grin.gif

 

[highlandsun]

Re: low internal resistance of rechargables a prob

Is it the shotgun-shell manufacturer's duty to worry about mixing 20 gauge shells with 12-gauge guns? 'cause battery manufacturers *do* worry about that, that's why there are no US battery manufacturers making/selling AA-size LiIons. Just as an aside...

 

[billw]

Re: low internal resistance of rechargables a prob

I'm curious as to just how you'd "cheaply" redesign a low-end
electronic flash to limit battery current. Feel free to use
any of the designs at http://www.misty.com/~don/samflash.html
Do not under any circumstances increase the flash recycle time
for those cases where someone uses normal alkaline batteries
with their "high" internal resistance...

I've done a fair number of experiments with converting disposable
camera flashes into strobes and such. They generally work fine
with rechargable batteries, but don't overdrive them voltage wise,
or they fry pretty quickly.

OTOH, this is likely to be a REAL problem when/if manufacturers
start doing Li-ION or Li-polymer in the same form factor as existing
lithium coin cells (2016, 2032, etc) There are an AWFUL lot of
circuits out there that count on a 2016 having a built-in current
limit. (Hmm. Mostly LED flashlights. How about that?)
(I guess that means I don't expect these to appear. They have
the "wrong" voltage too. Too bad - it's a nice form factor.

BillW

 

[koala]

Re: low internal resistance of rechargables a prob

I have seen some manufacturers build their battery compartment with the spring on positive side and a flat on the negative. I was sort of 'tricked' on a few occasion inserting the battery wrongly but it's still working. I guess the polarity protection diode saved the day.

You *can* run your new automobil with leaded petrol but you will destroy your cat converter.

I am not sure what sort of packaging energizer uses in the States but in Australia, if you read the fine print, Energizer will offer to repair/replace any electronic goods that breaks down after using Energizer.

It all comes down to the end user, I think you should check warnings that came with the user manual. Some electronics hate rechargeable.

 

[Ray_of_Light]

Re: low internal resistance of rechargables a prob

I fully bake what Doug said. A device damaged from low-resistance cells is flawed, it is the result of a bad or improper design...

Anthony

 

[billw]

Re: low internal resistance of rechargables a prob

> A device damaged from low-resistance cells is flawed, it is
> the result of a bad or improper design...

I'm not disagreeing entirely, but my point is that some designs
may be neither easy nor cheap to fix. Take a look at the current
generation of Li-ion charger chips, and see how many of them assume
a "current limitted" transformer, for instance.

We've all been spoiled by the clever elegance of the incandescent
light bulb... (And I sometimes wonder what extremes you could
drive light bulb technlogy to if you DON'T require that the
filament be inherently self-limitting to the correct current...

BillW
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