Re: Polarity reversal protection,how to??

From: mike (spamme0_at_netscape.net)
Date: 11/13/04 

Date: Sat, 13 Nov 2004 02:15:22 -0800

Antonio Spedicato wrote:
> mike <spamme0@netscape.net> wrote in message news:<41954B03.9030000@netscape.net>...
>
>>Antonio Spedicato wrote:
>>
>>>Hy, i would to build a polarity protection for my dive light (12 volts
>>>nimh batteries) but i don't known ho to do it!!
>>>Can someone help me?
>>>There are 10 batteries 1,2 volts 3000 mah serial installed.
>>>Thanks
>>>Antonio-Italy
>>
>>Protection from what?
>>Does the light care?
>>Batteries in wrong? Use mechanical means.
>>Charger backwards? Use dedicated cable.
>>Other??? use fuse.
>>It can obviously get much more sophisticated if you can
>>describe exactly what you're trying to protect against.
>>100% protection is MUCH harder than 90%.
>>mike
>
>
> I forget a word......polarity reversal, this is the problem.
> For me is hard to do it..can you expplain me how i can protect batteries?
> Thanks

You need to remember MORE words. Polarity reversal where?
When installing the batteries?
When connecting a charger?
Some other thing we don't know about?
Might, depending on your objectives, be helpful to know the
current drain and technology of the lamp, depending...maybe...who knows...

Making some grand unsubstantiated assumptions, I'd say put the batteries
in, put a screw in the cover so some idiot can't get them out and use
a polarized charging connector.

Now, there are a whole bunch of issues surrounding charging. But you
haven't asked that...

Then there's the issue about leaving the switch on and reverse charging
some of the cells. Low voltage cutout is likely to be more of a
necessity than putting the cells in backwards.

I'm starting to rant, but what the heck, bits are almost free...
Rechargeable batteries are unsuited to use with flashlights. And here's
why. You need to turn the light off IMMEDIATELY at the first sign of
dimming to prevent cell reversal. If you haven't charged it in a week,
this may happen almost immediately when you try to use it.
So, do you want the light to turn itself off to protect the
batteries? Or do you want it to stay on as long as possible to help
you through the emergency?
"He was hit by a car in the dark...but the good news is that the
batteries in his flashlight were protected".
mike 

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