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Auto darkening Welding Helmet

My auto-darkening welding helmet has failed in the dark position i.e. the clear state is no longer evident, only the darkened state which is still adjustable through the shades DIN 9 to 13 via the pot on the helmet. The solar cells still charge the 2 lithium ion batteries which are showing the requisite 3V. Nevertheless, if the solar panel is covered up, the filter goes totally black.

I'd be grateful for any ideas. I can't find a circuit diagram on the Internet, and am figuring that I'll have to get a new helmet. Nevertheless, if a repair is feasible, I'd like to have a crack if only to better understand how it works.

Thanks

Martin

Reply to
Martin
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Well a brand and model would be helfpful. If the battery is replacable I'd suggest replkacing it anyway.

Reply to
PeterD

If they really are Lithium-Ion batteries, 3V is end-of-discharge and if there is any protection circuit to prevent under-voltage it will most likely have kicked in.

Reply to
rebel

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kicked

Do you have the ability to charge the batteries from an external source other than solar cells, like a battery charger with an accurate voltmeter?

Reply to
hrhofmann

is

kicked

I have, but I can't speak for the O/P.

Reply to
rebel

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here is

kicked

They are Panasonic Li cells with 3V stamped on the case. The helmet is probably 10 years old so you may well be onto something. I have been toying with disconnecting the batteries and - for test purposes - replacing with 2xAA batteries in series. And if that works then getting replacement batts.

Thanks for the advice and your thoughts.

Martin

Reply to
Martin

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e kicked

No, but I'm going to have a go at disconnecting the batts and connecting some AA batts to generate 3V and if that fixes it then replacing the Li cells. Your ideas have prompted me to do what was at the back of my mind. Many thanks.

Martin

Reply to
Martin

I tried using 2xAAs instead if the Lithium cells but it didn't help. However, I had a 2032 cell and, whilst its nominal voltage as stamped on the case is 3V, the actual voltage is 3.3V new. So, assuming that the 2 rechargeable Panasonic BR2330s would similarly show 3.3V when fully charged, my experiment with AAs may well prove nothing,

I realise I was wrong to call the batteries "lithium ion". They are rechargeable lithium coin cells, which I now realise is not the same thing. But if Rebel's comments still hold:

"If they really are Lithium-Ion batteries, 3V is end-of-discharge and if there is any protection circuit to prevent under-voltage it will most likely have kicked in."

then my best bet is to replace the batts with new ones. Having now disconnected the 2 batts, the clear vision state, when not welding, has returned provided the solar panel is covered.

I hope to report back when I have the new batts.

Thanks again for the guidance.

Martin

Reply to
Martin

On Tue, 30 Jun 2009 04:05:57 -0700 (PDT), Martin wrote as underneath my scribble :

You keep talking about Li 'cells' implying more than one if there are two in series you are going to need 4 Nimh to get the near required voltage! Charlie+

is

kicked

Reply to
Charlie+

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