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If you can justify the cost I would look at HID. Over here our wrecks are dark and the vis is often poor I have a 50w / 75w ( 12v downlighter bulb type ) canister torch which is OK - some of the guys that I dive with use the HID and it seems to cut through the water and illuminate the target without the backscatter that I get. We do no cave stuff ( no caves here! ) so burn time is less of an issue. Acrylic vs Delrin - Delrin ( acetal copolymer - Delrin is a trade name ) is going to be a lot tougher and with sufficient wall thickness near impossible to break or crack. I have heard it said that some prefer the clear acrylic as you can watch it as it floods !. Acrylic will crack if abused. Acetal is a bit soft and tends to scuff up and scratch quite easily - this is not relevant to this application - it just looks well used. Batteries - cycling - depends on the type of battery used - if you are using older style NiCad then its best to drain them down to about 1V / cell before recharge, any lower than this and you tend to find that one cell in the pack will get discharged completely or worse yet - reversed - NiCads do not like this. NiCads do not like being charged from a half discharged state - doing this leads to a gradual loss of capacity ( AKA burn time ). Newer NiMh batteries allegedly don't care and you can charge / discharge whenever you want. Personally I would be careful of over discharge ( <1v / cell ) until I had read data otherwise. Just my 2cc Paul At 10:11 17/08/2001 +1000, you wrote: >Hi all, > >My old canister light is getting a bit past it (cost me $80AUS (around >$40US) so can't complain) and not being very user servicable I'm looking at >a replacement. At this stage I'd be looking toward a 50 watt halogen (or >equivalent HID) with a canister that's 2-3 pound negative. A burn time of >50min to an hour would be adequate but I've hear it's best not to cycle the >newer batteries to their limit each time their used, true? Besides having >extra burn time seems a sensible precaution even for open water dives >(which is what the light would be used for, night diving mainly). Paul R Carre (Design Engineer) Polar Instruments Ltd Guernsey, Channel Islands email: <paul.carre@Po*.co*> Tel: + 44 1481 253081 Fax: + 44 1481 252476 www.PolarInstruments.com -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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