[Shop-talk] Which diodes for a battery charger?

[pethier at comcast.net]

Any diode tough enough to be used in a battery charger will not be damaged by an ohm-meter, so you can figure out the polarity that way.

Phil Ethier West Side Saint Paul Minnesota USA
1973 Triumph Stag LE22439UBW "uncle jack", Sapphire Blue
2004 Suburban 8.1, Sport Red, the only automatic of the bunch
2005 Lotus Elise, Bordeaux Red Pearl
2007 Saturn Ion 3 2.4, Berry Red
pethier at comcast.net
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----- Original Message -----
> From: "Karl Vacek" <KVacek at Ameritech.net>
> To: shop-talk at autox.team.net
> Sent: Tuesday, February 26, 2013 9:39:50 PM
> Subject: [Shop-talk] Which diodes for a battery charger?
> My old Schumacher battery charger has been dead for years. Used to be
> able
> to go to the factory for new diodes, fixed inexpensively while I
> waited, but
> they moved away. I'd like to repair it with better diodes this time.
> I'll
> also put a muffin fan into the case to help cool the diodes and the
> huge
> transformer.
> 
> 
> 
> The present diodes are little buttons that appear to just be clamped
> between
> a brass contact plate and an indentation in the aluminum flat plate
> heat
> sink. They're Motorola diodes, MR2502 on one transformer lead (a pair)
> and
> W9312 on the other transformer lead. The charger is 10 amps
> continuous, 30
> amps fast boost (duty cycle 10 minutes on, 12 minutes off), and 50
> amps
> motor starting (duty cycle 2 minutes on, 5 minutes off)
> 
> 
> 
> I look at diodes and see all sorts of ratings, and don't know what's
> better
> and what's overkill. May I please have a recommendation as to what
> rating,
> etc.? A part number to order from XXX company would be even better.
> 
> 
> 
> Also - are there positive and negative orientations to the diodes in
> there
> bow? They're not marked, and if their polarity is related to label
> orientation, then one pair is mounted with both oriented the same
> direction,
> while the pair on the other lead are oriented opposite each other.
> 
> 
> 
> Thanks!
> 
> Karl
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