[TR] Trickle Charger Wire Gauge?

[Paul Willoughby]

I owe you all a beer!  Thanks for the responses.

I think I'll skip the speaker wire and go with something a little heavier. 
No sense skimping on such a low cost item.  I'll just spray a little WD40 on 
the rusty old hinges of my wallet and blow some dust off a $10 bill.  [grin]

paulw
----- Original Message ----- 
From: "Randall" <tr3driver at ca.rr.com>
To: <triumphs at autox.team.net>
Sent: Sunday, October 18, 2009 4:04 PM
Subject: Re: [TR] Trickle Charger Wire Gauge?


>> I've never cut into one of these "Tenders" but I'd bet a beer
>> (and I'n not
>> talking an Old Milwaukee or Coors light, but a good Old
>> Speckled Hen ofr
>> Belhaven Twisted Thistle)
>
> Ok, Dave, you owe me a beer.  (Good thing I don't care for it, I'll never
> collect <G>)
>
>> that it has an IC voltage regulator
>> (LM317 or the
>> like) with active current limit and will limit to 1/2 amp
>> even if shorted.
>
> They do current limit pretty effectively; but the limit is not in the
> regulator.  Instead the "wall wart" transformer has such a high winding
> resistance that it just won't pass much current.  If shorted for any
> appreciable length of time (like connected to a deeply discharged 
> battery),
> the transformer burns out.
>
>> You'd have to be pretty clever to make one of these start a
>> fire.
>
> Nope, all it took was replacing the transformer with a somewhat beefier 
> one
> (from an old Hayes modem), that would deliver maybe 4 or 5 amps into a
> short.  Didn't actually catch fire, but got hot enough to melt the plastic
> case and char the label, before the pass transistor gave up the ghost.
>
>> If you are using a larger unit (eg: 5 Amp) you would want to
>> use larger
>> speaker wire or 16 gauge zip cord from the hardware store.
>
> Something to keep in mind; small wire also has a significant resistance,
> which may affect your charger if you use a long enough length of it.  For
> example, 24 AWG has about .025 ohms per foot, so a 20' length (40' total)
> would drop about 0.5 volts @ 500 ma.  That doesn't sound like much, but 
> it's
> more than the difference between a fully charged battery and a 50% charged
> battery (according to the table at
> http://www.batteryuniversity.com/partone-13.htm
> )
>
> BTW, Jim, this is DC, so no RMS correction needed.
>
> Randall