british-cars
[Top] [All Lists]

Re: battery chargers & current limiting

To: british-cars@Alliant.COM
Subject: Re: battery chargers & current limiting
From: mit-eddie!pwcs.StPaul.GOV!phile@EDDIE.MIT.EDU (Philip J Ethier)
Date: Tue, 3 Apr 90 8:18:59 CDT
> 
> >>
> >> When caught with a dead battery and no trickle charger I find putting a 7 
>1/2
> >> watt 120V bulb in series with the battery and charger and leaving it
> >> overnight gives a good trickle. No clue what the actual current is.
> >>
> > somebody stop me if I've dropped a decimal somewhere, but it looks to
> > me like this would limit  current to about 6ma even if the battery was
> > shorted.  This seems safe enough, in fact hardly enough to do any
> > good.   phile@pwcs.stpaul.gov
> > --
> > Login name: phile        In real life: Philip J Ethier
> > Phone: 298-5324
> >
>
> As long as there's not enough current going through the bulb to light it up,
> the resistance is drastically different.  I'm not sure if its higher or lower,
> but if it charges a battery I guess its lower.  In beginning electronics class
> we once built an oscillator that was voltage stabilized by using a little 
>light
> bulb in series with something.  It seems that the current-resistance curve of
> an incandescent light bulb was perfect for that application.  Maybe the 
>battery
> charger limiting works on the same mechanism.
>
>        Joe
>
Yes, I did forget about that.  I suppose a guy should measure the
resistance of the bulb cold to figure this out.  I think it  is LESS
than when hot.  I'm sure that the bulb will never heat in this
battery-charging use.   phile@pwcs.stpaul.gov
--
Login name: phile        In real life: Philip J Ethier
Phone: 298-5324


<Prev in Thread] Current Thread [Next in Thread>