NiCd batteries are charged by a constant CURRENT usually specified to be
C/10.
That is, the capacity of the battery is AMP-HOURS divided by 10.
At this rate they can generally be left on charge for a long time. Actual use by people is to leave
them on charge indefinitely. NiMh battery chargers are also constant current but usually have a
timer built in to shut them off after 6-10 hours.
I don't know the capacity of a night sun battery, but you said the charger was 450 mWATTS - Are you
sure it wasn't 450 mAMPS?
450 mA would imply a 4.5 A-Hr battery which seems about right for a nightsun.
13V/450 mW would imply 35 mA and a 0.35 A-Hr battery which is way too small for this application. An
alkaline AA battery is about 1 A-hr even though it's only 1.5 Volts.
SEE THE FIRST SENTENCE. A car battery charger is a constant VOLTAGE not CURRENT. The
current is HIGH.
YOU WILL DAMAGE THE BATTERY. It is also a safety hazard - it could blow up but will certainly vent
and spew toxic gases.
Since it's going to be trashed - charge it for 30 MINUTES only (assumes 10A charger) and outside
downwind of your house.
better to take public transportation until your new battery arrives.
Rocky
"Hjalmar Duklæt" <
[email protected]> wrote in message
news:[email protected]...
>
> "David Kunz" <
[email protected]> wrote in message
>
news:[email protected]...
> > Matt O'Toole wrote:
> > > Hjalmar Duklæt wrote:
> > >
> > >
> > >>>Your car battery charger is probably giving
> > >>>14.4 V and maybe 6A.
> > >
> > >
> > > Most car battery chargers seem to have a "start" mode of 20-50A, a
> regular
> > > charge rate of 10A or so, and a "trickle" charge setting of 2A.
> > >
> > >
> > >>No, I wouldn't do that to a new battery. The A-meter on the charger
says
> > >>it's putting out about 2 Amps and I'm keeping it in the garage while charging. The originale
> > >>charger is a 13V/450mW charger. I will only be doing this for a short while with my old
> > >>battery only until the new battery/charger arrives. Maybe I shall continue for a longer
> > >>periode
> just
> > >>as a test and see if the battery deteriorates quickly. I don't think
the
> > >>risk of an explosion is very high as long as I remember to switch off
> the
> > >>charger in time before overheating the battery.
> > >
> > >
> > > You're doing fine. Nicads are high current batteries, and in fact can
> be
> > > charged with even more current than that. But the more current, the
> more
> > > you risk damage from overcharging -- everything happens faster! 2A
> should
> > > be fine, though, as long as you can stop the charge before the
batteries
> > > warm up significantly -- which is actually a very good indicator of
full
> > > charge. You said you ordered a new charger already. That's good, but
> in
> > > the meantime you can certainly keep using your car battery charger, as
> long
> > > as you're careful.
> >
> > I thought that the battery had to be designed for fast charging. I know that I've read that not
> > all NiCads can be fast charged -- however, that could just be someone trying to sell THEIR
> > SPECIAL battery

. I personally wouldn't do it. I'd try something like a car light bulb in
> > series with it to drop the current down. The problem then becomes determining the full charge
> > voltage (when to stop).
> >
> > David
> >
> I really don't know but according to Matt it should be ok and I'll trust him. I know that I
> have to watch it carefully and stop charging as soon as it gets warm on the outside. But if it
> can be done without reducing the battery's life, then why can't they deliver such charger with
> the battery
in
> the first place? With the original charger it takes about 15 hours to
fully
> charge an empty battery and I have no more than 12 hours from coming home
in
> the afternoon till I have to take off in the morning.
>
> Hjalmar