Battery Charger & Booster

 After having a dead battery, and needing to call the local service station
to get my automobile started, I am considering buying one of these units.

How do they work?

Specifically, how do they provide the "boost" and, if there is a surge on
the lines when they do that, how much of a surge?

I'm trying to determine if the surge will be greater than the surge
capacity of my inverters.

Specifically, I am looking at two units.  One provides a 300A boost and the
other a 500A boost.  The one with the 500A boost (made by KT International)
specs 13A/120V input.  But, 500A/12V is going to be 50A at 120V plus
whatever is required for losses.

So how does this work?

Thanks.


-- ron  (off the grid in Downeast Maine)

 

International)

     There is a good bit of sales hype involved.  They are probably talking
about short circuit amps, and even that would be questionable.  In other
words, you may get 500 amps, but not at 12 volts.  For example: With typical
contact resistance and internal resistance you could end up with 500 amps at
(say) 1 volt which comes out to only 500 watts.  As long as the
charger/booster has a normal plug, it should draw no more than 15 amps.

BTW  The booster may not like a modified sine, particularly for a heavy
load.

Vaughn

 On Sat, 10 Jan 2004 16:04:53 GMT, "Vaughn"


Vaughn,

Are you guessing or saying this with knowledge of the particular products?

Are there some manufacturers that are better than others, in this regard?

What would you recommend for a device that will generate starting power in
the range?  I do know that my generator battery, which is rated at 220 CCA
at 0°F, was unable to start the car, so clearly I need something with more
oomph.  And it can't be one of those rechargeable packs with a built-in SLA
battery, as I'm off grid and would not be able to maintain it fully
charged.

Certainly there are any number of items which draw more than 15 amps
through a 15 amp circuit when starting up.  The compressors that carpenters
bring to a job site come to mind -- where they are rated for a 15 amp
circuit, but may have a starting surge of 70+ amps.

-- ron  (off the grid in Downeast Maine)

 

talking

typical

     You mean do I know what particular products you have been looking at
and have I tested them?  No and No.  What a stupid question!  I have the
same experiences as other posters here with similar products, and a lifetime
career in electronics.

     You have already done the math for yourself and now you know that there
is nothing magic in those boxes:  120 volts in and a 15-amp cordset give you
a maximum of 1800 watts available.  With 100% efficiency and 12 volts out
that gives you 150 amps output max.  Most of the boosters I have used will
not crank a car without first charging the battery.  That is not to say that
they are not useful gadgets, just don't believe the writing on the box.

Vaughn

 On Sun, 11 Jan 2004 15:30:17 GMT, "Vaughn"



That's clearly not what I meant.  After all, how in the world would you
know what products I have been looking at?


What a stupid response!


All I know is your name, not your background.


Could you answer this question?


There are other units that draw considerably more than their nameplate
rating for short periods of time.  My carpenter's air compressor draws
considerably more than 15A on startup, even though it runs just fine on a
15A circuit.

So my concern is that if these battery chargers do the same thing, in boost
mode, that if the surge were enough it might be more than my inverters
could handle.


-- ron  (off the grid in Downeast Maine)