Not enough battery ?

 

I have 1500W (3000W peak) pure sine inverter with a 12V battery (113
ah). The battery is in good shape and well charged. When I try to use
the inverter to start a 1200W (peak) application or more, the inverter
stop and make a signal (found nothing about this in the owner manual).
I suppose it is because I don't have enough batterie to generate 1200W
and the inverter don't seem to be the problem. Your opinion about the
situation (not my incompetence) is appreciated.

 



Check all of your connections.
Measure the battery voltage at the input to the inverter under load.
It doesn't take much wiring resistance to create a voltage drop when
100 amps is involved.  How old is the battery?  If it's internal
resistance has increased due to age, there will be a drop in
available voltage at the battery terminals when a load is placed
on the battery.  Is the battery wire big enough to handle 100 amps
without getting hot?  I'm guessing that you need 0 gauge wire to
handle that much current.

 

On Tue, 10 Jul 2007 09:25:56 -0700, bourque.asselin@sympatico.ca
wrote:


Your battery is 1356Wh at an unknown discharge rate. So in very simple
terms it could supply a 1200W load for a little over an hour. But in
the real world it won't work that way since you have to account for
losses, and most particularly in this case, Peukert's equation
http://www.amplepower.com/pwrnews/beer/
http://www.pcmag.com/encyclopedia_term/0,2542,t=exponent&iB877,00.asp .

All things considered I'd expect your battery to supply the load for
at least a few minutes before the voltage would drop to the point that
the inverter disconnects. Perhaps your cables are too small or too
long.

Wayne

 

 bourque.asselin@sympatico.ca wrote:


Just how BIG of wire are you using between the Battery and the Inverter,
and how long is it?  1200W at 12 Vdc is 100Amps.  That's ALOT of Amps
to push thru a medium, or small wire, and not get a voltage drop of a
couple of volts.  A 2Vdc voltage drop will make the inverter see only
10Vdc, which normally will cause the Inverter to shutdown, due to
Low Voltage condition.  I would suspect this is your problem, along
with not near enough Battery Capacity for that kind of service.


Bruce in alaska       who really likes 00 Welding Cable
                        for Battery Connections
--
add a <2> before @

 

On Tue, 10 Jul 2007 09:25:56 -0700, bourque.asselin@sympatico.ca wrote:


1200 watts is about 100 amps so that battery should be able to supply it. Check
the
terminal voltage AT THE INVERTER when you apply the load.  If it drops much below
11.5 volts then check at the battery.  If it also drops below about 11.5 volts
then
the battery is sulfating and going high impedance.  If the battery voltage
remains
above that then you need to increase the size of the 12 volt conductors and make
sure
all the connections are corrosion-free.

That small a battery won't supply 100 amps for long so if this is more than a
momentary load you'll need to increase the battery size.

One other comment. If this load is a motor then you may have special
circumstances.
Many inverters don't like the low power factor that starting motors present even
if
the watt draw is within specs.  It may be that the inverter is tripping on low
PF.
Get a Kill-a-Watt (~$20 from the net) and measure the starting PF.  If it's much
lower than about 0.6 then you may have to do something about it.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
You have a magnetic personality... That must be why all your mental floppies are
blank.