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Power Inverter Problem

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Posted by greg_kr on July 14, 2008, 12:07 pm

I have a problem with my 400 Watt Power Inverter. I made a simple
Solar Power Generator. I have a 12v (however now I learned it is
really 18V) rated solar panel which is outputs 1.26W. This goes to a
12V Marine Deep Cycle battery. I have the 400W power Inverter
connected to the Battery.

Initially the setup was working fine, but after a day or so of
charging the battery with the panel, using the Inverter on any type of
electronic device causes a alarm in the Inverter (this loud beeping,
is not explained in the Inverter instruction manual). I should mention
that the Inverter continues to function when this alarm is going off.
I hooked the Inverter up to my truck, and the alarm does not occur
there. So I am thinking I jacked up the Battery somehow.

When I test the Battery with a Multimeter I get it putting out 11.3
VDC. This seems fine to me, but the inverter does not like it. Did I
overcharge the battery or damage it somehow because the Solar Panel
was putting out more then 12V?

Thanks alot,


Posted by Duane C. Johnson on July 14, 2008, 1:38 pm
Hi Greg;

You havn't hurt the battery yet.

The inverter is complaining because the battery is very low in
voltage and probably near full discharge.

 > Did I overcharge the battery or damage it somehow because the
 > Solar Panel was putting out more then 12V?

A 1.26 watt panel can't possibly overcharge your battery.
It is much to small to be used in a system with a 400 watt

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Posted by Ron Rosenfeld on July 14, 2008, 8:32 pm

Assuming your meter is accurate, your battery is severely depleted, and the
plates may be sulfated.

A fully charged 12V flooded lead acid battery (and most marine deep-cycle
batteries are of this type) will measure 12.7-12.8V when fully charged and
under no load (or charging) for 3-6 hrs.  The manufacturer should have the
proper specifications as regards time at rest and voltage reading.  A
Surrette battery with CS plates, for example, would be almost completely

I doubt you will be able to charge your battery at all with so small a
solar panel.  What size and type of battery is it?  Can you check fluid
levels, or is it completely sealed.

You may have ruined the battery -- but from undercharging, not
overcharging.  However, it may be perfectly salvageable, depending on the
type, history, etc.

18V is a NORMAL rating for solar panels to be used in a 12V system.  You
need to put more than 12V into the battery in order for it to "take a
charge".  But, depending on the size of the battery, 1.26W may not be a
useful amount.

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