Check solar battery voltage and current

 I have Uni-Solar US-21 brand 21 watt solar module, MorningStar
SunGuard-4 (SG-4) pulse width modulation (PWM) charge controller, and a
Universal UB30H 98 Amp hour battery.

I can't get the battery charged.  I live in St Pete, Florida and the
panel gets about 4-6 hours of sunshine a day this time of year.  The
panel faces south.
After charging the battery, it won't run a small tv for even an hour.
Both solar items are brand new.

I am a beginner in electronics and have a couple of questions.
I have a multimeter, but I'm unsure how/where to connect to solar
module
to determine the voltage flowing into the battery when it is being
charged.

After the battery is charged, how can I determine the stored voltage?

When I have an electronic device connected to the inverted, how can I
check the watts/amps coming out of the battery?

Thanks,
DW

  Your tv may pull anywhwere from 34 to 75 watts. Assuming 75 watts, it
would take that panel 3+ hours of charging to run the tv for one hour. a
98 ah battery only stores about 50 usable ah without damaging the
battery, or 600 wh's, so if it really was fully charged (60 hours of
full sun), you should get 8 hours of use, then recharge for 30 hours
before you use it again.

Steve Spence
Dir., Green Trust
http://www.green-trust.org

dawatson833@hotmail.com wrote:

 dawatson833@hotmail.com wrote:

As Steve pointed out, you'll need a couple of weeks of charging to
fully charge the battery (and you'll never equalize it).

Tell us more about your load, what's the inverter and what's the
nameplate rating on the TV set?

 A battery monitor is what you need to determine how much battery
capacity you have left in real time. It consists of a special meter
with internal electronics and a shunt. You would install the shunt in
the negative cable between the solar panel connections to the battery.
All of your loads negative cables would also be connected to this
point. The battery monitor will show you voltage and amps going into
and out of your battery. You can also program the monitor with the size
of your battery and it will give you and indication in percent of the
state of charge ( how much energy you have left in it) You should not
deplete your battery more than 50% of its rated capacity if you want it
to last. I use a cruz pro meter and it works really well. Just do a
google search for battery monitor and you will find lots of them.
You can get a rough idea of state of charge by directly measuring the
voltage but it is not really the best way to do it. Set your meter to
measure DC voltage and connect it to the solar panel in full sun with
neg to neg pos to pos connections. You should have 18-21 volts or so.
And DC amp meter is what you really need to check it easily. Stored
voltage is taken directly off the battery terminals with no loads
connected to the battery. What you might consider is getting a 50 watt
panel and a couple of golf cart batterys from Sams club. Your panel and
battery are kind of small to recharge the system on a daily routine. Or
consider a smaller hand held TV from radio shack.  If your battery is
not a sealed type you can use a hydrometer to measure its specific
gravity to determine state of charge also. Not a real easy way to do it
however. The battery monitor can be mounted inside away from the
batterys which is nice. Mine has an alarm that I have set to 50% to
alert me if they get discharged to much.

Warren Lee

 I concur on the cruz pro unit. It's what we use. excellent monitor.
Handles puekert properly.

Steve Spence
Dir., Green Trust
http://www.green-trust.org

Contributing Editor
http://www.off-grid.net
http://www.rebelwolf.com/essn.html

gulffisher wrote: