Two panel/two battery read outs

[Jamestex]

Well hello everyone I just joined this forum on yesterday. I started building solar panels several months ago. After buying 6x6 inch cells that were pretty inferior I final settled on the smaller 3x6 inch cells. They do not break as easy though they generally produce less wattage.

I have built two panels of 62 watts each and connected them in series. Each panel has a blocking diode and a 7812 voltage regulator box attached. I get a reading on the out put side of panel (1) of 34-36 volts. Once I connect the panels to a 12 gauge two wire, that runs to my battery bank, the reading before connected to the battery bank is 24.1 volts at 9.5 amps. Two batteries are connected in parallel and then connected to a 2000 watt (4000 watt surge) inverter.

Once I connect the two wire to the batteries the reading drops to 11.9 and slowly rise to about 12.13 over a four hour period. I have been running two big screen TV

[Sunking]

Well James hate to tell you your batteries are dieing a slow death and will be ruined shortly, and in about a year your panels will quit working from moisture creeping into the panels.

First thing that sounds way off is your panel voltages and current compared to what you claim. You say you have made 2-62 watt panels (total of 124 watts), but according to your readings of 24.1 volts @ 9.5 amps = 229 watts. However you claim you used 3 x 6 cells and assuming you used 36 of them in series they should produce 16 to 18 volts each, connected in series should give you 32 to 36 volts output @ 3 amps = 120 watts. So something is not right in you math, nothing adds up.

As for the batteries you did not mention what Amp Hour capacity they are, only stated you had 2 12 volt batteries. So we have no idea of what storage capacity you actually have. Knowing what I know about 12 volt batteries they can be anywhere from 10 AH up to 100 AH. That is a range of 10 to the 1st power. However they are not near large enough from the sounds of you connected load.

You claim 2 large screen TV run 7 hours each day. Well you did not say how many watts each of them used so we can determine how much energy they use, nor did you mention your location to determine what size panels you need to run those power hogs. Just guessing off the top of my head they use 300 watts each.

OK here is an example of the process. I have to make a whole lot of assumptions here, so it is only an example, but it shouldn't be to far off.

2 TV's 300 watts each ran 7 hour per day. 2 x 300 watts x 7 hours = 4200 watt hours per day. Add fudge factor to account for a battery system charge efficiency, wiring losses, inverter/charge controller conversion efficiency = 1.5 x 4200 wh = 6300 watt hours Ok this means your solar panels have to generate a minimum of 6300 wh each and every day all year round. We use this number to determine the solar panel wattage needed.

To find the solar panel wattage we need your location to determine your insolation. Since this is a battery system we use your winter insolation. I will assume Dallas TX = 3.5 Sun Hours. So to find the solar panel wattage we take what the panels need to generate each day in watt hour (6300) and factor out the time element in hours to leave us the required wattage. So 6300 wh / 3.5 h = 1800 watts So in this example you would need a 1800 watt solar panel array.

For the batteries is straight forward. To make the batteries last about 5 years, you never want to discharge them more than 20% on any given day, and never ever discharge them more than 50%. So we need a 5 day minimum reserve capacity. This will give you rougly 2.5 days run time to account for some cloudy days. After 2.5 days you will reach the 50% magic number of death and have to shut down and wait for 2 sunny days to recharge. So to find the battery capacity we take the adjusted daily watt hours (6300) multiply by 5, and then divide that by the battery voltage you selected which you did by default of 12 volts. So you need [6300 wh x 5 days] / 12 volts = 2625 Amp Hours. That is about 1500 pounds worth of lead and acid in this example.

No lets go back to the beginning when I said your batteries are dieing a slow death. As you can see from this example your batteries and panels are likely way way undersized. So when you used them you discharge them way down to almost 0% state of charge. Then the next day your panels cannot recharge then as they are not near large enough to replace what was used the day before.

So give us the real numbers, the wattage of the TV's, how many hours you want to run them, and your location and then we can tell you what it will really take to do the job.

[Minnesota]

Why do you have a 12V regulator at the panel? The 7812 drops the higher voltage from the panel to just 12V and throws away a lot of power as heat.

[Sunking]

Why do you have a 12V regulator at the panel? The 7812 drops the higher voltage from the panel to just 12V and throws away a lot of power as heat.

I was going to point that out, but it is a moot point in light of the other problems. But you are right he is loosing 50% or more of the power with a shunt regulator. If he really wants to peruse this he is going to have to buy a good MPPT charge controller along with a truck load of batteries and panels if his 2 TV use as much power as I suspect.

[Jamestex]

Two batteries/two panels

Hey guys, thanks for the information. I will get the information and get back to you a little later.

[Sunking]

There are two ways to get the information.

1 Look at the name plate on the TV's. They will state the power input requirements. However they will be on the high side...

2 Most accurate way is to measure the power with a Kill-A-Watt meter. Do not use the watts, use the Volt Amps and power factor.

Will also need your location like a city and state.

[Mike90250]

batteries the reading drops to 11.9 and slowly rise to about 12.13 over a four hour period.

Murderer !!

[Sunking]

Murderer !!

My thoughts exactly. At 12.13 volts indicates 40% capacity at the very best. If he rested the batteries a few hour it will fall way lower after the surface charge discharges leving him around 10% capacity. Hate to tell him the damage is already done.

[Jamestex]

Two batteries/two panels: I'm back

Sorry, I was trying to be brief in the original thread. Now, I keep a log of what I have been doing because I do not completely understand everything that I am trying to do. After going back to the log and not relying on my (old) memory I found that I did run (fact) two TV

[Mike90250]

[QUOTE=Jamestex;11913]
I placed the 7812 voltage regulators on each panel (partially because I didn

[Mike90250]

Read here about Solar Charge Controllers
and here about MPPT controllers

Please, and then find an online electronics course and discover how wrong you are about

I understand that volts and watts are additive in series and the amps remain the same

[Sunking]

The battery discharged down to 10.9 volts so I was above the 20% threshold.

I live in Houston, Texas.

James I do not mean to be mean or cruel, but you have no idea what is going on. At 10.9 volts you were well beyond 20% DOD daily limit leaving 80% capacity left in the batteries. At 10.9 volts the batteries were past 100% discharged and completely useless. At 50% is 12.3 volts, you have never even made it up to 12.3 volts or 50% capacity.. For your viewing pleasure I offer:

100% = 12.7 rested for 4 hours after charge and discharge. In other words disconnected for 4 hours.
50% = 12.3 volts.
0% dead in the water = 11.85 volts

You are seeing 10.9 volts?

Basically you have already damaged your batteries, and there is no going back. It is like smoking for 30 years and learning you have COPD. No reason to stop smoking now, keep on smoking cause you are going to die soon whether you quit smoking or not.

You have no where near enough panel wattage or battery capacity to do what you want, or any type of charge controller that works. You are going to have to start completely over and spend several thousand dollars to reach your goal. You will be far better off plugging in your TV and toys into the wall socket and pay Reliance Energy a few dollars a month to run them.

[vermiman]

Read here about Solar Charge Controllers
and here about MPPT controllers

Please, and then find an online electronics course and discover how wrong you are about

watts = volts * amps

volts are additive in series.

amps are additive in parallel.

Since watts is a product of volts and amps, it is additive both in series and parallel.

Watts are additive when you add cells. No matter if you wire in series or parallel.

One .5 volts 6 amp cell .5v * 6a = 3w

Two .5 volts 6 amp cells wired in series (.5v+.5v) * 6a = 6w
Three .5 volts 6 amp cells wired in series (.5v+.5v+5v) * 6a = 9w
Two .5 volts 6 amp cells wired in parallel .5v * (6a+6a) = 6w
Three .5 volts 6 amp cells wired in parallel .5v * (6a+6a+6a) = 9w

Each cell adds 3 watts whether there in series or parallel.

I guess three cells in parallel is pointless since it will only give you .5v at 18a and 9w