Powering a TV off grid system

mbsimonds · June 2010

Hi all,

I am new to solar energy. I put together a solar panel using cells i found on ebay. 36cells which in full sun is putting out about 19-20v. I have a cheapy MPPT controller. I scored 3 solar gel batteries cheap($125) that are 96ah each. I have them hooked up in parallel connected to the controller for a 12v system. I have a cheap inverter with a so called rating of 800 watts and 1600watts surge. Eventually I plan on adding more panels as time and materials become available.

The system is not connected to my houses grid.

My problem is when I have a few lights on, then turn my small 27" TV on, my inverter goes into protection mode. If I turn the lights off, turn the tv on first, then my lights I have no problem. In fact I can turn other lights on and it runs everything no problem. I just have to turn the tv on first. Obviously the tv is drawing more power to start than is available.

My question is, is there a capacitor or something that I can add in line to provide the starting power for the TV? Or is my only option to buy a more powerful inverter?

icarus · June 2010

Re: Powering a TV off grid system

It sounds like you have too much load on, and your battery is dropping below it's low voltage disconnect voltage.

When you speak of "a few lights on" are we talking CFLs?

Let's assume 3 cfls= ~45 watts. A Small television might draw, ~125 watts, for a combined load of ~200 watts. 200 watts/12 volts=16 amps.

16 amps is more than enough to drop the voltage of a ~300 ah battery. Couple that with inverter efficiency and it would be no surprise to see a low voltage disconnect.

Please understand, that a single small panel such as yours isn't going to put much power into your battery. Your loads, 16 amps for 1 hour=16 ah of load.

If your panel puts out 3 amps that would be a surprise.(Remember, voltage from your panel means little without current (amperage). 3 amps in full sun, for 4 hours would= 12 ah of charge, add in another 20% for basic battery charging eff, charger and wiring losses, and you might realistically put in ~9 ah/day, enough to run your loads for less than one hour! On top of that, you battery wants a charging current of ~5-13% of Ah capacity. That would translate to ~15amps minimum.

My favorite link,,, again:http://www.batteryfaq.org/
http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

Tony

Kamala · June 2010

Re: Powering a TV off grid system

Your panel is home brew, correct?

Do you know the Isc of your panel? That is the magnitude of current that it can deliver to a short circuit. You have given Voc (open circuit voltage) as ~20V.

Physics aside, I think Tony has a good take on this problem. Too little charge, too much draw.

My 2 cents: Your battery bank is 288 AH of gel cell. Ignoring the math of charge discharge, I reject GELs as a mass storage medium. The charge requirements are too dissimilar to those of AGM and FLA (which are reasonably similar) and the gelled electrolyte can become "pocketed" from which there is no recovery. Also, you state that you have a "cheapy" MPPT controller and a cheap inverter. You can do this sort of thing "on the cheap" but I think it is unlikely that you can do it well that way.

Good luck! I mean it.

Craig

RCinFLA · June 2010

Re: Powering a TV off grid system

The TV will have a short duration surge current at turn on. When you say small 27" I assume it is a CRT type, not a flat panel. They draw about 200-250 watts. (A new 32" LCD would draw about 150 watts).

First thing is to make sure you are not losing it in wires from battery to inverter. For that inverter I would use #2 wire and keep the length less then six feet. #4 would be okay if lines are less then couple of feet. Welding cable is nice and flexible for this application.

Check voltage at battery post and at inverter terminals with 500-800 watt load on inverter.

Most modified sinewave inverters shut down at about 10.5 to 11 vdc at their terminals. A large capacitor across inverter output will do nothing for startup surge and can damage a modified sinewave inverter.

mbsimonds · June 2010

Re: Powering a TV off grid system

Thanks everyone for your replies.

icarus:

By a few lights, I'm talking about 3 40watt PC tubes. When I have those on, and try turning on the TV, inverter fault. When i turn the lights off, turn the tv on first, no fault. Then I can turn the lights on, even turn more than the 3 40w although I haven't tested what the limit would be.

I actually haven't had a problem keeping the batteries charged up. Although, I probably only use the lights/tv for an hour or so a night. It's in my garage which is set up as my man cave for now

But like i mentioned, I will add more panels as I go along.

Kamala:

I have no clue about ISC. I'm just starting out with solar energy and i'm sure as I go along I'll advance in understanding and complexity. But this is my starting point for now. In reality, my initial goal was to make a generator for my oil heating system in case of a power outage. I would only need enough power to run the igniter and circulator a couple times every hour. I haven't gotten that far to test the system on the heating unit yet. I'll get there soon. Because I have the unit, I figured I mine as well use it for more than just a reserve solar generator. That would be a waste of electricity

I think once I have a good understanding, I'll upgrade from cheap to decent, decent to good.

RCinFLA

I appreciate your response. You answer my question most direct to what I was looking for. After all, I am a "newbie". It is a CRT TV and an older model so I'm guessing it's drawing 2-250w you mention.

I will check the wire and follow your advice. I'll take a picture of the setup I have going now when I get a chance and I'll test out the voltage at the terminals when the TV comes on.

Thanks for not letting me waste my time with the capacitor route.

Could a Kill-A-watt be useful in measuring the wattage being drawn in this type of solar application?

mike95490 · June 2010

Re: Powering a TV off grid system

A capacitor cold only be useful at the DC input of the inverter, but to get a large enough one, with low internal resistance, would be very expensive. Most small inverters have a "low voltage alarm", which may share a generic "fault" light.

GEL batteries are not deep cycel batteries, and may have too high of internal resistance.

Low voltage cut out test:
Wire inverter into your car's battery, in the car, near house so you can power lights & TV. Use large gauge wire, at least 10 gauge, #8 is even better. Short lengths, not long 6' runs, too much loss in long 12V leads.

Switch off inverter.

Start car.

Turn on inverter (after car has started, while cranking engine, surges can fry inverter.

Turn on lights

Turn on TV A running engine should feed more voltage, and you car's starter battery cans supply very large surge currents.

--

If you have an automotive battery charger, hook it up to your battery bank, and see if the charger thinks the battery's are low, even with 20A charger, it would take several hours to recharge nearly 300A of low battery.
After charge tapers off, you could leave charger attached, and try the lights and TV experiment again, using the charger as the "infinite battery".

There has been talk of CFL bulbs having a "less than desirable" power factor, and your 22W lights might really be pulling 40W at peak, which can freak out an inverter.

Just some thoughts

icarus · June 2010

Re: Powering a TV off grid system

With all due respect,

I can't conceive of how you are "keeping your batteries charged up" from your PV. Your 40 watts of lights is 120 watts, the TV @250 watts loads look like this, for one hour.

370watts X 1 hour= 370 wh.

370/12volts=30.83 ah. Add in 20% for inverter loses and you would have a load of ~37 ah.(nearly 1/2 my daily total and I have 400 watts of PV) To get that back into the battery you are going to need ~50 ah of power.

My guess is that you are only surface charging the battery. Surface charge will show 12.6 volts but specific gravity check will reveal a much lower state of charge.

Tony

RCinFLA · June 2010

Re: Powering a TV off grid system

Use #4 or larger for 6 foot run from battery.

Use #6 or larger for 3 foot run from battery.

Do not use #8 or #10. It will give you too much voltage drop.

mike95490 · June 2010

Re: Powering a TV off grid system

RCinFLA wrote: »

Use #4 or larger for 6 foot run from battery.

Use #6 or larger for 3 foot run from battery.

Do not use #8 or #10. It will give you too much voltage drop.

Most of those wires will not fit into the connectors of small inverters,

but yes, go as large as possible for the wire size, and as short as practical. The resistance in wire for 30amps is a major player.

BB. · June 2010

Re: Powering a TV off grid system

If you get stranded (house type wiring, fine stranded welding cable not needed and not really as good as the standard stranded cable for this application)--just cut off a few strands at the inverter so you can fit the rest in. This will reduce the voltage drop substantially.

-Bill

mbsimonds · June 2010

Re: Powering a TV off grid system

Thanks again for the replies.

I think the wire might be a contributor. I'm using a smaller guage housing AC wire. Possibly #12(All I had laying around). I'll up the wire size first. I think maybe by taking some pictures it might help. In the end though, I think a better inverter might be my quickest solution.

mike90045

I'll try the inverter hooked up to my car and see if it faults the same way with the lights and television.

icarus

No disrespect taken.

Perhaps what you mention of surface charging is what is occuring. I have no way to test with a refractometer or hydrometer for specific gravity as these batteries are completely sealed. I'm testing at the battery terminals with a multi-meter.

Last night, I had the batteries charged up to about 14.00v according to my meter before adding a load to it. I used 3x 40w flourescent PC light fixtures for about 30-45min along with my TV 27" CRT for about the same amount of time. After I was done and turned everything off, I think the meter read around 13.3v or so of power at the batteries terminals. I'm not sure what they are right now as I am at work and they have probably charged back up again?!?

So if I can't test using specific gravity on these Gel batteries, how can I get a more accurate measure of what the charge is?

I'll take some pictures tonight. Try and pick some higher gauge wire for the inverter to battery connections.

icarus · June 2010

Re: Powering a TV off grid system

What kind of batteries are these? A voltage of 13.3 after loading is sort of odd. A fully charged 12 volt battery would read ~12.6-12.7vdc. How you are getting 13.3 after significant loading is a bit of a mystery. What is the nominal voltage of the battery? Perhaps they are 15 volt batteries, in which case you are rapidly killing them. I would check your controller parameters as well, as a sealed battery generally requires different bulk/absorb/float voltages than a FLA battery.

Please provide some detail on the battery configuration.

Once again, read the battery FAQ links to gain some understanding about your particular battery chemistry. Generally, a quick way to measure battery SOC is to use a volt meter at least ~3 hours after any charge/discharge activity has ended. Then one should briefly load a battery for a bit to dissipate the surface charge. Then a volt meter can give a reasonably accurate measure of battery condition. (The number is related to the specific battery chemistry however).

That said, a "dead" battery can show full voltage, it just won't have any capacity to carry that voltage for long.

Tony

dwh · June 2010

Re: Powering a TV off grid system

He's not just using sealed - he's using sealed GEL. To the OP; GELs are sensitive to OVER-VOLTAGE.

http://www.batterystuff.com/tutorial_battery.html#3

"GEL: The Gel Cell is similar to the AGM style because the electrolyte is suspended, but different because technically the AGM battery is still considered to be a wet cell. The electrolyte in a Gel Cell has a silica additive that causes it to set up or stiffen. The recharge voltage on this type of cell is lower than the other styles of lead acid battery. This is probably the most sensitive cell in terms of adverse reactions to over-voltage charging. Gel Batteries are best used in VERY DEEP cycle application and may last a bit longer in hot weather applications. If the incorrect battery charger is used on a Gel Cell battery poor performance and premature failure is certain. "

mbsimonds · June 2010

Re: Powering a TV off grid system

The batteries are Solarcraft Gel batteries. They are from a company who makes complete solar systems like these:
http://www.solarcraft.net/enclosure-model/mega-pak.htm

Apparently, the guy I got them from worked at a large company who had a helicopter landing pad and they used one of these systems to power the lights on the pad. I guess they upgraded and all the employees canibolized the unit and he scored the batteries.

They say 12v97ah. It also says "Charge voltage limited to 14.1v(2.35v per cell at 68%F)" if that makes any sense.

A picture of them.

A few more pictures:

mbsimonds · June 2010

Re: Powering a TV off grid system

Pics of the rest including the two light fixtures being lit and the tv. One fixture has two tube bulbs, other one is out.

If I turn the tv on before the lights everything works no problem. In fact I have turned on about another 200watts of lighting and it still runs them all.

mike95490 · June 2010

Re: Powering a TV off grid system

Big mistake I see in your photos.

The inverter MUST be connected to the batteries, move it down the wall, to 24 inches off the ground. That will shorten the cables a lot. The charge controller, in the fine print somewhere, will state "Do not connect inverter to the load terminals". A long cord on the 1220VAC side does not matter nearly as much.

2nd mistake is the interconnect wires for the battery,
http://www.smartgauge.co.uk/batt_con.html
has info on how to properly connect (on the diagonal) Load and charger can connect on same terminals

Cariboocoot · June 2010

Re: Powering a TV off grid system

And the 12 gauge is way too small.

This is where your Voltage is going and why your loads cause failure if turned on in the "wrong order".

"Charge Voltage limited to 14.1 V" means the batteries should not at any time receive more than that. Id est; Absorb set point is 14.1 V. With those wires they probably won't get whatever the set point is. No, really; it's amazing the difference the right wiring can make!

dwh · June 2010

Re: Powering a TV off grid system

They say 12v97ah. It also says "Charge voltage limited to 14.1v(2.35v per cell at 68%F)" if that makes any sense.

Yea, it means that if your charger is charging at 14.4v then the voltage is too high for the GELs that are limited to 14.1v. Check the charge controller manual - maybe it has a dip switch setting for GELs (not "sealed" because AGMs are the most commonly used "sealed" and they like a higher voltage).

That romex is way too small for battery LOAD connections. It might be big enough for the trickle coming in from the homemade PV, but it's SCARY small to feed an 800w inverter.

The inverter should be tapped directly off the battery through a fuse with a some big fat wire - not tapped off the charge controller (even IF the charge controller has a connection).

mbsimonds · June 2010

Re: Powering a TV off grid system

Ok... Disconnecting everything! I'll be back.

Cariboocoot · June 2010

Re: Powering a TV off grid system

Those "LOAD" terminals on some charge controllers are for light DC loads, not inverters. The manual would probably give a current limit like 15 or 30 Amps max. Probably "X - charge current". Definitely not for 80 to 100 Amps running an inverter.

RCinFLA · June 2010

Re: Powering a TV off grid system

Can't tell if #12 or #14 from pictures.

Peak voltage drop on #12 for that length will be over 2 volts at inverter rated power.

icarus · June 2010

Re: Powering a TV off grid system

200 watts of load at 12 volts is 16 amps. The rating of #14 wire is only 15 amps. Your wire size is half your problem! Where are your fuses?!

Personally, I certainly wouldn't worry about over charging those batteries with that panel. (The charge voltage may be incorrect) but that panel will never be able to put enough current in to a battery bank that size to overcharge it.

Your problem is going to be (if not already is) chronic undercharging!

Tony

mbsimonds · July 2010

Re: Powering a TV off grid system

Ok, so I disconnected everything. And this why we turn to forums for the right information. I appreciate it.

Tomorrow I will hit up Home Depot for some monster wire. As for fuses, there are 30a fuses in the inverter. Should I be putting in a fuse box/fuse of my own from the battery to the inverter? If so, how many amp fuse should I get? And a fuse between the panel and the controller?

mike90045

I looked over the diagrams in the link you sent me. I will rewire the batteries the way they suggest and connect the inverter directly to the batteries. My one question though is if the inverter will shut off on its own if the batteries are underpowered now that the controller is not regulating the inverter?

I'll also lower the inverter to 24" or less distance from the batteries as you mention.

icarus

At what point should I begin to worry about overcharging as I plan to add more panels in the future?

Cariboocoot

You are correct, the parameters for the max load according to the controller manual is 20A.

Tomorrow I will rewire everything like you guys suggest and will post more pictures and see where I stand.

I guess I have to count on the electric company to power my tv for tonight

icarus · July 2010

Re: Powering a TV off grid system

The fuses in the inverter are to protect the inverter, not the wire feeding it!

Every piece of wire must be protected by a fuse (or breaker) sized for the minimum wire size in the circuit. So if you are going to run #14 wire you would fuse that wire at 15 amps (Max) The fuse should be located as close to the battery terminal as possible, ideally on it, as any length of wire is subject to over load, and your battery represents a huge power source, very capable of burning up everything around it, including the house.

Try these fuses,,http://bluesea.com/category/5/22/productline/overview/379
Available at marine/rv dealers, bolt directly to the battery.

As for when you need to worry about over charging. That is what your charge controller is for. That said, make sure that the charge controller is properly configured to the battery type and spec. You mentioned that you had a "cheapy" mppt controller. I personally would be leery of a "cheapy" mppt controller. Many cause more trouble than they gain. With one small panel, there is going to be very little if any mppt gain from the controller anyway. If it was me, I would get a good Morningstar small controller.

The reality is that your homemade panel, guessing by it's size, (not knowing it's capacity) it is going to be hard pressed to put out more than ~1-3 amps, just barely enough to keep that ~300 ah battery bank in float at best, never really charging it properly from some state of discharge.

Tony

mbsimonds · July 2010

Re: Powering a TV off grid system

So low and behold, you guys were all right. I changed all the wiring with 6 gauge and rewired the batteries as shown in the 3rd diagram Mike showed me. I hooked the inverter directly to the batteries.

Turned on all the lights including 2 more 22watters and a 60watt. So at total of 224w in lights. Turned on the television and no fault.

I'll post some pictures of the new wiring when I break out the digital cam.

mbsimonds · July 2010

Re: Powering a TV off grid system

So I was only able to locate one 50amp fuse at a auto parts store. HD didn't carry anything I thought I could use. I'll go hunting again tomorrow and find one for each terminal. In the meantime I hooked up the fuse in-line after each terminal joins into one. I cut the wires the same length coming from each terminal.

The diagram I used:

I connected the controller and inverter after that.

icarus

I think the reason my meter was showing 13+ volts was the battery in the meter was weak. It is now showing 12v

icarus · July 2010

Re: Powering a TV off grid system

Better,,,

I would replace the wire nuts with either terminal strips, split bolt connectors or crimp fittings.

Now you need to figure out how to keep that battery bank charged until you have enough PV to keep it charge. I also suggest that if you are routinely running the kinds of loads you are using you are going to shorten the life of the batteries. 220 watts @ 12 volts is ~18 amps.

If you can't replace those AHs each time you draw you will be left with a pile of lead scrap.

Tony

mbsimonds · July 2010

Re: Powering a TV off grid system

Is 18 amps for 1 hour? How long would it take to replace 18 amps with one panel as I don't want the batteries to be worthless. If I can allow the batteries to recharge completely, that's fine i'll only use the system every time i'm able to recharge them completely. And 220 watts is ony counting the lights and not the television.

How many panels would you suggest is decent to keep the batteries charged daily?

And I agree with the wire nuts, they are temporary. Only thing I could find today.

icarus · July 2010

Re: Powering a TV off grid system

You first have to determine what your home made panel put out. With out knowing it's amperage capacity there is no way of answering your question.

220 watts for 1 hour is 220 watt/hours or .22kwh
220 watts from 12 vdc is ~18 amps,, 18 amps of 1 hour is 18 amp hours.

Tony

Powering a TV off grid system

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