Christmas Tree Lights

[squerly]

I tried running some Christmas tree lights off my solar system and the controler kept warning me of a low battery and then disconnecting. But testing the batteries shows they have a 95% charge. So I plugged the strings in one at a time. First string runs OK. Second string OK. But as soon as I connect the third string the controler shuts off the batteries.

So I bypassed the controler and ran the inverter straight off the batteries. First string OK, Second string OK, but as soon as I connect the third string the wires coming from the battery to the inverter start to get hot. Real hot! Appears to be a lot of resistance somewhere. Anyone have this problem before?

[Sunking]

Where is it getting hot? Sounds to me like it is over loaded.

[squerly]

Where is it getting hot? Sounds to me like it is over loaded.

It's getting hot right where the wire connects to the battery. After some thought, I'm thinking i just have too small a gage wire run between the battery and the inverter. I'm going to change it out tomorrow and see if that fixes the problem.

[Sunking]

It's getting hot right where the wire connects to the battery.

Very common problem. That tells you instantly you have made poor terminations. This problem is the most common point of failures and electrical fires. You either terminated the terminals onto the copper cable poorly, and/or poor connection to the battery post.

I cannot comment on your wire gauge because you have not specified the current or length.

I last comment and one which you need to be aware of. I do not know what type of lights you are using, but Christmas Tree lights are real power hogs. For example a 100 count string of the common C7 bulbs consumes 5 watts per bulb so a string or 100 uses 500 watts.

[squerly]

Very common problem. That tells you instantly you have made poor terminations. This problem is the most common point of failures and electrical fires. You either terminated the terminals onto the copper cable poorly, and/or poor connection to the battery post.

I cannot comment on your wire gauge because you have not specified the current or length.

I last comment and one which you need to be aware of. I do not know what type of lights you are using, but Christmas Tree lights are real power hogs. For example a 100 count string of the common C7 bulbs consumes 5 watts per bulb so a string or 100 uses 500 watts.

I don't know the wire gage as it was some that was laying around the garage, but I'm sure it is not heavy enough. I'll change that immediately. I'll check the termination point(s) at the same time. As for lights, I have 6 strings of 100 mini lights @ 41 watts per 100 (according to the box) so I figure 250 watts or 21 amps per hr.

Is the 21 amps per hr. still valid given I'm using a 12 volt system to power the inverter? Or has it increased?

[Sunking]

Is the 21 amps per hr. still valid given I'm using a 12 volt system to power the inverter? Or has it increased?

21 is close enough estimate, but really depends in the inverter efficiency and its power rating. Call it 25 to be safe. What is the inverter max power rating? That is what you want to size the wire for.

For example let's say it is a 500 watt 12 volt inverter. Minimum safe gauge would be 6 AWG, but still may not be large enough if the run is over 5-feet 1-way distance. But what I can tell you for sure if the wire is hot at a connection point is a sure indication of a poor connection. The added resistance with current flowing = watts, which = heat.

One last note here and a very common problem for anyone running high wattage 12 volt inverters. It requires very high currents, very large batteries, and very large copper wires. Even with it done right you can still run into problems because of the automatic low voltage shut off built into inverters. This may sound familiar to you because it is happening.

Your inverter shuts off. You examine the battery after it shuts off only to find it is OK and cannot figure out why the inverter shut down from low voltage. Well there is a number of reason and each contribute to the chain of events.

1. Battery Internal Resistance: As you draw more current from a battery, the internal resistance of the battery develops a voltage drop in proportion to the current demand. The more current you draw, the more voltage drop develops which mean the voltage at the battery post drops lower and lower. So even with a fully charged battery at rest with a voltage of 12.6 volts, can drop to 10 volts with say a C/2 to C/4 current load. Example say you have a 500 watt 12 volt inverter with a 100 AH battery. At full load of 500 watts demands 42 amps from the battery or a 100 Ah / 42 amps = C/2.38. That is a way over loaded battery and the post voltage will easily drop to 10 or less volts causing the inverter to trip off line from under voltage.

Rule of thumb for batteries is max current load on FLA batteries is C/10 to C/8, and for AGM C/4. The above example with a 500 watt inverter would require a minimum 400 AH 12 volt for a FLA battery or 200 AH AGM.

2. Wire and connector resistance: Same as above. Wire and connectors have resistance. Smaller and longer the wire has higher resistance. Current x Resistance = Voltage.

It all adds up.

[squerly]

21 is close enough estimate, but really depends in the inverter efficiency and its power rating. Call it 25 to be safe. What is the inverter max power rating? That is what you want to size the wire for.

It's a 1,250 watt AIMS inverter. I replaced all of the previous wiring with 4 gage and the overheating problem went away. The distance from the battery's is 12". (inches, not feet) When all the lights are on the inverter is reading over 40 amps. (Kind of hard to tell exactly what the amp draw is because the meter on the inverter is sketchy) Anyhow, that's a whole lot more than what I had counted on and pretty much makes this a no-go.

The project runs just fine now with the new wires, but i'd have to have several more batteries to make this turkey run for very long. I guess I could look into changing out to LED's, but damn.... how much is this Christmas cheer supposed to cost???

Thank you Sunking. As always, excellent advice...

[Sunking]

how much is this Christmas cheer supposed to cost???

Thank you Sunking. As always, excellent advice...

You are welcome as always. Sorry I cannot help you out with the economics and the reality it brings. LED's are an improvement in power consumption somewhat, but it only shifts the cost from panels and batteries; to the lights themselves so you are screwed either way.

Why don't you do it the old fashion inexpensive way and plug it into your house power? You get all the lights you want for dirt cheap power.

[squerly]

Why don't you do it the old fashion inexpensive way and plug it into your house power? You get all the lights you want for dirt cheap power.

LOL, because the house if 1/2 mile up the road. No power down by the gate except the solar setup I have for the electric gate opener. I think I'll call Duke Energy tomorrow and see if they can drop a wire for me. Even if it costs a couple thousand dollars it will be cheaper than solar.

[Sunking]

LOL, because the house if 1/2 mile up the road.

OK you got me. My bad.

[Mike90250]

... I guess I could look into changing out to LED's, but damn.... how much is this Christmas cheer supposed to cost???.......

A single 12V "marine battery" with a cheap-o 150W mod-sine inverter can power dozens of strings of LED lights a night. 200w of panel would recharge it, if you have good sun. Or just haul the battery back and forth (or use 2 and swap them) to charge from ac outlet.

[TnAndy]

LOL, because the house if 1/2 mile up the road. No power down by the gate except the solar setup I have for the electric gate opener. I think I'll call Duke Energy tomorrow and see if they can drop a wire for me. Even if it costs a couple thousand dollars it will be cheaper than solar.

If you already HAVE a solar setup for the gate, it might not cost too much to simply expand it some.

My gate is also a long way from the house (1500'), but I ran 120vAC down to it originally to avoid having to use a solar powered opener. Now, the funny part is, I have THAT circuit in my subpanel of "critical circuits" on my solar backup system......ahahahaaaaa

[solorone]

It's a 1,250 watt AIMS inverter. When all the lights are on the inverter is reading over 40 amps. (Kind of hard to tell exactly what the amp draw is because the meter on the inverter is sketchy) go.

I guess I could look into changing out to LED's, but damn.... how much is this Christmas cheer supposed to cost???

.

You need a good clamp on amp meter, to cut out some guess work. A fluke meter is great for this, but $$, surely there is a good cheaper meter out there now.
After Xmas, LED lights will be cheap, switched over to them 4 years ago, power draw is minuscule, wife keeps some on year around.

[squerly]

You need a good clamp on amp meter, to cut out some guess work. A fluke meter is great for this, but $$, surely there is a good cheaper meter out there now.
After Xmas, LED lights will be cheap, switched over to them 4 years ago, power draw is minuscule, wife keeps some on year around.

I've got a kill-a-watt around here someplace but after two days of looking I decided it wasn't that important anyhow. Wife found a few thousand LED's at Kmart today and I'll make another run at it with those. Thanks everyone for the help and Merry Christmas!

[tandrews]

An observation for consideration:
Not all led strings are so efficient...

I bought a sale string (10' rope light) of "christmas" LEDs for ambient lighting in my shiny solar shed.
On a 12v DC power supply they drew almost 5amps to make useful light.
The rope light was designed for AC and as such had resistors on every LED in the string.
In contrast, three handheld 26LED worklamps in series drew just over half an amp.
Same voltage, no resistors and made my foiled shed like daylight.

I did try some "battery operated" LED strings as well, but their output was so puny they fell out of the running.
Just something to consider when 120v items get repurposed.
Add in inverter losses and you may be wasting energy for the same output as dedicated 12v appliances.