Can I plug in a lamp to my inverter to test the state of my batteries?

[kathyg]

Hello: I want to plug in a 100 watt lamp to my inverter to see how long my batteries last. I am testing two 12 volt marine batteries (27dc2) to determine if they are good enough to keep. I connected them in series to my AIMS 24 volt Inverter (https://www.aimscorp.net/2000-Watt-Pure-Sine-Inverter-Charger.html). Now that I charged them to "full capacity" (the green light is on Float Charge), I want to know what power they really have. I used it run my house and it lasted only 2 hours and 40 minutes. I estimate I run a max of 200 watts an hour. That would tell me the batteries are not holding the charge if you figure those two batteries should have 1200 watts. MY QUESTION IS: how do I plug it in? I plugged into the GFI outlets on the side of the inverter but the lamp does not come on. Thanks!

 

[Jim Burrow]

Yes, you can. that is what I did last year to test my 2424lv. Note don't think because you have a 100-watt bulb that the load is 100 watts. It turned out that my 100-watt bulb was really only drawing 80 watts. You should use a watt meter to measure the wattage or a Voltmeter and an RMS current meter and then multiple the voltage times the RMS current to get the true wattage.

 

[kathyg]

Yes, you can. that is what I did last year to test my 2424lv. Note don't think because you have a 100-watt bulb that the load is 100 watts. It turned out that my 100-watt bulb was really only drawing 80 watts. You should use a watt meter to measure the wattage or a Voltmeter and an RMS current meter and then multiple the voltage times the RMS current to get the true wattage.

I tried plugging it in but the lamp does not turn on. Thanks for the advice about the real watts. I don't know how to measure what a lamps uses.

 

[kathyg]

I tried plugging it in but the lamp does not turn on. Thanks for the advice about the real watts. I don't know how to measure what a lamps uses.

Wait. I have a Kilowatt meter- I can use that.

 

[Rider]

I tried plugging it in but the lamp does not turn on. Thanks for the advice about the real watts. I don't know how to measure what a lamps uses.

Check the trip/pushbutton on the GFI breaker to make sure it's not tripped.

 

[Jim Burrow]

Check the trip/pushbutton on the GFI breaker to make sure it's not tripped.

Ok, for my controller, it needs a minimum of 80w to turn a light on. Even at 80 watts, the light wants to flicker. Try putting in a larger wattage bulb. Note, don't use an LED for your test. it probably will not light. Try plugging in two 100 watt bulbs to the output of your controller/inverter. Or any combination wattage of bulbs and try to get up to at least 120 watts to 150 watts or thereabout. Your bulbs should light now.

With respect to my house, after I go to bed after 11:00 pm, my house power draw has been as low as 98 watts and everything stays on. There was a couple of times the power went out and I'm sure it was because the power draw from the controller dropped below 90 watts or maybe below 80 watts where I know the controller will turn off.

 

[Bud Martin]

The Wattage on the DC input side of the inverter will be higher than the Wattage on the AC output side of the inverter due to conversion and system loss, so the inverter may consume 120W on the input side of the inverter to produce the usable output of 100W on the AC output side of the inverter. You also do not want to discharge the LA batteries below 50% SOC.

 

[Jim Burrow]

Excluding minor power losses, "Power in" equals "power out". For example, load 120 volts at 10 amps.
load side, 120x10=1200 watts. then on the battery side, 12 volt powering 1200 watts, current from the battery is then 1200/12=100 amps. Hence, the power of the battery must equal the power of the load. - minus any losses of wire resistance, heat, length of wire, how good you are at sodering or crimping just to name a few.

 

[kathyg]

Problem solved: The button on the GFI outlet had to be pressed to activate the outlet! If all problems were so easily solved!

Check the trip/pushbutton on the GFI breaker to make sure it's not tripped.

I actually discovered the GFI button before I read your post (proud of myself). Thanks so much for replying!

 

[kathyg]

Ok, for my controller, it needs a minimum of 80w to turn a light on. Even at 80 watts, the light wants to flicker. Try putting in a larger wattage bulb. Note, don't use an LED for your test. it probably will not light. Try plugging in two 100 watt bulbs to the output of your controller/inverter. Or any combination wattage of bulbs and try to get up to at least 120 watts to 150 watts or thereabout. Your bulbs should light now.

With respect to my house, after I go to bed after 11:00 pm, my house power draw has been as low as 98 watts and everything stays on. There was a couple of times the power went out and I'm sure it was because the power draw from the controller dropped below 90 watts or maybe below 80 watts where I know the controller will turn off.

Thanks. I did not know that low draw could cause an outage. Wow. Is that dependent on settings in the controller? Right now I am testing the batteries with just the batteries and the inverter.

 

[Jim Burrow]

Thanks. I did not know that low draw could cause an outage. Wow. Is that dependent on settings in the controller? Right now I am testing the batteries with just the batteries and the inverter.

Yep! that will do it. I found that out the hard way too after I first installed my system. lost a few night's sleep trying to figure what was going on. - ain't these projects fun!

 

[kathyg]

Ok, for my controller, it needs a minimum of 80w to turn a light on. Even at 80 watts, the light wants to flicker. Try putting in a larger wattage bulb. Note, don't use an LED for your test. it probably will not light. Try plugging in two 100 watt bulbs to the output of your controller/inverter. Or any combination wattage of bulbs and try to get up to at least 120 watts to 150 watts or thereabout. Your bulbs should light now.

With respect to my house, after I go to bed after 11:00 pm, my house power draw has been as low as 98 watts and everything stays on. There was a couple of times the power went out and I'm sure it was because the power draw from the controller dropped below 90 watts or maybe below 80 watts where I know the controller will turn off.

I am testing the two batteries now with two 60 watt incandescent bulbs. The Kill-a-watt meter says they two bulbs are using only 100 watts. That is something I would not have known if Jim had not told me. Now - do I have to sit and watch that bulb all day? Maybe I will plug a radio into the test so I will know when the battery dies!

 

[kathyg]

When I tested the two marine batteries this morning after charging them and before doing the load test, they read 13.2 v and 13.5 v. And together (24 volt system) they read as 26.6 volt. If I decide to put these into service with one solar panel (315 watts), are they close enough in voltage to be used together without one damaging the other? After I do the load test, I will know the total power they providing . I will report back later.

 

[kathyg]

Results of the test of the power in two marine batteries:

1. Charged the two 12 volt batteries to show FLOAT mode on the AIMS inverter - using the grid
2. Plugged in two 60 watt light bulbs that registered a load of 108 watts on my Kill A Watt meter.
3. The batteries went dead after 2 hours and 44 minutes.
4. Multiply 2.75 hours by 108 watts= 295 total watts available in the battery

Now I have been told to conclude that these batteries are no good because the provided only 295 watts of power in such a short time on a small load. Two 12 volt batteries should give me 12 volt X 105 amps X 2 batteries = 2520 watts X 50% useable watts = 1260 watts. Should I run the desulfator on these batteries? Or give up?

 

[kathyg]

Results of the test of the power in two marine batteries:

1. Charged the two 12 volt batteries to show FLOAT mode on the AIMS inverter - using the grid
2. Plugged in two 60 watt light bulbs that registered a load of 108 watts on my Kill A Watt meter.
3. The batteries went dead after 2 hours and 44 minutes.
4. Multiply 2.75 hours by 108 watts= 295 total watts available in the battery

Now I have been told to conclude that these batteries are no good because the provided only 295 watts of power in such a short time on a small load. Two 12 volt batteries should give me 12 volt X 105 amps X 2 batteries = 2520 watts X 50% useable watts = 1260 watts. Should I run the desulfator on these batteries? Or give up?

My Inverter supposedly uses 26 watts so maybe I should add 72 watts to the 295 for a total of 367 watts provided by the two batteries.

 

[kathyg]

Results of the test of the power in two marine batteries:

1. Charged the two 12 volt batteries to show FLOAT mode on the AIMS inverter - using the grid
2. Plugged in two 60 watt light bulbs that registered a load of 108 watts on my Kill A Watt meter.
3. The batteries went dead after 2 hours and 44 minutes.
4. Multiply 2.75 hours by 108 watts= 295 total watts available in the battery

Now I have been told to conclude that these batteries are no good because the provided only 295 watts of power in such a short time on a small load. Two 12 volt batteries should give me 12 volt X 105 amps X 2 batteries = 2520 watts X 50% useable watts = 1260 watts. Should I run the desulfator on these batteries? Or give up?

Another brain teaser for me: The now two dead batteries test 11.6 and 12.4 volts, or together they test 24.4 volts. What does that tell me?

 

[Rider]

You're running in 24V mode? Batteries in series? One battery may be good, the other bad. The bad battery will pull the good one down. Charge the 'good' (12.4VDC) battery with a conventional battery charger, let it rest 6-12 hours and check it again,

 

[Rider]

My Inverter supposedly uses 26 watts so maybe I should add 72 watts to the 295 for a total of 367 watts provided by the two batteries.

Don't confuse watts with watt-hours. Watts is the amount of power drawn in any given moment in time. Watt-Hours is how much power you use over a period of time. A battery is rated in Watt-Hours or Amp-Hours.

 

[Hedges]

I am testing the two batteries now with two 60 watt incandescent bulbs. The Kill-a-watt meter says they two bulbs are using only 100 watts. That is something I would not have known if Jim had not told me. Now - do I have to sit and watch that bulb all day? Maybe I will plug a radio into the test so I will know when the battery dies!

Mechanical timer?
But not good to fully discharge battery. Better to look up what voltage is 50% SoC at your discharge rate, plot a few readings over time to predict when it will get there, stop before fully discharge. 50% SoC, 30% SoC, or whatever you've determined you would like to use.

 

[kathyg]

Don't confuse watts with watt-hours. Watts is the amount of power drawn in any given moment in time. Watt-Hours is how much power you use over a period of time. A battery is rated in Watt-Hours or Amp-Hours.

I think I have a grasp on that. Do you see an problem with my math?