Deep cycle battery won't run LED lights very long...why not?

Hi, everyone! Thanks for letting me pick your collective Brain!

I recently purchased a deep cycle battery, a pure sine wave inverter, and a battery re-conditioner/trickle charger. I intend to build a small solar array in the spring. In the mean time, I am experimenting with charging the battery with my 1250 watt generator => trickle charger => battery. I know that this is a terribly inefficient way to go about things, but it's just a temporary way to begin the learning process about battery power and a way to avoid having to transport the battery back and forth to charge it from house power, so please forgive the transgression!

In any case, all that I typically power with the battery is a 50' run of LED rope lights out at my yurt. They are 110V plug-in type lights, plugged right into the outlet on the inverter. I believe the draw is pretty low (approx 33W) but even once the battery is fully charged to 12.5 or 13V, I can not run the lights very long (approx 45 minutes) before the inverter begins to alarm, indicating that the voltage of the battery has dropped below some critical threshold. (I think at that point the battery is down to about 11 - 11.5V).

Does this make sense to anyone with more than my very rudimentary electrical understanding (i.e. me)? I had hoped that the lights would just keep running until the battery was fully drained... what gives?

Looking forward to where this leads,

Joe

Hi Joe,

I need to know a little more information.  Specifically I need to know how big your battery is in amp hours.  Actually a 33 watt draw sounds pretty heavy to me for the purposes of running lights, although I have never tried running a string of lights.  I have only tried running a couple of individual LED's but those were anywhere from 0.1 watt up to a full 1.0 watt.  Maybe there is some voltage regulator in the string that accounts for the larger power draw?

But at any rate, I would need to know the battery in Amp Hours first.  Incidentally I find these to be fun little projects.  I recently built my own version of what you described.  Although I have never had to put it to the real test, it consists of a 15 AH SLA battery and a charge controller contained in a .50 cal. plastic ammo can that I bought from Amazon.  If you give me a few minutes I can probably dig up a link to my old thread on the topic.

Let me know about the battery and we can start crunching numbers.

Eric

Thanks for the rapid reply, Eric!

Universal Power Group 12V 100Ah Solar Wind AGM SLA DEEP Cycle VRLA Battery 12V


In Awe,

Joe

Is your string of lights nominally a 12v or a 120v a/c?

120v a/c

Found it!

Here is the old thread to my building the "battery generator."  A battery generator is really a misnomer is this case as all I really have is a battery connected to a charge controllers and a couple of different output voltages--none higher that 12v dc.  I state in the thread that I would like at some point to build a full fledged 120v a/c device based on a rolling tool case.  My little "battery box" was about $100 all in.  The full sized version will be much more expensive.  Incidentally, a LOT of the expense of the little battery box went into buying an excess of components that I did not need.  For instance, at the time, I only needed perhaps 3 feet of copper wiring, but the smallest length I could buy was 50'.  Fortunately I have excess left over for the big build.

https://permies.com/t/135729/permaculture-projects/Building-pair-battery-generators


Eric

thanks, Eric, but I don't see the link, haha!

Joe,

OK, so some basic math tells me there is either something wrong with the battery or with the power conversion somewhere between your battery generator to the light string itself.  If the light string were running from 12v dc and required no conversion, then a 33 watt draw from a 100 ah 12v battery should run a very long time.  A 100 ah, 12v battery should give you 1200 watt hours run time, or a little more that 36 hours of run time while running the mere 33 watt light string.  I have a feeling that the power loss is not in the string itself or the string would be getting very hot (is it?  If so, that might be the culprit).  Have you tried running any other device to attempt an estimate of power draw and run time?

If other devices seem to work well (or at least better) then I would assume that the issue is in the light string--perhaps a partial short causing a high power draw.  If other items similarly draw down the battery quickly then I would think that the issue would be in the power unit itself.  Possibly the circuitry is bad.  Alternately, the battery is not up to par.  I don't have an easy way to test either of these assumptions unless we partially disassemble the power unit and disconnect the battery and try running something directly from the battery itself to see of the battery works aside from the rest of the circuitry, but I am pretty certain that this will take us into void-the-warranty situation quickly.

I would start with trying to power something other that that particular string of lights, even if it is just another string of lights.

Thoughts?

Eric

Joe,

I got excited about finally finding the old thread and then forgot to cut-and-paste!  Kinda a palm to face moment.

Eric

Thanks, Eric! That's what I thought, without doing any math... I'll give you the link to the inverter - maybe there's something that will jump out at you there... think its 1000W...

I've charged rechargeable AA batteries, my phone, my bluetooth speakers, etc from the battery via the inverter - does not seem to trigger it so quickly. Again, it's not that the battery is dying, it just seems to be getting drawn down to a level that the inverter "deems" insufficient? Is that possible?

https://www.amazon.com/Power-TechOn-Inverter-Outlets-PS1002/dp/B0131L8NLM?pd_rd_w=FHYv3&pf_rd_p=a92e0124-cfa8-4f1e-82b5-a4a348d97008&pf_rd_r=YYNBWAFFFJBJ5M6TFG04&pd_rd_r=0dab872e-2bd4-417c-a899-3b7ca40b8895&pd_rd_wg=XEDJL&pd_rd_i=B0131L8NLM&ref_=pd_bap_d_rp_35_t

GoWISE Power 1000W Pure Sine Wave Inverter 12V DC to 120V AC with 2 AC Outlets + 1 5V USB Port, 2 Battery Cables, and Remote Switch (2000W Peak) PS1002

I just had another thought.  While running the light string, do you notice any heat coming from the battery?  1200 watt/hours is a lot of energy to be exhausted in a mere 45 minutes regardless of where it is going.  If the battery is indeed charging to a full 1200 watt/hours (100 amp/hours at 12 volts) and then discharging in under 1 hour, I would think that the battery would get quite warm--even hot.  If that is the case then that screams to me that there is something wrong with the circuitry somewhere, likely a partial short circuit (I assume that the whole device comes with either circuit breakers or fuses--correct?  Hopefully these are not blown or tripped).

If the battery is cool, then it sounds to me like the battery is not actually charging to its rated potential, meaning you may have a bad battery.  

Other symptoms to look for would be excessive heat coming from anywhere along the electrical path to the lights including anywhere along the light string.

This is my mind running through possible ways to identify ways to examine power losses.  Stop me any time you think you have had enough.

Eric

Thanks, Eric! Again, the battery is only being drained from 12.5V down to about 11.5V, but that's enough to freak out the inverter for some reason....

Here's the link to the generator, too...

Not trying to send you down a rabbit hole that is not of your making, my friend! Don't spend any more of your valuable time on it than you like, ok?

https://wenproducts.com/products/1250-watt-gas-powered-inverter-generator-carb-compliant

Joe,

I forgot for a moment that this was a build and not a stand-alone pre-purchased unit.  This makes things much easier.  My inclination would be to try to run as many 12v items directly from that battery as possible just to rule it out.  Something to me smells fishy about the inverter if you have been able to charge so many other items without problems.  I don't suppose you have a volt meter, or even better, an amp meter.  If you did you could measure the actual voltage, or even better, the current, running into and out of the inverter.  I would not be surprised if the light string were the highest draw item of the items you mentioned.  I would also really look at that one light string.  Is it basically like a Christmas light string?  Those are pretty cheap and highly prone to failure.  I would not be surprised at all if there were a partial short in the line somewhere.  Another line might be able to confirm or reject this hypothesis.

But it is good to know that that one battery is charging any number of devices without problems.  In fact, in retrospect it seems like the only problem is the light string--am I correct?  If so, then this is an easy fix.  I would consider plugging in that light string to a regular outlet and feeling for any hot spot anywhere from the initial plug to the very end of the line, just to check for hot spots which might be shorts.

My ideas are running rampant now--stop me when you need to!

Eric

Eric Hanson wrote: I would consider plugging in that light string to a regular outlet and feeling for any hot spot anywhere from the initial plug to the very end of the line, just to check for hot spots which might be shorts.

My ideas are running rampant now--stop me when you need to!

Eric

Eric, out of curiosity, would one of those "kill-a-watt" plug-in watt monitors help here for Joe's projects?  Looks like they are about $30 and perhaps not a bad investment for someone tinkering with power usage into the future.  Do these work with inverters the same way they would with a normal 120V power outlet?

So I don't have an inverter on my battery box, but I have run it below a 1 volt drop in voltage without anything noticeable happening to anything being powered by the device.  If a single volt drop causes the inverter to stop working then you don't really have a 100 Ah battery.  At most you have about 1/12th that amount.  This is really too bad as this means that whopping battery is mostly wasted.

But hopefully this is not the case.  Again, I would go back to trying to power a bunch of other items and see of you can get the other devices to induce a greater-than-1V-drop.  If this is the case, then I think that the inverter is safely ruled out.  Just as a thought, have you considered running something like a 60W incandescent bulb?  This should be a much higher power draw than the light string and would be a real test.  Again, if the incandescent bulb works but the light string does not, then I would think that the problem lies not in the inverter but in the light string.  This might sound like a far-fetched idea, but you could try to power your computer with the device.  Computers do not require 1000 watts, but if you can even get the computer started, you would at least know that it could pull some serious wattage for at least a brief amount of time (but at the same time, I understand wanting to be careful around electronics).  A laptop would be safer though less dramatic.  You could plug in any number of devices just to test the power draw and see if the setup you have can handle those devices, especially for more than an hour or so.  If the whole setup can handle something like a 60W light for something like an hour or more, then I would really think seriously about that light string.  Otherwise I would be very concerned about the inverter.  It sounds like you can confirm that the battery itself is functioning more-or-less normally.

Eric

I think a Kill-a-watt would be a great tool for this project and I may get one for myself.

Thanks, guys! Yes, Eric, I do have a volt meter - I'll pull it out and get you some more numbers...

I think you may have hit the nail on the head about the rope lights, though - although they are nearly brand new, there is about a 4' section that does not light.... oddly enough, there is about 6' of lights beyond these dark bulbs that do light, so juice is getting to them somehow.... could it still possibly be a "short" where they're dark? The ones that are lit beyond the dark bulbs do not appear to be any more dim than the bulbs preceding the "short" - maybe I'll just return them and see if a properly functioning one exhibits the same symptoms...

John, yes, I know the kill-a-watt you're talking about - don't have one, but have frequently thought it would be handy to have. Though, as I said, I do have a pretty good volt meter, so maybe I could garner the same info from that? Not sure, as I said, my electrical knowledge is pretty rudimentary...

Joe,

Were you around when the battery "failed?"  The reason I ask is that according to the specs on Amazon, the inverter has a low voltage alarm.  I would think that you would hear this alarm go off if the problem was indeed a low voltage problem.  I am having a hard time believing that the voltage drop you described is going to qualify though.

The part about the non-functional 4' section of lights does concern me though.  Obviously this is not enough of a short to completely drain the battery, but according to the specs, the inverter does have thermal protection.  I am wondering if the power draw was high enough that it tripped the thermal protection overload.  If so, this would explain why the battery was still essentially still fully charged yet not functional.  Perhaps by the time you recharged the battery the inverter would have cooled down and been functional again.  I think returning the lights and replacing them would be a good idea.  It would not take much of a short to radically increase the power draw and that could be dangerous.  It sounds like we might have our culprit, but I would still like to see how things work on other higher draw items that are known to not be faulty.

Eric

It's always preferable to go full DC if possible, especially if you have a deep cycle battery. As well, the rule seems to be "you always need more storage than you think." But this setup should run longer than it does now.

Possibilities:

- Your battery is not being fully charged

- Your battery has low electrolyte levels

- Your inverter has an outrageous power draw (some pure sine wave units are notoriously inefficient)

- Your rope lights have a much higher power draw than you think; it is often printed on them; and the draw of several strings will be additive

Edit: if you want to play with off-grid power systems, a voltmeter/multimeter is essential equipment IMO

At this point,  I am questioning the inverter.

John,

I am curious about your thoughts on the inverter.  It looks like we have some dysfunctional lights which would be the first component I would want to discard.  We also have a record of operating on other items.  What makes you think the inverter is the issue?  You may well be correct, but I am just wondering how you got there.

Eric

I agree the inverter is the most likely suspect, as well as that light string.
Get some 12 volt led's and wire them to the battery. I think you will like how long they last.
Invest in a high quality pure sine inverter its money well spent.
Invest in 2 six volt t-105 size deep cycle golf cart battery's.

Hi Eric,

I am suspecting the inverter because it is signaling a problem after a minimum of drain.  This is not to say there may not be other problems as well.  

John,

Actually, I see your point.  I suppose the next logical test then would be to first load up the battery with 12v devices as Thomas suggests just to confirm that the battery is indeed working properly.  Assuming that it is we could then move on to the inverter and try the same tests but with a bunch of different devices but NOT the questionable rope light.  I would think that if the battery discharges below 11.5 volts (and hopefully much, much lower) then we can assume the issue is in the rope light.  If the alternate loads still cause the inverter to flip out at 11.5 volts or so, then you may be correct that there is a problem in the inverter.  Though I am still suspicious of the rope light that does not function properly.

Good thoughts!

Eric

I have to wonder if the low voltage kickout on the inverter is set to high?

Joe Krein wrote:Hi, everyone! Thanks for letting me pick your collective Brain!

I recently purchased a deep cycle battery, a pure sine wave inverter, and a battery re-conditioner/trickle charger. I intend to build a small solar array in the spring. In the mean time, I am experimenting with charging the battery with my 1250 watt generator => trickle charger => battery. I know that this is a terribly inefficient way to go about things, but it's just a temporary way to begin the learning process about battery power and a way to avoid having to transport the battery back and forth to charge it from house power, so please forgive the transgression!

In any case, all that I typically power with the battery is a 50' run of LED rope lights out at my yurt. They are 110V plug-in type lights, plugged right into the outlet on the inverter. I believe the draw is pretty low (approx 33W) but even once the battery is fully charged to 12.5 or 13V, I can not run the lights very long (approx 45 minutes) before the inverter begins to alarm, indicating that the voltage of the battery has dropped below some critical threshold. (I think at that point the battery is down to about 11 - 11.5V).

Does this make sense to anyone with more than my very rudimentary electrical understanding (i.e. me)? I had hoped that the lights would just keep running until the battery was fully drained... what gives?

Looking forward to where this leads,

Joe

hi joe how big is the inverter? Next would be what is its standby by power consumption. Finally at what voltage does the low voltage alarm go off? A lot of cheap inverters have an alarm set to go off at a high voltage to avoid you not being able to start your car. My solution would be to find a small inverter say 75 to 150 watts to run the lights. Much more efficient and cheap... see if that works. Next would be is the trickle charger doing its job, finally, possible battery problems...
Cheers,  David

David,

This thread is getting long fast, but Joe did post a link to the inverter a while back.  You can find it HERE:

https://www.amazon.com/Power-TechOn-Inverter-Outlets-PS1002/dp/B0131L8NLM?pd_rd_w=FHYv3&pf_rd_p=a92e0124-cfa8-4f1e-82b5-a4a348d97008&pf_rd_r=YYNBWAFFFJBJ5M6TFG04&pd_rd_r=0dab872e-2bd4-417c-a899-3b7ca40b8895&pd_rd_wg=XEDJL&pd_rd_i=B0131L8NLM&ref_=pd_bap_d_rp_35_t

It is a 1000 Watt inverter if that helps.

Eric

I speculate that the battery isn't getting fully charged in the first place... A trickle charger doesn't put out enough energy to charge a 100 Amp hour battery in any reasonable time frame, maybe not at all. They are designed essentially to counteract the slow leakage of charge due to the internal chemistry of the battery, they are not much use for charging a depleted battery.  If the trickle charger is putting out 1 Amp (a typical rating), it would take 100 hours to charge a 100 Amp-hour battery. That's 4 days and 4 hours!!!

I expect a fully charged lead/acid battery to have a voltage closer to 14.4 volts. A typically recommended charging rate for a 100 Amp-hour battery is 30 Amps. Which will charge it in about 3.5 hours if fully depleted.

Joseph,

I agree that a trickle charger puts out a puny amount of electricity, but I am pretty sure it puts out enough volts to charge the battery adequately.  It has minimal amperage.  He did state that he started with a charge of 12.5 volts and it quit at 11.5 volts.  I would think that either of these figures would be plenty high enough for continued work, especially if powering something like a rope light.  This leads me to believe that the battery itself is not at fault.  Do you disagree--I am just curious how/why and what your thinking is.  Now if the voltage was lost quickly--and a 100 ah battery losing a volt of charge in a short time would be a rapid loss--might trigger a thermal protection overload, depending on how sensitive that setting was.  I could also believe that if there was a setting for the inverter to quit at a high voltage (like 11.5), then this also might be the culprit.  I do find it troubling that this "test" was performed using defective lights while numerous other items apparently worked just fine.  This is what leads me to think the issue is in the rope light somewhere.

But like you I am trying to diagnose this remotely and I could be wrong.  I am just wondering how we all get to our various conclusions.

Eric

I agree with Joesph.  My new batteries top off on the 14v range... maybe 14.5.  As I commented earlier, I suspect there are several issues.

Well I suppose we have designed an interesting pair of tests for him.  1)  Test the battery itself by charging/running a bunch of items directly from the battery.  2)  Replace that rope light with almost anything and see if we can get a better run time and a more significant voltage drop-off.  One way or another we should be able to rule out the battery being bad or the rope-light being the culprit.  I guess that would leave the inverter.  I wonder if there are any adjustable settings on the inverter that may be causing this issue.

At any rate, I think this thread has really boiled down the possibilities for Joe and at this point I am really curious to see what works out for him.

Eric

As previously mentioned, you need a far more powerful charger – one that can take the full generator output, and a battery that can take it as well.
Otherwise you are wasting fuel.

So … 1200W from the generator. 3C charge rate, so 3 · 1200W = 3600Wh. At 12V that is 3600Wh / 12V = 300Ah.
12V DC tape lights are readily available. (As are other 12V lights). Using an inverter wastes efficiency (and idle power).

What I use on my little battery box is a little charge controller.  The nice part about the charge controller is that it can take electricity from a variety of voltages and charge the battery quickly until it is full at which point it becomes a trickle charger and basically keeps the battery topped off.  If memory serves, the little charge controller I had was about $30 and was good from about 5-30 volts.  

I would bet that this is one item on Joe's list as his setup did not sound like a comprehensive setup--more like a preliminary set of equipment to eventually mounted and connected properly.  I think this is still in an experimental stage which is all well-and-good as he can find problems and root out the issues before the pieces are mounted.  And it is good he is doing this as he has already run into one issue and hopefully this can be solved relatively easily and certainly without any disassembly.

Eric

hit the nail on the head about the rope lights, though - although they are nearly brand new, there is about a 4' section that does not light.... oddly enough, there is about 6' of lights beyond these dark bulbs that do light, so juice is getting to them somehow.... could it still possibly be a "short" where they're dark?

Start by replacing these. They are defective. They're probably wired in a series/parallel configuration & only one section is bad.

Changing to DC lights will save a lot of conversion losses. In my mind running LEDs from an AC source is wasteful simply because LED's operate on DC. So called AC LED strings must be converted to DC first to for them to function. In a light string like that it's probably nothing more than a single diode, also known as a half wave rectifier. That wastes more than 50% of input power before it ever reaches the lights.

The data sheet for that inverter shows it's 90% efficient. So you're losing (at least) 10% there. I have a similar inverter & it has circuitry to cut off when voltage gets low to prevent completely draining the battery.

Joseph,

I fully agree that if Joe were charging a completely dead (or anywhere near dead) battery, a typical trickle charger would be woefully inadequate.  I have a car battery charger in my garage and it has a trickle setting rated to 2 amps.  If Joe only had to charge his 100 Ah battery from 11.5-12.5 (I am going to assume that the charger gives out 15 volts--I am just making that number up, but it has to be higher than 12.5) then at 2 amps I am guessing that this is about a 3ish hour charge.  It could be done on his little generator, but you are correct that this is far from the most efficient way to do so.  That would be a far cry from the 4+ day wait time for charging a dead 12v 100 ah battery though.  I would certainly hope that Joe is not running all the way through an entire 100 ah deep cycle battery with the small items he has run though.

I am not trying to pick nits though.  Joe stated that he has charged other items with his setup and he has charged up his battery before using his generator-trickle-charger setup so I believe that he has in fact used some of the charge of the 100 ah battery and then recharged it with his generator.  This brings me back to why he is having his battery run "out" after 45 minutes when he is running his rope lights.  The thought I had (not necessarily correct though) is that faulty rope lights were somehow causing some type of overload protection--either voltage or thermal, I don't know.  Another possibility is that his inverter is excessively sensitive to very small changes in the battery output (this is assuming that his battery is running at rated capacity).  If the second possibility is the culprit then either he has a bad inverter, or there is a setting that needs adjusting (can inverters be adjusted?  I don't know.).

Either way, Joe has stated that he has measured the charge of his batteries at being within 1/2 volt of 12 volts.  I know that a 12 volt battery can be charged to over 12 volts, but I don't think this should be taken to indicate a faulty battery.  I think more likely his problem either lies within the inverter or the problematic rope light.

Actually I think this thread has been a pretty good trouble-shooting tool and we seem to have taken a very vague set of symptoms and narrowed them down to 2 likely causes.  Either his inverter is excessively sensitive or his rope lights are creating an excessive power draw.  At this point I could see either as being equally likely.  But more importantly, through these exchanges we have narrowed down a set of simple tests he can easily perform to find the offending culprit.  There may yet be other possibilities that none of us have thought of yet so I will not close the door on those possibilities, but we at least have two probabilities that Joe can run with.

Eric

Mike, I agree that the faulty rope lights are a poor way to measure pretty much anything.  There could be a simple line break or there could be a minor short.  Either way, they are faulty.  Also, I agree that the DC to AC to DC LED's are a lot of conversion waste when one could simply run straight from direct DC.

I am still designing my inverter setup, but one feature that I intend to work in will be direct 12v power expressly for these type of situations.  

Thanks for chiming in,

Eric

If the low-voltage cut-off of the inverter kicked in, the most straight forward explanation is that the battery is fully discharged.  I don't have any reason to doubt the functionality of the inverter, or the rope lights. The simplest explanation is that the battery didn't get fully charged, and was mostly depleted before the inverter and lights were connected.

The test that I recommend, is to fully charge the battery with a 30 Amp charger for a minimum of 3.5 hours, or a 10 Amp charger for at least 10 hours. (Or with the trickle charger on grid current for 5 days). Then see how long the LED light string will operate.

Can't take energy out of a battery that was never put into it to start with.

Joe,

I have done a bit of research and Joseph may be correct about the battery being discharged.  From what I have read, a 12v battery, despite the term, actually charges upwards of 13+ volts in its fully charged state, but you already basically knew this when you saw that your battery was charged past 12v.  Ironically though, an SLA battery has a dangerously low discharge at around 11 volts and can become damaged if discharged much below that amount.  So with that in mind, an 11.5v cutoff, while sounding almost full is actually just short of dangerously low.

I agree with others here that you probably want to get a more powerful charger to make charging both more efficient and more practical.  Even better would be something like a charge controller.  I mentioned this in an earlier post on this thread, but I have a solar charge controller on my battery box that cost about $30 and accepts a range of voltage inputs from around 5-30 volts.  This makes it ideal for a variety of charge sources, but my personal favorite is a little 28 watt solar panel, but I am getting ahead of myself here.  Important to this conversation is that the charge controller acts as a fast charger when the battery is low and acts like a trickle charger when the battery just needs to be topped off.  I think you will like the results.

You have a promising start to your project.  Where do you plan on taking it?  How will you mount all of this?  What other equipment will you add, etc.?  I love these little projects and I have ambitions to expand mine into something a bit bigger.

Good luck and please let us know what you think/how things work out.

Eric