Will I burn my garage down and the forest with it?

[Tom&Shelly]

We installed strobe lights to discourage rodents from living in our basement. We also have a garage without commercial power that has a rodent problem, and I'd like to try something similar. So I bought this thing off the interwebs, that has a battery in it, and includes a charger connected to a cigarette lighter style plug:



I believe the battery is two 18650 Li-ion cells. They measure about 18 mm diameter by 65 mm long. They are wired in parallel and the open circuit voltage is 3.94 v, while the output when the light is on (steady) is 3.88 v. (Straight out of the box, with no recharging.)

We keep our teardrop in that garage, and have a solar panel to maintain the battery. So, one thing I can do is to plug it into the cigarette lighter style outlet in the galley of our teardrop. In that case, the teardrop battery will keep it charged, while the solar panel and charge controller will keep the teardrop battery maintained.

But I'd also like to use this in the garage while we have the teardrop up in New York for the Summer. The charger claims it takes 12-32 volts input, so it is evidently a charge controller of sorts itself, and I should be able to connect it directly to the solar panel output. But, the claim by the manufacturer is that the cells have about a 6 hour life between charges, so I'd be deeply discharging it every night, and it might stay that way for hours, to days if we get cloudy weather.

So my question is: Is that a bad thing to do to lithium ion batteries? And how bad? If I left it for a Summer, would I have to replace the cells, or might I come back and find the thing started a fire? Or at least cooked the rest of the electronics?

Informed replies preferred, but hey, I realize beggars can't be choosers!

Seriously, thank you for any insight!

Tom

[swoody126]

i spread slices of Irish Spring(original formula) around my barn when the vermin begin appearing

sw

[Tom&Shelly]

i spread slices of Irish Spring(original formula) around my barn when the vermin begin appearing

sw

I have some that now are half eaten....

Tom ;-)

[twisted lines]

They love the coating on the wires too

[bdosborn]

But, the claim by the manufacturer is that the cells have about a 6 hour life between charges, so I'd be deeply discharging it every night, and it might stay that way for hours, to days if we get cloudy weather.

So my question is: Is that a bad thing to do to lithium ion batteries? And how bad? If I left it for a Summer, would I have to replace the cells, or might I come back and find the thing started a fire? Or at least cooked the rest of the electronics?

Li-ion batteries don't degrade when they sit discharged (unlike lead acid). So if the manufacturer did their homework and the unit shuts down properly when the battery is discharged it should be fine. I think Li-ion batteries have around 500 full charge/discharge cycles.
Bruce

[Tom&Shelly]

But, the claim by the manufacturer is that the cells have about a 6 hour life between charges, so I'd be deeply discharging it every night, and it might stay that way for hours, to days if we get cloudy weather.

So my question is: Is that a bad thing to do to lithium ion batteries? And how bad? If I left it for a Summer, would I have to replace the cells, or might I come back and find the thing started a fire? Or at least cooked the rest of the electronics?

Li-ion batteries don't degrade when they sit discharged (unlike lead acid). So if the manufacturer did their homework and the unit shuts down properly when the battery is discharged it should be fine. I think Li-ion batteries have around 500 full charge/discharge cycles.
Bruce

Thank you Bruce. I'm guessing they have the automatic shut off; but then that's what I guessed about my last cell phone and the battery ended up swelling up. I should probably try cycling the strobe a few dozen times before we leave and check to make sure the cells haven't swelled. I'll leave it in the middle of the concrete floor, so heat won't be too fatal.

We won't use if more than a year, without changing the cells. That should, I hope take care of the maximum number of charges issue.

Again, thank you!

Tom

[RJ Howell]

I've been running 18650's for years now, in the house, garage and in the camper. I have both 'safety top' and non, hasn't been issue with either. I do use same precaution of temperature during recharge. My understanding has always been that's where the main issues are.

What I saw traveling was mostly flicker style strobes lights. Is what you have a flicker or spinner? Also mostly white and I could see how they'd be annoying! Will be heading back to the southwest this winter and will do something of the same. Very interested how this works out for you.

[Tom&Shelly]

I've been running 18650's for years now, in the house, garage and in the camper. I have both 'safety top' and non, hasn't been issue with either. I do use same precaution of temperature during recharge. My understanding has always been that's where the main issues are.

What I saw traveling was mostly flicker style strobes lights. Is what you have a flicker or spinner? Also mostly white and I could see how they'd be annoying! Will be heading back to the southwest this winter and will do something of the same. Very interested how this works out for you.

Thank you! I think these cells do not have the built in protection since they are only 65 mm long, and I read on the interwebs that the protection takes another few mm. When I replace them, I might buy the ones with protection and figure out how to squeeze them in. I'm hoping the low cell charge cut-off electronics on the circuit card under the cells does what it should and is sufficient.

Anyway, these just flicker. The LEDs are yellow, as well as the globe. They go off for a second then on with flicker. Another mode has the LEDs constant on. The 3 bay garage is dark enough, I expect one with the flicker mode will be enough. One potential problem is that there is a push button switch to change modes, and it might default to "off" when the battery discharges. I'll experiment and report.

We actually got the idea of strobes from some "Rid-a-rat" flashing LEDs that run on AA cells that we have in the engine compartments in our vehicles. They seem to have stopped some serious problems we had with rodent damage and nest building there. If necessary I could buy a few more for the garage, but those are pretty dim, and I think it might take quite a few to cover the garage.

Tom

[Tom&Shelly]

CAUTION--This is a description of my mod of the flashing light described above. It includes some technical detail and may not appeal to the average tear drop builder.

So that push button, "off/on steady/on flash" had me defeated....for awhile. Problem is, when the battery is disconnected, or--I presume--totally discharged, the system goes back to the "off" mode, and, without someone there to push the button, when the sun comes up and recharges the battery, it stays off. This light is really well designed, but by wanting it to come up flashing, to deter rodents, I'm not intending to use it as the designers intended.

In desperation, I took it apart, and soldered a wire across the switch. After that, when I plug the battery in, the light comes on steady. Okay, I have a nifty Li-ion battery with charger, and, I believe, safety circuit. (It seems like there might be a thermal sensor taped to one cell.) Actually, that's probably worth about half of the $25 I paid for the light, right there. I also have a really nice array of amber LED's.

Okay, I'm a man of the 80's (and can even remember when that phrase was in vogue!), and my circuit engineering knowledge mostly dates to that period. So why not try making a new flasher circuit out of a 555 timer? That worked, but rather than the 160 mA the array used to draw, now it's only a few mA, with a corresponding loss of brightness. The good news is that the total current drawn from the battery is correspondingly lower, and so the battery should last longer! But it's way too dim to use in the garage to deter mice. (I suspect. I won't actually claim to know what is going on in a mouse brain. Unless it is a mouse who learned circuit theory in the 1980's.)

Looking through my junk box for a solution, I found a bag of IC chips that Mom gave me after Dad passed. Dad had written on there that they were some sort of CMOS buffer (CD4503B). I tried one and indeed the array took more current. "Aha", I said, suppose I gang them? Tested it with three chips (6 buffers/chip), and got it up to about 40 mA. I have 12 chips, and enough wire wrap IC sockets that I could gang them all. Again, the current draw on the battery is basically what the LEDs are fed, so I suspect it's going to work okay. Also, the buffers have a tri-state mode, so I can control the current, and therefore the brightness and battery life, by switching as many in as desired.



Seems like it might work! And it even clears out some junk I've held onto for 40 years!

Tom

[bdosborn]

Seems like it might work! And it even clears out some junk I've held onto for 40 years!

Nice!
Every time I think I should throw all that crap in the garage out I use something that's been there for years.
Bruce

[Tom&Shelly]

Seems like it might work! And it even clears out some junk I've held onto for 40 years!

Nice!
Every time I think I should throw all that crap in the garage out I use something that's been there for years.
Bruce

Thank you Bruce. I'm lucky enough to have an understanding wife! (And Shelly reminded me of that when I read her your post!)

I pondered whether I really want to wire up about a dozen buffer chips, and decided I'd try a power transistor, also in my junk box. Found a circuit in a "timer cookbook", also from the 1970's, which I never threw away ("what if the internet fails, and all we have are the electronics from the 70's/80's, and the reference books from then?"). It was for a 2N3055, which I didn't have, but an NPN transistor in the TO-3 case that I did have worked fine.

Now, I get full current through the LEDs when lit. I tweeked the 555 circuit so it flashes about once every 5 seconds or so. After charging the battery, I'll run it to see if it lasts a day or two. If so, I think it'll be a winner, and I'll figure out how to package it neatly.

I hope the mice, rats, squirrels, and chipmunks hate it enough to keep from making nests of our paper towels and sleeping bags!

Tom

PS--Chipmunks are cute; but not enough to nest in my garage!

Tom

[Tom&Shelly]

So, the modified circuit ran for a day and a half, and I suspect it would run for a week or more without recharging, since the flash is so short. I tried to match the timing on the "Rid-a-rat" devices we keep in our car. Of course, this is much brighter since we're hoping it covers our garage. I just used a 555 IC timer from my junk; I could have bought a newer power saving version, but there seems to be no need.

Decided it was ready to package. Been saving a Christmas cookie tin for just this sort of thing



Plenty of room, someday, to move the batteries "downstairs" when the original set wears out. I'll probably add some battery holders so I won't have to solder in the new ones.

Took it down to the garage, and it immediately began charging, and flashing. The switch only cuts out the batteries, not the current coming from the solar panel. The cigarette lighter style plug charger does indeed take the raw solar panel output and controls it to 12 volts. I'm now running it in parallel with the charge controller built into the teardrop



I'll go down and check it for the next few days, but I think it's a winner!

Tom

[bdosborn]

Let us know if it keeps the mice away and maybe we'll try one at our cabin.
Bruce

[Tom&Shelly]

Let us know if it keeps the mice away and maybe we'll try one at our cabin.
Bruce

I'll do that, but of course absence of evidence isn't necessarily evidence of no rodents! They also seem to be seasonal, so it may take a year to prove it one way or the other. All I can say for sure is that since we put the Rid-a-rats in our engine compartments, we haven't had any nests or chewed wires. We've also been using mint or potpourri scents. Between them, we've had fewer troubles.

Tom

[Tom&Shelly]

In case any one is interested in my specific design (there are many ways to accomplish this, of course) here's a link to the strobe from Amazon

https://www.amazon.com/Wireless-Security-Emergency-Flashing-Warning/dp/B08112GNBS?ref_=ast_sto_dp&th=1

and here is the diagram for the modified circuit



The 1N914 diodes, btw, make the on and off times independent of each other. Actual times depend on the voltage across the chip, so I experimented with the capacitor and resistor values until I found what I wanted.

There is a little red LED on the control circuit card that seems to flash while charging, and glows steady while the charger is on and the battery is charged. After recharging initially, during the day, it now blinks for a moment after each "strobe" and then glows, so the batteries seem to stay fully charged. Not sure, but that might lower the battery life.

Tom