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paulz
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# Posted: 27 Oct 2021 01:08pm - Edited by: paulz
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Is this one of those lithium cells you're always talking about? Is there a generic name?
Is it OK to leave one wired directly to a USB port indefinitely with no cutoff or is it too much voltage?
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Brettny
Member
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# Posted: 27 Oct 2021 01:28pm
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That's an 18650 battery. I believe USB is 5v..so it's under voltage.
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ICC
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# Posted: 27 Oct 2021 01:32pm - Edited by: ICC
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yes that is a lithium ion cell.
Not sure what you mean by "wired directly to a USB port indefinitely"
IF the cell is connected to a charger that it was intended for, then the charger circuitry will have a voltage it shuts off at and a lower voltage that it will start being charged again. Leaving that plugged in will be okay, but may shorten the cell's life by keeping it at near to 100% all the time.
Do not hard wire it up directly to the USB output voltage. You will ruin the cell and probably start a fire. Note that if one of these is burning they do emit toxic gases.
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ICC
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# Posted: 27 Oct 2021 01:38pm
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The ICR on the label indicates it is a LiCoO2 type, very common lithium ion cell. They have great energy density which is good but also a lower thermal runaway temperature than some other lithium types. (they can cause fires at a lower internal temperature)
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paulz
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# Posted: 27 Oct 2021 04:09pm - Edited by: paulz
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Here's what I'm up to:
I have a half dozen of these motion/light sensor solar powered LED lights, both inside and outside. Nice because if I walk into the shop for a tool for example, I can see to get it without turning on the inverter and shop lights. Also have them outside in the usual places, but since my sun is so limited I measured what the panel put out, 5v and change, so I have them connected to USB ports instead of using the solar panel.
Been working fine for a year or two but this one has crapped out. Got dimmer and dimmer then nothing, despite being connected to USB. So I opened it up this morning, battery only had 2.7 volts. I jumpered a USB cord direct to the battery as in the top photo for half an hour, lights up great now, just off the battery. Battery showing 3.4
Being that the solar panel put out 5v, there must be shutoff circuitry between the input jack and the battery (which I bypassed for this test) and perhaps it is no longer working, so the battery is not charging. I tried eliminating the battery and running straight off the USB, the light blinked off and on continuously, leading me to think this is a bad thing, and since it failed while still plugged in it is meant to run off the battery not the input voltage.
In any case, the battery is holding 3.4, so it's not that..
Thanks guys.
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ICC
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# Posted: 27 Oct 2021 04:46pm
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FYI, the li-ion cells should not be discharged less than 2.4 to 2.9 volts, depending on the type of chemistry used and perhaps upon how cautious the manufacturer is being.
Too low a voltage causes changes within the cell. These chemical changes can result in the cell exploding when placed on charge. The better chargers will not charge when the at rest voltage is in a dangerous area. It is hard to say how good the system built into those lights is.
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lburners
Member
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# Posted: 27 Oct 2021 06:15pm
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Jeesh Paulz how many projects do you have going?!
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paulz
Member
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# Posted: 27 Oct 2021 08:20pm
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Ha, well this wasn't a project until this morning. Maybe I'll try a resistor off the USB cable to knock it down some and try it direct without a battery, since it's plugged into the USB all the time anyway.
The project I wanted to get done this year was my tractor port but I got involved in clearing trees and brush for fire prevention and killed too much time. I have the area excavated but we got a boatload of rain out here finally so it's a mud puddle now. I did rough out the area (20x36) with stakes today.
Then a couple days ago my neighbor got a new UTV and said come over and take the old one. It's a Bush Hog 4x4, kind of obscure but I think it just needs some electrical work.
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Brettny
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# Posted: 28 Oct 2021 05:44am
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You can get new 18650 cells prety cheap. Most lithium tool batteries or even hand held vacuums have those cells too.
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