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xallero
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# Posted: 19 Dec 2021 12:48pm
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Hey Cabiners—
I've had one 12V 125aH SLA battery sitting around for a while and thought I'd use to power a couple light bulbs in my woodshed.
Two lights (12V bulbs in a standard 120V fixture) wired in series to a standard household switch and the battery. Pretty simple! Pretty infuriating...
I used 18 gauge wire and nothing worked.
I used 14 gauge wire and still nothing.
Am I doing something wrong? I feel like I've tried everything imaginable!
I wired the negative from the (-) battery terminal to the first light, and then to the second. Then to the switch. From the switch I wired the (+) positive wire to the standard toggle switch, then to the lights, and back to the battery's negative terminal.
I threw an inline fuse in there between the (+) battery terminal and the switch, I think it was. Still nothing.
What the HELL?! I'm a damn noob.
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darz5150
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# Posted: 19 Dec 2021 01:28pm
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Quoting: xallero I wired the negative from the (-) battery terminal to the first light, and then to the second. Then to the switch. From the switch I wired the (+) positive wire to the standard toggle switch, then to the lights, and back to the battery's negative terminal.
This might be the problem. The switch only disconnects/interrupts the power.
Try running the negative to the lights from the battery. Then hook the + wire from the battery to the switch. Then out of the switch to the lights.
You might want to check your fuse also.
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gcrank1
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# Posted: 19 Dec 2021 02:21pm - Edited by: gcrank1
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Think of powering anything dc first as just the two wires going to the device. The pos+ is typically the 'center-post' if the device, in your case the fixtures, same on cig-lighter sockets. It is good to follow 'convention'.
You hook each up to + and - to the battery and it works, disconnect one and it doesnt; you are the switch.
Now, if you wire a switch into either wire it becomes the switch that you were.
An aside, What kind of bulbs and wattage are they?
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Nobadays
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# Posted: 19 Dec 2021 03:05pm
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Quoting: xallero and back to the battery's negative terminal.
It shouldn't go back to the negative term... dead short. Check your fuse, as was said.
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razmichael
Member
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# Posted: 19 Dec 2021 04:00pm
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As per darz5151 plus, remember that led lights must be wired the right way - they contain electronics that will not work is you flip the -+ around
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ICC
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# Posted: 19 Dec 2021 04:15pm
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Quoting: xallero Two lights (12V bulbs in a standard 120V fixture) wired in series to a standard household switch and the battery.
As a self-professed "noob" what do you mean by "wired in series" in the above quote?
Series to me, when talking DC power, means the negative of one DC light is connected to the positive of the other light. Much the same as connecting two 6 volt batteries in series to obtain 12 volts. IF, that is what was done then the two 12 volt lights, in series, need 24 volts to operate.
If that is NOT what you meant then none of that would apply.
If the negative from the battery connects to the negative of the first light and then continues to the negative of the second light you would have a parallel connection. Just to get the terminology correct for those of us who believe in correctly naming stuff.
One of the most handy tools when working with electricity is a good multimeter.
So, Check that the switch actually works.
Check that either light actually works... screw the 12 volt lamp into a socket and touch the wires to the battery terminals. What happens. Reverse the wires in case it is a polarity problem as was mentioned. I personally have no idea if polarity matters with a 12 volt bulb that threads into a std household socket. DC led's do need correct polarity to operate but it is also possible to build DC devices that detect and switch internally for polarity.
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Brettny
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# Posted: 19 Dec 2021 04:16pm
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Essentially you wired up those lights as if there 6v. By running 2 of them in series you made the voltage drop by half. LEDs prob wont handle that. You may have even destroyed them.
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gcrank1
Member
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# Posted: 19 Dec 2021 05:12pm - Edited by: gcrank1
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Fwiw, there are (I have some) 12vdc leds that are not polarity sensitive.
Have also had old rv Edison type incandescent bulbs, a simple resistance wire filament, they dont care about polarity but do they suck the amps; ie, a 50watt bulb uses 4+ amps per hour, even a 25w is half of that. For comparison a 9w led is supposed to equal about a 60w 'regular' bulb and uses less than 1amp.
Conclusion: Use LED's
Thing is that old type bulbs are commonly thought of as 'watts' and led's are measured and sold by 'lumens' (which is a much better measurement of how they illuminate). So look for info on the packaging of something about, say, '60w equivelent'.
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ICC
Member
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# Posted: 19 Dec 2021 05:18pm - Edited by: ICC
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You want it wired something like the picture... Lamp polarity is not noted as most likely those edison base bulbs are self correcting for polarity. BUT the convention would be to connect the + wire to the center contact of the edison base and the negative wire to the screw shell.
BTW, a std household switch may burn out prematurely when used on DC current, though led's daw so little current that will be minimized.
IF the led lights were wired in DC series as I described there is no danger to damaging them. LED's are damaged by too high a voltage, or too high a current flowing through them. Too low a voltage as would happen with the led's in series will only cause them to not operate.
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old greybeard
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# Posted: 19 Dec 2021 05:52pm
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As noted it sounds like you wired in series, not parallel.
Causing a voltage drop by half. I've been going from 12 v cfl to leds and the ones I bought are ac or dc, 11-30v. Don't think polarity matters on the ones I bought. At least not that I ran into as all lit with my previous wiring. But I wired my DC 20 years ago and probably had + to all the center posts.
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Peewee86
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# Posted: 20 Dec 2021 08:37am
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Another observation: Your first sentence “ I've had one 12V 125aH SLA battery sitting around for a while…â€
How long is “a while� Lead acid batteries will self discharge at a rate of 3-5% per month. What is the state of charge of the battery?
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gcrank1
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# Posted: 20 Dec 2021 06:36pm - Edited by: gcrank1
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Fwiw, that 125ah sla will maybe have been that when new. If it is the typical,consumer grade 'marine deep cycle' is only one step up from a car battery.
After some use and a year or two it will only be 80% of that, so maybe 100ah.
If its life has taken it deeper than 50% soc (state of charge) repeatedly that bat may only be 60% of what new was, so maybe 75ah.
Remember, a lead acid battery really only has 1/2 of its ah's 'usable', when new at 125ah that was 62ish, go deeper regularly and you murder the battery.
That base stays the same....so when you have an older battery at 80% you only have 38ish ah's to use, if its now a 60% bat you have 13ish ah's to use.
If your lights draw, say 2amps (thats per hour) you get 6 to 19 hours depending upon your battery health.
So when you get the lights on, and if the battery is fully charged, you only get 3hrs of good light before they fade to dim, you will know your battery is pretty well toast. Or not.
When it hits a max low of 12.2ish volts you need to recharge it fully.
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