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Post by esox07 on Mar 31, 2018 11:32:22 GMT -5
I was installing a battery voltage meter/usb port panel in my trailer yesterday. I patched into the outside amber light for power. After doing some testing, I forgot to disconnect the battery before patching into the wiring. Well, when I tried the voltmeter, it didn't work. So, I turned on the lights in the trailer and some wouldn't come on, but others would come on but at a very low level. They have all been converted over to LED. I couldn't figure it out. My first thought was that I popped a fuse, since some of the lights came on partially, I figured it was getting "some" power, so that wouldn't be it. But, after a minuted, I figured I should check anyway. Sure enough, one of the fuses was popped. I replaced it and now everything works great.
My question is, why did the lights come on partially when the fuse was popped? They were obviously getting some power, just not enough to fully power them.
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Post by lynnmor on Mar 31, 2018 16:00:11 GMT -5
The bulbs that were dim were providing a path to ground.
What I don’t understand is that you connected to an amber light, I suppose you mean a porch light, not a clearance light. A clearance light would only have power when lights are turned on in the connected tow vehicle.
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Post by esox07 on Mar 31, 2018 16:04:25 GMT -5
Yah, that amber colored porch light, not the running or driving lights.
But how could the "dim" bulbs get power to light up if the fuse was blown on their circuit. That would mean no 12V+ going to the lights. I don't see how just a connection to ground could provide any power to the lights.
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Post by lynnmor on Mar 31, 2018 18:25:17 GMT -5
If the working circuit has a less than perfect ground, some current can travel thru the dim bulbs to the ground on that circuit. It only takes a small amount current to light an LED. You would do well to track down and improve any ground connections you can find.
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Post by esox07 on Mar 31, 2018 19:03:57 GMT -5
I am not trying to challenge you lynnmor, but how can current travel through a bulb to the ground if there NO CURRENT going to the bulb? The fuse was blown. It was the same after I pulled the fuse as well. So there is no way there should be any 12V+ current going TO the bulb.
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Post by Edd505 on Mar 31, 2018 22:06:33 GMT -5
Not sure how your getting power but many LED's are polarity sensitive. I assume you spliced into the amber, did you revers the polarity?
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Post by nvguy on Apr 1, 2018 0:24:19 GMT -5
Lynnmor is right on target. What was probably happening is the resistance in the negative circuit to the battery is higher than the resistance to go "backward" thru the LEDs and then thru what ever else is on that same circuit maybe the voltmeter you installed or maybe thru the fuse block itself, as some have circuitry that has small LEDs to indicate if a fuse has blown.
Good question Edd505, LEDs are polarity sensitive, but maybe the LEDs used here have a current regulator that isn't polarity sensitive (just a guess).
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Post by esox07 on Apr 1, 2018 8:25:20 GMT -5
NO, I did not change the polarity on any LED lights. I just spliced into the LED light circuit. The fuse block does have a little red LED that shows the fuse was blown. So, that is what is allowing the slight bit of current to feed through that circuit and light up the LED lights??? I guess I can understand that.
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Post by lynnmor on Apr 1, 2018 8:52:41 GMT -5
Lynnmor is right on target. What was probably happening is the resistance in the negative circuit to the battery is higher than the resistance to go "backward" thru the LEDs and then thru what ever else is on that same circuit maybe the voltmeter you installed or maybe thru the fuse block itself, as some have circuitry that has small LEDs to indicate if a fuse has blown. Good question Edd505, LEDs are polarity sensitive, but maybe the LEDs used here have a current regulator that isn't polarity sensitive (just a guess). Thank you, you saved me some typing. I was going to draw an illustration or explain how that might happen. I mentioned checking grounds so he might find that less than ideal connection. LED lamps might be plain with no circuitry to correct polarity, or they might have a rectifier that does the correction, or they may have circuitry that corrects polarity and voltage. The first must be installed with polarity correct, the second can be installed either way, and the last should have a longer life but may cause TV interference. I use the second type.
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Post by esox07 on Apr 1, 2018 11:52:48 GMT -5
OK, thanks for the great information guys. Enjoy your Easter Sunday.
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Post by esox07 on Apr 1, 2018 14:06:52 GMT -5
Oh, I got it all fixed and the voltmeter installed:
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Post by lynnmor on Apr 1, 2018 20:35:53 GMT -5
Nice addition. Print out a state of charge chart so that you can quickly determine how much charge is left in the battery. For example, that 12.2 volts you show equates to 60%. Here is a good website with a chart and a lot of information for an RVer. link
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Post by esox07 on Apr 1, 2018 20:50:20 GMT -5
Hmmmmm, I didn't realize that 12.2v was only 60% charged. I will have to put the battery maintainer back on it. Thanks.
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Post by lynnmor on Apr 2, 2018 9:15:36 GMT -5
Hmmmmm, I didn't realize that 12.2v was only 60% charged. I will have to put the battery maintainer back on it. Thanks. A "maintainer" might not have enough power to get the battery anywhere near fully charged. If you can plug in the trailer, the onboard converter/charger will do a much better job. Leave a maintainer on for at least five days, or the trailer plugged in for two days. After you believe that the battery is fully charged, disconnect power and run some 12 volt loads in the trailer for maybe 15 minutes to dispense of any surface charge and then check voltage again and you should be over 12.5 volts. Always disconnect the battery, by removing the negative cable or use a disconnect switch, soon after disconnecting from external power. Devices in the trailer will discharge the battery in a few days. A battery should NEVER be discharged below 40% and ideally never below 50%. As you can see, the 12.2 volts is near the limit of discharge. Keeping a battery at full charge, as much as possible, will prolong its life. Do read all the information in the website I linked earlier.
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Post by esox07 on Apr 2, 2018 10:05:23 GMT -5
Yep, I have a battery isolator switch right at the battery. I did read that web site you posted. Good stuff there.
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Post by Edd505 on Apr 3, 2018 20:38:28 GMT -5
So what was the issue with the dim LED's
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Post by esox07 on Apr 3, 2018 20:41:41 GMT -5
You should ask one of the electrically inclined members who know more than me, but evidently it is a backfeed issue due to the fuse being blown and the little blown fuse indicator LED by the fuse being on.
Here is a quote: "Lynnmor is right on target. What was probably happening is the resistance in the negative circuit to the battery is higher than the resistance to go "backward" thru the LEDs and then thru what ever else is on that same circuit maybe the voltmeter you installed or maybe thru the fuse block itself, as some have circuitry that has small LEDs to indicate if a fuse has blown."
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