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 > LED light and 12v Voltage? UPDATE-OOPS!/Got Kohrees too.

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Gdetrailer

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Posted: 11/13/20 08:51am Link  |  Quote  |  Print  |  Notify Moderator

If it is turned off, should not be an issue while charging, however one would have to remember to make sure every one of these lights are turned off before turning on the charger.

You do have several options that may be better..

1 add a current limiting resistor, will drop brightness slightly, would need to do some work to determine the resistor wattage and resistance.

Ideally you would need to insert a ammeter capable of reading 2A or less to get the current draw at battery resting voltage. Then you calculate the voltage drop across the resistor needed (charge voltage - battery resisting voltage).

Divide current draw at resting voltage by the voltage drop the result is the resistance needed.

Example, 13.8V battery, 14.7V charge = .9V drop needed.

LEDs at 13.8V draw 100 ma (.1A)

Gives you resistance of .9 ohms (not common resistance in small wattage resistors would have to sub in 1 ohm)

power dissipated by resistor is .09W so a 1/4W-1/2W would be fine (common wattages)

Look up Ohms Law and Watts law..

2 add one or two diodes in series, each diode will drop .6V to .7V reducing the voltage and current to the LEDs. Doesn't require much work and should get the fixture to a safe voltage/current.

BurbMan

Islip, Long Island

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Posted: 11/13/20 09:57am Link  |  Quote  |  Print  |  Notify Moderator

14.7 is very high voltage...most converter/chargers like my PD run at 13.6 and even in boost mode are only 14.1. Maybe unplug from shore power so you have battery voltage back in the 12.6 range and see if the lights work. If not, I would say you friend them!


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BFL13

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Posted: 11/13/20 10:21am Link  |  Quote  |  Print  |  Notify Moderator

BurbMan wrote:

14.7 is very high voltage...most converter/chargers like my PD run at 13.6 and even in boost mode are only 14.1. Maybe unplug from shore power so you have battery voltage back in the 12.6 range and see if the lights work. If not, I would say you friend them!


PDs are supposed to do 14.4, but newer ones meant for Li batts do 14.6.

If you are only seeing 14.1 from yours at the battery (as opposed to at the converter, you have a wiring issue.

14.7 is not "very high", since that is a common voltage specification for many batteries to be recharged at. So RV LEDs should be able to take that.

Many Rvers have switched to LED and are happy, so either they got the good ones or maybe never used a higher voltage that would fry them.

Thanks to all for the good info. Learning the hard way is my usual method! [emoticon]


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MrWizard

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Posted: 11/13/20 01:48pm Link  |  Quote  |  Print  |  Notify Moderator

I think you have AC ripple in your converter DC output, any voltage regulation chip will not be happy with that

I installed Kohree ? RV led fixtures 2yrs ago
They get hit with charging voltage everyday
Sometimes 15v, still have the OEM led lamp boards,

* This post was edited 11/13/20 02:02pm by MrWizard *


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BFL13

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Posted: 11/13/20 01:56pm Link  |  Quote  |  Print  |  Notify Moderator

Mr Wiz, I was using a 55 amp version of the 75 amp you have/had. Is there a way to check for/measure AC ripple?

ISTR Mex asked about ripple with these converters and got me to check something, forget what, and he said that meant there wasn't much or any ripple--not sure! I will look in the archive, but not much hope.

No luck with archive. Does converter ripple come from itself or from the 120v input?

* This post was edited 11/13/20 02:09pm by BFL13 *

RJsfishin

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Posted: 11/13/20 02:13pm Link  |  Quote  |  Print  |  Notify Moderator

Never a problem w/ leds @ 14.6 PD converter, but all my leds came from Napa


Rich

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pianotuna

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Posted: 11/13/20 02:25pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13,

From the poor filtering on the converter for ripple.


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My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

BFL13

Victoria, BC

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Posted: 11/13/20 02:30pm Link  |  Quote  |  Print  |  Notify Moderator

The ads say these have "exceptionally clean AC to DC power", so how can there be any ripple? [emoticon]

and one of the specs is " < 1% load regulation" if that has anything to do with ripple.

Just claims "filtered" so no need for a battery. If it were just ripple and not the 14.7, then it would be safe to leave the solar on when that LED is on--not much need there anyway in daylight.

ktmrfs

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Posted: 11/13/20 03:02pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

If it is turned off, should not be an issue while charging, however one would have to remember to make sure every one of these lights are turned off before turning on the charger.

You do have several options that may be better..

1 add a current limiting resistor, will drop brightness slightly, would need to do some work to determine the resistor wattage and resistance.

Ideally you would need to insert a ammeter capable of reading 2A or less to get the current draw at battery resting voltage. Then you calculate the voltage drop across the resistor needed (charge voltage - battery resisting voltage).

Divide current draw at resting voltage by the voltage drop the result is the resistance needed.

Example, 13.8V battery, 14.7V charge = .9V drop needed.

LEDs at 13.8V draw 100 ma (.1A)

Gives you resistance of .9 ohms (not common resistance in small wattage resistors would have to sub in 1 ohm)

power dissipated by resistor is .09W so a 1/4W-1/2W would be fine (common wattages)

Look up Ohms Law and Watts law..

2 add one or two diodes in series, each diode will drop .6V to .7V reducing the voltage and current to the LEDs. Doesn't require much work and should get the fixture to a safe voltage/current.


while this may solve the 14.7V problem, the LED's will likely be quite dim when the battery or charger goes to 13V, or even dimmer as the battery discharges to 12.4 or so.

And LED's for decent life over a variable input voltage range need to be driven by a constant current source to fix the brightness. Not any form of voltage source. LED junction voltage drops as temp rises, and if driven by a voltage source that results in a current increase, more junction voltage drop, more current..... then poof.

The best LED drivers actually use a pulsed current, LED's brightness is a non linear function of current, so higher current = much more brightness. so pulse the current and keep the RMS current to a good value= bright light, long life. Need to pulse the current fast enough not to cause visual flicker. but with the IC's available today not a problem.

all this doesn't come for free, that's why there are cheap LED lights and more expensive ones. You get what you pay for.


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MrWizard

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Posted: 11/13/20 03:10pm Link  |  Quote  |  Print  |  Notify Moderator

Some multi meters have Hertz setting for measuring Frequency, you can try using that ! If it reads 30 or 60 you half wave or full wave ripple,

the A.c. Voltage range doesn't go low enough to measure AC voltage ripple on a 13>14v D.C. Line

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