12v led's from battery

[JohnW2]

i run 9-12v 10w led chips direct no control but ...

Is there perhaps some talking at cross-purposes going on here .... Are you talking about LED chips (i.e. LED elements) or LED lamps/bulbs?

Kind Regards, John

 

[big-all]

Is there perhaps some talking at cross-purposes going on here .... Are you talking about LED chips (i.e. LED elements) or LED lamps/bulbs?

Kind Regards, John

yes was just trying to share my experiences on what i had found but more off an aside as a possibly connected point off interest

 

[JohnW2]

... we are talking about lamps you would buy in the local supermarket.

Indeed, assuming that one coould find 12V LED lamps/bulbs in such a place.

... So the big question is if the extra voltage from a battery will overload the device? A lead acid battery has a nominal voltage of 12, but it can be anywhere between 11 - 14.8 volt depending if on charge or not and what state of charge....

Indeed - but, as I said, if they are designed to work on AC, and given the very crude circuitry likely to be within a product one buys in the local supermarket, it's very likely that, when fed with 12V RMS (which is presumably what a true transformer would provide), it is very probable that the current-controlling part of the circuitry (as you say, very probably just a resistor) will be receiving a peak voltage approaching the peak of the supply, namely about 17V.

Kind Regards, John

 

[JohnW2]

yes was just trying to share my experiences on what i had found but more off an aside as a possibly connected point off interest

Fair enough, but to feed any bar LED element(s) from a voltage source without any explicit means of current limitation will usually be disastrous - unless the voltage source has a high internal resistance!

For example, if one connects a string of LED elements in series across, say, a charged car battery, one of two things will happen. If the number of LED elements is such that the sum of their forward voltages is greater than the battery voltage, then nothing will happen (no light and no damage). However, if the sum of those forward voltages is less than the battery voltage, then there will be a lot of light for a millisecond or three, after which you'll have a pile of dead LEDs (and maybe a puff of smoke!).

Kind Regards, John

 

[big-all]

Fair enough, but to feed any bar LED element(s) from a voltage source without any explicit means of current limitation will usually be disastrous - unless the voltage source has a high internal resistance!

For example, if one connects a string of LED elements in series across, say, a charged car battery, one of two things will happen. If the number of LED elements is such that the sum of their forward voltages is greater than the battery voltage, then nothing will happen (no light and no damage). However, if the sum of those forward voltages is less than the battery voltage, then there will be a lot of light for a millisecond or three, after which you'll have a pile of dead LEDs (and maybe a puff of smoke!).


Kind Regards, John

this is why i prefer to under rate them to work on the mid range or less as you get far less consumption and as such off around perhaps 15-20 set ups ranging from 2.5v to 36v over about 10 or so years i have had no failures but only because i have experimented with different heat sink sizes and checking say overvolt gradually in o.5v stages to work out perceived light levels to consumption levels to a point off destruction

 

[JohnW2]

this is why i prefer to under rate them to work on the mid range or less as you get far less consumption and as such off around perhaps 15-20 set ups ranging from 2.5v to 36v over about 10 or so years i have had no failures but only because i have experimented with different heat sink sizes and checking say overvolt gradually in o.5v stages to work out perceived light levels to consumption levels to a point off destruction

I have to say that sounds like a very iffy and hazardous way of doing things Have you really never killed an LED element doing that? (if not, what do you mean by "..to a point of destruction"?).

Without any explicit current control, you are totally reliant on the internal resistance of the source (and reliant on it not changing). What source are you using - presumably not batteries, if you are able to get 0.5V steps? Furthermore, if you're having to use large heat sinks, that is presumably an indication of poor efficiency (i.e. wastage of energy).

Kind Regards, John

 

[big-all]

more keeping components standard as in had several old bits off ally bar from bar clamps cut to 6" lengths as you can fix 4x3w up to 6x3w 1 or 2 10w or 2bars side to side for one off the newer 24 -32 segment leds [approx number]
the 0.5 increments would be fully using series parallel led/batteries and different combinations and specific batteries with different volt levels
no control equipment just a volt meter
i prefer things to run cool so overdo the heat sink to make sure to allow all eventualities

 

[JohnW2]

Good luck

Kind Regards, John

 

[algas]

I think I will just try them, they will work or they wont.

 

[bernardgreen]

they used to be at home and have a transformer in the fitting which I would do away with if powered by battery.

Probably been said already but if these lamps were 230 volt when used in the home then the " transformer " in the fitting is not just a voltage changer it is also a current controller.

If you connect 12 volts DC directly to LED elements ( chips ) without a current limiting device between battery and element then the elements will be destroyed.

That said there are LED elements which can be connected directly to a 3 volt battery apparently without any current control. The current control is a semi-conductor "resistor" built into the LED element, these are typically found in simple battery operated fairy lights.

 

[big-all]

the slower the charge rate tends to give you a lower top voltage
where as high boost charges tend to give you a hugher top voltage