Lithium battery output

[jonfromhamilton]

Hi guys
This is a battery question but not vehicle.
I've got a 9v alkaline and a 9v lithium ion battery here and they're attached to an led chip.
The output on the lithium would be about two and a half times to the alkaline but they both measure the same voltage across the points.
Can anyone tell me why the lithium battery has a higher output? The led chip is heating up a lot with the lithium one and so so much brighter.
I figure the voltage is dictated by the battery and the amp draw is dictated by the led chip but not sure why it's happening

[gwagensteve]

Are you measuring the voltage across the battery which make the LED is on? (i.e the battery is under load)

[jonfromhamilton]

Just across negative to positive in the battery alone

[stevesierra]

Jon

you need to measure the current not the voltage , voltage is constant however current will vary with a resistive load

typical alkaline battery will have 700ma however lithium can be up to double 1200Ma ..1.2 amps

[jonfromhamilton]

I put a normal click on torch on the lithium battery and it has an inbuilt switch and not as bright it's not heating up at all so it's gotta be the draw on the bigger led chip.
I wonder if it's supposed to work with a heatsink and I'm just wiring it on like a n00b

[jonfromhamilton]

Chanzon High Power Led Chip 10W Orange (900mA / DC 9V-11V / 10 Watt) Super Bright Intensity SMD COB Light Emitter Components Diode

That's the Amazon description although putting it on a normal alkaline battery it doesn't overheat

[Matthew]

Lithium will be providing a higher current which produces more lumens which also produces more heat. A lot of leds need a current limiting driver to prevent them from drawing excessive amps and burning out. Using a heat sink is also a good idea to increase longevity as most leds don’t like heat.

[gwagensteve]

OK, with more information it all makes sense.

An alkaline 9V battery (I assume you mean an MN1604 - smoke alarm style battery) won't be able to deliver 10W. They're for low power devices.

A lithium battery will easily deliver 10W, which is why the LED is both brighter and hotter.

Volts at rest has nothing to do with it. Volts under load will tell the story - the lithium will stay at 9V, the alkaline will be collapsing to 7 volts or so as it can't flow enough amps. That's why you can't start your car with a 12V torch battery but you can with a car battery - both are 12V, but the torch battery can't flow enough amps to do the job. It's a measure of internal resistance of the battery.

Crudely, Watts = Volts X amps.

[jonfromhamilton]

I had assumed the standard alkaline battery was the benchmark but it's the other way around if the lithium is true 9v.
It is a 10w led so I think I need to realise it's meant to run with a heat sink or something

[gwagensteve]

I don’t understand what that means. Any battery is only nominally it’s rated voltage. A 12v lead acid battery is 12.7v at full charge and 12v with no load is basically pretty flat. Alkaline batteries are nominally closer to their rated voltage but it’s neither here or there. The current the battery can deliver is what’s important and an alkaline battery can’t deliver 10 Watts. (Which is 1.1A at 9v) the lithium battery can, easily.

Comparing different types of battery at rest as a measure of performance is meaningless and confusing.