Why are my LEDs so dim?

[HappyHippyDad]

It's a long shot, but have you checked the voltage at the lamps? If the Tx is some distance away, and the supply cable is thin, then it could be below the minimum voltage at the lamps.

Most LED's can work at pretty low voltages. Possible, but I think it may be more of an ultra long shot ?

 

[Lucien Nunes]

We need to know what the 'transformer' is. An electronic 'transformer' designed for halogen lamps is not simply a transformer, they are often high-frequency AC output and only suitable for halogens. The fact that it is rated at 20-60W 11.6V makes me think it is of this type. 11.6V is used to slightly under-run the halogens to make them last longer. I would therefore not expect this unit to work with LEDs, and it might damage them.

The LEDs sound like they have active electronics within if they are capable of operating on a wide range of voltages. Nonetheless they would then be described as 'constant-voltage' and hence would require a constant-voltage DC power supply unit or constant-voltage LED driver within their specified voltage range. The LEDs do not seem to be constant-current otherwise the current would be stated.

 

[marconi]

I suspect your MR16 10-30V led lamps are direct current only and will require a suitable power supply driver to produce it:

MR16 LED Bulbs 12/24v - litecone.co.uk - https://www.litecone.co.uk/mr16-led-bulbs-12v-24v.html

and:

24v LED Drivers - litecone.co.uk - https://www.litecone.co.uk/24v-led-drivers.html

The lamps contain a bridge rectifier circuit so that the pins are not polarity sensitive ie: it does not matter which way around you plug the two pins into the lamp holder.

Your current ex-halogen lamp transformer does not provide the correct constant voltage waveform even though the lamp's internal bridge rectifier converts the transformer's alternating output to a uni-directional voltage waveform - it is not constant. For reasons I will not go into now the lamp's internal voltage regulator (so it can operate over 10-30V range) only works when the input is constant as from a battery.

A trial if you fancy: Connect a halogen and then one of your LED lamps across your car's battery- I expect them to be of the same brightness. Be careful not to short the wires!!! Please tell us what you find.