Electrical question please

I need a little help please
I have a Lister A and to make it work at shows rather than just have a pump I also connect it to an alternator or a generator (have both) charging a 12v battery and run a lighting set which has about 130w of lights, 2 x 60W headlights and a few side lights.

I have a JAP 2S gen set which on the plate says it produces 24/30V at 21amps. Testing it with a multi meter shows a pretty much constant 30v. What I would like to do is drop the voltage to 12v and run the lighting set. I have seen this on Amazon, would it do what I want it to do.  

https://www.amazon.co.uk/Converter-Adapter-Voltage-Regulator-DC15-40V/dp/B01KQWWSLA/ref=sr_1_3?crid=C92K7KGWC6DB&dchild=1&keywords=24v+to+12v+dropper&qid=1588523394&s=electronics&sprefix=24v+to+12v+dropper%2Celectronics%2C170&sr=1-3

If it will not any other suggestions please

Looks like it will do the job, probably designed for commercial vehicles with 24 volt systems to run the more common 12 volt stuff.

Just make sure it has adequate air cooling for the heatsink fins.

Wire the bulbs in series, or a series/parallel mix.

StuartTurnerSteve wrote:Wire the bulbs in series, or a series/parallel mix.

What he said.

Under no load the voltage will be up from normal running.  Wiring two 12 volt bulbs in series will be roughly equivalent to a 24 volt bulb.  Check the wattage of the twelve volt bulbs. Watts = Volts X Amps.
For example, an 18 watt / 12 Volt bulb will draw 1.5 amps.

Please correct my 'O' level physics if I got it wrong Steve.

Yep, I'd wire 2 parallel circuits in series, so you are splitting your 24V into 2 12Vs in the series circuit. Then a number of bulbs in parallel to draw up to 20amps. Or how every much you want to load it. I'd probably just run 24V bulbs, they aren't too hard to get hold of, 8 of them would load it up well.

Thanks Gents, I must admit I had not thought about wiring in series because the light unit is wired up in parallel for 12v running. I like the idea of running series lights and a quick look on eBay shows sets of 4 LED spots with an input voltage of 9-30 and an output of 48W for about £14.00. I could make another light unit just for the JAP, I am thinking of 2 sets of 2 lights wired in series and then the 2 pairs in parallel will give 96 watts which, if my maths is right, will be 8 amps. Can anyone see an issue with that please?