Hooking up lights directly to EUC battery WITHOUT stepdown converter

[JeremyB]

I'm pretty sure this will work, I just want to do a sanity check before I test it... 

Using 12-24v LEDs that are meant to be ran off a car/boat battery - I could run 5 of them in series which should accept 60-120v, therefore I could run them directly off my 100v EUC battery. Right? 

Or, if I used ebike lights that accept 10-60v, I could just run 2 of them in series directly off the battery. 

 

Thoughts? Why wouldn't this work? 

[RagingGrandpa]

It depends.

If you're talking about the diodes alone, without other components involved, then yes, put enough of them in series that their forward voltages add up to the supply voltage.

But I think those car lights are not 'just diodes' - there's a little power supply circuit inside them. Stringing 5 power supplies in series causes uncoordinated oscillation of the input voltage that each sees, and may cause them to fail, either suddenly or slowly over time.

In any case, watch out for possible failures you could cause if the new connections become shorted. If you short-circuit the main battery outputs of the EUC, you will cause a crash.
Fuses help, but they should be rated for >100V DC (no automotive fuses!). Low-current fast-blow 250VAC fuses are good.
If you could use the EUC charging circuit to supply the lights (not the main battery outputs), even better- shorts there usually don't cause EUC shut-off.