A relay that works with both 12 and 24 volts?

[pollenface]

I've upgraded my sons ride-on electric car to run on an 18v makita drill battery.

other mods include
2x 12v 8000rpm gearmotors in series to halve battery voltage to each wheel (works like a differential)
20a pwm reversible motor speed controller
rubber tyres

A freshly charged 18v drill battery is about 21.5v. My issue is I can only find either 12v -OR- 24v relays. It currently has a 24v relay which is fine until the battery falls to about 50% hence the reason I'm looking for a relay which can work around 18-20v.

Alternatively I could use a small step-up converter to maintain 22'ish volts at the relay.

 

[NVS]

You could install a constant voltage/constant current step up converter. Just need one big enough to handle the current draw.

AITIAO 2PCS 600W Constant Current Boost Converter DC-DC 10V-60V to 12-60V Output Step-up Transformer Module CC CV Voltage Regulator Large Power Driver 10A Adjustable Booster Power Converter https://smile.amazon.com/dp/B09L4RKDSS/ref=cm_sw_r_apan_i_8ARJ7N9WCNVAB8SE5JVA