reduce 48v to 12v

[tjamesbo]

My son built an childrens electric car which runs off a 48V system however when he wired it up he had 48v going through the ignition switch, needless to say it didnt last long before arcing / melting destroyed it, so i said it needs stepping down to 12V for the ignition switch and that couild then be used to energise a relay which will do the 48V switching ?? having only a limited knowledge of electrics does this sound a reasonable soluition to the problem ? how do I step it down ? simple resistor or what ? and is the relay the correct solution ? electronics gurus please advise

 

[SpikyMikey]

DC-DC converter?
https://uk.farnell.com/xp-power/dte6048s12/dc-dc-converter-12v-5a/dp/2643376

 

[Benzowner]

It may not be the voltage, more likely the current and just stepping the voltage down may not solve the problem.

 

[Flyinspanner]

Could he use a household isolator switch - cheap and good for 100A and up to 400v

 

[Ted]

I think you are overcomplicating things.
If the switch is failing it is either because it is not up to the job/faulty or because excessive current is flowing through it.
I would determine which of these and correct it.
It could also be switching an inductive current that ‘sparks’ as the current collapses, but that is a whole different ball game and you would need to look at the circuit design.

 

[pmcgsmurf]

Current draw will be killing the switch.

Use the switch to turn on/off a Sold State Relay and use this to connect the motor.

 

[johnsco]

48 volts is not high-voltage.
It would not, in itself, lead to arcing / melting.
Switching high-current with an inductive load is a likely cause.
Unless you can determine what is causing the arcing / melting, dropping the volts to 12 volts using the dc to dc converter may only result in destroying the converter as well.
Think of an ignition coil ...... 12 volts in ....... the contact breaker opens switching off the current to the coil ..... and thousands of volts appears at the HT lead.
Don't test this with your finger !!

 

[BigJase88]

Current draw will be killing the switch.

Use the switch to turn on/off a Sold State Relay and use this to connect the motor.

This

 

[Meldrew2]

It's CURRENT that burns out switches from arcing, and stepping down the voltage will increase the current.

A better - and simpler solution - is to use a heftier switch.

After all, light switches rarely burn out, and they carry 230 volts.

 

[Deleted member 126251]

This

^^ That.
However it wouldn’t do any harm to install a small step down converter to the switch which then energises the solenoid. DC makes big sparks so @48V may still damage the switch contacts.

 

[Wearsthefoxhat]

Heavy duty relay.. Farrell do ones with a 48v dc coil and with contacts rated at upto 30A.. have the ignition switch energise the coil and run the high current through the relay contacts.. a latching relay so made , ( on )when the key is on and open, (off) when the key is turned off..

 

[geoffus]

Is all the power going through the ignition switch ?
How are you limiting the motor speed or is it on full power all the time ?
Sounds to me you need a 48 volt speed controller, but it may depend on the current draw of the motor.

36/48V 350W Brushless DC Motor Speed-Controller For Electric Scooter E-Bike J7X7 | eBay

Power: 350W. Phase angle: 60°/120° universal. Speed limit and current limit function, anti-flying function, complete power failure function, over temperature protections function, self check function, anti-theft function.

www.ebay.co.uk

 

[AntMB]

48 volts is not high-voltage.
It would not, in itself, lead to arcing / melting.
Switching high-current with an inductive load is a likely cause.

It's likely to be a DC load.