I have a remote controlled relay, but the amp ratings are too low I think. What would be the simplest option to remotely control a 24V, 30A load? It likely has a higher spiking amperage (it is a 24V DC motor).
24V 40A, 50A and even 100A automotive relays are common. I just Googled "24V 50A relay" and got heaps of results here in Australia, like this one, ( https://www.autobarn.com.au/narva-relay-24v-4pin-50a-blister-pack-1-el03111 ), so there would be similar results in your region. Try Googling the same search term.
Is this 30A the rated current or the stall current? If its the rated current then the stall current will
be 100's of amps and you'll need a proper contactor rated for DC, which won't be cheap. Physically
switching inductive DC at high current isn't easy as you've several kW available to sustain a fireball
(big spark). At least its low voltage - the automotive relay is probably the way to go, but expect the
contacts to wear quite rapidly (or even weld shut!). Never open then immediately close the relay,
give it a second or two to cool first to be on the safe side.
There are tricks you can play like having two relays in parallel, one with a low value resistor in series.
You switch this on first (we are talking about 1 ohm or so), allow the motor to start turning with limited
current and then switch the main relay (which won't see such high stall currents). Switching off is
the reverse, and should reduce arcing significantly. This also reduces the mechanical shock to the motor
and peak currents from the battery.
The resistor should have a generous power rating, and you shouldn't leave it heating up for
more than a second or two anyway - it could dissipate upto 600W peak.
What about a starter relay? That should work I would think
How do they work though? The small wire gets 12v and the body of the part is ground?
David82:
I have a remote controlled relay, but the amp ratings are too low I think. What would be the simplest option to remotely control a 24V, 30A load? It likely has a higher spiking amperage (it is a 24V DC motor).
First ...
You need a relay that is actually rated for DC Amps.
Is the relay in your picture rated for "AC Amps only" ?
Can you measure the Amps Inrush with a "Peak Hold" Voltmeter?
The starting amps might be near the stall amps.
Also, there will be a huge inductive kickback voltage from large coil type relays.
Consider using a Solid Sate Relay or paralleled mosfets.
I was going to just get two, common 12v starter relays. One for each battery. They are engaged when the thin wire receives 12v so I would just use the RC relay shown in the picture to send 12v to the two 12v starter relays at the same time. Should be very straightforward... (famous last words)
David82:
I was going to just get two, common 12v starter relays. One for each battery. They are engaged when the thin wire receives 12v so I would just use the RC relay shown in the picture to send 12v to the two 12v starter relays at the same time. Should be very straightforward... (famous last words)
Some Starter Relays are not rated for Continuous Duty
Make sure your Starter Relays are rated for your Duty Cycle.
Oh, sorry, here