Recommendations for a 48 vdc contactor.

[Mundo]

I am looking around for a 48 VDC contactor, space is a concern. Any tips?

[amberwolf]

At what current rating?

[Mundo]

Sorry for being vague.

I'd like to be able to use a keyed switch to turn off & on my Ping battery.
It's a 48 VDC 20 AH battery, with a higher rated BMS. My guess is, a contactor/relay rated at 30 or 40 amps, with 48 volt signal/coil wires.

I've done some searches and only come up with how something functions, no links. I know there are electro-magnetic, solid state and mercury switches. I am assuming electro-magnetic switches are most appropriate!?

Any help would be appreciated.

Thanks, Bob

[DrkAngel]

eBay search solenoid - golf carts

"solenoid 48V" search under all categories might find better match.
Check "Include description" for better selection.

[amberwolf]

It's a 48 VDC 20 AH battery, with a higher rated BMS. My guess is, a contactor/relay rated at 30 or 40 amps, with 48 volt signal/coil wires.

If you don't know the max currents (sustained, at least) that your system will draw, it's difficult to size your contactor correctly. You may not need one anywhere near as big as that, if your bike typically only draws 10A, for instance. Or if it draws 80A sustained all the time, you may need a much bigger one. Do you have a wattmeter or a multimeter with a high-current setting?


As DrkAngel posted, golf cart stuff will probably work.

You can also get keyswitches themselves that can handle the current, and skip the contactor entirely.

What I recommend, to keep wear to the contacts to a minimum, is adding a precharge circuit that you press a button or flip a switch, and it connects a precharge resistor across teh main contacts to first charge up the caps on your controller, before you turn the key. That way there isnt' any arcing across the cotnacts, which is what usually damages them. Without arcing, even a switch rated for less than the max peak currents you will draw may last for years.


You can also get a multi-position keyswitch, and use the first position for precharge. Turn key to that, wait a few seconds, then turn to "on", which either directly connects things or engages a contactor.


Magnetic coil types are easier to deal with, but the others could work for you too, if you can work out the mechanical activation for them.

[DrkAngel]

eBay search solenoid - golf carts

"solenoid 48V" search under all categories might find better match.
Check "Include description" for better selection.

The golf cart solenoids are designed for continuous operation, and are capable of 200-400amps. (can't hurt?)
As opposed to a starter solenoid, designed for intermittent and brief use.

Alternative -
2 NEW OMRON G8P-1A2T-F 48VDC 48V DC RELAY/CONTACTOR 30A - 2 for $9.99

[teklektik]

Alternative -
2 NEW OMRON G8P-1A2T-F 48VDC 48V DC RELAY/CONTACTOR 30A - 2 for $9.99

Not a good choice - DC rating is only 20A at 24v DC. Do not use the AC rating as an indication of DC capacity - very different.

[Mundo]

Okay,

Thanks for replying to my questions.
I ordered the solenoid pictured below.

Next, will be making a pre-charge resistor thingamajig.

There was a recent post about pre-charge resistors, but I haven't found it yet.
The biggest question, what size is the resistorThanks to everyone for your help.

Bob

[teklektik]

Pre-Charge Resistor Help.

330ohm at 2W-5W should be fine - what I use to precharge dual Xlyte 12 FET analog controllers. No need to go with huge resistors - the high current draw is transient (1-2 seconds) then essentially zero.

[alsmith]

Okay,

Thanks for replying to my questions.
I ordered the solenoid pictured below.

Next, will be making a pre-charge resistor thingamajig.

There was a recent post about pre-charge resistors, but I haven't found it yet.
The biggest question, what size is the resistorThanks to everyone for your help.

Bob

Who is your supplier for the solenoid?
thanks

[El Duderino]

Al,

I've been using this one:

http://www.thetoolboxshop.com/sw60b-8-a ... 7302-p.asp

local to us too (well... in the same country at least!)

Cheers,
C

[teklektik]

I've been using this one:
http://www.thetoolboxshop.com/sw60b-8-a ... 7302-p.asp

If you're going to use a contactor instead of directly switching the controller logic power, this one is pretty nice. Here's the datasheet:

[alsmith]

Al,

I've been using this one:

http://www.thetoolboxshop.com/sw60b-8-a ... 7302-p.asp

local to us too (well... in the same country at least!)

Cheers,
C

That's great, thanks! That never came up on my web searches, it's ideal, thanks. And free carriage too!

[Dauntless]

So if I'm using a motor that's 48v, 130 amp continuous, is a 200 amp contactor a comfortable overkill, or do I need to stay closer to the 130 amp?

Is it okay to go up to maybe 72v? (Just getting a stack of contactor questions answered in one post.)

[alsmith]

So if I'm using a motor that's 48v, 130 amp continuous, is a 200 amp contactor a comfortable overkill, or do I need to stay closer to the 130 amp?

Is it okay to go up to maybe 72v? (Just getting a stack of contactor questions answered in one post.)

It should be a 48V coil, other voltages may not work (in this case 48V might not be enough to reliably operate a 72V coil). The main switched contacts can be a higher voltage/amp rating.

[Mundo]

Here's the contactor I purchased...

http://www.ebay.com/itm/190662101880?it ... 60&vxp=mtr