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Author Topic: 200A on-off switch  (Read 1977 times)
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MAXPAYNE
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« on: July 05, 2014, 09:15:24 09:15 »

I will use the rocker switch to connect/disconnect the battery...

I will design the switch circuit. Any idea what will be the best option ?
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« Reply #1 on: July 05, 2014, 09:29:38 09:29 »

Not sure exactly what the question is, but I would use a 36V or 48V golf cart solenoid to do the switching, most are rated at least 400A if not higher and they are easy to source and easy to interface to pretty much any control circuit...
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« Reply #2 on: July 05, 2014, 09:49:12 09:49 »

Not sure exactly what the question is, but I would use a 36V or 48V golf cart solenoid to do the switching, most are rated at least 400A if not higher and they are easy to source and easy to interface to pretty much any control circuit...

Well, problem is supply voltage is 33.6V Li-Po battery. but solenoid voltage is 36V. Sad

anyway do you have the link of 36V solenoid ?
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solutions
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« Reply #3 on: July 05, 2014, 10:01:39 10:01 »

What is that "ESC" thing?

Why aren't you keeping it from turning on (MUCH smaller switch)?
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« Reply #4 on: July 05, 2014, 10:11:35 10:11 »

What is that "ESC" thing?

I think ESC= Electronic Speed Control

Max why you dont use automotive relay with high capability current like
http://www.digikey.com/product-detail/en/G9EC-1-B%20DC24/Z1619-ND/585489
or few MOS-FET's in parallel as low side switches?
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« Reply #5 on: July 05, 2014, 10:31:33 10:31 »

Well, problem is supply voltage is 33.6V Li-Po battery. but solenoid voltage is 36V. Sad

anyway do you have the link of 36V solenoid ?

The voltage difference is nominal in this instance at least for a 36V version, a 36V solenoid should operate just fine at 33.6V...  48V versions might not operate properly with a 33.6V coil voltage but you never know, some are wound to work down to 12V or 24V on the coil, so check the datasheets...  As for a link just Google '36V golf cart solenoid' or 'golf cart solenoid' plenty of hits and options to choose from...

Quote
Max why you dont use automotive relay with high capability current like
http://www.digikey.com/product-detail/en/G9EC-1-B%20DC24/Z1619-ND/585489

Generally significantly cheaper to just get a common solenoid like I suggest vs a relay like that...
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MAXPAYNE
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« Reply #6 on: July 05, 2014, 11:02:28 11:02 »

What is that "ESC" thing?

Why aren't you keeping it from turning on (MUCH smaller switch)?

ESC stands for Electronic Speed Control as XOR mentioned.

I cant use much smaller switch here as there will be continuous current of 150A through the (ESC+motor)

I think ESC= Electronic Speed Control

Max why you dont use automotive relay with high capability current like
http://www.digikey.com/product-detail/en/G9EC-1-B%20DC24/Z1619-ND/585489
or few MOS-FET's in parallel as low side switches?

I think contactor/relay will be the best option here. problem is the coil voltage will have to be around 33.6V. I found only 28V or 36V contactor.

Can you give me a sample ckt of MOSFET parallel switch ?

Posted on: July 05, 2014, 03:33:50 pm - Automerged

The voltage difference is nominal in this instance at least for a 36V version, a 36V solenoid should operate just fine at 33.6V...  48V versions might not operate properly with a 33.6V coil voltage but you never know, some are wound to work down to 12V or 24V on the coil, so check the datasheets...  As for a link just Google '36V golf cart solenoid' or 'golf cart solenoid' plenty of hits and options to choose from...

Generally significantly cheaper to just get a common solenoid like I suggest vs a relay like that...

I found one-
http://www.ddmotorsystems.com/sol200spec.pdf

The spec says, "Operating voltage in cold state at (20 ± 5)°C (VDC) Pickup --- 24V". Does it mean coil will energize and close the ckt at 24V ?
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« Reply #7 on: July 05, 2014, 01:14:25 13:14 »

http://www.autoelectricalpartsuk.co.uk/products/Switches_/Battery_Isolators/Durite_Marine_Battery_Isolator,_Fixed_Knob__060511.html?gclid=CjkKEQjwxN6dBRDavZLpufuu9L8BEiQA4Vx1b6Qt6aOvgdFqbZhDt2sSC0U1-9QSIN9-gpETLKBBfH3w_wcB

these are a lot cheaper then coils, if you go with coil/relay type isolator, then have a look at 12v automobile battery isolator (note: not starter coil, as these are not to be energized for long periods) these have a 12volt coil at 5ma, use a resistor to match your supply.
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« Reply #8 on: July 05, 2014, 03:09:01 15:09 »

I digging on my old documents and I found this....maybe this can help you to figure out how can solve this problem
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« Reply #9 on: July 05, 2014, 05:07:58 17:07 »

Most ESC is high power mosfet in full bridge configuration, if all the mosfet is turned off then no current goes to the motor - and if the controller of the ESC work in low power mode then the current used can be almost neglilible.

So what i am thinking of is how about making your own low standby power ESC? Just an idea.

If the switch can not be avoided then as i remember Infineon has some high power (hundred amps) High Side Switcher.

-ichan

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MAXPAYNE
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« Reply #10 on: July 05, 2014, 05:14:46 17:14 »

Most ESC is high power mosfet in full bridge configuration, if all the mosfet is turned off then no current goes to the motor - and if the controller of the ESC work in low power mode then the current used can be almost neglilible.

So what i am thinking of is how about making your own low standby power ESC? Just an idea.

If the switch can not be avoided then as i remember Infineon has some high power (hundred amps) High Side Switcher.

-ichan



yap. thats a good idea. but I prefer using a direct current breaking method. Smiley
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« Reply #11 on: July 06, 2014, 12:04:19 00:04 »

Ichan did a good job providing more detail about what I was saying.

So you "prefer using a direct current breaking method" - clearly it's not your money because we are talking about less than $5 in what we proposed versus the sticker shock you will get by using a solenoid. Clearly, just as it took a few posts to tell us that it was 150 amps,you are not telling us everything. Vehicles require a mechanical disconnect, but that was not framed in the problem either. Big secret.

"I will design the switch circuit" - you're not designing anything, just bolting in an expensive,unreliable, solution that will lose a fair bit of power in the switch contacts at those currents.

Yes...do the math: contact resistance times 22,500.

Anyway, spend the money and proceed with bolting in the 100 year old tech "circuit design". And don't get too surprised when you are dissipating a couple dozen watts from the switch contacts.

You should also thank people that were helpful and who took their time to respond to help you out, not just vote up your favorites by pushing the button.

I still love you, if you are worried about what I wrote here  Kiss

 Grin
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MAXPAYNE
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« Reply #12 on: July 06, 2014, 06:35:47 06:35 »

Ichan did a good job providing more detail about what I was saying.

So you "prefer using a direct current breaking method" - clearly it's not your money because we are talking about less than $5 in what we proposed versus the sticker shock you will get by using a solenoid. Clearly, just as it took a few posts to tell us that it was 150 amps,you are not telling us everything. Vehicles require a mechanical disconnect, but that was not framed in the problem either. Big secret.

"I will design the switch circuit" - you're not designing anything, just bolting in an expensive,unreliable, solution that will lose a fair bit of power in the switch contacts at those currents.

Yes...do the math: contact resistance times 22,500.

Anyway, spend the money and proceed with bolting in the 100 year old tech "circuit design". And don't get too surprised when you are dissipating a couple dozen watts from the switch contacts.

You should also thank people that were helpful and who took their time to respond to help you out, not just vote up your favorites by pushing the button.

I still love you, if you are worried about what I wrote here  Kiss

 Grin


Ichan provided details, I should have really thanked him. however solutions, I didn't get from your post, what you tried to mean.

I have already told in my first post that about 200A will be flown. Please see closely the attached block diagram in my first post.

It is my cousin's electric skateboard and he just wants a simple solution to disconnect the battery using the rocker switch. So its clearly not my money. Tongue

I didn't know about the golf cart solenoid, thats why I mentioned "I will design the switch circuit", as I have to deisgn MOSFET based switch then.

I always thank people who helps me. But if you say I have to thank all the people for each of their post who replied to my thread, I am afraid I can't.

No offence solutions, just it was my view. Kiss

 Grin
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« Reply #13 on: July 06, 2014, 10:07:27 10:07 »

Use this: http://www.harborfreight.com/battery-disconnect-switch-97853.html

I use them on my cars when they are parked for a few weeks. Harder to steal as well.
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MAXPAYNE
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« Reply #14 on: July 06, 2014, 10:31:40 10:31 »

Use this: http://www.harborfreight.com/battery-disconnect-switch-97853.html

I use them on my cars when they are parked for a few weeks. Harder to steal as well.

I prefer using this one, http://www.ddmotorsystems.com/sol200spec.pdf

But, I need to be clarified about this parameter, "Operating voltage in cold state at (20 ± 5)°C (VDC) Pickup --- 24V".

Does it mean coil will energize and close the ckt at 24V ?
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« Reply #15 on: July 06, 2014, 11:42:34 11:42 »

I prefer using this one, http://www.ddmotorsystems.com/sol200spec.pdf

But, I need to be clarified about this parameter, "Operating voltage in cold state at (20 ± 5)°C (VDC) Pickup --- 24V".

Does it mean coil will energize and close the ckt at 24V ?
I could help you on this but want a thank you first Tongue
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« Reply #16 on: July 06, 2014, 12:05:52 12:05 »

ok . done .. Tongue
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« Reply #17 on: July 06, 2014, 02:30:40 14:30 »

here you go,but you need to do the reading Tongue
 http://www.allaboutcircuits.com/vol_4/chpt_5/1.html
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« Reply #18 on: July 06, 2014, 09:43:23 21:43 »

I would prefer to use P-Channel mosfet, in parallel if needed - as simple as pulling up the gate to Vin and then connecting it the ground to turn it on.

There are mosfet specially designed to act as load switch with many protection features, BTS555 from Infineon for example.

-ichan
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« Reply #19 on: July 06, 2014, 10:31:43 22:31 »

I wondered about the 200A figure. A 200A is quite a lot of current!!  When Maxpayne mentioned skateboard, I even got more confused.
I googled electric skateboards and I found that the power rates of the skateboard are ranging from 150W to 800W. Some websites are selling skateboard kits with fuses rated at 30A!! Check here:
http://fiikelectricskateboards.com.au/spares/kits/electric-skateboard-kit-250w-spares
The 200A SW is overkilling and consider that you must use wireless remote controlled, so it will not be a clean power cut after all.
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« Reply #20 on: July 07, 2014, 12:23:23 00:23 »

+1 I would use mosfet rather than mechanical switching.
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« Reply #21 on: July 07, 2014, 04:32:31 04:32 »

Dear Parmin,
I don’t think that the solenoid is an option, sounds useless in such application.  The skateboard use a gun shaped remote control that has only 2 possible movement, throttle and break, the natural position should mean no motor drive (motor terminal open circuit). I consider that the throttle will be a PWM MOSFET with over-current limiter/protection "in case it gets blocked by an obstacle” and the break is a way to short the DC Motor leads. An H-bridge will do just fine satisfying such 3 states.
 
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« Reply #22 on: July 07, 2014, 10:17:38 10:17 »

I wondered about the 200A figure. A 200A is quite a lot of current!!  When Maxpayne mentioned skateboard, I even got more confused.


You seem to have a problem with a 6.5HP motor on a skateboard.

Let the kids kill themselves - more young ladies for us old guys...
 Tongue
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« Reply #23 on: July 08, 2014, 12:24:24 00:24 »

Faros, frankly I do not give a hoot to whatever the OP is going to use the switch for.
The vote for mosfet is that for a high current switching they have less problem than mechanical solutions.
Specially for a motor connection when ON signal is close to a short circuit.
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« Reply #24 on: July 08, 2014, 02:39:06 02:39 »

+1 I would use mosfet rather than mechanical switching.


+1 for high current mosfet also
+1 for 6.5 HP suicide skateboard.
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