Relay for up to 100V DC?

Talk about anything and everything here within reason.
Post Reply
rg12   100 kW

100 kW
Posts: 1255
Joined: Jul 26 2014 4:22pm

Relay for up to 100V DC?

Post by rg12 » Jan 11 2020 4:43pm

I have this load tester with 5 units of 5ohm 1500w resistors.
I connect and disconnect manually to change current draw and want to connect all 5 to 5 relays and have 5 switches to increase the current with.
I'm using it with batteries up to 100V (24S).
So I have about 15A in average and 20A max at 100V for each resistor of 5ohm.
There are plenty of cheap relay boards on eBay like this one:
https://www.ebay.com/itm/250V-30A-4-Cha ... SwZ2BbpVPO
That go up to 30A but they are all rated 250V while if you look at the relay itself it says 250VAC/30VDC
Do you think I will fry it at 100V from a battery?

billvon   1 GW

1 GW
Posts: 3051
Joined: Sep 16 2007 9:53pm
Location: san diego

Re: Relay for up to 100V DC?

Post by billvon » Jan 11 2020 5:17pm

rg12 wrote:
Jan 11 2020 4:43pm
That go up to 30A but they are all rated 250V while if you look at the relay itself it says 250VAC/30VDC
Do you think I will fry it at 100V from a battery?
Yes. It will arc if you try to switch it under load.
--bill von

rg12   100 kW

100 kW
Posts: 1255
Joined: Jul 26 2014 4:22pm

Re: Relay for up to 100V DC?

Post by rg12 » Jan 11 2020 5:55pm

billvon wrote:
Jan 11 2020 5:17pm
rg12 wrote:
Jan 11 2020 4:43pm
That go up to 30A but they are all rated 250V while if you look at the relay itself it says 250VAC/30VDC
Do you think I will fry it at 100V from a battery?
Yes. It will arc if you try to switch it under load.
Damn...
Any solution from eBay without going to digikey and ordering a single relay that will come without a pcb?

billvon   1 GW

1 GW
Posts: 3051
Joined: Sep 16 2007 9:53pm
Location: san diego

Re: Relay for up to 100V DC?

Post by billvon » Jan 11 2020 6:06pm

rg12 wrote:
Jan 11 2020 5:55pm
Damn...
Any solution from eBay without going to digikey and ordering a single relay that will come without a pcb?
If they are resistive loads, just use MOSFETs. They are cheap and easy to use. You can get a 120V, 60A MOSFET for about $1.50. You can drive them with TTL signals (0-5V)

If you really want an assembled thing, use a DC SSR. They are a LOT more expensive ($50 or so) but they can be connected with no other parts. A 200V 40A DC SSR is about $50 and comes with screw terminals.
--bill von

rg12   100 kW

100 kW
Posts: 1255
Joined: Jul 26 2014 4:22pm

Re: Relay for up to 100V DC?

Post by rg12 » Jan 11 2020 6:15pm

billvon wrote:
Jan 11 2020 6:06pm
rg12 wrote:
Jan 11 2020 5:55pm
Damn...
Any solution from eBay without going to digikey and ordering a single relay that will come without a pcb?
If they are resistive loads, just use MOSFETs. They are cheap and easy to use. You can get a 120V, 60A MOSFET for about $1.50. You can drive them with TTL signals (0-5V)

If you really want an assembled thing, use a DC SSR. They are a LOT more expensive ($50 or so) but they can be connected with no other parts. A 200V 40A DC SSR is about $50 and comes with screw terminals.
Found this for $7.5 shipped :D
https://www.ebay.com/itm/DD220D40-Ssr-4 ... Q&LH_BIN=1
It's rated for 40A and 220VDC which I doubt chinese ratings but I will run it at about 15-18A 70-100VDC
About less than half it's ratings...
Do you think I will need a heat sink for it?

Bikegirl   1 W

1 W
Posts: 52
Joined: Apr 02 2019 5:30am

Re: Relay for up to 100V DC?

Post by Bikegirl » Jan 11 2020 9:18pm

I used a zeva contactor and precharger for a 72v system, works well with a cheap ass reducer giving 12v for the start system, and rated dc circuit breakers.

https://www.zeva.com.au › ...
Smart Precharger - Zero Emission Vehicles Australia

https://www.zeva.com.au › ...
Gigavac P195 Minitactor - Zero Emission Vehicles Australia

AU $20.59 | Step down Transformer Electric DC Converter Adapter 48V 72V 96V TO 12V 10A USB 5V
https://a.aliexpress.com/NsYpON0G

Sent from my SM-G950F using Tapatalk


markz   100 GW

100 GW
Posts: 9363
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Relay for up to 100V DC?

Post by markz » Jan 11 2020 11:09pm

Buying from Fleabay, I'd want 200Vdc and 40A for the sellers specifications, as they would be over exaggerated.

rg12   100 kW

100 kW
Posts: 1255
Joined: Jul 26 2014 4:22pm

Re: Relay for up to 100V DC?

Post by rg12 » Jan 12 2020 4:31am

markz wrote:
Jan 11 2020 11:09pm
Buying from Fleabay, I'd want 200Vdc and 40A for the sellers specifications, as they would be over exaggerated.
That's exactly what I posted, 220VDC, 40A and I'm using less than half.

john61ct   100 GW

100 GW
Posts: 5000
Joined: Dec 18 2018 2:06pm

Re: Relay for up to 100V DC?

Post by john61ct » Jan 12 2020 5:41am

eBay sells robust contactors from Gigavac, Kilovac, Tyco, Schneider, ABB, Crydom, Crouzet

not just the poorly spec'd Chinese SS stuff

rg12   100 kW

100 kW
Posts: 1255
Joined: Jul 26 2014 4:22pm

Re: Relay for up to 100V DC?

Post by rg12 » Jan 13 2020 5:07am

john61ct wrote:
Jan 12 2020 5:41am
eBay sells robust contactors from Gigavac, Kilovac, Tyco, Schneider, ABB, Crydom, Crouzet

not just the poorly spec'd Chinese SS stuff
These brands are expensive especially when I need 5pcs.
I rather buy a chinese one and use half it's specs for $7 than buy 5pcs $70 brand contactors

john61ct   100 GW

100 GW
Posts: 5000
Joined: Dec 18 2018 2:06pm

Re: Relay for up to 100V DC?

Post by john61ct » Jan 13 2020 7:53am

Sure, not reco'ing for you specifically, just pointing out eBay is good for higher quality as well.

I've been collecting top notch DC contactors 200A many 500A, for an average of about $15 each.

One dud out of a dozen so far, and eBay refunded me in under 48hrs even though the seller tried to state "as is".

markz   100 GW

100 GW
Posts: 9363
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Relay for up to 100V DC?

Post by markz » Jan 14 2020 12:10am

john61ct wrote:
Jan 13 2020 7:53am
Sure, not reco'ing for you specifically, just pointing out eBay is good for higher quality as well.

I've been collecting top notch DC contactors 200A many 500A, for an average of about $15 each.

One dud out of a dozen so far, and eBay refunded me in under 48hrs even though the seller tried to state "as is".
That is a good run for dud ratio.

The AS-IS gotta laugh at that, I guess they are trying to take a jab at the buyers who are new(er) to ebay and dont know the rules precisely.

User avatar
danielrlee   10 kW

10 kW
Posts: 502
Joined: Mar 29 2013 8:30am
Location: Wiltshire, UK
Contact:

Re: Relay for up to 100V DC?

Post by danielrlee » Jan 14 2020 2:28am

markz wrote:
john61ct wrote:
Jan 13 2020 7:53am
Sure, not reco'ing for you specifically, just pointing out eBay is good for higher quality as well.

I've been collecting top notch DC contactors 200A many 500A, for an average of about $15 each.

One dud out of a dozen so far, and eBay refunded me in under 48hrs even though the seller tried to state "as is".
That is a good run for dud ratio.

The AS-IS gotta laugh at that, I guess they are trying to take a jab at the buyers who are new(er) to ebay and dont know the rules precisely.
On eBay, "as is" is a fair declaration if the condition is specified as 'faulty or suitable for spares'. 'New' or 'used' condition means that the item must be "fully functional".

EBay policy states that buyers are not covered by the 'money back guarantee' for 'not as described' cases where the item condition is specified as 'faulty or suitable for spares'. In practice though, eBay often ignores its own policy on such matters.
https://TorqueTech.co.uk : Electric bike spares, parts & accessories : 10% discount code ’ENDLESS10

john61ct   100 GW

100 GW
Posts: 5000
Joined: Dec 18 2018 2:06pm

Re: Relay for up to 100V DC?

Post by john61ct » Jan 14 2020 6:23am

Yes those three options for condition is what rules for not as described.

Only "Not Working Parts Only" status removes warranty protection.

Writing As Is or No Returns is just a bluff if posted as Used.

But be careful about Local Pickup, that can hurt warranty claim, some say must be shipped by the seller

markz   100 GW

100 GW
Posts: 9363
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Relay for up to 100V DC?

Post by markz » Jan 14 2020 4:40pm

Thats why I see some sellers always put down "For Repairs" so they got a bigger lee-way on the sellers part.
Overall ebay is on the buyers side if everything is truthful and honest.

john61ct   100 GW

100 GW
Posts: 5000
Joined: Dec 18 2018 2:06pm

Re: Relay for up to 100V DC?

Post by john61ct » Jan 14 2020 5:32pm

To the point it would be easy for a buyer to scam the sellers.

With great power comes responsibility, don't abuse it or they'll take it away.

Post Reply