# 48VDC input signal relay for 110V Output

#### Vonncp

Joined Sep 21, 2022
3
I have no experience on automation with power control and I am researching on how to make a simple ON/OFF switch that will close (Normally open) if 48VDC signal is ON and needs to be able to support 100A 100VAC it is for a battery charger.

#### DickCappels

Joined Aug 21, 2008
9,606
They make relays with 48 volt coils and 100 amp contacts. Name-brand ones sell for between US$100 and$300.

This one sold through Alibaba.com is offered for US\$28.50, not sure what the minimum quantity is:

https://www.alibaba.com/product-det...html?spm=a2700.7724857.0.0.4ae666dfUG2Aou&s=p

Maybe somebody can find a better deal.

Notice at the end of this thread is a list of similar threads that may be of some help.

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#### panic mode

Joined Oct 10, 2011
2,394
what kind of source is 100VAC and can supply 100A?

btw. you want o make sure that your product is properly sized. normally at least 20% above the nominal. And probably more for devices that store energy or are nonlinear (that includes any charger/rectifier).

btw. i have used many different relays and contactors and product ratings are sometimes apples and oranges.
for example an AB relay 100-C series, rated for just 9A will easily outperform Omron relay G9L... rated for 10A when same (over)current goes through their contacts. G9 will always have contacts weld before 100C has same defect. Products manufactured in different parts of world simply have different safety margins and looking at the product it is clear that 100C is obviously larger. the current rating is simply more conservative..

contactors and relays serve basically same function but construction is different.
for large loads i would rather go with a contactor or maybe an SSR (quiet option)

#### Vonncp

Joined Sep 21, 2022
3
what kind of source is 100VAC and can supply 100A?

btw. you want o make sure that your product is properly sized. normally at least 20% above the nominal. And probably more for devices that store energy or are nonlinear (that includes any charger/rectifier).

btw. i have used many different relays and contactors and product ratings are sometimes apples and oranges.
for example an AB relay 100-C series, rated for just 9A will easily outperform Omron relay G9L... rated for 10A when same (over)current goes through their contacts. G9 will always have contacts weld before 100C has same defect. Products manufactured in different parts of world simply have different safety margins and looking at the product it is clear that 100C is obviously larger. the current rating is simply more conservative..

contactors and relays serve basically same function but construction is different.
for large loads i would rather go with a contactor or maybe an SSR (quiet option)
I did some research after posting the idea of what I needed and I understand better now (I assume) What I was looking was for a relay with the signal coil to be 48V and the contact switch has to be able to support 100A 110VAC or 50A 220VAC so either a single or double contact depending whether I will use a 110V or 220V power source. I am doing 50% above nominal that is why Amps are so high but I am looking for reliable and long lasting.

Also I have found relay coils are more commonly on 24VDC but the source I will get the coil input is 48V so I have decided to use a Step down dc-dc converter and this will solve the coil voltage issue.

Appreciate if you have any comments.

#### panic mode

Joined Oct 10, 2011
2,394
24VDC is far more common as that is what industry runs on - practically every machine in every plant in every country is using IO and controls that run on 24V. This is why they are so common. but products with different coil voltage including 48V are available too. product you are after will have a pretty large coil. it will definitely need suppression (diode across coil) or whatever is feeding will be smoked the moment that coil is de-energized.

#### Vonncp

Joined Sep 21, 2022
3
24VDC is far more common as that is what industry runs on - practically every machine in every plant in every country is using IO and controls that run on 24V. This is why they are so common. but products with different coil voltage including 48V are available too. product you are after will have a pretty large coil. it will definitely need suppression (diode across coil) or whatever is feeding will be smoked the moment that coil is de-energized.
It will be feeding a battery charger for lithium batteries 55V 60A the charger has an input of 220V AC

#### panic mode

Joined Oct 10, 2011
2,394
you need to make that story straight. first you mention relay for 110VAC 100A, then you say it is 220VAC. Relay contacts rated for 110VAC may not be rated for 220VAC. which is it? what exactly you want to do? are your next post going to mention 240VAC, 277VAC, 400VAC, then 480VAC then 600VAC? single or three phase? this is not a game and someone can get badly hurt or killed. you may want to get someone qualified to deal with this.

#### JDiaz

Joined Nov 4, 2019
11
Could be better if you can send a schematic to see what you trying to do, You can use Solid State relays instead of mechanical relays, since those are sealed. Also an IGBT array could work for this purpose.