Relays

czyhorse · October 2010

Need some help here. My plan is to purchase a Victron BMV-600. This battery monitor has a "Discharge Floor" setting, where you can set a limit to the depth of discharge of your battery, and once that level is met, the monitor will activate a relay.

My question for you all (being that I am not an electrician) is could I use this feature to switch my Exeltech XP1100 inverter off via a relay? If so, how do I know what size or type of relay to use? I have no prior experience of working with relays, so any help would be appreciated.

Thanks.

RCinFLA · October 2010

Re: Relays

Exeltech XP1100 has a remote on-off switch. Use it to turn off inverter.
"REMOTE” connection is on the barrier terminal strip located under the Rear Cover.

Putting a relay in a high current battery line should be avoided as it would require a very large contactor to keep the contact resistance low. Any relay with that capability would likely draw 5 watts or more for its coil.

czyhorse · October 2010

Re: Relays

That was my thought...utilizing the remote on/off on the back of the inverter. Can I use a relay in this situation? Any ideas on what type/size?

I'm not understanding your second comment about putting a relay in a high current battery line (do you mean a relay in the + or - leads from the battery?)

RCinFLA · October 2010

Re: Relays

It's a low voltage, low current control line. The relay in battery monitor can run it directly.

dwh · October 2010

Re: Relays

czyhorse wrote: »

That was my thought...utilizing the remote on/off on the back of the inverter. Can I use a relay in this situation? Any ideas on what type/size?

I'm not understanding your second comment about putting a relay in a high current battery line (do you mean a relay in the + or - leads from the battery?)

A relay or contactor is usually an electromagnet which is activated by a switch. So, you can use a low-voltage low-amperage switch to control the magnet, which can then pull the contacts to switch on a larger voltage or current.

One well-known example would the Ford Starter Solenoid. Your ignition switch supplies a low-amperage 12v to the electromagnet and the magnet connects the starter directly to the battery.

A similar unit would be used for a split-charge relay:

http://www.landroverweb.com/Images/Splitchargerelay/Relay.jpg

You connect your small switch to the small terminals on the relay, and the big battery cables to the large terminals. When you turn on the switch, the relay connects the big terminals together.

A contactor is similar. You can use a standard 120v wall switch to turn the electromagnet in the contactor on and off, and the contactor can switch on whatever big loads - parking lot lights, warehouse lights, giant 3-phase air compressor, etc.:

http://www.google.com/images?um=1&hl=en&safe=off&client=firefox-a&hs=6cM&rls=org.mozilla%3Aen-US%3Aofficial&biw=1366&bih=593&tbs=isch%3A1&sa=1&q=contactor&aq=f&aqi=g10&aql=&oq=&gs_rfai=

In your situation, since your inverter has a connection for a remote on/off switch, you don't need a relay on the big battery line. You should be able to connect your battery monitor straight to it. (CHECK the voltage specs on both ends to make sure they are compatible.)

You battery monitor has a little relay in it - the circuit board turns that relay on and off with a small voltage, making/breaking the connection on the big side. Your inverter has a low-voltage that needs a switch, so you connect that to the large side of the little relay in the battery monitor.

But if your inverter didn't have a connection for a remote switch, then yes, you'd have to wire a relay in the positive line between battery and inverter. You'd need a relay that can be activated on the small side by whatever voltage your battery monitor's switch control uses, and can handle whatever voltage/amperage is required on the big side.

Or you might need two relays. Say you use a split-charge type relay on the battery wire and it needs 12v 2a to activate the small side, but maybe your battery monitor's switch output can only handle 1a. Then you'd have to get a little relay that can switch 2a on the big side, and be controlled by 1a on the small side, and hook its big side to the small side of the big battery relay.

Hence the term "relay".

czyhorse · November 2010

Re: Relays

Thanks DWH and RC...I've got a better understanding of my situation now.

I'm going to experiment with running a wire from the battery monitor relay to the remote connection of my inverter, test it under a non-critical load, and see how it goes.

czyhorse · November 2010

Re: Relays

I've been looking into this a little bit more and discovered that the Victron battery monitor's relay contacts are normally open. If I connect this to the remote terminal on the inverter, then I would not have power to the inverter under normal conditions.

Exceltech's manual states:

Using 12-18 gauge wire, make remote on/off connection from the rear panel terminal labeled "remote" to one pole of a small toggle switch. Then from the other pole of toggle switch, make a connection to battery negative (-). Make sure the toggle switch is in the off position.

If using the remote switch, the front panel switch must be off. (If either switch is "on", the inverter will turn on. Both switches must be off for the inverter to turn off).

It seems that I should incorporate a relay to hold the remote terminal and battery neg. connection in place (normally closed) until the battery monitor reaches a specified depth of discharge, to trip the relay and break the connection, turning the inverter off. Attached is a schematic I came up with. I need some help to see if I'm on the right track with this or not.

zeuspaul · November 2010

Re: Relays

My plan is to purchase a Victron BMV-600.

Thanks for the thread. I am also looking for a way to shut off an Exeltech inverter. Your posts pointed me to battery monitor options. I don't know the status of your purchase. As an option it appears like the Xantrex Link battery monitors have a programmable output switch with an option for NO or NC. The LinkPro has more advanced options for the voltage conditions of shut off.

Zeuspaul

BB. · November 2010

Re: Relays

When connecting a relay to a digital device... Make sure the device can drive the voltage and current needed for the relay.

I would expect the "where should this go" should be the negative ground of the panel meter.

Also, with digital switching of relays, you should have a "snubbing diode" to prevent inductive kick back of the relay (several hundred volts) from damaging the digital output of the battery monitor:

Please note--I made a mistake. The drawing below is good for showing how to connect a snubbing diode--However, the drawing is not correct for connecting to a Victron Battery Monitor.

[FONT=Fixedsys]+}=========+======)
           |      )
         ------   )
           /\     ) Relay
          /  \    )
         ------   )
           |      )
-}=========+======)[/FONT]

When the meter turns off, the relay will attempt to keep the current flowing and the diode will clamp that voltage to 0.2 to 0.7 volts (depending on the diode selected). Instead of a couple hundred volts across the Battery Monitor signal output.

-Bill

waynefromnscanada · November 2010

Re: Relays

dwh wrote: »

But if your inverter didn't have a connection for a remote switch, then yes, you'd have to wire a relay in the positive line between battery and inverter..

Actually, I've added remote control to a bunch of inverters. Just requires soldering a couple of little (~20 gauge) wires to the on/off switch terminals in the inverter, one to each of the two switch terminals, then connect these wires to a little relay mounted on, or right beside the inverter. In my cases, the run from the switch in the house, out to the power shed is over 100 feet, and the little relay coil is 12 VDC. When I flip the switch in the house, it sends 12 volts out to the little relay coil, which then closes it's contacts and signals the inverter to start in exactly the same way as if you had switched the inverter on in the normal way. I like the idea of using the little relay, as it eliminates direct connection of long wires to the delicate and sensitive control circuits in the inverter, especially important during a lightening storm.
Food for thought.
Peace

czyhorse · November 2010

Re: Relays

zeuspaul wrote: »

Thanks for the thread. I am also looking for a way to shut off an Exeltech inverter. Your posts pointed me to battery monitor options. I don't know the status of your purchase. As an option it appears like the Xantrex Link battery monitors have a programmable output switch with an option for NO or NC. The LinkPro has more advanced options for the voltage conditions of shut off.

Zeuspaul

Glad to see I'm not the only one trying to accomplish this. I have, however, already purchased the Victron monitor, so it looks like I'm going to have to go the relay route to get this to work.

czyhorse · November 2010

Re: Relays

BB. wrote: »

When connecting a relay to a digital device... Make sure the device can drive the voltage and current needed for the relay.

I would expect the "where should this go" should be the negative ground of the panel meter.

I'm having some difficultly determining what size of relay to use. Victron doesn't have much information about the relay contact other than it's rated at 60V / 1 Amp max. I measured the voltage across the remote terminal strip of the inverter and it is 24V as I suspected. Does this mean I can use a 24V / 1 A relay? or is there another way to size this thing?

Also, when you refer to the "negative ground of the panel meter" would this be equivalent to the negative bus on the load side of the shunt in my panel? Thanks for all your help, Bill.

BB. · November 2010

Re: Relays

Typically, the digital outputs look like a relay contact to ground... The output is either floating, or grounded. So, technically, it can take any power source up to 60 volts and 1 amp. It would be nice to confirm that with Victron.

Next, the Inverter, we would hope, should have a light pull-up resistor to 24 volts, and you just ground the output (a few 10's or 100's of milli-amps) to turn the inverter on (or off). I did a quick look at the Exeltech website, and did not see any specifications--You probably need to contact them for details.

Then, back to my embarrassing mistake... It has been too long since I thought about interfacing the typical digital to external circuits.

To redraw the diagram:

[FONT=Fixedsys]Battery +Bus ~1 amp fuse}=========+======)
                                  |      )
                                ------   )
                                  /\     ) Relay
                                 /  \    )
                                ------   )
                                  |      )
Meter Output}=====================+======)[/FONT]

The Battery bus (protected by an appropriate fuse of 1/2-1 amp or so, powers the relay. And the Meter provides the Switched Ground to the relay.

If you are going to power the 24 Volt Remote directly (and the the polarity is correct--I.e., Victron Grounds the output when you want inverter on, and the inverter turns on when its remote line is grounded).

In theory, you would just connect the Meter Output directly to the Remote Terminal on the inverter... You may want to place a 1/2 fuse inline with the remote terminal wiring "just in case".

-Bill

czyhorse · November 2010

Re: Relays

Okay, Bill...just when I was starting to understand everything...after reading your post I'm more confused than ever.

The Battery bus (protected by an appropriate fuse of 1/2-1 amp or so, powers the relay. And the Meter provides the Switched Ground to the relay.

If you are going to power the 24 Volt Remote directly (and the the polarity is correct--I.e., Victron Grounds the output when you want inverter on, and the inverter turns on when its remote line is grounded).

In theory, you would just connect the Meter Output directly to the Remote Terminal on the inverter... You may want to place a 1/2 fuse inline with the remote terminal wiring "just in case".

Have I interpreted your diagram correctly in the following picture? Let me know if I've got this right...

BB. · November 2010

Re: Relays

IF I have guessed correctly on both the inverter (ground the inverter remote terminal it turn it On or Off--don't know polarity) and the Victron controller's output is just a Open/Ground mechanical or electronic contact (of the desired polarity--I.e., Battery Monitor grounds to turn inverter on)--Then yes, your drawing is correct.

If the polarity is wrong--Using the Normally Open contact pair will give you the opposite signal sense.

And, where he wire comes from the Positive Battery Bus--there should be a small fuse to protect against short circuits in the wiring from the +Bus to the relay (just normal safety precaution).

From one of the Victron Manuals (BMV-6xx series PDF):

DF: Discharge floor. When the state-of-charge percentage has fallen
below this value, the alarm relay will be activated. The time-to-go
calculation is also linked to this value. It is recommended to keep this
value at around 50.0 %.

ClS: Clear SOC relay. When the state-of-charge percentage has risen
above this value, the alarm relay will be de-activated. This value
needs to be greater than DF. When the value is equal to DF the relay
will not be activated depending on the state-of-charge percentage.

Potential free contact
Mode Normally open
Rating 60 V/1 A max.

So, from the Victron Manual--It looks like the alarm contact closes to ground when the battery is "Low". And open when the Battery state of charge is high.

However, the manual is vague about how many alarm contacts there are (one, two?) and if there is some mix of functions (voltage relay settings and SOC relay settings).

I have to go right now--but it does need more research to be sure how it all plays together.

-Bill

czyhorse · November 2010

Re: Relays

I found a relay module manufactured by ELK that looks like it may fit the bill. It may save me from doing some soldering.

ELK 912B Relay Module
http://www.smarthome.com/1299/ELK-912B-Relay-Module-12-24-Volt/p.aspx

Relays

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