Bit of an electrical quandary ....

[wildebus]

Trying to do something and what is happening is not very logical and I am wondering if I am missing something, so if anyone has any ideas ....

So the goal ... I want to add control to a setup in order to stop a Lithium Battery charging when it is below a certain temperature.

I bought a Temp Controller that has a Relay that will either be open or closed depending on the temperature the temp probe is reading.
The B2B Charger (Victron Orion) has a 2-pin remote input that means it will only be allowed to operate if the two pins are shorted
The Mains Charger (Multiplus) has exactly the same arrangement on an remote/auxiliary feed input.

So the theory is that if I connect the two pins of the charger to the two pins of the Temp Controller, when the relay closes, the Remote input is shorted and the charger is allowed to work.
This is the effect of the remote input on the Multiplus
First the Remote/Aux input is left closed (two pins connected)

And when it is open (two pins not connected together)

(Passthru means there is AC power into the Multiplus but nothing going to the batteries)
The two screenshots above were taken when connected to the Temperature Controller and turning its relay on and off.

I can control the B2B charger in exactly the same way and it works as well. So what is the quandary?

Well, I want to be able to control both Chargers as want no charging from either source when the temp is low. And both chargers are controlled the same - short pins to enable, open pins to disable.
But when I connect both sets of wires together - one of each charger to one side of the relay, and the other wires of each charger to the other side of the relay - there is an automatic short somehow even when the relay is open. But if only one of the chargers is connected to the Temp Controller, it works correctly.
Now there is a workround I am pretty sure I could use with extra hardware and would only cost an extra £3 or so, but extra hardware equals more potential failure points so would prefer not to.

I did try connecting both charger remote inputs in a ring - so the wire would go "RELAY OUT" -> "B2B 1"; "B2B2" -> "MP1"; "MP2" -> "RELAY IN".
That way, when the relay is closed the ring is made and the pins of each are connected, just in a longer route.
Doing this resulted in the B2B having the remote control as wanted, but the Multiplus never being allowed to work.

Is there something I am missing on why this is not working? not applying any voltage to anything, just really based on a connection going short-circuit/low resistance.

 

[Nabsim]

Two temperature sensors, one for mains charger one for B2B. That’s what I did. Not got anything for the solar as worked on the theory of its below 5 degrees it isn’t going to give me more than 10 amp charge

 

[wildebus]

Two temperature sensors, one for mains charger one for B2B. That’s what I did. Not got anything for the solar as worked on the theory of its below 5 degrees it isn’t going to give me more than 10 amp charge

I was hoping to avoid that and have just the one.

My workround would be to have that one output drive two external relays that will provide the switch signal - one to each charger. that keeps them isolated, but it is two more things to fail and two more things to draw a slight current.
What annoys me is having to use a £6 external temp controller to send a signal to a very expensive (200x that cost) charger to control it when that charger has its own temp probe but won't use it for this purpose. A poor show from Victron in this respect.

 

[xsilvergs]

@wildebus

Is the relay a single pole change over (three contacts C, NC, NO) in the Temperature Controller?

 

[wildebus]

Just a basic latching relay - two contacts and open or closed. EMR as you can hear and feel it open and close.
Using individual external relays (the basic 4 or 5 pin ones) for each charger could be a good way to go, but the extra power use can add up.

I do also want another device controlled by the Temp controller .... A Heating Pad which comes on when the batteries are below the set temp to provide warming so they can be charged.
I am thinking they could be turned on when both the following conditions are met:

1. Battery below temp
2. Charger input is live (either B2B input voltage is above 13V (engine on) or EHU plugged in)

That way you are not using battery power to warm a battery when charging is not available anyway?

The other aspect is failsafe mode. Almost certainly would want it failing open to protect the batteries from a low-temp charge.
I think too many people do think Lithium Batteries are a simple drop-in and that is all you need to do. A ready to fit, self-contained, low-cost protection unit would be very handy

 

[xsilvergs]

Well I don't know if this would work as I don't have either a Multiplus or an Orion but first reply, by Robert says "I can confirm that you need to pull the H pin high to turn the device on".
https://community.victronenergy.com/questions/49423/orion-smart-engine-switch.html

If that does work could this work, forget the connection to Gnd?

 

[xsilvergs]

@wildebus

Do you use the Isolated or non-Isolated Orion or do you have a preference?

 

[wildebus]

The Orion is interesting in its remote setting. The flexibility is very good - you can control it with a Low Signal on the left, a High Signal on the right or just connect the pair together (which is how it is shipped).
For my B2B/VSR switching, I used the "Low" method. worked great. For this temperature control test, tried both "Low" and the "tied together" - same results. Something to do with when both devices are in the picture as individually they are good. Just weird!

Isolated or non-Isolated Orion?
I think the only difference to the user between the two is the isolated needs two ground cables. In a motorhome/campervan where the starter battery is grounded to chassis it makes no difference I think (I am guessing isolated is really for boats?).
I have only used or supplied the isolated to date however as non-isolated are hard to get hold off and have a long lead time.

 

[SquirrellCook]

So if I got this correct you’re trying to switch two switches with one device. Have you considered the switches might be polarised? If so and simple wire swapping doesn’t cure it, what about inserting diodes to isolate them from each other?

 

[wildebus]

So if I got this correct you’re trying to switch two switches with one device. Have you considered the switches might be polarised? If so and simple wire swapping doesn’t cure it, what about inserting diodes to isolate them from each other?

I have thought that could be a factor and reversed one.
I will be doing some more fiddling today and building a WUMDRSU* I think.


Wildebus Universal Multiple Device Switching Unit.

 

[Nabsim]

Is this not a good use of your rpi?

 

[wildebus]

Is this not a good use of your rpi?

It could be, but I am looking for a standalone solution that could go in any van. As Lithoum gets more popular, I think there is a market for a plug-in temp protection unit - and I don't think things like Arduinos and Raspberry Pi's would fit that.

 

[PeteS]

You havent said so what are the voltages on the two pins that you connect together?
Are you able to measure the current that flows once the input is shorted, Are they the same?
You have assumed that the input circuitry is the same but by connecting the pins together of the different units you may have produce a potential divider such that the switch over threshold is not being met on one or both.
I would imagine that the input would be a series resistor for static purposes and either a pull up or pull down acting in conjunction with whatever bit of logic its using.
Thats the only way I can think that they dont work.

 

[wildebus]

You havent said so what are the voltages on the two pins that you connect together?
Are you able to measure the current that flows once the input is shorted, Are they the same?
You have assumed that the input circuitry is the same but by connecting the pins together of the different units you may have produce a potential divider such that the switch over threshold is not being met on one or both.
I would imagine that the input would be a series resistor for static purposes and either a pull up or pull down acting in conjunction with whatever bit of logic its using.
Thats the only way I can think that they dont work.

I haven't checked any voltages and it will likely be a variation there.
I am taking a different tack on this and will be building a multi-relay setup so each device remains independant which makes it a lot more flexible

 

[wildebus]

Well, I worked out a little circuit this morning ...

Wanted the two relays controlled together (so I would only need one Thermo-relay to fit and setup) but being able to have those relays separate so they can be setup to use different 'control' outputs.
Relay Output #1 will go to the Victron B2B - that wants a 0V on its remote input to enable it. So I do the following:
set JP1 to DOWN (0V passed to JP2).
set JP2 to UP (0V continued to Relay INPUT)
set JP3 to RIGHT (CON1 bottom connected to NO)
This means when the Thermocontroller Relay closes (temp above min setting), the CONTROL line goes high, relay #1 activates and 0V is sent through to CON1 Bottom and the B2B is enabled

Relay Output #2 goes to the Victron Multiplus and needs something different ... That just wants the pair of wires on its Aux control port connected together.
So for that the position of JP1 doesn't matter as it is ignored, and I set JP2 to DOWN. This connects CON1 Top to the input of the relay
JP is set to RIGHT, so now when tthe Thermocontroller Relay closes, CON1 Top and CON1 Bottom get linked together.

With the three jumpers JP1, JP2 & JP3, I can accomodate any control signal requirements that a device will have, be they high or low to enable, high or low to disable, make or break to enable, or make or break to disable

That is the theory ... what is it like in practice?
Knocked up the design on a piece of PCB board and connected it up quickly ...

And it actually worked! (I am using a relay on a Victron Cerbo that is pretending to be a Thermocontroller, but it will work identically in terms of sending a control level signal).

I think this could be very handy for anyone wanting to control multiple charging devices and disabling them all if a Lithium Battery drops below a set temp to avoid very expensive damage (you have to stop them all. Mains, Solar and Split-Charge!)
What is handy is that you can also reposition the jumpers to essentially by-pass the temp controller as well (say in the warmer months when there is no chance of a temp drop, just turn off the temp controller and move JP3 for example).

 

[SquirrellCook]

Wow so many Jumpers, is it cold or a mass suicide? But seriously....

Well done Dave, but I wonder if it's too much for a british standard human to understand?
Have you had a think about misplaced jumpers and will it fail safe?

 

[wildebus]

Wow so many Jumpers, is it cold or a mass suicide? But seriously....

Well done Dave, but I wonder if it's too much for a british standard human to understand?
Have you had a think about misplaced jumpers and will it fail safe?

3 jumpers per relay. If you had less, you would lose the universal flexibility. I think it would be a matter of listing where the jumpers go for a particular scenario in a little leaflet?
The fail safe would I say be provided via the fused supply. Although these are 10A relays, the power requirement is tiny - a 1Amp fuse is more than enough so no risk of high current. reversed polarity into a charger remote could be a potential issue (which is true of anything you connect on a 12V device), but that would probably blow the fuse before any problem would arise as the fuse is so small.

The good think about relays is if they fail, they fail in a non-distructive way. May stick open or stick closed, but either way, they stick in a state they are usually in anyway regularly at some stage and the device they are connected to accepts, so it matters not other then the device (charger in this case) either stays enabled or stays disabled - so if connected right to start with, zero danger on a fail.
The way the setup I described using on my chargers works, the default fail-safe would be to disable the chargers - so if the thermocontroller failed and so didn't drive its relay, the result is the chargers will not enable. Same is true if the fuse blew.

 

[wildebus]

Thought I would add a little indicator to show when the chargers are enabled. So dropped in an LED (Green = Safe for Charging )
Left side is Relays disabled, right side of pic is Relays enabled (so say temp above 5C).

 

[Nabsim]

Hmm, maybe a bit of that board and some components would replace my faulty control unit

 

[wildebus]

Hmm, maybe a bit of that board and some components would replace my faulty control unit

Quite possibly. And can put in into a little box for protection from elements and knocks ...