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edgargw22 avatar image

How does Cyrix-Li-ct work?

I just replaced my original battery combiner with the Victron Cyrix-Li-ct. I tied the small read lead to both my dashboard wire (AUX START) and to AM Solar's AMS Lithium Control Module v4.2 to the ALT + and - connectors.

Can someone explain to me how this relay is supposed to work? I have 3 typical scenerios: (1) vehicle running (class A motorcoach) with no solar, (2) shore power and (3) dry camping with plenty of solar.

Is this a "one-way" solenoid? Are both lithium batteris and chassis batteries affected in the above scenerios?

I've included the data sheet from Victron for your refereance.

Datasheet-Cyrix-Li-ion-230-A-EN.pdf

battery chargingalternator
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3 Answers
dazey77 avatar image
dazey77 answered ·

The above describes the basic operation but seems to have omitted the battery disconnect terminals, there are the two main terminals but also a battery disconnect that is designed to allow a bms to stop the charging. Out of the box the relay will not close unless the control ports are the correct state . From memory you ground one and hold one at 12v to start charging

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Hmmm are you thinking of the Cyrix-li-charge? I know that model requires a separate 12v signal; the Cyrix-Li-ct, however, does not - it functions exactly like the Cyrix-ct except it has higher voltage thresholds to compensate for the higher resting voltage of LFP batteries.

dazey77 avatar image dazey77 Justin Cook - Bay Marine Supply USA ♦ ·

Nope, it even mentions the control signal on the data sheet that is posted. i even have a smaller Cyril-Li-ct in my van controlled by a bmv712 (12/24 120 variant)

dazey77 avatar image dazey77 Justin Cook - Bay Marine Supply USA ♦ ·

you can’t see the terminals due to the photo angle but you can see their function printed on the unit

Hi Dazey. Yes, you are correct. The Cyrix-Li-ct does come with a control cable. For this discussion, I'm assuming it's ON. I want to understand what this battery-to-battery switch will do on it's own.

Thank you for your comments - really appriciate this discussion...

@dazey77 aha, indeed, thanks for correcting me on that! Most of our customers will simply jumper that wire straight to the Bat2 POS connection terminal because the vast majority of them are using drop-ins without an external BMS to send signals, so I completely forgot that this was an option on the Li series.

Hi @dazey77 would you please expand on this idea of setting the state properly before use? I can't find it anywhere, and my relay isn't functioning as I expected.

Its in the manual /datasheet:

Pay attention to the 'Charge Disconnect' statements as this is what connects to the control terminals. The IF statement is the important one. If its high, if its not it does nothing.

As it says, if the control output is free floating, it disengates.

Cyrix-Li -ct The functionality of the Cyrix-Li -ct is analogous to the Cyrix-ct.The Cyrix-Li -ct will parallel connect a lead acid starter battery and a LiFePO4 battery:-if the Charge Disconnect output of the VE.Bus BMS is high, and-if it senses 13,4V (resp. 26,8V) or more on one of its power terminals.The Cyrix will disengage immediately:-when its control output becomes free floating, signalling cell over voltage or cell over temperature, and/or-when battery voltage drops below 13,2V.Start assist function: a short positive pulse will close the relay during 30 seconds (see figure on page 2).A built-in transient voltage suppressor will limit the voltage spike that may occur when the Cyrix suddenly disengages due to cell overvoltage or over temperature.

@dazey77 OK then we agree - I had misunderstood your post to suggest that if you somehow primed the device it could work as Justin described (without any control signal). From the manual I understood the device required a high control signal, but then again the docs also say that it works like the cyrix-ct (which appears not to require a high control signal) and Justin's answer below also said it wasn't required,

Anyways, I've confirmed that functionality on the bench: the control terminal must be high & the minimum voltage must be met.

My last concern then is whether or not the li-ct offers some protection for the Li ion battery when the control terminal is always high. The manual only shows the li-ct being used together with a VE.BUS BMS as the relay control, and that device is specifically for handling Li ion batteries.

Thanks for your time.

abogaard avatar image
abogaard answered ·

Hello, I am here because I am having difficulty getting my cyrix-li-ct to function as described in one of the answers. From @Justin Cook - Bay Marine Supply USA answer on Feb 22 it seems that the control cable is not necessary, however it appears to me that it is necessary.

My house battery is currently at 13.9V and the relay will not close.

I can get it to temporarily close by energizing, and then disconnecting, the control terminal (85), but it closes again a short time later (I believe this is the start-assist functionality).

Perhaps I needed to set the relay to the correct state when I opened it as per @dazey77 reply?

I'm sure others would be aided if we consolidated the correct pieces of the responses here into a final answer :)

I would like for the relay to function as described in @Justin Cook - Bay Marine Supply USA answer from Feb 22. Is it possible without a BMS? If not, what are the proper settings for the BMV712?

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@abogaard, my initial response earlier was just an "in a nutshell" description of how the device works, it was not intended to be -nor should it be taken as- a substitute for familiarizing yourself with the user manual. You do need to follow the installation instructions, including providing a ground as well as a control signal from either a BMS, a simple ignition-switched 12v source, the relay-out of a BMV, or several other possible configurations.

This is a device that can be connected and set up in easily a half-dozen (or more) different ways, all of which, if done correctly and configured to your specific needs, are correct. There is no single correct answer for any device that can be used in a myriad of ways.

@Justin Cook - Bay Marine Supply USA thanks a lot for your reply :) And also for your initial in a nutshell description, which I found very helpful and is not at all described in that manual we've all seen. I've read that thing front to back a couple times and the various configurations you mention just aren't clear from it.

As far as I can tell, the original poster's question still stands - how does this device work without pin 85 connected? Does it truly sense V on either side and do some smart opening and closing without a control signal?

I ask because two of your replies on the thread appear to be in conflict (maybe I am misunderstanding)

when the Cyrix sees ~13.6v at either side of it (ie, start battery on one side and house bank on the other side) it closes and connects the two battery banks together.  

versus

just to be clear, the Cyrix -by itself- isn't cycling on and off unless something that it's connected to is telling it to do that.

So does it need a control signal, or not?

@abogaard, I can see why that might be confusing - part of it is because I was replying specifically to behavior that the OP was describing, and part of it is simply non-standard terminology, so to be clear: "cycling" on and off is not normal behavior for the Cyrix; I draw a line of differentiation between normal operation, where it closes at one voltage and opens at another, and "cycling", where it's repeatedly opening and closing... it doesn't "cycle" unless it's being told to (in fact it has intelligent timers built in that are designed to specifically prevent "cycling").

All that being said, let me try to rephrase the Cyrix-li-ct operation (and I may well go back and add all this to my original answer to avoid future confusion): Yes, vbatt must be present on pin 85 for the device to function.

The Cyrix uses a microprocessor to control its operation, so I'm going to give its operating conditions as such: the processor uses IF/AND logic to close the relay (joining the batteries) and it uses EITHER/OR logic to open the relay (disconnecting the batteries).

IF vbatt is present on pin 85 AND voltage is above the thresholds described in the manual on either 87 or 30, the Cyrix closes and connects the two batteries together.

If EITHER vbatt on pin 85 OR voltage on 87/30 falls below the thresholds described in the manual, the Cyrix opens and disconnects the two batteries.


Now, vbatt can be supplied a number of ways depending on your system and what you're trying to accomplish. For purely automatic v-based operation, one can simply jumper pin 85 to 87 or 30, and the Cyrix will open and close based purely on the voltages present at 87 and 30.

Alternatively, on a system with an external BMS that has an "allow to charge" port, pin 85 of the Cyrix could be connected to the BMS's allow to charge port, thus allowing the Cyrix operation to be controlled by the BMS (this configuration is reflected in the diagrams shown in the manual).

Alternatively, on a system with, say, drop-in batteries like Battle Borns that don't allow you to interface with the BMS, you could wire pin 85 to an ignition switch (or a manual switch, for that matter) that would allow it to close only when the ignition is on, or only when your switch is in the "On" position.

Alternatively, pin 85 could be connected to the relay-out of a BMV-7xx with the BMV configured to provide vbatt to the Cyrix based on SOC or other factors.

...and plenty of other options. These are highly versatile devices, and so long as you understand the basic operating principle, you can use them in a wide array of applications, too numerous to be included in the manual. But yes, one way or another there must be vbatt present on pin 85 for the device to be able to close.

abogaard avatar image abogaard Justin Cook - Bay Marine Supply USA ♦ ·

hey @Justin Cook - Bay Marine Supply USA that all makes great sense and fits with how I understand the manual, thanks again for your thoughtful response and your time.

Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

@Edgargw22 given that AM Solar's AMS unit is not a Victron-manufactured or supported unit, I can't speak to how that's working in the system or how it might affect the performance of the Cyrix. That being said, on its own the Cyrix is a very simple bidirectional voltage-sensitive relay; in as few words as possible, when the Cyrix sees ~13.6v at either side of it (ie, start battery on one side and house bank on the other side) it closes and connects the two battery banks together.

So, in normal operation (leaving out the AMS entirely), when you're driving down the road and your alternator is charging your start battery, the start battery will be over 13.6v and the Cyrix will close, permitting charge current through to your house bank.

When you're parked, charging your house bank from shore power, when your house bank reaches 13.6v the Cyrix will close, permitting charge current through to your start battery.

When you're charging your house bank from solar, when your house bank reaches 13.6v the Cyrix will close, permitting charge current through to your start battery.

In all conditions, after the Cyrix has closed (joining the two battery banks together), it will stay closed until both sides reach the low voltage threshold of ~13.3v, at which time the Cyrix will open and disconnect the two banks after a timer, or will immediately disconnect the two banks when they fall below ~13.2v.

That's its operation in a nutshell; again, however, that is not taking into account the AM Solar device, since that's not a Victron-supported item - for information on how the Cyrix interacts in the system with the AMS installed, I advise you to contact AM Solar.

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Again Justin - really appriciate your answers... The Cyrix-Li-ct does come with a Control Cable (small 12v red & black wires) that's supposed to go back to the VEBus BMS (but in my case it goes back to the non-supported AM Solar's AMS). For this discussion, I'm assuming it's ON.

I am a little worried about charging levels of my chassis batteries (normal lead acid) vs my house Lithium batteries, and making sure I don't have a "run away" alternator (Delco Remy 28si Heavy Duty Alternator).

The datasheet has this chart (see below) that I'm trying to interpert. I think there are different connection times depending on voltage levels (the higher the voltage, the less time there's a closed connection, I assume to protect the batteries or the alternator). But it doesn't talk about how long it's OFF before it attempts another connection. I would think you would want if OFF for a period of time to allow the batteries & alternator to rest.

I guess if I wanted total control over this, I should install the Victron DC-to-DC fully configurable charger - but the number of times that I really need alternator charging is minimal - most of my charging comes from solar & shore powers.

TIA!

1582474831248.png (54.4 KiB)

@Edgargw22, just to be clear, the Cyrix -by itself- isn't cycling on and off unless something that it's connected to is telling it to do that.

Under most circumstances, if your engine is running the Cyrix will be closed and will be passing charge current from your start battery through to your house battery, and a short period of time after you switch your engine off, the Cyrix will open and disconnect the two batteries. There isn't a cycling on/off operation that naturally occurs unless the AMS or BMS is telling it to do that, which is certainly possible.

Many of our customers run these while using drop-in LFP banks that don't have external signalling capability, so simply jumper the POS control wire to the BAT2 POS connection, and then run a small on/off switch that disconnects the Cyrix's GND connection should they ever wish to manually disconnect the Cyrix; this is a viable solution for those who don't have external signalling devices and/or prefer a degree of manual control over its operation.

edgargw22 avatar image edgargw22 Justin Cook - Bay Marine Supply USA ♦ ·

Hey Justin, thanks for taking time to answer my questions. I really appriciate this information.

Hello, sorry I'm confused.....If my starter battery is an AGM with a charge dropping from 12.7 to say 12.2 over a period of time when would the cyrix li ct ever close if it opens (disconnects) anytime either battery falls below 13.3??

I have solar charging Lithium batteries which can also be charged via a unidirectional isolator connecting the starting AGM battery and the Coach Lithium batteries. No External BMS. I would like to replace my unidirectional isolator with the Cyrix-Li-CT so my full starting AGM battery would keep charged by the Lithium batteries when parked for a couple of weeks.