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Cyrix Battery Combiner

Strange behaviour Cyrix

I have 2 batteries in the boat, one is start, one is household. I,ve recently rewired the whole system. But now the voltage over both batteries is allways the same. The only thing that could connect both batteries is the cyrix, however if I understand it correctly the cyrix shouldnt connect them together when there is no charging power from pv or alternator ? The cyrix is not connected currently apart from the plus wires. The override wire and the minus wire haven`t been installed yet. Might this trigger this situation ? I don`t know what the default relay state is of the cyrix when not active.

leverg asked
Matthias Lange - DE commented ·

1 Answer

Cyrix Li CT 230A pin layout

Dear Community,

I find the description of the pin layout for the Cyrix Li-CT 230A in the brochure and on the device extremely confusing.

Below is a picture from the backside.

Is it

pin 1 = generator

pin 2 = Lithium Battery

or the other way ?

Thank you very much !



peterz asked

0 Answers

Sanity check please...

Hi there,

I'm wondering if I can get some feedback about my proposed system. Diagram is below. My concerns are about whether I should be using the Cyrix-ct battery combiner instead of an ArgoFET isolator. Should the MPPT controllers feed to the start battery? as well as the house batteries?

Larger version of pic at DC supply and charging.pdf


marc-kelly asked
marc-kelly edited ·

0 Answers

Cyrix ct-li

Has anyone used a Cyrix ct-li to connect a high-power 12V vehicle charging system with lead-acid batteries to a 400AH (non-Victron) battery system (Battleborn, 4x100AH parallel connected, built-in BMS)?

What prevents the 400AH of LIFePO4 batteries sucking down very high charge currents (perhaps 400A) and overloading the vehicle alternator (rated 250Apeak, but reports suggest better run at <150A for extended duration to avoid overheating).

What cuts off overcharging the LiFePO4 batteries?

Any better suggestions for charging the house batteries? The rest of the system is basically a Victron MultiPlus 12/3000/120 and downstream 12V and 120V loads.

neilhunt asked
neilhunt answered ·

2 Answers

Cyrix-li-ct not charging house battery (with BMV 712)

Hi there, I hope someone can help.

I have a 100ah lifepo4 battery which is combined with the starter battery using a Cyrix-li-ct. The cyrix is earthed to the starter battery on the lower terminal and connected to a BMV 712 on the upper terminal. The BMV relay is configured to close when the state of charge gets low, and I can hear the relay clicking open and close when I fiddle with the settings/invert. The alternator is producing 14.4 volts with the engine running, but I'm seeing absolutely no current pass through the relay.

Is there something else I might be missing, or do I perhaps have a broken cyrix module?

tristan asked

0 Answers

Problem with Cyrix ct contact 86
good morning.
I have a problem with the victronenergy Cyrix Ct 120.
I did a somewhat different installation from the manual.
I put a switch on contact 85 start assist to start the engine with the service batteries.
In addition I also put a switch on the negative contact 86 of the coil.
In this way I disconnect the cyrix to prevent the panels from charging an already charged engine battery every day.

but if one day I decide to reconnect the cyrix with the switch on the negative contact, once the cyrix closes with voltage greater than 13.2v, it is always closed ... and does not open with voltage less than 12.8v.
To get it to work properly again, I have to operate the "start assist" contact switch and then turn off the "start assist".
In this way, the cyrix resumes its automatic functioning.
But every time I turn it off from the negative and then reconnect it, it then gets stuck in the closed position.
Anyone know why this happens?

francesco asked
francesco commented ·

0 Answers

Cyrix-ct 120 - Different battery types


I just bought a Cyrix-ct 120. My startbattery is a couple of years old sealed lead acid battery and my house battery is a brand new AGM battery.

My alternator is connected to my start battery.

I also have a solar panel and an MPPT 100/20 regulator which is connect to my house battery.

Is it OK to have different battery types connected to the Cyrix, or will I damage my batteries. For Example the SmartSolar MPPT is det for AGM charging, hyras This voile potentiellt over charge my startbattery since Cyrix is bi-directional?

Also do I risk that my older startbattery will wear down my new AGM battery the the breaker is closed due to solarcharge or the alternator?

dannen asked
francesco answered ·

4 Answers

Cyrix-ct won't disconnect what could be the problem?

Installed on an RV with solar system on coach batteries. Batteries wire as shown in photo. My Cyrix-ct was connected last evening. The coach battery was 13.6V, the vehicle's was 12.3. The Cyrix flashed and then engaged. The next morning both batteries settled at 12.83V and Cyrix remaind engaged. This afternoon (solar charge) both batteries are at 14.6V, Cyrix remains engaged. When should I expect to see the unit dis-engage? Do I have Battery 1 and 2 wired correctly.

Steve asked
francesco answered ·

2 Answers

Argo fet or Cyril-ct?


I’d like to use your products in my 30 feet sailing boat in order to charge the starter battery ( 1x 70 Ah battery ) and the services batteries ( 2 x 115 Ah flooded batteries put in parallel).

Is it better to use your Argo FET 100-2 battery isolator or your Cyrix-ct 12/24-120?


skuner asked
francesco commented ·

2 Answers

Cyrix-CT-Li and SuperPack LiPo batteries

I have two Victon SuperPack 200Ah batteries connected in parallel with a BMC-712 to a Cyrix-Li-Ct and my Sprinter's lead battery. I understand that the power flow is supposed to be one way but but this morning the Sprinter's battery is dead. I drove the Sprinter yesterday.

Since the SuperPacks have an internal BMS, I dont have an external/second BMS. I was advised to wire the Cyrix with battery to Sprinter battery, Lion terminal to one of the SuperPacks, then terminal 86 to ground and 85 to the one of the SuperPacks's postive terminal. Is this correct?

Advice is greatly appreciated.

Tom asked
Tom answered ·

2 Answers

Cyrix-ct 12/24V-120A Battery Combiner and low output alternators.

Looking at fitting the Cyrix-ct 12/24V-120A Battery Combiner to charge the trolling motor battery on my boat. The starting battery is a sealed expanded calcium, the trolling motor battery is a 120ah AGM and the engine's alternator puts out 16 amps.

Will this combination work to keep my batteries charged?

I'm currently using a basic VSR which continually switches while running the engine. Will the Cyrix-ct 12/24V-120A Battery Combiner solve this problem?


leezor asked
leezor commented ·

2 Answers

Can the Orion-Tr Smart Charger be in series with a Combiner Relay?

Does the Orion TR Smart Charger have voltage present on the input terminal with no source connected? I ask this because the set-up I have already includes a voltage sensing combiner relay closest to the Start battery. The combiner won't close-in to admit input power to the charger unless there is a voltage present.

j9g asked
alex-rhys-hurn answered ·

1 Answer

Cyrix-i Battery Combiner 12v effect on charging unit


I'm keen on fitting the above to combine two battery banks BUT my motorhome charger unit is already near the max of its capacity i.e. 200amps. I'm not sure how many amps power the combiner allows to cross the relay or whether the charging unit will exceed its design if a link the banks in this way. Will the charging unit still only work within its design limits ie still think its connected to a smaller bank and the residue current will just go through the combiner to the new bank or will the charger have to supply additional current to its design parameters.

jezam asked
jezam edited ·

0 Answers

Significant issue with Cyrix Li-Charge

On a recent installation Victron Smart batteries are being charged by Victron MMPT solar controllers and a Balmar alternator though a Cyrix Li-Charge 230, the latter is controlled by a VE Bus BMS. This is an installation exactly as per the schematic diagram supplied by Victron.

The problem is that the Cyrix Li-Charge is opening, (disconnecting) the battery almost exactly every 60 minutes for a few seconds then closing again. This is causing significant problems for the Balmar alternator regulator.

My understanding is that the Cyrix needs 13.7V on the charge terminal in order to close. The only way I can see this working is if any charging source is set to a minimum float voltage of 13.7 which according to the Victron charging recommendations for their LFPs is too high.

It is worth mentioning that the charge connect circuit from the BMS is always high, as it should be under normal operation.

On another installation I have done I have used a Battery Protect as the HV disconnect device but I gather this is not now recommended.

What is the solution to this dilemma? It is not acceptable for the Cyrix Li-Charge to open every 60 minutes when the charging sources drop into float mode.

Tim Chapman asked
Tim Chapman edited ·

0 Answers

Cyrix CT always hot and draining both batteries

Hello. I have a very simple install in my 4x4 (Mercedes ML 320). I have a normal acid extra battery in the back of my car, only for few equipments. I realize in the last days, I am not moving the car so much, the voltage indicator for the "service" battery was in 11.9 (with the tester, 12 volts, very few, even after driving for about 2 hours in one week ago), and the starter battery was also similar (12.1 volts). The batteries are "separated" well, not moving power between one and the other, just the Cyrix CT is always "warm". Even after a night, if I touch the Cyrix, is a little warm. I think is always using "a lot" of power. I know, I can solve it using a switch and disconnecting the positives, but is really the Cyrix using "a lot of power" in stand by and I need to disconnect it ?

Here a picture and a explain....

Pin 87 = To service/second battery (one meter away with a fuse)

Pin 30 = To main car power supply, taking the power from the cigarette lighter from the back of my car.

Pin 86 = To a common negative.



Today I am going to make more test, I will put and amp tester between the Cyrix and the "main battery" and the same with th service and I will take measurements about how much amps and running..

Thank you

Hipolito Gonzalez asked
Hipolito Gonzalez answered ·

3 Answers

Does this schematic look ok - any improvements

I have added a lithium battery to my motorboat and I am proposing to connect it as per the sketch below. I already have the shunt, smart shunt, mppt and battery chargers. From my research I think it will work? Be interested in any comments, suggestions for improvements, thanks.


madian asked
Rob Fijn answered ·

1 Answer

Cyrix Li-Charge operation

I have, on a friends boat, a fairly standard Victron LFP set up with a VE Bus BMS controlling a Cyrix Li-Charge for over voltage protection and and Battery Protect for under voltage protection.

My assumption is that under normal conditions the Cyrix relay should always be closed and passing charge current, either from the solar or the engine alternator.

What appears to be happening is that the Cyrix relay is clicking open when the engine is running, even though the voltage on its output terminal is only 14.1V.

Can anyone provide any insight as to why the Cyrix is opening? Am I right in my assumption that it should be closed at all times under normal operation as long as the charge disconnect wire from the BMS is high?

Tim Chapman asked
Tim Chapman commented ·

1 Answer

Understanding Cyrix terminals

Hi all.

You have bat1 and bat2 connections on cyrix. I understand Bat1 goes to starter battery and Bat2 goes to leisure battery. But, which connection is Bat1? The one behind (to the back) or the one in front?

Does it make a difference if I connect them the other way?

I have 230A version with the control cable.

Many thanks.

leventtopcu asked
Daniël Boekel (Victron Energy Staff) answered ·

1 Answer

Blue Sea 7603 Replacement - MultiPlus, Cyrix-ct, SmartShunt & RPi


I’ve currently got a ‘Blue Sea 7603 - 10A BatteryLink Charger’ and an APC UPS. I purchased the Blue Sea because it can use AC shore power to charge two isolated battery banks with a 3 Stage 10A battery charger but also it can use DC power from the alternator to charge both the Start and the Auxiliary battery through an integrated 65A ACR (Automatic Charging Relay - Automatically combines batteries during charging, isolates batteries when discharging and when starting engines).

The problem with it though is that there is no monitoring or visibility of what's going on apart from a panel mount 'display' consisting of a couple of LEDs. I've recently had a problem with my Auxiliary battery not seeming to hold charge and I'm struggling to troubleshoot and having to use a multimeter, etc.

I recently learnt that the MultiPlus 12/500/20-16 has a second output intended for charging a starter battery albeit limited to 1A. Therefore would a MultiPlus and a Cyrix-ct be a suitable replacement for the Blue Sea and an APC UPS?

I've added a SmartShunt, VE.Direct to USB Interface (for the SmartShunt), MK3-USB (for VE.Bus on MultiPlus) and a Raspberry Pi with Venus OS to meet my requirement of greater monitoring and visibility of what's going on. However how will I know the status of the Cyrix-ct?

Is there a panel mount display which can interface to my configuration?

Thanks in advance for your advice.



knotty asked

0 Answers

Victron Cyrix CT 120A cable and fuse


I find it a bit difficult to understand which cable thickness and fuse I would need to use for the Cyrix CT 120A.

For the main connections (30/ 87) I plan to use a 25mm² wire and 120A fuse as is described in the product's datasheet. The cable length would be about 6M.

What I don't understand is which thickness and fuse to use for the start assist (85) and connection to the battery (86). The datasheet says the fuse can be 0,1A, which would indicate a rather thin wire can be used. But I don't understand how that's possible: my starter engine would draw a lot more than such a small fuse and wire could handle.

Second question: do I really need to connect the negative of my "appliance battery" to the negative of the "start battery"? Can't I just ground them both?

Kind regards,


marcj asked
marcj answered ·

2 Answers

Cyrix ct 230 and Smart Solar 100/30 controller

I am installing 400W of solar panel on my boat with a Smart Solar 100/30 controller primarily to charge my 420Ah service bank. I would like to be able to trickle charge my starter battery with the solar input also. Could I therefore do this by incorporating a Cyrix ct 230 between the MPPT contoller and the batteries?

gasdoc asked

0 Answers

Cytrix impact on SOC when coupling 2 independant offgrid solar system ?

Dear readers,

I have 2 independants off-grid solar system that I would like to combine during the charge. both systems are using a BMV702.

If I use the cytrix with a connection battery to battery, I will loose the SOC of my BMV702. Would it be possible to connect the Cytrix after the shunt of each battery) ? I hope my question is clear enough... Thanks for you advice, BR oscar

oscar7777 asked

0 Answers

smart battery protect or a cyrix-ct?

In my old boat I’m working to improve the electric system.

I’d like to have 2 avg batteries either connected with a smart battery protect or a cyrix-ct to make sure that one of the batteries can always play as starter battery, even if services loads are consuming too much energy.

Moreover, in the future I’m planning to have the service battery charged also by solar panels.

so basically the two batteries are the same ones, when they are above a threshold they should be in parallel, while when there is the risk to discharge too much the starter battery, the circuit should be open.

what is better to use? A smart battery protect or a cyrix-ct? Why? Would this work when in the future I will add solar panels connected to the service battery? Any recommendation?


marco-beta asked
marco-beta answered ·

2 Answers

Cyrix Li-CT or Orion DC-DC charger?


I'm planning to have an alternator charging of my leisure LiFePO4 battery in my camper van. I have standard Lead Acid starter battery connected to an old van alternator from the 80'.

What would be more safe for my LiFePO4 Victron 150ah battery and for my old van alternator (I don't want to overheat the alternator).

Would Cyric Li-Ct would be a safe solution or should I go with the DC-DC charger?

Thanks for answers!


slowjoe asked
slowjoe commented ·

1 Answer

Cyrix-ct with 2 channel charger

I have 5x100Ah house bank and 1x100Ah start battery. Victron Cyrix-ct connecting the 2 banks. I have just installed a new charger with 2 output channels. Is it ok to connect each battery bank to its own output channel or does the Cyrix require that only one bank is connected to charger and then the Cyrix passes the charge to bank number 2?

piperbill asked

0 Answers

Engine charging causing hysteresis

Hello, I have a Victron Cyrix-CT charging my Battle Born Lithium batteries while the engine is running. I get a High Limit (hysteresis) warning when I'm at full charge and driving since it hits 14.8 volts. The BMS will prevent a charge if it exceeds 14. 7 volts. So I would assume that this is just noise that I don't need to worry about. If that is the case does anyone know how to stop getting alerts on it? Thanks for the feedback

Voltage: 14.81
Low limit (hysteresis): 11.8 (12.2)
High limit (hysteresis): 14.8 (14.7)
Wait time: 60 seconds

kaplan78 asked
indian commented ·

1 Answer

Victron Blue Power charger 12V/15A - combination with 2 batteries, is it enough


I've got a Victron Blue Power Charger 12/15, the older model without bluetooth.

I have a 150Ah Victron battery as house battery for all equipment. I also got a 60Ah starter battery attached to my outboard. Between the two I installed a Victron Cyrix-ct 12/24V-120A.

Now when I am at the marina, can I use my charger to charge the batteries? Is it powerful enough for this set-up? Can I leave this charging all the time? I have got a remote power-switch installed so I could also just charge the day before when I want to take my boat out a day..

Hope to hear you soon,

Kindest regards, Marcel

marcel-nl asked
indian answered ·

1 Answer

Cyrix-ct 12/24 V 120 A not engaging


I have a Cyrix-ct 12/24 V 120 A connected between one starter battery and two domestic batteries. When the engine is running the voltage between pin 30 (starter battery) and pin 86 (negative) is 13,95 V, but the batteries is not connected. The domestic batteries are down at 12,36 V. I have been running the engine for two hours. I even tried to connect pin 85 (start assist) to the starter battery. Nothing happened.

Is my unit broken?

Best regards

M. Kindt, Sweden

kindt asked
indian commented ·

0 Answers

Cytrix-ct ground connection


I just got my Cytrix-ct for installation of a second battery in a motorhome. The accessibility of the starter battery makes it difficult to connect port 86 directly to the negative of the battery. My (very simple) question is: Can I connect port 86 directly to any other ground point of the vehicle instead?


alytes asked
indian commented ·

1 Answer

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