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Cyrix Battery Combiner

control Cyrix or BP with BMV instead of BMS

Is it possible to control the disconnect function in Cyrix Li-ct (or Battery Protect) with the relay function in BMV712 (instead of the BMS)?

I would like to use the BMV alarm functionality to disconnect the alternator from the house battery when SOC gets close to 100%.

trostek asked
astor commented ·

1 Answer

Cyrix Li ct between Balmar 220A alternators and 614 external regulator.

@Daniël Boekel (Victron Energy Staff)

Hi Daniel,

Per your comment on my previous thread I am writing about 2 issues I am having. They are different so I will put them in 2 posts.

I have wired in a Cyrix Li-Ct between my house and start battery per this diagram:


If I attach the voltage sense to the Lithium batteries the voltage rises to 18v. If I attach the voltage sense to the start battery voltage is correct but I only see about 108 amps coming out of the alternator.

Any ideas?


Jon S asked
Jon S commented ·

3 Answers

CYRIX-LI charge and BMV 712 settings for overcharge protection

I have a 200Ah lithium battery bank connected to my starter battery/alternator via a Cyrix-Li Charge 230A controlled by the BMV 712-Smart.

It's currently configured to only connect when the starter battery is over 14.1V (indicating that the engine is on) and to cut off when the starter drops below 13.7 (when the engine turns off). I'd like to add another condition that my lithium battery bank must be below 95% to protect against overcharging. Not having luck with the state of charge. Anyone have guidance?

Desired Logic:

ENGINE ON, BANK < 95% = Closed Circuit (aka charging)

ENGINE ON, BANK > 95% = Open Circuit (aka not charging)

ENGINE OFF, BANK < 95% = Open (aka not charging)

ENGINE OFF, BANK > 95% = Open (aka not charging)

evolutionyst asked
evolutionyst edited ·

0 Answers

Best way to wire house battery to the engine alternators on boat with 12 m distance between them


I need to rewire a boat that has two small engines with 70A alternators. The house battery is 12 meters away and I am wondering if this requires a DC-DC charger to properly charge the house battery instead of using an Cyrix Battery Combiner. All batteries are AGM. Concerns I have are overcharging of the starter battery and undercharging of the house battery due to voltage drop.

In the current setup the previous owner wired one engine alternator to the house battery and the second one to the 2 starter batteries. I am not happy with that setup as I want to keep my starter batteries separated and I also would like to use both alternators to charge our house battery. We have no gas on board, so use quite a lot of electrical power for cooking and the likes.



FS67 asked
jsalbre answered ·

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

0 Answers

cyrix Li-charge and solar controller

Can I use a Cyrix Li-charge as an overvoltage charge cutoff on Victron 250/85 controllers? I see that the Li-Charge doesn't connect unless the charge voltage is over 13.7. Won't this prevent the solar controllers from operating? Also, if the Cyrix disconnects while the solar controller is charging, will that damage the solar controller?

Monoceros asked
Matthias Lange - Service Team Döbeln DE answered ·

1 Answer

Controlling Cyrix li-ct and Li-charge simultaneously?

Is it acceptable to wire both a Cyrix Li-Ct and a Cyrix Li-charge to the single Charge Disconnect port on a VE-Bus BMS?

Current plan is to have 1125 watts of solar wired to a Cyrix Li-Charge 120 and a Balmar XT (170 amp alternator) wired to a Cyrix Li-Ct 230 (with appropriately wired AGM start battery).

Blinkerfluid asked

0 Answers

Maintaining charge in starter battery using Cyrix-ct 12 in combination with Argo Fet

My current 12V system uses an Argo Fet 200 Amp to separate the starter battery bank from the house bank. Both banks are lead accid. I'm now looking for a way to keep the starter battery charged when not using the engine. My house bank has 2X 160W panels with a Victron 100/30 MPPT controler. (see attached diagram for more info).

I'm wondering if a Cyrix-ct 120A would do the trick, how to fit it in the current diagram and what the risks are? I would also like to be able to switch of the Cyrix when not needed (when we are on the boat)

Windhoos main DC power distribution-Windhoos main DC power-3.pdf

Windhoos asked
gbarnaud answered ·

1 Answer

Cyrix-ct 120 and domestic battery in sleep mode

For the cyrix-ct 120, it says:

"In order to prevent unexpected operation during installation or when one battery has been disconnected, the Cyrix-ct 12/24 will not close if the voltage on one of the two battery connections is lower than 2 V (12 V battery) or 4 V (24 V battery).

My trailer has a wireless brake controller in between the 7 pin connector and the domestic battery, and goes into sleep mode preventing the domestic battery from sending/receiving any power through the 7 pin. Because the cyrix never sees >2v on the trailer side while the brake controller is in sleep mode, the cyrix never activates. Is there a way to disable the <2v feature, or is there a way to get it work given the domestic battery side may be in ”sleep" mode? Currently, it fails to work in my setup due to the wireless brake controller going into sleep mode.

Solman asked
Solman commented ·

1 Answer

How does the start assist on Cyrix ct? I have a problem
hello, I purchased the cyrix ct 120A relay.
I already had a similar relay from another brand, not bidirectional but unidirectional.
I installed the Cyrix as shown in the diagram: 86 chassis, 30 start battery, 87 service battery, 85 start assist, on the positive service battery with switch.
But there is a problem: acting on the start assist, the cyrix should close for 30 seconds and then open.
instead it is always closed. and the only way to open it is to disconnect the negative contact 86.
Did it arrive defective or am I doing something wrong?

buongiorno,ho acquistato il relè cyrix ct 120A.
Avevo gia un rele simile di altra marca, non bidirezionale ma monodirezionale.
L ho installato come da schema: 86 telaio, 30 start battery,87 service battery, 85 start assist sul positivo service battery con interruttore.
Ma c'è un problema: agendo sullo start assist, il cyrix dovrebbe chiudersi per 30 secondi e poi aprirsi.
invece  resta chiuso sempre. e l unico modo per aprirlo é staccare il contatto negativo 86.
Mi è arrivato difettoso oppure sbaglio qualcosa?

Francesco asked
Francesco answered ·

3 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
Paul B answered ·

1 Answer

Lithium and starter constantly in parallel when on shore power

Hi, I've recently installed a lithium bank and use a cyrix li ct to connect them for solar and alternator chargin via the starter battery. This system works great when unplugged - cyrix kicks in when there is enough solar or alternator charge and disconnects when not. However, when I'm connected to shore power and charging the lithiums with the muliplus the cyrix (rightly so) remains engaged. Just wonder if there is any damage that can be caused to either starter or lithiums doing this? If so I will just put a simple switch in the wire from the charge disconnect circuit and turn off the cyrix when on shore power.

stocksy asked
Justin Cook - Bay Marine Supply USA answered ·

1 Answer

Cyrix Li Load, is it bidirectional

Looking at the Cyrix Load as a battery protection, this will feed the motorhome 12v electrics, and inverter however the 12v connection is via the motorhome electrical distribution block, this also provides via a mains charger on hook up, the charge to the same battery, I was looking to protect with the cyrix, question is, are these devices bi directional, I'm assuming these are just relays?

AdrianM asked
Matthias Lange - Service Team Döbeln DE commented ·

1 Answer

cyrix li ct and charge modes, bulk, absorption, and float


I wonder if Cyrix Li Ct reduces the charge current when the Lifepo4 voltage is 13.8V and above. Can it charge in absorption mode and float mode?

I don't have a Quattro nor anything like that (and I can't, don't have enough room anymore).

If the Cyrix Li Ct is not as smart as it should be, what can I do to reduce the amps from the alternator when the Lifepo4 is nearly fully charged?

I have a ve bus BMS but I assume the cyrix li ct opens only when the charge disconnect signal is off (what about the absorption during charging??)

Thank you.

drumond asked
drumond commented ·

2 Answers

Why is the Cyrix Li CT draining my battery?


I thought the Cyrix Li Ct would charge only my 200Ah auxiliary lithium battery in my van.

When I switch on the van engine, it reads 14.2V on my starter engine (the starter battery is an old one, I will replace it next month) and 13.58V on the Lifepo4 (around 50% charge at this very moment).

Or when I turn off the van engine, it's also the other way around, the lifepo4 is depleting and charging my engine battery (they tend to have the same voltage as soon as I switch off the engine, around 13.1V each). I don't want that to happen at all.

It is like my Cyrix Li Ct was useless. For information, I also have a Ve.bus BMS. Everything is plugged like it is shown on the connection diagram given by Victron.

How can I prevent the Lifepo4 to NOT charge the starter battery when the engine is turned off?

Do I have a defective Ve.bus BMS or is it the Cyrix Li Ct that doesn't work properly?

Thank you.

drumond asked
drumond edited ·

2 Answers

Cyrix-ct 12 / 24V 120A, Intelligent Battery Combiner, 12V STARTER BATTERY

a question: The ct 120 cyrix can work when the vehicle is at 12V while the system trailer is 24V, and if not, is there any part that will improve the connector to make it work. Thank you for a quick reply please.

krispin asked
Matthias Lange - Service Team Döbeln DE answered ·

1 Answer

Low temperature cut off with Venus temperature sensor

Dear all,

I have a LiFePo Battery which is connected to a MPPT 150/35.
The MPPT is connected to a Venus GX via VE.Direct.
The Venus GX has a temperature sensor connected.

I need to disable the charge of the battery below 5°C.

My first idea was to setup a VE.Smart Network with a Smart Battery Sense, but in the FAQs there is information not to use this if a Venus GX is connected.

The next idea was to use the Venus temperature sensor with the "Shared Temperature"-Feature, but I found out, that this was planned for Venus OS v2.20, but then not released.

I have read that "Shared Temperature" is only available in connection with a BMV-702.

So the only solution is to use a BMV-702 with a temperature sensor and the "Shared Temperature"-Feature enabled in the Venus GX or is there any plan to include the Venus Temperature Sensor in the near future?

What is the best solution for a temperature cut-off in combination with a Venus GX?

Thank you


MartinK asked
MartinK commented ·

1 Answer

Cyrix-ct 12 / 24V 120A, Intelligent Battery Combiner, 24V STARTER BATTERY


So I have the Cyrix-ct 12 / 24V 120A, Intelligent Battery Combiner. My truck has a 24v Starter Battery. My Domestic Battery's are 12v. Will it be safe for me to connect the Cyrix-ct 12 / 24V 120A as described in the manuel or should I have purchased another product? My worry is that it is a rather small device and generally 24v to 12v DC chargers are rather big... or should I purchase a 24v to 12v DC chargers and place in between the Cyrix and the domestic battery?

Thank you


albert.c.castro asked
albert.c.castro commented ·

1 Answer

Cyrix li CT issues

Hi all,

I have just got the above battery combiner and found that the stated voltages in the documentation to be inaccurate.

It states that the unit will combine the batteries if the voltage is 13.7v or more on either terminal. I've done serveral tests with the use of 3 multimeters and the BMV 712 battery monitor installed and the unit is engaging when the batteries are at just 13.3 V.

Also, something I didn't think about, but the 13.2 V disconnection, in my opinion, is too low. My lithiums sit at around 13.2 V and once connected both they and the starter battery stays that way unless I place a heavy load on it dropping the lithiums and said starter battery down below 13 V. I would have thought that having the disconnection set at 13.4 V would make more sense and give a disconnection once any charging source has been removed.

I'll live with the issues, but does spoil what could be a brilliant device as I feel all my other Victron products are (MultiPlus, Venus GX, Isolator Transformer, BMV 712, Battery Protects...)

If I'm missing something here then please let me know as I hope I'm wrong and can get this functioning as originally intended.



stocksy asked
Justin Cook - Bay Marine Supply USA answered ·

1 Answer

Can Cyrix-Li-Ct work without a starter battery ?

We are installing a Lithium HE system on a boat. One alternator is dedicated for the Lithium batteries, so there is no starter battery. The question is can we connect the alternator directly to Cyrix-Li-Ct ?

Gonenc Ozkul asked
Justin Cook - Bay Marine Supply USA answered ·

1 Answer

What is the right connection diagram for Cyrix ct 230?

The two diagrams (attached below) that are part of product documents are confusing with respect to the interpretation of the battery ports on Cyrix ct 230. It isn't clear at all which port is for start battery (I guess this is what is meant by battery 1) and which one for house battery.

Please help.

Thanks a lot for advice



refik asked
refik commented ·

1 Answer

Cyrix Li charge over voltage

I have an over charge / over temperature alarm signal on my Cyrix Li charge but I can’t see why it should be showing this.

I have 4 150ah victron lifepo4 battery’s connected for 24 v system.

Looking at the victron app, battery temperature 21 c is ok and battery voltage 26.57v

I have 735w of solar (3 panels wired in series) thru victron 250/60 mppt.

Over voltage also occurs at night when there is no solar input .

Any answers gratefully received


Mojo asked
Mojo answered ·

2 Answers

Cyrix-ct 230A / Battery connection


I just installed a Cyrix CT 230A in my car. After I finished the installation I recognized that I connected my starter battery to the port "Battery 1" (because I thought Nr 1 must be the main battery in the car and my aux battery to the port "Battery 2". Now I've seen that it looks like it is turned around in the manual. But I'm not sure because the ports are not numbered in the manual. Do I have to change my installation?

Thank you very much for helping!





David6886 asked
refik answered ·

3 Answers

Location of the cyrix

Hello, I've installed a cyrix battery combiner on my van :

Start batterie 95mAh

Aux batterie 100mAh

My devices use max 125W, I've followed the instructions properly appart from 1 thing, i did not put the cyrix close to the start batterie, instead it's close to the aux one (I know it was written not to do so but there's a lack of space at the front next to the start one and i thought it would not be a big deal). Is it a big problem to have it located there? should I change it's position and bring it close to the start batterie ?

Also I have a fuse between the cyrix and the aux batterie, the first time I used the electricity in my van I noticed after a day that the aux batterie was not charging, and the fuse was actually blown (maybe after a day of use) I checked everything and changed the fuse and now it seems to be working. (fuse 60A and cable section 16mm2) Could this be related to the position/location of the cyrix, or was is just a one incident and now everything ok?

Thank you for your time

vesselin asked
Justin Cook - Bay Marine Supply USA answered ·

1 Answer

Mini BMS charge disconnect


Can the charge disconnect be connected in parallel to two devices? The link below shows two diagrams - one where it controls a MPPT and one where it controls a Cyrix Li-ion. My question is can the connection be paralleled to both devices?

Stevo07 asked
Daniël Boekel (Victron Energy Staff) answered ·

1 Answer

Cyrix-ct does not work

When the cyrixct is connected with with the 86 pin to the minus of the battery, the relais stays closed and no current is going through. When the engine is running the voltage is abive 14,5v but it stays closed. When i do not connect the minus pin 86 to the battery the relais switches and stays open, but it does not close when the voltage is low and when the engine stops. Does anyone know if the cyrix-ct is broken or do i do something wrong?

fokke jongerden asked
Wildebus commented ·

2 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
Wildebus commented ·

3 Answers

Will a Cyrix with a charging second battery trigger start assist?

I would like to use a Cyrix-ct 12/24V 120A with a second battery that's also charged by a solar panel. The Cyrix is bidirectional, so a fully charged battery on a sunny day will also charge the first (starting) battery. Will both batteries be used if I start the engine in that situation? Will this effectively be a start assist? Obviously, I would want to do that with my AGM battery.

TurboTomNL asked
JohnC commented ·

2 Answers

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