Cyrix Battery Combiner Image

Cyrix Battery Combiner

Why is it okay to have Lithium bank and Starter battery combined with Cyrix Li-CT

Hi, I would like some further information on why its okay to use a Cyrix Li-CT to combine your Starter battery to your Lithium batteries?

-Wouldn't there be a possible chance that you can overcharge your start battery as the Lithium will be just continually taking as much amps as possible?

-When charging via solar or shore power you will also have your batteries combined.
-I wouldn't think that have a Gel or Lead acid battery connected into your Lithium system would be a great idea

Wouldn't putting a 3 stage regulator (so the alternator doesn't burn out) on your alternator to charge your lithium and then a DC-DC charger to your starts be the safest option?

Looking for the best and safest way to utilize the alternator in lithium installs.


Adam Robb asked
Paul B answered ·

1 Answer

Cyrix CT and engine starting in parallel
I have a cyrix CT 120A relay between the starter battery and the service battery which is a victronenergy agm deep cycle 110 ah.
Obviously the cyrix does a start with the batteries in parallel most of the time, that is, if the batteries are in solar charge or if the batteries are fully charged.
In your opinion is it harmful to the agm victronenergy?
I believe it is absolutely not harmful, as during start-up, the smartshuunt only marks 30A of absorption on the agm for less than 1 second.
I think This is because the resistance of the positive cable in series between the batteries and starter motor means that 80% of the starting power is supplied by the starter battery.In fact starter battery have a much more short and more thick cable, that cause a lot less drop voltage and supply more amps to the motor. But some peaple say me that's is no good.... 
In fact, the total absorption for starting is about 120A and are divided as follows: 30A on the agm services and 90A on the starter battery.
Furthermore, the data sheet of the agm victron says that it tolerates inrush currents of 500 CCA at - 18 degrees, and absorption of 880 amperes for 5 seconds.
So 30 amps 2/3 times a day for less than 1 second shouldn't hurt.
What do you think?
However, I have equipped the cyrix with a switch on the negative of the coil to exclude it during start-up.

francesco asked

0 Answers

Boat setup: 12v house bank, 48v electric propulsion bank, solar array

Hi, I am about to buy a used sailing trimaran and can't quite wrap my head around the ideal electrical setup. Any help would be much appreciated.

  • The boat has an existing 12v house bank (100ah lifepo4) which is sufficient at sea
  • All wiring and electrical appliances are 12v optimised
  • A 12v to 220v 2000W inverter is installed for power-hungry appliances
  • I've got 6 x 100W semi-flexible solar panels and plan to use 3x Victron 100 / 20 MPPT charge controllers
  • This should enable to keep the battery topped most of the time, with little electrity use at night

Additionally I'm planning to add the following:

  • 48v electric engine as secondary propulsion (sails 95% of the time)
  • 6.0KW max draw, 1.0KW max hydro regeneration
  • 8.9 KW lifepo4 dedicated propulsion battery from manufacturer

I would like to intelligently combine the two systems/batteries as I expect that usually one or the other has more energy than it needs. So a bidirectional 12v - 48v charge system / battery combiner is what I am looking to implement.

I'm aware of cyrix products but not quite sure how to implement them in a 12v / 48v system.

Thanks for reading, curious about your ideas and solutions.

simonsails asked
simonsails commented ·

1 Answer

Victron gel 110ah absoption time

Hi, i want to know how many time i must set on my mppt charger for the absoption phase : i have 2 battery gel 110ah // > 220ah

all days, my controleur when the sun is up, do an absoption phase (i's set it for 30mn) and after this 30 mns, the float phase is automatic.

30mn, is too long? too short? ...


Vinyl Addict asked
michelg answered ·

1 Answer

How to connect Cyrix ct 120A

Single 110A alternator, starter battery domestic battery bank, solar panel with MPPT and battery monitor system on starter and domestic bank using 200A shunts connected on +ve side.

Since the Cytrx installed battery monitor does not appear to work.

gill43 asked

0 Answers

What is an "typical" current draw for a Cyrix Li ct from a non smart alternator to Lithium

I have just upgraded to 2 x 100Ah Solarking drop in lithium batteries.

I installed a Cyrix Li ct to charge from my lead acid/Non smart alternator.

I am drawing 8 to 12 A from the Alternator side of the connection.

Is this a typical/safe current draw for a 170A alternator?

andrew-childs asked
andrew-childs edited ·

0 Answers

Cyrix-ct 12/24 120A leiasure battery not charging VW T5 2005


On one side, 87, Pos 14.45 volts,on the other side, 30, 7.74 volts. All leads and contacts good. Leisure battery was fully charged, overnight use without engine running dropped it to 9.97v. I did not do a long enough run to help recharge it. However a 125 mile trip shows the leisure battery now at 7.74 volts. No leads on 85 or 86.

Can you advise please?

Kind regards


ian5972 asked

0 Answers

deep cycle 220ah gel batteries cycle of charge

Hello community.

I have a question that has probably been answered before but I cant seem to find an answer.

I have three 220AH deep cycle gel batteries (brand new) installed on my boat. The connection is in parallel.

We also installed a solar array of 730W (series connection of two panels) connected to a 150/70 MPPT. We connected the MPPT directly to the battery bank as we do not have space on the bus bar.

My question is what is the voltage on the batteries when they are 80% discharged. and 50% discharged.

I am very confused as to the voltage of the cycles and want to make sure we are doing it right.

Many thanks


jordaanp asked
Ulrich answered ·

1 Answer

Generator and solar charger connected to battery at same time? (MPPT and Multiplus)

In this reference design and this other design the positive from the MultiPlus/charger and the positive of the MPPT solar charger are not permanently connected - they are separated by the Cyrix Li Charge. Is the Cyrix necessary to separate these parts, or could they be permanently connected?

From the docs

The Cyrix-Li-Charge will connect a battery charger with 3 seconds delay:

- if the Charge Disconnect output of the VE.Bus BMS is high, and

- if it senses 13,7V (resp. 27,4V or 54,8V) or more on its battery charger connection terminal, and

- if it senses 2V or more on its battery terminal (the Cyrix will remain open, if not connect to the battery)

#1 requires an input from VE.Bus, which AFAIK is incompatible with non-Victron batteries (which I hope to use). So if the Li-Charge is not necessary, I would remove it. Is it necessary? What goal does it achieve? And why would it be a good idea to disconnect the MPPT and Orion, but not disconnect the MultiPlus?

If the Cyrix is necessary then I could drive it from a relay using some other logic, though my goal would be to allow the generator to charge the batteries (via the MultiPlus) at the same time that the PV/solar charges the batteries.

This design does that, but makes no reference to a generator, but presumably the MultiPlus would accept that AC input.

I see there are other designs that permanently connect a Smart Charger to an MPPT (not MultiPlus).

Tangential question: Are the 'Main Switches' (1, 2, 3) in these designs intended to be isolation switches (to be placed in open position for servicing, repair, storage, etc)? Or do they exist to allow the user to 'change modes' of their system? E.g. from one charging source to the other? (and by extension may require such user interaction). I assume the former, but would be good to get confirmation.


tom saffell asked
tom saffell edited ·

0 Answers

cyrix li-ct combiner cycling rapidly while charging

Hi i have large 200 amp 24v alternators that charge the engine agm batteries and then the cyrix between engine and 1000 ah smart batteries.

If the soc of Li batteries is high enough 60-70% then the cyrix closes contact and charging is perfect.

if the soc of Li batteries is 20-60% then the cyrix will not close and hold contacts [tends to switch on and off]

If i close the emergency parallel switch between engine and smart batteries then charging is good at any soc.

I think the setpoints for the cyrix are incorrect for proper combining at all soc.

rona asked

0 Answers

Cyrix LI not charging leisure battery.

Hello, everyone. I have the setup below in my van.

I don't have the yellow signal connected from 85 to +

My lithium leisure battery isn't charging off the alternator. Is the yellow signal cable the reason why?

Everything else works fine.

I can't find an answer as to what the yellow cable does.




leon-rudge asked
Matthias Lange - DE answered ·

1 Answer

Cyrix or FET diode bridge ?
Hi everybody,

I am in the process of upgrading my boat from a single battery to separate battery banks. I have a few questions about that.

1. what / which technology is best to use and connect to charge both banks with the chargers (shore power, alternator, wind and solar).
2. I have been looking for Cyrix and FET Diode bridges and do not know what is best and how to connect. And if a Diode is a 1 way system how do the chargers know when they are full.
3. What are the best universal settings for AGM batteries if I want to set the BMV712, Smartsolar and shore power charger. Now I notice that my old lead battery is not yet full according to the charger, but the BMV gives 100% and keeps bulking for 30min.

all tips and help welcome :)

greetings Ian



ian-macleod asked
ian-macleod edited ·

0 Answers

charge two batteries from a mppt 75/15 using a Cyrix-ct


I have a Victron MPPT 75/15 charging my secondary battery. My idea is to charge the engine battery using the Cyrix-ct connected to my secondary battery.

Is that possible?

polamoros asked
smoketest answered ·

1 Answer

Connection Cytrix et Argo 120-ac

Bonjour ,

je suis en train d upgrader mon installation electrique de mon camping car.
J avais actuellement une batterie porteur de 100A et une batterie lithium de 150A, avec un cytrix pour gerer le tout pour une charge alternateur. Le tout relié avec du 25mm².

Jusque la tout marche impec.

J ai ensuite rajouter une batterie 200a lithium et j ai pris un argo 120-2AC, j ai connecte la sortie du cytrix sur l inmput de l argo puis les deux outputs sur chaque batterie.

Probleme j ai plus aucune charge.

Je vois bien au multimetre qu a la sortie du cytrix j ai plus aucune tension, d apres ce que j ai lu sur les forum ca viendrait du faite que le cytrix check aussi la tension en output et pas qu en input comme je l aurai cru. Or les diodes de l argo bloque le signal retour.

Comment puis je contourner ce probleme?

Merci d avance

yuharla asked
Thierry Cortassa (Victron Energy Staff) answered ·

6 Answers

How to connect an argo 120-2AC after an cytrix-CT

hello everybody,

I have actually an cytrix-ct connect with my motor battery and the second battery in my van.
I upgrade the electrical capacity with an second lithium battery, so i have buy an argo 120-ac.

I connect the output of cytric to the input of argo 120-ac and the two output of 120-ac to each battery.

Problem i have no charge ...
I think the cytrix don't know my load because argo don't let the signal up to him.

Anybody have already do that or someone know i can fix it.

Can i use the the output compensation to connect to the cytrix output thanks that the cytrix can see something?

yuharla asked

0 Answers

how to combine 12v and 24v circuit on boat

i just found out the cyrix-ct does not allow two different voltage levels.

can anyone help me which device(s) i need to allow me to charge my 24v system with my 12v alternator in a way that my 12v (starter) battery doesnt get emptied by the 24v (trolling) circuit


jab asked
jab answered ·

2 Answers

Lithium battery (not a Victron)...but with a Cyrix-CT (...not a Cyrix-Li-CT)

A few month ago, I hade to change my GEL batteries by a lithium battery on my camper. The seller told my "you have a Cyrix, so you can have a lithium battery".

I know discover that the Cyrix-CT connect ALWAYS my lithum battery with the engine battery (...which is a lead battery of course)

==> The voltage of the two (very different) battery are always the same

==> When I strat my engine ON...the lithium battery always "helps" the engine battery"

==> Big problems for the future.

==> What solution can you propose to me?...I could replace ce Cyrix-CT by a Cyrix-Li-CT...but it is written on the manual that I need to have a Victron VEBus BMS

Thank you in advance

xdorland asked
xdorland answered ·

2 Answers

Cyrix Li Charge disconnects every 60 minutes

This will be the third time I have presented this issue on this forum. Having spent over NZ$10,000 on Victron equipment for a Lithium installation on a boat and engaging with is forum and the local Victron dealer I still have a Cyrix Li Charge that doesn’t work properly. The relay opens for a few seconds exactly every 60 minutes 24 hours a day. The dealer has replaced the Li Charge and the new one exhibits the exact same behaviour.

The installation is pretty much exactly as Victron documentation with the Li Charge being controlled by a VE Bus BMS charge disconnect terminal.

Either the Cyrix Li Charge is not suitable as charge disconnect relay or there is some problem with my installation. In either case I cannot get the local dealer or anyone through this forum to engage with the problem.

I am attaching a schematic of my installation.


Tim Chapman asked

0 Answers

Battery combiner limiting current

I am searching a current limiter between the batteries. I have a battery set including slipring between sets. So I need to protect the slipring. May be I can add a cyrix ct-120a before slipring. I expect that if charging current is over 120A, cyrix ct-120A will limit the charge current to 120A by making voltage low. Is it possible?

ihanci asked

0 Answers

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

119 Posts
155 Users

Topic Experts

10 Points