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Cyrix Battery Combiner

BMV-700 Monitor Settings with BAT412101104


Please can you help me figure out what the correct values for the;

    • Charged Voltage
    • Tail Current
    • Charge detection time
    • Peukert exponent
    • Charge Efficiency

should be on my BMV 700.

The BMV is monitoring 3 victron Gel BAT412101104 in the setup outlined below.



Any help would be very much appreciated.



ruffian asked
pwfarnell answered ·

2 Answers

MPPT 30/100 and 50/100 forces Cyrix Li Charge to go into overvoltage error

I have 2 MPPT Smart Solar charger (30/100 and 50/100) together with 3 Orion TR connected on a VE.Bus controlled LiFePo battery in van.

My idea was not to load up to 100% SOC all the time (goal is to charge up to 80%). Therefore I planned to interrupt charging based on SOC measured by a BMV700 and using the built in relais to interrupt the VE-Bus signal to the cyrix Li charge relais.

So far so good, stopping the charging process works fine, BUT ....

the MPPT charger has an ideling voltage on battery out terminals of about 16.2 V when battery is disconnected. Cyrix Li Charge recognize this an overvoltage (more than 16V) and prevent to reconnect chargers to the battery.

Any ideas, how to overcome this situation?

richi1230 asked
richi1230 commented ·

2 Answers

Cyrix-Li-Ct connecting 24V LiFePo4 battery pack to 12V Starter Battery

In my RV I will have 12V starter battery, but due to high amperages I think about making hotel battery 24V to cut them by 2.

If I connect Cyrix-Li-Ct on the one side to 24V battery and on the other to 12V starter battery will it work? Or it will break?

Is such connection safe at all?

nysander asked
richi1230 edited ·

1 Answer

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
ralph-vallis answered ·

2 Answers

Batteries voltage drops quickly when Multiplus switch to inverter mode

Hello Everyone,

Since December 2020, I have installed a backup system to help me to overcome the electricity problems in my offices, and since the commissioning all the system was working properly.the system is composed of 12 gel batteries 12V-210Ah C20 brand Leoch, a Color control and a Multiplus II 48V-5000/70.The installation powers only a few laptops, a few lamps and a small printer, so that our power consumption never exceeds 1200W.

Everything was working well and we had more than 8 hours of autonomy without the SOC of the batteries even reaching 70%, however for the last 4 days, in case of a power cut, after 5 minutes the low battery alarm sounds and the multiplus turns off.

Checking each battery individually in a chain of batteries in series forming a group of 48V, I noticed that the difference in voltage between batteries was enormous, one has a voltage of 9.87V, while the others are at 11.35, the other at 12.35V, this difference in voltage surprises me enormously and I wonder what could be the cause of this because everything was working properly, the settings of the charger well configured in VE configures for a Gel battery, and the room well air-conditioned to optimize the life of the batteries.

What makes it even more complicated is that the Color control mentions an SOC of 98%, but the voltage drops rapidly and the MultiplusII shuts down, followed by a High DC ripple message.

Can you please help me?

Thank you in advance to @Guy Stewart (Victron Community Manager), @Alexandra @Thierry Cortassa (Victron Energy Staff) ,thank you also in advance to anyone who can help me find a solution to this problem, because it's already been three days that I am forced to turn to the generator and the fuel costs are starting to weigh on my business, the pictures of the system are here if that can help.

WhatsApp Image 2021-08-22 at 17.16.27.jpegWhatsApp Image 2021-08-22 at 17.16.27 (1).jpeg


Deutch asked
Deutch commented ·

2 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
centaur16 commented ·

0 Answers

Has Anyone Actually Destroyed an Alternator?

I would like to know if anyone out there has actually managed to destroy their alternator by using a Cyrix LI CT and a lithium battery bank?

(I do know about 'the video' and why a DC/DC converter is the 'correct' solution. However, this is expensive in comparison to Cyrix and one loses some nice functions such as bidirectional charging and start assist).

If it's such a no no to use a Cyrix, why does Victron sell it?

Looking forward to hearing some real world experience.


davidq asked
batak answered ·

3 Answers

Gel batteries behaving strangely, any ideas?

Apologies for the length of this post but I wanted to include what I feel is relevant information.

I have a bank of 3 x BAT412121104 gel batteries on my sail boat, they are linked up to a 12/40 Centaur Charger which is left on while we’re away from the boat. I use a ODELCO DCC 4000 battery monitor to see what the batteries are up to. When the batteries and charger were installed 3 years ago I recalibrated the battery monitor to 390 amp/hours.

When the batteries 2018 were new the battery monitor was reading 376 amp/hours, after a year (2019) this was 378-384 amp/hours but the next year (2020) around 365 amp/hrs. This year (2021) they seemed to deteriorate quickly down to 270 amp/hrs.

One weekend while moored for 48 hours the voltage got down to 12 volts and we had to charge with the engine. While on the mooring we were using about 2 amp hours for the fridge and a bit of led lighting at night. After that episode the batteries were still reading 270 amp/hours after charging.

Last weekend after anchoring for 24 hours the windlass dragged the voltage way down causing the nav instrument to turn off, the engine was running but that didn’t seem to have any impact.

But after recharging the batteries were reading 309 amp/hours and each time they are charged (I turn the charger off overnight due to the constant noise) they seem to gain 10 – 20 amp/hours and when we left the boat were reading 351 amp/hours and 12.77 volts after being off the charger over night. The people who fitted the batteries said it was to be expected that the batteries would loose 30% of their capacity after 3 years, which was a bit disappointing as I was expecting a significantly longer service life than that.

Sorry for the long story but can anyone give me a clue as to what’s going on? Do I need to replace the batteries or have they staged a miraculous recovery?

mikejulietgolf asked
JohnC commented ·

5 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
justmurph answered ·

2 Answers

CYRIX-CT Battery Coupler - Charge Engine battery from Leisure batteries ?

Hi All,

I have two leisure batteries in my Camper Van which will are charged by the Solar MPPT Controller (and the Alternator when the engine is running). The Engine battery is not connected to the MPPT Controller, and can go flat if, unused during the winter.

What I want to ensure is - that the CYRIX-CT Battery Coupler can charge the Engine battery (from the Leisure Batteries) when the engine is switched off. Can the Cyrix do this ?

Many Thanks !

danny007 asked
pwfarnell answered ·

2 Answers

12V Wiring diagram Cyrix CT120 and shuntless ammeter

Dear community,

I'm designing the electrical system for my boat which I'm building step by step. I split up the start- and service battery with a Cyrix CT120 and want to measure the current of the service battery with an ammeter (+/-60A). In other words, I want to see if the service battery is being charged or discharged. Looking at the service battery part of the system; I have one main-switch installed for emergency shut-off and another one for the consumers. The last one will be swithed off when the boat is not being used while the first mentioned will normally be on.

I'm looking for feedback on the design, in particular how the service battery is connected to the Cyrix unit and the position of the ammeter.

Thank you very much in advance for any feedback you might have.

Kind regards,



San Sylvestre Conversion.pdf

hbhoekie asked

0 Answers

Cyrix-Li-Ct Limiting SuperPack Charge

I have noticed that my Cyrix-Li-Ct limits the charge of my Victron SuperPack batteries (3x200ah Victron SuperPacks) to approx 13.4v.

The Cyrix-Li-Ct terminal 87 is connected to 120Amp fuse then the vehicle's battery via a 1/0 cable to my vehicle's battery. Terminal 30 goes the batteries; terminal 85 goes to batteries pos and 86 to my negative bus bar. This was the wiring recommendation from the battery seller.

When I start the van I see the voltage around 13.40v and the amperage as a negative number and within a minute or so it jumps to a positive number (+100 amps) and the voltage increases to above 13.6v but then a couple minutes later it drops to lower positive numbers. The battery voltage rarely reaches 13.5v and current will get as low as 18 amps. 3 BMV712 screen shots attached

Do I need the Cyrix-Li with the SuperPacks? If so, do I have this correctly wired? If correct, why aren't the batteries charging to 14.2v?




Tom asked

0 Answers

Strange sound while charging new gel battery, is this normal?

I just installed a 330ah battery bank with three parallel 110ah 12V gel battery's. While charging, one of these battery's makes a strange sound. Like it is bubbling. When I noticed, the charger was at absorption stage at 14.3V and 6amps. Does this mean the battery is broken (or will get soon...)?

jdvt asked
jdvt answered ·

2 Answers

Cyrix-Li-ct: will it overcharge/damage the gel/starter battery?

Will the Cyrix-Li-ct battery combiner overcharge/damage the Gel starter battery? The gel and LifePO4 batteries are connected together whenever one of the batteries has >= 13.4V (and the LifePO4's VE.Bus BMS isn't sending a charge disconnect), so when the alternator is on (rare), when the MPPT/solar is working (daily), and when the MultiPlus-II is charging the LifePO4 (likely often). Is this ok for the gel starter battery?

If this is ok, then I don't need to have a separate trickle charger for the gel starter battery right?

trougnouf asked
trougnouf commented ·

1 Answer

Cyrix-Li-ct connecting between starter and coach lithium without BMS control

I have lithium batteries with built in BMSes (Lynac Lithium, 440Ah at 12V) that do not have an external logic signal to prevent over-charging. I would like to connect my Cyrix-Li-ct to permit charging from the engine alternator/starter battery when the engine is running, without overcharging.

What should I use as the input control signal to the Cyrix? I have a SmartShunt, Cerbo GX, MultiPlus, and SmartSolar - but it is not clear to me which of these can be used to gate the connection for both a) engine running (I guess this would be that the vehicle battery >14V) AND b) the lithiums are not already charged (I guess this would be something like lithium battery <14V?)

Or is there another easy way to do this?

Thanks in advance,


greg-johnson asked

0 Answers

Cyrix battery combiner kit cable question

I received the Cyrix-ct Battery Combiner Kit today. The relay can handle 120A and the alternator of my van supplies max 90A. All good so far.

I've bought the kit to connect a 180Ah AGM semi traction leisure battery to my starter battery/alternator.

The kit comes with 10mm2 power cables. I've read online that cables of 10mm2 and this length can handle 30A max. Aren't these too thin for the 90A my alternator provides, let alone the 120A the Cyrix can handle? Or is your experience that these cables are perfectly suitable for the job? After all, they won't put them in the kit for nothing.

I now doubt whether I should return the kit and buy a separate Cyrix with thicker cables. I'd love to hear what you guys think about this.

victorg asked

0 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
Matthias Lange - DE commented ·

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
cappugwash answered ·

4 Answers

Charging Battle Born (LiFePO4) batteries from a Delco Remy 50dn (24v 270amp) alternator

Hello Victron Community,

For a few weeks now I've been struggling to find the right solution to charge my LiFePO4 batteries from my bus alternator. Here are the relevant technical details:

  • Delco Remy 50dn heavy duty alternator (24v 270amps); oil cooled, belt driven, externally regulated
  • 2x3 Battle Born batteries (12v 100ah) in seriesxparallel for 300ah at 24v (internal BMS)
  • Cyrix-li-ct relay connecting start batteries (2x group8 lead acid)

I consulted Battle Born and a few others in the industry and was told that this setup should work. The alternator is rated for heavy continous use and the Battle Born batteries can take charge from the alternator with the normal caveats (i.e. the alternator voltage will not be able to take the batteries to full SoC, etc.)

In practice, however, what I'm seeing is unworkable and I'm concerned I may actually damage my alternator/system. With the engine on and the relay engaged (solid blue light), I see a cycle that lasts 3-4 seconds and repeats ad infinitum. For a few seconds there is no current flow. Then, for a split second, a large in-rush of current (160+ amps) and a voltage spike of over 30 volts. Followed by no current and a return to 28 volts.

I've recorded the behaviour on video here:

Does anyone at Victron or in the community have an idea as to why this is happening? In the video you can hear the relay making a noise that is a bit disturbing as well.

Thanks in advance for any advice.

Micah Quinn asked
Micah Quinn commented ·

3 Answers

Cyrix-CT 12/24 120A wiring diagram where start assist is not being used -- will this work in combination with Orion 12/24 Converter?

I've been using the non-smart version of the Orion 12/24 Non-isolated 10A Converter for alternator charging between my 12v vehicle system and my 24v house battery. I've been turning it on and off manually using a circuit breaker but would like to make this process automatic for obvious reasons and would like to do so in as elegant a fashion as possible. After researching, I decided that the Cyrix might be able to work in this situation. I wired it up as showing my attached diagram. However, once I started the vehicle and engaged the system, I did not getting any current.

One thing I did not do is connect the small negative terminal of the Cyrix, since I assumed that this was only necessary when using the "start assist" feature, which I am not using. Is this incorrect? Would this solve the problem, or is the cyrix simply not suitable for use with the Orion converter?



Stephen Otto asked
Matthias Lange - DE commented ·

1 Answer

Best way to wire Cyrix on a three bank battery system

I have a 5kva inverter ,2victron batteries (430 amp hrs ) two 12 v starting batteries & two domestic batteries .The alternator is 120 amp and have two Cyrix splitters .Currently one splitter goes from the engine batteries to the house batteries and the other Cyrix goes from the house batteries to the inverter batteries .Also have solar but that’s for another day .Is this the best way to wire the Cyrix or should they both feed of the engine batteries ?Many thanks in advance

riverside-marine asked

0 Answers

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
Adam Robb commented ·

2 Answers

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

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

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