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Cyrix Battery Combiner

MPPT 75/10 with CYRIX CT switches off load output when engine started

First post here, hello everyone! So I've installed a Smartsolar MPPT 75/10 in my campervan and also fitted a Cyrix CT, wired with 16mm2 cable between the auxiliary and starter batteries. The load output on the MPPT runs small devices (phone charger etc). All working fine during testing.

I ran my campervan this morning with no problem. Later this afternoon I started the engine and the MPPT load output switched off almost immediately (had to disconnect everything to get it back on).

When I went out this morning the batteries would have been at around 12.5v, this afternoon they'd been charging so around 13.5v (MPPT in float mode).

I can't think why this is happening - Any ideas as to what would cause this?

kubicixfactor asked
kubicixfactor answered ·

1 Answer

Cyrix or Argo FET

What are the main differences between the cheap scheme 1 and the more expensive scheme 2?

I have no shore power but i will add PV in the near future.

Thank you,


mapi69it asked
mapi69it edited ·

2 Answers

Cyrix for Lead Acid start and service bateries with 180 Amp Smart alternator

Hi there,

is it ok to build a system to charge a secondary battery (lead Acid 105Ah) with cyrix-ct?

Alternator is 180A


Many thanks in advance

lucas-bisiani asked
lucas-bisiani answered ·

1 Answer

Does the MPPT have reverse current protection from the battery?

I'm looking at a description of the Cyrix Battery combiner and I would like to confirm if this device can be used for protecting the MPPT from reverse current from the battery.

MPPT data sheet does not explicitly mention reverse current protection from the battery side (but mentioned for the solar side). Does MPPT have its own internal reverse current protection or are diodes necessary to prevent damage from back current?

btank asked
Triton edited ·

2 Answers

Will starter battery trickle charger cause Cyrix Li Ct to close?

System: van with a Cyrix Li Ct and a Smart Lithium Battery bank.
Will attaching a trickle charger to the starter battery cause the Cyrix to close, thus trickle charging the house Lithium battery bank?

Could this cause a starter battery to never get a trickle charge, and degrade?

roachmon asked
Matthias Lange - DE answered ·

1 Answer

Cyrix-Li-ct or Buck Boost in an electric car?

Can I use a Cyrix-Li-ct to charge an additional battery from an electric car/van? Or should I use a Buck Boost?

I've read that in recent cars with a smart alternator you must use a Buck Boost instead of a Cyrix-Li-ct. If I understand correctly it's because these alternators do not provide a constant voltage ( Is that the only reason?

But in an electric car there's no alternator. Instead there's a DC-DC converter that charges the 12 V service battery from the ~400 V traction battery. And this converter seems to provide a constant voltage when the engine is started (about 14.5 V).

So can I use Cyrix-Li-ct here? The price difference between the two items is huge (80 € vs 1280 € for 100 A).

quantumquest asked
quantumquest edited ·

0 Answers

Using Cyrix Li-Charge to turn off MPPTs

Hello, my dealer had installed a Cyrix LI Charge that would disconnect the MPPTs in case the cells get overcharged.

I currently have a problem that one of my batteries is not balancing. (one of the cells gets too high). So the Cyrix turns off the MPPTS while they are active. And then they don't get turned on. Here are my questions:

1. From what I understand, it is not good to disconnect the batteries, while the MPPTs are active, and yet, that's exactly what the Ciryx is doing. Is this ok, or will it damage the Solar / MPPTs? How true is it that you should always have a battery connected to MPPT while it is producing.

2. If the battery is disconnected from the MPPT using the Cyrix, then within 10 or so seconds, the output voltage on MPPT becomes 16.4 volts (I have Victron smart 100/30 mppts). So Cyrix doesn't turn them back on, because it considers that the voltage is too high. (at least that's what I read in some of the posts).

3. I am having a horrible time contacting my dealer / installed that installed my system. So I dont know who to talk to about this problem

Please advise.

Thank you in advance

grant-1 asked
grant-1 edited ·

0 Answers

Cyrix CT : Question

Bonjour, j'ai 2 batteries et j'ai installé mon cyrix en respectant le schéma de montage. Batterie 1 pour le démarrage et 2 pour le service. Si je coupe la batterie 1 avec le disjoncteur, le bateau démarre quand même. Le cyrix reste-t-il ouvert s'il ne détecte qu'une seule batterie ?

Merci pour votre aide

figatellisti asked
figatellisti answered ·

2 Answers

Cyrix CT : Question with circuit breaker

Hello, I have 2 batteries and I installed my cyrix respecting the assembly diagram. Battery 1 for starting and 2 for service. If I cut battery 1 with the circuit breaker, the boat starts anyway. Does the cyrix stay open if it detects only one battery?

Thanks for your help

figatellisti asked
figatellisti answered ·

1 Answer

problem with cyrix-CT 12-24 120a

Hi, i'm in a boat 12v, and I have a cyrix between the service batterie and the motor batteries.

The alternator charge the motor batteries,

then the service thanks to cyrix-ct 12-24 120.

We put the regulator of the solar panel to the services batterie. I was thinking that maybe it'll not go the motor, but now we tested, and when it's charging, all the batteries have the same voltage.

Last day, when we were pre-eating the motor, we saw 9A down on the services batterie... The thing is our service batterie is 22OA AGM, and the motor is 11OA acid normal.

So we are wondering if we are getting ours batteries in trouble going on with that... ?

Is the Cyrix rotten ?

Or if we sould put the solar panel regulator also on the motor batterie and charge the services trough the Cyrix... ?

There is the electrical scheme of the boat


Thanks for the answers

jeanluca asked

0 Answers

Can a cyrix-ct work one way for charging.

Can a cyrix-ct work one way (from the alternator to the house battery) and only pass the other way (home battery to start battery) if you pressed the assist.Now when the house battery is charged and topped up, the Cyrix switches to charge the starter battery this is not intended..

stephan-fok asked

0 Answers

Recalibrate Victron battery monitor!?

Interesting one, I have a Cyrix CT, to charge my house batteries of the vehicle batteries. My house batteries were down to 60%. It was freezing outside and had trouble starting so I hit my Cyrix CT start assist button, which connects my house batteries to my vehicle batteries to help start the engine. Worked great, the only problem is now my Victron battery monitor reads 100%, when it's really 60%. I see why this happened, but does anyone know a quick way to recalibrate? I looked into zero calibration, but that doesn't seem like the fix. Thank you

kaplan78 asked
kaplan78 commented ·

2 Answers

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
morissen answered ·

1 Answer

Will cyrix ct 120 connect full starter to a consumed service bank and cause damage?

I wonder if I use my service battery to say 11.9, and then start my engine, the cyrix will open to charge both, and I fear a lot of amperes will flow to damage the cables. Does that happen? Has it ever happened.?

morissen asked

0 Answers

Cyrix -ct 120, draining both batteries?

When I leave the boat and the batteries are:

STARTER Batt.=13,0v

HOUSE Batt.=12,5v

after 24h with everything OFF the batteries have both the same voltage (~12.7v).

I thought right away that the Cyrix is connecting both batteries and when I tested with a voltmeter, there is indeed connection from both poles of the Cyrix. Is this a normal behavior?

See video HERE.

My current setup is:


zuzullo asked
morissen answered ·

7 Answers

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