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Hipolito Gonzalez avatar image
Hipolito Gonzalez asked

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.


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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



Cyrix Battery Combiner
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7 Answers
Hipolito Gonzalez avatar image
Hipolito Gonzalez answered ·

Hello again. Today I went to my garage and the battery 2 (service) was in 12.1 and battery 1 in 12.2, after yesterday only driving for about 45 minutes. Without any load in the service and only the normal load in main battery the power was going doing again. The Cyrix was warm (like "always" or like "working") and I use my tester and put between the fuse (coming from the service battery) to the Cyrix. With everything "off" I got the following "usage"


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I think is a lot of power usage.

0.1 amp/hour, make 2.4 amp/24 hours draining from more or less each battery.

In 10 days without running my car (is my secondary car, travel car, adventure car) (is normal to be stopped for 10 days) the 1/2 of my service battery (40 aH) is gone, and the main battery is 90 aH, it could be a problem.


I don't know why is using so much power the Cyrix....



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bathnm avatar image
bathnm answered ·

I have seen a similar parasitic draw on my Cyrix-CT 120A, however this was when the main battery was being held at float and looking for the devices drawing current. When I disconnected the negative, I had roughly a .1A reduction in load. I am surprised however that yours has not disconnected the batteries, If the voltage drops to between 12.8v and 12.4v for 3 minuets it should disconnect.

At the moment when I am not onboard the boat I actually disconnect the negative and leave the two batteries isolated. As they are both fully charged it is not an issue. I then reconnect the negative while I am onboard.

What I find interesting is that the data sheet says the current consumption when open in <4mA and when closed 220mA.

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Hipolito Gonzalez avatar image
Hipolito Gonzalez answered ·

Thank you @Bathnm .

But my Cyrix is disconnecting BOTH batteries, if I do a volt measure in each "end point" I have different voltages (it means they aren't connected). For example, before turning on today the car, I had 12.1 and 12.2 but "power" was going to the ciryx and it was "hot" (I think 40 C degress). If I turn on the car, I can ear the CLICK (engaging) and the voltage goes up to 13.6 more or less


It is working at moments I turn on the car, the only "problem" I think the the power of the "electronic" is "so much" and in 10 days could "kill" both batteries.


I am going to buy another and test, maybe mine is bad (6 months installed, really not yet used for the "quarantine" in Spain) Just installed in the car, but I didn't do really a long trip and use all the night the battery with the fridge, lights, inverter, tv etc etc.....


But I am checking everything always!

Thank you

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volknkn avatar image
volknkn answered ·

Hello everyone, I faced with same issue on today. I haven’t use my car for 24 hours and my both batteries are sapareted by kill switch. But when I touch my Cyrix-Ct, it was really warm. What should be happened?

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salaatti avatar image
salaatti answered ·

Same problem here. Installed on a boat.

1x 97Ah AGM start battery

1x 74Ah Lead acid house battery


Installed as per instructions. The boat is 3 years old so could be referred as new and all connectors and cables done in professional manner.


Boat was not used for 4 weeks, mains disconnected. Only bilge pump and Webasto heater connected directly to batteries. Both batteries dead with 6,x volts.

Firstly disconnected Webasto and bilge pump but still 0.1 amp draw. Finally I was able to suspect the Cyrix ct. The unit was a little warm also.


Decided to buy a new unit and now monitoring situation. The old unit was less than 3 years old so if this is the life expectancy of the Cyrix ct and/or both batteries (about 400€ per round = one AGM, one Lead Acid and one Cyrix ct)... it is an expensive hobby.


I have seen two other strings / topics on this matter on this forum but there was no solution on the matter nor comment from Victron.


@Hipolito Gonzalez How was this resolved or any suggestions by others?


@Guy Stewart (Victron Community Manager) Could you please comment on this?

Has there been defective units or what seems to be the problem?


Please do not ask me to contact the local supplier because the problem is the high amperage draw and they cannot do anything about it. The manual states less than 4mA but my unit was taking 100mA which is far from acceptable.

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Hipolito Gonzalez avatar image Hipolito Gonzalez commented ·
Hello my freiend @salaatti

I bought a new one and problem solved.

Also you have maybe another problem, you are mixing two different king of batteries. They have different voltage charge!



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salaatti avatar image salaatti Hipolito Gonzalez commented ·

Thank You @Hipolito Gonzalez, highly appreciate your quick reply!


Ok that’s good to know that the issue was a defect product and this might be a solution also in my case. I’ll report back after a few days whether the batteries keep charge or not.


I don’t see any problem in having different capacity batteries since both are the same voltage, 12 volt system in parallel. 95% of boats with 2-battery systems have different capacities in start and house banks and the only difference in my system is that the start battery is a bigger AGM due to cold climate and Mercury outboard high demand on start. The house battery is only for nav equipment and other electronics used always underway thus always charged by the outboard alternator when under load.


If @Guy Stewart (Victron Community Manager) could share some input on this matter if the Cyrix ct is not capable in balancing between two different sizes of power banks and/or use mixed (AGM+LA) parallel installation - that should be stated with bold and block letters in the product description so that consumers can avoid buying products that are not suitable for certain systems (most pleasure boats).


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salaatti avatar image
salaatti answered ·

Confirmed. 3-year-old Cyrix Ct was the cause of battery drain.

Replaced with new unit and problem solved.

Too bad that Victron is unable to comment on this issue. Maybe they think this concerns only a limited number of devices but to me it seems that these problems are rather common and international. 80% of customers decide to stay quiet and not express their concerns on discussion forums so this is just the tip of the ice berg.


I certainly hope that I am not forced to replace my batteries every 3rd year.

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salaatti avatar image
salaatti answered ·

Replaced the unit and after two weeks decided to check the boat > Voltage 11,80 on both batteries.


So Cyrix-CT is basically designed to drain batteries.


No comment from Victron itself.


Decided to disconnect the unit. Will have to check on other manufacturers.

What a useless product.

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