CTEK MX5 charger voltage

[moonshine]

I plugged in my CTEK MX5 charger yesterday on the AGM setting, so it should take the battery to 14.7V as per the bulk charge phase (3) of AGM programme below 

I've got a victron Smartbatterysense https://www.victronenergy.com/meters-and-sensors/smart-battery-sense attached to the battery. It a cracking little bit of kit. It let's me check the battery voltage by BT, and also data logs the battery voltage.

Anyway, I was surprised the CTEK MX5 appears to be taking the battery voltage well above the 14.7V AGM setting. To maybe 15.3V

What are your thoughts? To me, I am surprised and it does not seem correct  ( I'm going to email CTEK)

 

[TV8]

Does the first column say 15.8 volts?

[moonshine]

41 minutes ago, TV8 said:

Does the first column say 15.8 volts?

Yes, but the desulfidation phase is very short. It's just to clean the electrodes. It was in phase 3/4 when the voltage was >15.1V

[iborguk]

Just for info what battery do you have in the car ?

Thanks

 

[moonshine]

19 minutes ago, iborguk said:

Just for info what battery do you have in the car ?

Thanks

 

A reasonablely new OEM porsche one 

[greenman986s]

Where is the smart sensor connected?

[moonshine]

1 minute ago, greenman986s said:

Where is the smart sensor connected?

Directly to the battery. +/- terminals.

CTEK is connected to plug in connector wired to the battery +ive terminal and chassis ground 

 

Ctec

[iborguk]

What was the charge level of the battery before the charging started ? 

What temp were the surroundings the car was in during charging ? 

What does a multi-meter say vs the Victron when you're seeing the higher voltage ?

Edited January 14 by iborguk

[moonshine]

56 minutes ago, iborguk said:

What was the charge level of the battery before the charging started ? 

What temp were the surroundings the car was in during charging ? 

What does a multi-meter say vs the Victron when you're seeing the higher voltage ?

Battery was at a good to fair SOC prior to charging. Car not driven for a couple of weeks, SBS saying battery voltage before charging at 12.3V (70%for an AGM battery)

Currently sitting at 12.78V 10hrs after charging disconnect, which is 100% SOC 

4C

Dont know, didn't put a multimeter on it, but the victron SBS is a quality bit of of kit and is reliable 

 

Edited January 14 by moonshine

[TV8]

Voltage is in a relationship with current and resistance. Did a lot of sorting out of dodgy earths on my triumphs and TVRs. I was very surprised to have to do it on my 996. Do you get the same results if you connect the charger direct to the battery?

[moonshine]

41 minutes ago, TV8 said:

Voltage is in a relationship with current and resistance. Did a lot of sorting out of dodgy earths on my triumphs and TVRs. I was very surprised to have to do it on my 996. Do you get the same results if you connect the charger direct to the battery?

With an AGM Battery on a car with automatic start stop, one should not connect the -ive terminal of the charger direct to the battery - it should go to the chassis ground.

there is a shunt (essentially a coulomb counter) on the negative battery lead - and if you connect a charger direct to the negative posts of the battery, this is bypasses - which messes up things.

[TV8]

3 minutes ago, moonshine said:

With an AGM Battery on a car with automatic start stop, one should not connect the -ive terminal of the charger direct to the battery - it should go to the chassis ground.

there is a shunt (essentially a coulomb counter) on the negative battery lead - and if you connect a charger direct to the negative posts of the battery, this is bypasses - which messes up things.

Sounds like a bit of a mine field to me! I recall people talking about having a battery coded to a car and I am so glad I have a 986! Good luck

[BBB]

From Victron’s forum. As I read it, the disparity between the CTEK voltage and the Victron readings could come down to the resistance of the wires in each piece of circuitry. In my own view, the difference doesn’t matter, if the CTEK charges your battery correctly.

“There is a quality of power called Ohms law, basically there is a relationship between voltage, current and resistance. The power electronics that draw, or push current will cause the voltage to drop, or rise.

If the product uses these same wires to sense the voltage, then it can appear that the voltage is higher or lower than it will appear at the battery terminals taken from a voltage sensing device that is not drawing or pushing any current.

Further to that, the size of the wires that are selected by the installer on site will also affect this current carrying voltage reading for these charging or load products. There is a lot more detail about these effects (and how significant they can be in certain circumstances) in the Ohms Law chapter of the Victron book Wiring Unlimited here.”

https://community.victronenergy.com/questions/142549/lets-try-a-second-time-whats-the-accuracy-of-victr.html

 

[iborguk]

38 minutes ago, BBB said:

From Victron’s forum. As I read it, the disparity between the CTEK voltage and the Victron readings could come down to the resistance of the wires in each piece of circuitry. In my own view, the difference doesn’t matter, if the CTEK charges your battery correctly.

“There is a quality of power called Ohms law, basically there is a relationship between voltage, current and resistance. The power electronics that draw, or push current will cause the voltage to drop, or rise.

If the product uses these same wires to sense the voltage, then it can appear that the voltage is higher or lower than it will appear at the battery terminals taken from a voltage sensing device that is not drawing or pushing any current.

Further to that, the size of the wires that are selected by the installer on site will also affect this current carrying voltage reading for these charging or load products. There is a lot more detail about these effects (and how significant they can be in certain circumstances) in the Ohms Law chapter of the Victron book Wiring Unlimited here.”

https://community.victronenergy.com/questions/142549/lets-try-a-second-time-whats-the-accuracy-of-victr.html

 

I’d suggest use a multimeter to verify the numbers.

Edited January 14 by iborguk

[moonshine]

10 hours ago, iborguk said:

I’d suggest use a multimeter to verify the numbers.

I plugged it back in this morning 

The victron Smartbatterysense reports identically (to the mV) to a multimeter with probes touching the battery posts. Step 4 is at 15.15v to 15.20v

A bit of googling suggests this might be normal, with 14.7V the charging voltage at 25c, and as temperatures fall towards 0c, charging voltage can rise.

I've emailed CTEK to see what they say 

 

 

 

 

Edited January 15 by moonshine

[Greenman]

I’m not sure if this this is expected/normal (though I suspect it is), but you will have noticed that when driving the car the battery can often charge at 15.2v (as shown in the dash). So this seems like it would be an effective safe charging voltage.

[andygo]

54 minutes ago, Greenman said:

I’m not sure if this this is expected/normal (though I suspect it is), but you will have noticed that when driving the car the battery can often charge at 15.2v (as shown in the dash). So this seems like it would be an effective safe charging voltage.

Remembering of course that you have you have the voltage display enabled on your dash. When I first got my car i was concerned about the charging whilst driving voltage at 15.2. I was concinced the battery was on the way out so the dealer coughed for a new battery which displayed the same values. (Oops, sorry dealer!   )

[moonshine]

I got a reply from CTEK  

In short, nothing to see here... Move along  😂👍.

as follows.

Thank you for contacting CTEK! 

Due to the CTEK being a temperature compensating charger the voltage might be increased to give the same effective charging when it's cold around the battery. 

The base of 14.7 V is when the ambient temperature is 25 °C any degree above or below will adjust the voltage. So at 0 °C the charger would output 15.21 to 15.37 V 

This is not harmful for your battery or your electronics. When it's cold you need a higher voltage to get the same effective charging. 

Med vänliga hälsningar/Best Regards,

 

[iborguk]

59 minutes ago, moonshine said:

I got a reply from CTEK  

In short, nothing to see here... Move along  😂👍.

as follows.

Thank you for contacting CTEK! 

Due to the CTEK being a temperature compensating charger the voltage might be increased to give the same effective charging when it's cold around the battery. 

The base of 14.7 V is when the ambient temperature is 25 °C any degree above or below will adjust the voltage. So at 0 °C the charger would output 15.21 to 15.37 V 

This is not harmful for your battery or your electronics. When it's cold you need a higher voltage to get the same effective charging. 

Med vänliga hälsningar/Best Regards,

 

Thanks for following up, always good to understand the details.

[cozzykim]

Just to be awkward, I just bought a CTEK CT5 (actually, because it was almost brand new/unused and cheaper than a new MSX 5.0

This is supposed to be the best version for start/stop vehicles, and it has no configuration necessary.

Anyone else got one?

I'm now trying to figure out how to use it with the bonnet closed on my grass 'driveway' so that I don't get unwelcome rainwater in the frunk.

[Paul P]

10 minutes ago, cozzykim said:

Just to be awkward, I just bought a CTEK CT5 (actually, because it was almost brand new/unused and cheaper than a new MSX 5.0

This is supposed to be the best version for start/stop vehicles, and it has no configuration necessary.

Anyone else got one?

I'm now trying to figure out how to use it with the bonnet closed on my grass 'driveway' so that I don't get unwelcome rainwater in the frunk.

run the cable to the back edge of the bonnet - between the wipers and the back edge - you should be able to close the lid fine. If you get the ctek extension cable then you can put the ctek under the car - or in a tupperware box to keep the weather off of ( although I believe they are supposed to be waterproof) - I did similar for Mrs car during lockdown. 

[BBB]

1 hour ago, cozzykim said:

Just to be awkward, I just bought a CTEK CT5 (actually, because it was almost brand new/unused and cheaper than a new MSX 5.0

This is supposed to be the best version for start/stop vehicles, and it has no configuration necessary.

Anyone else got one?

I'm now trying to figure out how to use it with the bonnet closed on my grass 'driveway' so that I don't get unwelcome rainwater in the frunk.

One of these, plugged into an external socket.

https://www.amazon.co.uk/Masterplug-WBXBFG10B-MP-WBXBFG10B-Weatherproof-Extension/dp/B0062GTL42/ref=sr_1_5?crid=26RT2CCTX0RH0&keywords=waterproof%2Bextension%2Bbox&qid=1706535406&sprefix=waterproof%2Bextension%2Bbo%2Caps%2C83&sr=8-5&th=1

The CTEK plugged into the centre console charging socket, the unit sits nice and dry in the passenger footwell, its lead draped over the sill, close and lock the door, and then plug the CTEK into the masterplug box linked above.