Temp. sensor on charger; Keep? Or not?

[Jan V]

My CTek MXS25 chargers got a temp sensor,

 

Will charge at 14,4 volt @ 25 C

Charging at 14,63 volt @ 18 C (tested today)

If the sensor is removed (cut), charging will be 14,4 volts at all time.

 

What I should do? :-S

 

Cut or keep?

 

[Brambles]

Hi,

Couple of comments 1st which are make sure you have the correct mode set on the charger. 2nd is 14.63 volts is same as you had from alternator on other thread so am wondering if you had the charger switched on when you were testing the alternator.

 

I am not so sure it will be a fixed 14.4 volts across all temperature ranges as the charger has very likely a built in temp sensor over ridden by a remote sensor.

 

But, to answer your question as it is stated, 14.4 volts is too high when you get over 30 degrees C. Very much too high if you get temperatures up towards to 40 degrees.C.

 

You should be looking at temperature compensation of between -2 and -5 mV per cell per degC. . So in effect the voltage drops as temperature rises.

 

Your 14.63 volts is slightly on the high side but could just be your volt meter accuracy, or the batteries are still warming up to day time ambient temperature and were actually less than 18 deg C.

 

I certainly would favour having a battery temperature sensor as so much more accurate for the charge voltage required. It is also a massive safety feature should the batteries get too warm, the charger will shut down the charge. Seems a bit daft to buy an expensive MXS25 and not use the sensor.

 

 

[Jan V]

Brambles - 2017-05-21 12:40 AM

 

Hi,

Couple of comments 1st which are make sure you have the correct mode set on the charger. 2nd is 14.63 volts is same as you had from alternator on other thread so am wondering if you had the charger switched on when you were testing the alternator.

 

I am not so sure it will be a fixed 14.4 volts across all temperature ranges as the charger has very likely a built in temp sensor over ridden by a remote sensor.

 

But, to answer your question as it is stated, 14.4 volts is too high when you get over 30 degrees C. Very much too high if you get temperatures up towards to 40 degrees.C.

 

You should be looking at temperature compensation of between -2 and -5 mV per cell per degC. . So in effect the voltage drops as temperature rises.

 

Your 14.63 volts is slightly on the high side but could just be your volt meter accuracy, or the batteries are still warming up to day time ambient temperature and were actually less than 18 deg C.

 

I certainly would favour having a battery temperature sensor as so much more accurate for the charge voltage required. It is also a massive safety feature should the batteries get too warm, the charger will shut down the charge. Seems a bit daft to buy an expensive MXS25 and not use the sensor.

 

 

Thanks for your reply on this;

 

The 14,63 volts is not the same volts as in another tread;

Also measured by two different instruments.

Same vehicle but different battery.

Start- and leisure batteries are separated.

 

This 14,63 reading on the leisure battery was done by a "CTek Sense" just after startup.

CTek Sense is a little gadget connected to the battery which measure ambient temperature and voltage.

Presented via bluetooth to my iPhone.

 

My CTek MXS25 charger sensor is located by the battery positive connector (as CTek manual).

 

I read elsewhere that if you cut the temp sensor the CTek charger will use 14,4 at all time.

Was done to get flat voltage and higher currents to his LiFePo4 batteries with internal BMS.

 

This is different and you are right;

And I guess CTek did make this charger with the temp sensor for a reason.

I will keep the sensor.

 

 

 

 

[Brambles]

When you started the engine, was the Ctek charger still connected to the leisure batteries.

Depending on your set up the Leisure battery voltage could be connected directly to the engine battery so the voltage increased above the alternator voltage. S'pose this should be on other thread.

 

 

[Jan V]

Brambles - 2017-05-21 8:34 AM

 

When you started the engine, was the Ctek charger still connected to the leisure batteries.

Depending on your set up the Leisure battery voltage could be connected directly to the engine battery so the voltage increased above the alternator voltage. S'pose this should be on other thread.

 

 

Was not running engine.

 

The AC charger was late last night on float and was at 13,75 volts @ 19 C Battery

The charger doing what it suppose to do.

 

 

[Brambles]

Jan V - 2017-05-21 7:47 AM

 

Brambles - 2017-05-21 8:34 AM

 

When you started the engine, was the Ctek charger still connected to the leisure batteries.

Depending on your set up the Leisure battery voltage could be connected directly to the engine battery so the voltage increased above the alternator voltage. S'pose this should be on other thread.

 

 

Was not running engine.

 

The AC charger was late last night on float and was at 13,75 volts @ 19 C Battery

The charger doing what it suppose to do.

 

I was responding to your alternator voltage on other thread.

It always gets confusing when there are two threads on same topic.

 

 

[Jan V]

Brambles - 2017-05-21 9:05 AM

 

Jan V - 2017-05-21 7:47 AM

 

Brambles - 2017-05-21 8:34 AM

 

When you started the engine, was the Ctek charger still connected to the leisure batteries.

Depending on your set up the Leisure battery voltage could be connected directly to the engine battery so the voltage increased above the alternator voltage. S'pose this should be on other thread.

 

 

Was not running engine.

 

The AC charger was late last night on float and was at 13,75 volts @ 19 C Battery

The charger doing what it suppose to do.

 

I was responding to your alternator voltage on other thread.

It always gets confusing when there are two threads on same topic.

 

 

Sorry about the confusion...

 

At the time I felt there was two different issues.

 

To clarify;

Alternator giving 14,63 volts at idle speed to the starter battery;

AC charger giving 14,63 volts @ 18 C to the leisure battery (when alternator not spinning)

The two batteries (and their charging circuits) was separated.

 

By luck, (or unluck);

same level; on two different loops; measured with two different tools

 

:-D

[Brambles]

Re the Alternator.

 

It will be interesting to see what the voltage does if you rev the engine, say 1500rpm and over 2000 rpm.

Then again after the vehicle has been driven and alternator has got nicely warmed up do the same tests at idle, 1500 and over 2000.

Also with headlights on and off so you have results with a decent load and without.

 

 

[aandncaravan]

The Temperature sensor has two basic functions, as Brambles states it prevents battery degradation when the battery gets warm, but it also allows faster charging if the battery is cold.

 

A cold battery will safely handle a higher charge rate, so the charger can safely put out a higher charge rate until the battery temperature rises.

As the battery temperature comes up, the charger should back down the voltage to prevent battery damage. This is especially critical with a Gel battery as they are more prone to heat degradation than any other Lead Acid battery.

 

If someone 'Motorhomes' in in cooler climes, there may be an even bigger advantage to using the Temperature sensor as the lower temperatures may enable significantly faster, safe charging

 

 

The temperature sensors that stick on the battery casing (or worse just sit inside the Battery locker) are much less effective for Gel and AGM batteries, it needs to be a Battery terminal type temperature sensor which reacts fairly quickly to heat from the Plates.

 

In a Wet Acid battery the mobile acid near the Plates, gets warm and rises by convection drawing in cooler, fresh Acid behind it. The warm acid then circulates to the Casing where the sensor will react to the rising temperature.

 

With a Gel battery, the Gel is pretty immobile so heat takes much longer to migrate away from the Plates. So by the time a Gel batteries casing feels warm the Plates may have been at damaging temperatures for some time.

 

I think the increased voltages you are seeing from the charger with the sensor connected are a result of the battery being quite cool?

 

See our webpage http://www.aandncaravanservices.co.uk/nordelettronica.php about halfway doqn, that uses charts from Victron Energy to show the damaging effect of charging Gel/AGM in higher temperatures.

 

 

 

[Jan V]

Brambles - 2017-05-21 9:46 AM

 

Re the Alternator.

 

It will be interesting to see what the voltage does if you rev the engine, say 1500rpm and over 2000 rpm.

Then again after the vehicle has been driven and alternator has got nicely warmed up do the same tests at idle, 1500 and over 2000.

Also with headlights on and off so you have results with a decent load and without.

 

 

I will do the test...

 

In this moment the glue for the new solar panels and cable treads are drying.

Hopefully ready for test monday or tuesday, and then I will post the measured results.

[Jan V]

aandncaravan - 2017-05-21 12:33 PM

 

The Temperature sensor has two basic functions, as Brambles states it prevents battery degradation when the battery gets warm, but it also allows faster charging if the battery is cold.

 

A cold battery will safely handle a higher charge rate, so the charger can safely put out a higher charge rate until the battery temperature rises.

As the battery temperature comes up, the charger should back down the voltage to prevent battery damage. This is especially critical with a Gel battery as they are more prone to heat degradation than any other Lead Acid battery.

 

If someone 'Motorhomes' in in cooler climes, there may be an even bigger advantage to using the Temperature sensor as the lower temperatures may enable significantly faster, safe charging

 

 

The temperature sensors that stick on the battery casing (or worse just sit inside the Battery locker) are much less effective for Gel and AGM batteries, it needs to be a Battery terminal type temperature sensor which reacts fairly quickly to heat from the Plates.

 

In a Wet Acid battery the mobile acid near the Plates, gets warm and rises by convection drawing in cooler, fresh Acid behind it. The warm acid then circulates to the Casing where the sensor will react to the rising temperature.

 

With a Gel battery, the Gel is pretty immobile so heat takes much longer to migrate away from the Plates. So by the time a Gel batteries casing feels warm the Plates may have been at damaging temperatures for some time.

 

I think the increased voltages you are seeing from the charger with the sensor connected are a result of the battery being quite cool?

 

See our webpage http://www.aandncaravanservices.co.uk/nordelettronica.php about halfway doqn, that uses charts from Victron Energy to show the damaging effect of charging Gel/AGM in higher temperatures.

 

 

 

Thanks for your feedback (to all of you guys)

Makes it easier for a "amateur" doing the correct stuff.

 

The temperature measured by the CTek Sense is done by the Sense internal sensor.

In other words its the ambient temperature displayed.

 

In this case (motorhome) I do have 3 CTek sensors;

AC MXS25 sensor, Dual D250S sensor, and Smartpass sensor.

 

There is two 100Ah GEL in paralell.

Then I need to decide witch positive to measure.

 

I am trying to pull all the energy from one positive terminal only;

In other words all conncections done to one of the two batteries.

The battery no 2 will not have any equipment connected to the terminals.

 

 

Would it be a good idea to glue the tempsensors on the battery top in close proximity of the battery positive terminal?

(On the battery "in use"...)

 

Just a little drop of what I call "super glue"

My experience with tape etc. is that it will fall of after a short periode of time.

[Jan V]

Started the engine;

 

Measured at lighter outlet.

Meter used multimeter Fluke

 

Started, at idle; 14,41 volts

At 2500 rpm no headlights 14.58 volts

At 2500 rpm with headlights 14,48 volts

 

Can not explain earlier 14,63 volts....

but earlier the alternator was charging both start and leisure batteries.

This last measure was done when alternator only charged start battery.

[aandncaravan]

The Battery terminal Post is metal and in direct physical contact with the Metal 'Plates so if the Plates get warm, so will the battery Post.

The plastic casing in the region of the Plates may be several degrees cooler.

 

Unless your temperature sensor accurately monitors the real battery Plate temperature, you might be better off without temperature compensation if you have Gel batteries?

 

 

 

 

 

 

 

 

 

 

[Jan V]

aandncaravan - 2017-05-21 8:21 PM

 

The Battery terminal Post is metal and in direct physical contact with the Metal 'Plates so if the Plates get warm, so will the battery Post.

The plastic casing in the region of the Plates may be several degrees cooler.

 

Unless your temperature sensor accurately monitors the real battery Plate temperature, you might be better off without temperature compensation if you have Gel batteries?

 

 

GEL ....yes...

 

The CTek sensors is a plastic covered sensor...6-7 mm

 

My friends 2 x 100 Ah batteries is the kind with two posts for both polarities, total of four

One traditional, and one treaded (8 or 10 mm) next to the traditional

I am only using the treaded ones;

Maybe I could drill a hole into the post for my sensors?

Would give a better reading... I guess

 

I would guess there is a PT100 inside....

Maybe I could use my knife and carefully make the sensor diameter smaller,

 

In my old motorhome I had my sensors squeezed in between the two batteries.

The batteries was installed long side by long side... millimeters gap

 

In my own new motorhome I have the same questions...

Got 2 x 160 Ah GEL.... does not come cheap :-(

 

And then again, I am kind of concerned about those sensors are to keep or not.... since I have GEL

 

Should I cut? Or not? .....8-)

 

 

(Learned a new word today; I did not know the english word for ... battery POST)

[aandncaravan]

Would you be able bolt a small piece of Copper square to the Battery Clamp and cable tie the temperature sensor to this, then fold the Copper over so the sensor is between the Copper square and the battery Clamp upper surface?

 

Or maybe cable tie it directly to the battery clamp top?