Temperature controller

[Derekoak]

I bought a dollatec w1209 temperature controller to provide better temperature control for my lithium heater system than the bi metallic button which I find does not switch accurately enough. The button is supposed to close at 5C but does not close until 2C.
Anyway the cheap electrical temperature switch says do not input above 12 volt on the packet when it arrived. As it might be exposed to alternator voltage at up to 14v I imagine it will fail. Is there another switch that would be more accommodating?

 

[Nabsim]

You can use a voltage regulator/buck converter and set it at 12V, that will sort it for you

 

[Derekoak]

I have one of those but it says that the output will be more than the input. If I must buy a down voltage one I thought I might as well get a different temperature controller? The buck converter I have was to boost 12 to 17 volts for a blue tooth speaker charging. I seem to remember it was only about £4.
Still if it is easier to get a converter. I will look.

 

[wildebus]

I use these ones for small electronic devices and LEDs - https://amzn.to/30VkVxG. Find them pretty handy.

 

[Derekoak]

I use these ones for small electronic devices and LEDs - https://amzn.to/30VkVxG. Find them pretty handy.

I would prefer screw terminal rather than solder.
Did you not suggest a temperature controller in the last few months? I could not find the post.

 

[Derekoak]

I asked the question on the amazon site linked to the sale of the dollatec and got 5 replies saying it should be fine, some from people who use them with lithium batteries for heating. So for the risk of £5 I am going to try it as intended despite the warning on the packet.

 

[SquirrellCook]

Typically reviews go like this.……I haven’t unpacked it yet, but it’s wonderful and does everything and more.

 

[Nabsim]

Why not spend £5 on a voltage stabiliser then know you have correct input power?

 

[Derekoak]

I bought a step down voltage converter, this one

Security measure

order.ebay.co.uk

XL4015. on a you tube video it is supposed to reduce voltage down to a minimum of 1.25v.
I connected it to the input and a red led lit. I tested the input voltage at 12.65v. I would the blue voltage rheostat down by screwing anticlockwise but the lowest the output voltage would go to was 12.45v.
There is another rheostat supposed to control current but with no serious current occurring it has no effect.
Is it dud?

 

[SquirrellCook]

Many of these things don’t perform as you’d like without a load.

 

[wildebus]

The one I linked to earlier steps down perfectly

 

[Derekoak]

Many of these things don’t perform as you’d like without a load.

I was afraid to attach it to the temperature switch which said do not attach to more than 12v, until I had an output of less than 12v. I shall have to try it. I could attach it to the coil of a relay.

 

[PeteS]

Dont attach it to the coil of a relay as when the power is removed you will get a much higher back emf voltage unless the relay has a diode across it.
More importantly I looked up the spec for the 3.3v regulator on the W1209 pcb and its max voltage rating is 15v so it should be fine, if your still unsure put a silicon diode in line such as a 1N4001 in series with the supply to it as that will have a 0.7v drop across it.

Mine is still working fine after 14 months without the diode. In my case I use it to inhibit a BMS if temp is below 5C

Edit,
dont be tempted to put more than one diode in series as there is already a series diode on the pcb dropping it by 0.7v already for reverse polarity protection.

 

[Derekoak]

Many of these things don’t perform as you’d like without a load.

That works, with the relay coil load. I could adjust the voltage to just under 12v, then connecting the temp switch instead of the relay the switch worked too.
Now I have to look online for the switch manual

 

[Derekoak]

Dont attach it to the coil of a relay as when the power is removed you will get a much higher back emf voltage unless the relay has a diode across it.
More importantly I looked up the spec for the 3.3v regulator on the W1209 pcb and its max voltage rating is 15v so it should be fine, if your still unsure put a silicon diode in line such as a 1N4001 in series with the supply to it as that will have a 0.7v drop across it.

Mine is still working fine after 14 months without the diode. In my case I use it to inhibit a BMS if temp is below 5C

Edit,
dont be tempted to put more than one diode in series as there is already a series diode on the pcb dropping it by 0.7v already for reverse polarity protection.

I am sorry I did not see your post.
I was successful anyway.
When the setup is complete I should have my lithium voltage, when ignition is on, to the voltage controller stepped down to 11.9v which brings power to my temperature sensor, this one WHICH I THINK IS A W1209?

DC 12 V Thermostat Temperature Switch Thermal Sensor -50 to 110 °C : Amazon.co.uk: DIY & Tools

Free delivery and returns on all eligible orders. Shop DC 12 V Thermostat Temperature Switch Thermal Sensor -50 to 110 °C.

www.amazon.co.uk

It says it copes with a 10 amp relay. it will connect to the coil of a 30 amp relay. The relay will allow a 12 amp heating current to my heat pads until the temperature sensor switches off.
So when it is cold and the battery is below 5C, my bms s are stopping any charge, I can switch on the ignition 10 minutes before we drive off to warm the batteries using leisure battery power so they can charge immediately on driving. If I forget the first 10 minutes or so of drive will not be charging but will be heating the battery until the bms s allow charging.