Log In | Register
Skip to main content
Topic: Controller temperature compensation... (Read 506 times) previous topic - next topic
0 Members and 6 Guests are viewing this topic.
Controller temperature compensation...
Doing some testing of our solar charging performance during winter days, and was concerned that the controller voltage output seemed somewhat high. Specification for flooded-cell settings is 14.4V absorption and 13.7V float at 25C, and my battery monitor showed about 14.7V and 14.3V respectively. I use a remote RTD temperature sensor, and the correction from that is listed as:

-5mV/degree C/cell from 25C

So, my guess at outside temp of 50F corresponds to about 10C, so the change from 25C is -15C, a 12V battery has 6 cells, and the calculation becomes:

-0.005 X -15 X 6 = 0.45V

So, the absorption voltage should be 14.4 + 0.45 = 14.85V, and float should be 13.7 + 0.45 = 14.15V, both very close to my readings. A chat with a tech rep from the manufacturer confirmed my readings were normal. This illustrates the importance of temperature compensation AT the battery location, since that may be very different from the controller location, usually inside the rig.

Steve
2004 FL
2013 Honda Fit
Re: Controller temperature compensation...
Reply #1 –
Better solar controllers come with a temperature probe, I place them in between the two batteries.
As Steve points out, the temperature probe is a necessary part of a solar charging system that performs efficiently.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Controller temperature compensation...
Reply #2 –

"Better solar controllers come with a temperature probe"

This is one place where Victron falls short. You have to buy a thirty dollar add-on (Victron Smart Battery Sense) to have a function that should have been standard.

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Controller temperature compensation...
Reply #3 –
Quote from: Andy Baird  - 
"Better solar controllers come with a temperature probe"

This is one place where Victron falls short. You have to buy a thirty dollar add-on (Victron Smart Battery Sense) to have a function that should have been standard.

Being Bluetooth should make it a lot easier to install if a temperature probe isn't already present.

When replacing an older controller, if the old controller has an existing thermistor probe, the old probe can be cut off, at the battery, end and the new probe (provided or optional) can be spliced in.

Larry
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Controller temperature compensation...
Reply #4 –
Ah a blast from the past .....  my experince with setting up the temperature compensation with the Blue Sky controller.

Blue Sky Solar Boost 3000i

glen
personal fine art photo stuff
TF Mack | Flickr
It's all good .......
2014 Twin King
Re: Controller temperature compensation...
Reply #5 –
Are temperature sensors controller-specific?  For example, I just replaced my HPV-22 controller with a SB3000i.  I connected the red & black wires of the old temperature sensor to the SB3000i, but now I'm wondering if that's a problem or if I can compensate in any way by changing the temperature compensation in the settings of the SB3000i.
Re: Controller temperature compensation...
Reply #6 –

I'll take a guess at this, and hopefully more knowledgeable members can give us the straight scoop. Most temperature sensors are thermistors--devices that change their resistance with temperature. One thermistor might have a working range between 20° and 150° F and change resistance 2 ohms per degree of temperature shift within that range. A different thermistor might have a working range between  5° and 110° and change 2.5 ohms per degree. There's an infinite number of possibilities.

Thus I would not bet on different types of sensors being interchangeable, and I would not bet on being able to make them so by altering the temperature compensation setting of the solar charging controller. What you can do, as others have mentioned in the past, is use the same wires to connect  your new controller to a new temperature sensor that's designed to work with it.

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Controller temperature compensation...
Reply #7 –
Quote from: Andy Baird  - 
I'll take a guess at this, and hopefully more knowledgeable members can give us the straight scoop. Most temperature sensors are thermistors--devices that change their resistance with temperature. One thermistor might have a working range between 20° and 150° F and change resistance 2 ohms per degree of temperature shift within that range. A different thermistor might have a working range between  5° and 110° and change 2.5 ohms per degree. There's an infinite number of possibilities.

Thus I would not bet on different types of sensors being interchangeable, and I would not bet on being able to make them so by altering the temperature compensation setting of the solar charging controller. What you can do, as others have mentioned in the past, is use the same wires to connect  your new controller to a new temperature sensor that's designed to work with it.

I suspect you're right, Andy, but I'll see if others know enough about the details of these two specific sensors (the ones used for the HPV-22 and the SB3000i) so that I know if I need to purchase the SB3000i-specific sensor and then cut the sensor off and put it on the old wiring.  Thanks for your input!
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Controller temperature compensation...
Reply #8 –
Quote from: Morgueman  - 
I suspect you're right, Andy, but I'll see if others know enough about the details of these two specific sensors (the ones used for the HPV-22 and the SB3000i) so that I know if I need to purchase the SB3000i-specific sensor and then cut the sensor off and put it on the old wiring.  Thanks for your input!

I would try asking Blue Sky’s techs this question.
If in doubt, buy and splice in the correct sensor. If you can solder, it isn’t a diificult project.
A new sensor is cheaper than another set of AGMs.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Controller temperature compensation...
Reply #9 –
Quote from: Larry W  - 
I would try asking Blue Sky’s techs this question.
If in doubt, buy and splice in the correct sensor. If you can solder, it isn’t a diificult project.
A new sensor is cheaper than another set of AGMs.

Larry

No greater truth has ever been told.  I will not be chancing the AGMs over a $29 sensor.
Re: Controller temperature compensation...
Reply #10 –
Eric;  The temperature sensor specified for the SB3000i is on page 9 of the manual. It is optional. If you do use it:
  "  OPTIONAL BATTERY TEMPERATURE SENSOR
 Install the optional battery temperature sensor as shown in Figure 4. The temperature sensor will be automatically detected by the 3000i.
 WARNING: Use only BSE temperature sensor p/n 930-0022-20. Other temperature sensors or electrical connections to the
temperature sensor terminals may damage the 3000i, void the limited warranty, and may cause charge voltage to become
uncontrolled. Note that temperature sensor wires are polarized RED/BLK. The sensor will not function if installed reverse
polarity. The temperature sensor lug has no electrical connection to the sensor element. You may may connect it to any battery terminal. "     Or in between the house batteries.   Anybody can download this manual.    RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB