Forum Discussion

hammick's avatar
hammick
Explorer
Apr 10, 2015

Temperature compensation conversion ?

I'm not smart enough to figure this out.

My Interstate GC2 battery specs base temp compensation on 10 degrees Fahrenheit above or below 80 degrees F.

My Blue Sky charge controller bases it on one degree Celsius above or below 25 degrees C.

Below are the Interstate specs and default setting of my controller. Looking for advice on whether I should leave the controller at default setting or convert to interstate specs and if so what is the conversion? I am installing the Blue Sky temp sensor. Thanks.

Interstate specs

Notes: 1. All charging voltages shown above are for 80 degrees F. For every 10 degrees above 80 F reduce voltage by 0.028 VPC. For every 10 degrees below 80 F increase the voltage by 0.028 VPC.


Blue Sky specs

Default setting: (–5.00mV/°C/cell)
setting range: 000 – 800 (–0.00 to –8.00 mV/°C/cell)
setting steps: 10 (0.10mV/°C/cell)
description: Battery temperature compensation factor (decimal point missing in display such that 500 = –5.00mV/°C/cell
Default provides overall factor of –30mV/°C for 6 cell 12V battery)
  • Almot's avatar
    Almot
    Explorer III
    Apr 10, 2015
    Get a remote display for your controller, or replace the controller with another model that allows remote display. Then you will have more freedom in controller location. Display is (usually) connected with a network cable, can be several feet long if necessary. It is important to place controller close to batteries, while display needs to be where you can see it.

    My preference would be a display with interface, i.e. where you can actually "do" something rather than just look at it. Majority of them don't have this capability. Morningstar remote display allows "some" limited commands, if memory doesn't fail me. To do more, one has to either use a laptop, or again take a screwdriver and access the actual controller. So far I've seen only one remote interface that allowed any command possible, - Rogue MPPT, now discontinued. There could be others, but not cheap.
  • hammick's avatar
    hammick
    Explorer
    Apr 10, 2015
    Thanks for all the replies. I will leave the default setting on the CC.

    I will be installing the CC next week in the same place as the Go Power CC that came with the trailer. The Go Power cannot be programmed and has 14.4v absorption and 14.7v equalization and I wanted something fully programmable.

    Flush mounted on the bedroom wall with bathroom wall directly on other side. Probably the worse place as far as fishing wires. If I can't get the temperature wire fished without tearing stuff apart I will leave it inside the wall. With some patience I should be able to fish to the refrigerator/converter area and then drop below the floor from there to route to battery.
  • Almot's avatar
    Almot
    Explorer III
    Apr 10, 2015
    0.028V per F = 0.5V per C.

    80F must be a typo. It's usually 77F = 25C.

    Oh yeah, temp comp does change few tenth of volts from cool morning to hot noon. Was annoying in my rig since my batteries start from 75-80% SOC in the morning and get into Absorption well before noon when it's still cold, so Abs goes from 14.7V default to 15V or higher. But, since they are AGM, I moved them to inside space, and now it doesn't change that much.
  • westend's avatar
    westend
    Explorer
    Apr 10, 2015
    The temp compensation in the controller is probably real good. I have a Morningstar controller with the temp probe and it does a good job of it. I see a few tenths voltage change, depending on the seasons.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Apr 10, 2015
    Hi,

    Blue Sky got it right. The lawyers at Interstate got it wrong.
  • Ed_Gee's avatar
    Ed_Gee
    Explorer II
    Apr 10, 2015
    25degrees Celsius is 77degrees Farenheit. That is close enough to 80 deg.F in my book. I wouldn't bother changing the charge controller over the difference.

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