Charging LiFeP04 batteries below freezing

Discussion in 'General Technical Questions and Answers' started by KD6ZXG, Oct 19, 2021.

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  1. KD6ZXG

    KD6ZXG Ham Member QRZ Page

    I posted this on another forum site, but I did not get too much response so hopefully I can get more assistance here.

    Our club recently purchased a LiFeP04 battery for our mountain top repeater site. I found out that this battery should not be charged below freezing. I am having trouble finding a solar controller that can be programed to stop charging at a specific temperature. I know that the Epic PWRgate can, but it is limited to 30 volts coming from the solar panels and our solar panels can generate up to 40 volts. I had looked at several temperature controllers on Amazon that can be placed between our existing solar controller and the battery that can be programed to stop the charging at freezing. However, most look pretty light duty with mixed reviews and I need something that will handle at least 20 amps.

    Any suggestions on a good quality 12 volt temperature controller switch or a solar controller that can be programmed to turn off at at specific temperature?
     
  2. K8DO

    K8DO Ham Member QRZ Page

    The receiver generates heat. Package the battery against the receiver cabinet and heavily insulate the package. Have a temperature sensor that opens air vents when the package rises above a given setting.
     
    K0OKS and NG1H like this.
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    Some setups have Battery Heaters.
     
  4. W4EAE

    W4EAE XML Subscriber QRZ Page

    I would contact Victron Energy. Their solar charge controllers are top notch, and they are temperature sensing--but I have only ever used it for high temp cutoffs. I do not know if a low-temp cutoff is possible, but it quite possible.
     
    KC6ETE likes this.
  5. K0OKS

    K0OKS Premium Subscriber QRZ Page

    I was thinking you could use some of the simple USB lens heaters (basically resistance wire heaters) to keep the batteries warm. Of course safety and fire concerns have to be addressed.

    These are really more appropriate for batteries you might use in the field where you are monitoring them, rather than in an unattended box.
     
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    They make Battery Heater Mats that are made for the job. T-Stats built in.
     
    K0OKS likes this.
  7. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Even better!
     
  8. KC6ETE

    KC6ETE Ham Member QRZ Page

    For our RV (4x 26AH Dakotas) I use four reptile heater pads controlled by an Inkbird thermostat (all from Amazon), and insulation around the batteries.
    I set it up to maintain 40F, and it went through the winter here in Colorado just fine.
    The inkbird controller lets you change the setpoints as needed. I put the thermal sensor inbetween the center two batteries.
     
  9. KV6O

    KV6O Ham Member QRZ Page

    Why not a simple mechanical (bi-metallic) thermostat?
     
    K7JEM likes this.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    That would work. The power used is not all that much, A small T-Stat could handle it.

    In the day we would turn the headlights on to heat the battery up.
     

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