Small lithium hotspot battery

EstragonEstragon Registered Users Posts: 3,589 ✭✭✭✭✭
I have a Netgear/Sierra wireless cell hotspot, which has a small battery similar to a cellphone battery.  I've had it for years, and the battery has lost much of (but not all) its capacity.

My plan is to leave it at the cabin for some remote monitoring stuff, and have (DC) power to it controlled by a rPi/relay setup.  So far, I haven't found a way to shut it off remotely except by just cutting the power.  Having done so, it continues to run for a short time until the battery runs down, then does a shutdown.  It monitors internal and battery temperatures, and appears to prevent charging in sub-freezing temps.  It also runs with no battery installed, but obviously can't do a controlled shutdown if the power is cut.

My question is whether it would be better to leave the battery in, letting it cycle (on for ~1hr daily), or out (not sure of the risks of uncontrolled shutdown).  The cabin will be mostly unheated, with inside temps ~ -15°C / 5°F.  I'm guessing the WAN/LAN radios running will warm it up enough at least some of the time for charging.  Any thoughts?


Off-grid.  
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter

Comments

  • Dave AngeliniDave Angelini Solar Expert Posts: 4,422 ✭✭✭✭✭
    Too many unknowns to give a decent answer. You know that is pretty cold for LFP, even NMC will not be happy long.

    When I do unattended cold places, I use costco and just build a sacrificial LA or AGM 12v battery and a  2 or 300 watt solar panel.

    Happy New Year hey ;)

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Registered Users Posts: 3,589 ✭✭✭✭✭
    Happy new year :smile:

    It will be powered by 12v LA and a small (300w) "floater" array.  Eventually I'll replace the battery hotspot with a more rugged one with 700mhz band, but a new cell modem and 700mhz capable booster will run $1,500 or so.  Maybe they'll come down as 5G rolls out?  In the meantime will try to get by with existing.

    I'm not really concerned much about losing more capacity if I leave the battery in, more with whether there's any significant risk (eg thermal runaway) doing so.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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