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A common knowledge and practice on lithium-ion batteries is that they significantly loose the capacity and cannot be charged when their temperature drops below 0 deg of Celsius due to increased degradation (lithium plating). I'd like to charge the 1.2Ah lithium-ion battery from a solar panel but in winter season (sometines minus 25 deg C) some pre-heating would be required.

The lithium-ion batteries heat up when loaded and I wonder if this phenomena can be smartly used. Is this a common practice? Are there any ICs or known circuits that would control this process? What other options do I have except for using a lead-acid battery?

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  • \$\begingroup\$ "Efficient heating" is not a valid concept electrically. IF you use electricity to heat resistively it is 100% efficient - it's what you do with the heat and where it is produced that counts. Insulation is going to make a large difference. Battery self heating ion discharge is a valid heat source - but the battery needs to be warm before you discharge it. Lead acid is also very poor at sub zero temperatures. Insulate well enough to need minimal energy to heat and you may then need cooling at other times. If the battery is very cold then directing all PV input to heating until warm enough .... \$\endgroup\$ – Russell McMahon Jan 27 '14 at 15:03
  • \$\begingroup\$ ... is probably wise. Battery may well not like extreme cold even if not discharging and some means of limiting minimum temperature may be needed. | Solar thermal heating of the battery would be more efficient than conversion to electricity for heating. Even when Tambient is subzero you can get direct solar heating to a black maqtte surface and dish or mirror can help heating. You can get non steered solar gain of 2 or 3 with mirrors (see solar cooker boxes). Dishes need steering. ... \$\endgroup\$ – Russell McMahon Jan 27 '14 at 15:08
  • \$\begingroup\$ ... | Spehro's suggestion re burying may be workable. A deep hole may provide a source of warmth even if battery is near surface. \$\endgroup\$ – Russell McMahon Jan 27 '14 at 15:09
  • \$\begingroup\$ @RussellMcMahon: Even if 100% of electricity will get converted to heat somewhere, efficiency is the fraction of energy that goes someplace useful. \$\endgroup\$ – supercat May 26 '17 at 17:53
  • \$\begingroup\$ @supercat We agree :-). I'd hope you'd know that I understand that concept. My comments are made within that framework but, perhaps not clearly enough. | I said " ... it's what you do with the heat and where it is produced that counts. ..." m-> If the load is within the same insulated space as the battery then the load heat is useful. If heat energy from outside the electrical system can be added (as I suggest may be the case) then it's "free energy" as far as battery use goes. || So, yes, I agree. ||| FWIW - I'd imagine that you and I would very seldom disagree on electronics issues. \$\endgroup\$ – Russell McMahon May 27 '17 at 6:16
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Could you simply located the battery buried down a couple meters (below the frost line)? Then it would be warm in the winter and cool in the summer, without wasting energy heating it.

Otherwise, there's a trade-off between keeping the battery warm (you want to have insulation to minimize the wasted energy) and keeping it cool in the summer (you want to get any heat out, especially when charging).

It's not hard to find something to do what you're asking for.. maybe look for "heat tracing" that will run off of 12V. They're self-limiting PTC resistance cables used to prevent pipes from freezing.

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  • \$\begingroup\$ Burying is not a case unfortunately as the device is going to be operating on a "foreign" ground (I cannot interfere the ground structure over there). \$\endgroup\$ – tml Jan 27 '14 at 17:15
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Build a heater around the battery out of nichrome wire. Using a temperature sensor of some kind, when the temperature is below freezing, divert the charge current into the heater instead. Insulate the container, taking into account the need not to overheat in summer.

Exactly how to control it depends on what you already have as a charge controller. You could use a thermistor (such as the NTC thermistor in the battery pack) and an op-amp comparator. Or a temperature sensor and a microcontroller, which would also let you log temperature and charge currents. Or a bimetallic strip (non-electronic, reliable, may be hard to find one with the desired temperature behaviour).

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