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I am working on an off-grid solar project, and I need to store the energy my solar panels produce in batteries. I will use sealed lead acid batteries because they require little maintenance and are less expensive than lithium batteries.

Lead acid batteries perform optimally at a temperature of 25 Degrees Celsius. To save money, I will build an enclosure for my batteries using wood. Since I am off the grid, I do not have a HVAC system installed. I will have a fan and a space heater, but these heat and cool unevenly.

How should I go about storing my batteries so that they do not experience temperature extremes and are properly ventilated?

After accounting for losses due to inefficiency, to meet my energy requirements, I will use 12 Crown 6CRV220 batteries. I will 3 sets of 4 batteries in series and wire all 3 sets in parallel. The entire battery bank will be 24 V and 660 Ah.

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  • $\begingroup$ Please describe the series/parallel and bank arrangement, along with switch gear. We need battery make/model as well. List all battery monitoring features of your charger and controller. You want to enable the features of your charger and controller as best as possible. $\endgroup$
    – Phil Sweet
    Aug 11 '20 at 20:02
  • $\begingroup$ Don't use wood. Use acid-proof plastic, or line with lead sheets. $\endgroup$
    – Phil Sweet
    Aug 11 '20 at 20:04
  • $\begingroup$ @PhilSweet Sorry for the delay, but I edited my answer and provided information on the battery model and arrangement. $\endgroup$
    – Dev Dhruv
    Aug 15 '20 at 19:32
  • $\begingroup$ You can avoid the coldest part of the regime by understanding that about 10% of the round-trip energy to the system will be lost inside the battery enclosure. So you have a unavoidable heat source as long as the batteries are working. You want to avoid rapid temperature changes, temperature gradients within the battery (avoid cold floors), and temperature differences across batteries. Most quality converters will have a remote battery temperature port and an optional sensor dongle. Space between batteries, a small circulation fan, insulated floor, and a temp controlled vent fan ought to do it. $\endgroup$
    – Phil Sweet
    Aug 16 '20 at 18:14
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Remember that in a car, a lead-acid battery is subjected to routine temperature excursions from -20F to +140F under the hood, and this does not ruin the battery. The critical issue with long-term storage of lead-acid batteries is not temperature cycling but something else called self-discharge, in which the battery gradually loses it charge state and becomes discharged during periods of non-use. If a discharged lead-acid battery is allowed to sit idle for ~months, the plates get fouled with sulfate deposits and the battery is ruined.

This can be avoided by putting the battery on a battery tender which is a small DC power supply that applies a tiny "trickle charge" current to the battery so it is always at full charge conditions. This is also called a "float charge". This prevents sulfation and allows the battery to last for many months in the idle state.

Battery tenders are not expensive and are commonly available for batteries of different sizes.

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