We need Deep Cycle Batteries for Solar Panels. Deep cycle batteries can withstand a deep discharge. Your car starter battery may survive a 100 deep discharges, but a high spec Deep Cycle Battery can withstand about 1200 deep discharges. Solar Panels generate low currents and charge batteries slowly. ‘Solar’ batteries are optimised for high battery efficiency. Batteries have their own internal resistances which waste power both while charging and while discharging. A battery’s efficiency is the ratio of how much energy the battery can actually transfer to the load (discharging energy) vs how much energy it takes from the source to get fully charged (charging energy). Batteries for solar applications generally have an efficiency of about 85%. This is a spec sheet for a Solar Battery: http://addoworld.com/solar-smf-gel-battery.pdf:  solar-smf-gel-battery. This is what the spec sheet tells us.

  • DFS12-200 has an internal resistance of less than 4 milliohms, which is very good. The smaller the better.
  • If you discharge it over 10 hours, load current of 20 A, you can maintain a terminal voltage of nearly 11 V and get a discharge capacity of 200Ah. The greater the load, the faster it will discharge and the less efficient it will be. The terminal voltage will also be degraded.
  • It is less efficient at cold temperatures.
  • If you store it at room temperature, without using it, it will self-discharge to about 75% in a year.
  • Maximum charging current is 60A and max discharge current is 600A (5s).
  • It’s as heavy as a person. (63kg).

Take a look at the specifications of the other batteries in the brochure. The Featured Image is from: http://addoworld.com/solar-batteries.html

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