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Lead Acid Battery Efficiency - what you are losing using a battery (Read 3238 times)
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Lead Acid Battery Efficiency - what you are losing using a battery
Aug 8th, 2011 at 6:28pm
Looking around, the short answer is about 70% efficiency.

It does depend on the charge amps and the discharge amps. For higher amps it's a little less, this seems to be due to the chemical nature of the battery, that the liquid doesn't circulate fast enough for higher power, and heat loss.

So buy bigger batteries than you need and they will be more efficient for your system.

However, they all have a "shelf" life since the chemicals eat at each other so you need to pick a battery that justifies the money you will spend on it vs. the money you will save in efficiency over the years it operates.

You may also need to calculate in the efficiency of your charger and AC inverter to come to a total system efficiency of somewhere around 40% or 50%.

A typical Grid Tie Inverter will be 80% at the low end, and 90%+ at the high end (half it's rated power typically). That's straight from your solar Panels to the grid where it's used right in your house or turning your meter backwards.

Some references:

"A lead-acid battery has an efficiency of only 75-85%. The energy lost appears as heat and warms the battery. Keeping the charge and discharge rate of a battery low, helps keep a battery cool and improves the battery life. The above losses don't include losses in the charging circuit which may have an efficiency of anywhere from 60% to 80% - thus the overall- total efficiency is the product of these efficiencies and ends up being 45 to 68%."

"Charge/discharge efficiency, 50%-92%"

"Lead acid batteries 70%", European Rechargeable Battery Association PDF file from 2010

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