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groingo
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# Posted: 29 Oct 2013 03:39pm
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I have two 6 volt 115 amp hour deep cell batteries.
I use a 12 volt / 120 volt converter and use a total of 0.50 kwh a day (24 hours).
If I recharge the batteries when they reach 80%....how often should they be recharged?
Come on Don, I know you live for this kind of stuff!
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MtnDon
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# Posted: 29 Oct 2013 03:54pm
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Quoting: groingo 12 volt / 120 volt converter
inverter
The battery electrolyte is at what temperature, during discharge cycle, not any elevated temperature that may result from charging? And is that temperature constant through the year or what is the worst case, coldest temperature?
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groingo
Member
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# Posted: 29 Oct 2013 05:44pm
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Quoting: MtnDon The battery electrolyte is at what temperature, during discharge cycle, not any elevated temperature that may result from charging? And is that temperature constant through the year or what is the worst case, coldest temperature?
Rephrase question....Ballpark number based on daytime temp of 60-65 degrees and night 30-40 degrees.
Charge temp unknown.
All I remember is a couple years ago I was recharging once every three days or when batteries hit 80% charge and was using a lot more power.
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MtnDon
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# Posted: 29 Oct 2013 05:52pm
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Quoting: groingo Rephrase question.
The temperature of the electrolyte matters because at temperatures below 80 F (rounded number; STC is 77 F)) the battery performance falls. If the electrolyte is at an average of 40 F for example 18% of the label capacity is unavailable / lost.
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razmichael
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# Posted: 29 Oct 2013 06:20pm
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And what is the Peukert's exponent of the batteries (and how 'smooth' is the .5kwh /day draw? Why does this remind me of Monty Python and "What... is the air-speed velocity of an unladen swallow?".
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groingo
Member
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# Posted: 29 Oct 2013 06:33pm
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I withdraw the question.
Just too many variables, will just do it and see what happens.
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MtnDon
Member
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# Posted: 29 Oct 2013 07:27pm
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Yes, many variables. Since I already had my calculator out I'll give my answer anyhow. Theoretically with a few environmental adjustments it looks like just about 2 days between recharging. Some guessing there on temps, efficiencies, etc.
Another question is how is that 80% figure arrived at? Voltage or specific gravity? Voltage readings are usually off unless the batteries have been at rest, no charging and no discharging for several hours.
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groingo
Member
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# Posted: 30 Oct 2013 05:10pm
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Quoting: MtnDon Yes, many variables. Since I already had my calculator out I'll give my answer anyhow. Theoretically with a few environmental adjustments it looks like just about 2 days between recharging. Some guessing there on temps, efficiencies, etc. Another question is how is that 80% figure arrived at? Voltage or specific gravity? Voltage readings are usually off unless the batteries have been at rest, no charging and no discharging for several hours.
Funny how this stuff works, I had guessed two days three tops....thanks for the help and confirmation all.
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