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Post by blade3609 on Nov 22, 2019 1:51:44 GMT
I had a question about battery voltage / battery charge. According to a sheet i found online , the batteries are drained to 50% when the voltage is 12.1
I have an inverter connected to the battery bank , and it is using 90 watts. When my voltage meter reads 12.1 i disconnect the 90 watts as i think the batteries are drained to 50 percent. However after the disconnect the battery voltage goes to 12.3.
Are the batteries drained to 50 percent or not?
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Post by tattoo on Nov 22, 2019 2:05:55 GMT
Are the batteries drained to 50 percent or not?
Well it depends on several things.......
The 12.1 is with a load on it? I call that sag...... Your 12.3 is at rest like you said so your batteries are at 70%.....
12.1 is 50% at rest without any load on it....... Voltage in a battery should be figured at rest........
On my system I've seen my voltage at 11.9 at sag or startup and at rest it will go back to 12.2...... That's my take others might look at it differently........ I don't worry about it unless my at rest is below 12.0v....
This is the chart I use....... I have a copy taped to my solar board even though I don't look at it anymore but I did in the beginning..........
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Post by Admin on Nov 26, 2019 19:43:11 GMT
I had a question about battery voltage / battery charge. According to a sheet i found online , the batteries are drained to 50% when the voltage is 12.1
I have an inverter connected to the battery bank , and it is using 90 watts. When my voltage meter reads 12.1 i disconnect the 90 watts as i think the batteries are drained to 50 percent. However after the disconnect the battery voltage goes to 12.3.
Are the batteries drained to 50 percent or not?
The resting voltage being at 12.0-12.2 is about 50% of the battery capacity. Under load, the voltage displayed could be anywhere from 11.5-11.7V. The 50% is a reference as it will preserve the battery life. If you discharge at less than 50% your batteries will only last longer.
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Post by donandann on Dec 19, 2019 16:29:17 GMT
I recently purchased a 100 Ah Renogy Lithium battery and my old rules about 12.1 volts and 50% charge are now out the window. Is there an inexpensive way to know the percent of charge of the Lithium battery? These batteries hold their voltage long into the discharge cycle and the manual recommends only using 80% of the charge so what can I use to know when I have reached 80% of charge?
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Dec 19, 2019 17:03:07 GMT
I looked in ebay for "battery capacity meter". They have some for lithium batteries, and for regular batteries. On the quick check, I saw all types, some with LCD displays. I am looking for something that transmits the values to my computer.
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Post by tattoo on Dec 19, 2019 21:38:44 GMT
I recently purchased a 100 Ah Renogy Lithium battery and my old rules about 12.1 volts and 50% charge are now out the window. Is there an inexpensive way to know the percent of charge of the Lithium battery? These batteries hold their voltage long into the discharge cycle and the manual recommends only using 80% of the charge so what can I use to know when I have reached 80% of charge? Well by my chart 80% is somewhere around 11.58 for a lead acid battery etc....... But with a Li battery does it drop down to 11.00? ?? Or does it stay at 12.00 until it shuts off? I'm curious as I've never wanted to buy a Li battery just yet.........
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Post by Guest on Dec 21, 2019 0:04:29 GMT
90 watts for 6 1/2 hours comes to 48.75 amp hours.
So, assuming that you have a fully charged battery and no other load, you can run a 90 watt load for a little over six hours without discharging your 100 Ah battery more than 50%.
50% of 100 Ah = 50 Ah
50 Ah at 12 volts = 600 watt hours
50 x 12 = 600
600 / 90 = 6.67 Hours (6 hours 40 minute)
It would probably be a good idea to limit the 90 watt load to 6 hours.
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Post by Admin on Dec 23, 2019 20:12:44 GMT
I recently purchased a 100 Ah Renogy Lithium battery and my old rules about 12.1 volts and 50% charge are now out the window. Is there an inexpensive way to know the percent of charge of the Lithium battery? These batteries hold their voltage long into the discharge cycle and the manual recommends only using 80% of the charge so what can I use to know when I have reached 80% of charge? Well by my chart 80% is somewhere around 11.58 for a lead acid battery etc....... But with a Li battery does it drop down to 11.00? ?? Or does it stay at 12.00 until it shuts off? I'm curious as I've never wanted to buy a Li battery just yet......... LFP batteries ahve a different discharge curve than typical lead acid:
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Post by tattoo on Dec 23, 2019 21:17:55 GMT
LFP batteries ahve a different discharge curve than typical lead acid: Yep that's exactly what I was thinking but I wasn't sure.......
Thanks for the chart that's impressive............ It's a shame them are so expensive...............
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