I have 2000W of solar voltaics feeding 3 banks of 4x12v batteries giving me 48v for my inverter. I am using this to run 2 computers running scientific programs. Over night there is no charging, only depletion of the batteries and I'm wondering how low I can reasonably drain these batteries before I affect the lifetime. They are all wetcell deep cycle batteries. With no significant load on them they will drop to about 49v overnight but go lower if I leave the programs running. So what's a minimum safe voltage to not shorten the lifetime?
How low can I reasonably drain my batteries?
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Each battery manufacture usually supplies some type of document stating the number of cycles a battery can perform in it's life. The more it is discharge the lower the number of cycles.
Most FLA seal batteries show the longest life happens if you do not discharge more than 25% each time. Others show the most at 20% discharge. They also post the minimum value of volts it should be before the life is shortened. I believe that voltage is between 12.3 & 12.4 for a 12v battery.
IMO a 48 volt system going down to 49 volts is too low and will shorten the life span of one if not all of those 4 batteries. -
maybe you need balancing repair system , which designs for expanding lithium battery life time and get much more longer life for your battery pack.Comment
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Also just jumping into a thread without introducing yourself raises a red flag to the Moderators.Comment
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The problem is improperly sized system, as in undersized. Your batteries would not be dropping that low if the panel wattage and battery capacity are designed for the expected load. You should be able to run 4-5 days before you get that low.MSEE, PEComment
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Your battery bank design is far from optimal. Three parallel strings is unstable. It would be useful to have a DC clamp ammeter to help diagnose the problem. The basic issue is that when charging the batteries, current does not divide equally among he three strings of batteries. As the imbalance grows, you may have one string discharging into another string. One bad cell in one string will pull the whole bank down to its level.
If there is a bad battery, diagnose it asap and remove that string from the battery bank.
Have you checked voltage and SG of each of your batteries?
--mapmakerob 3524, FM60, ePanel, 4 L16, 4 x 235 watt panelsComment
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