June 8, 20233 yr Hi Everyone, Want to ask for your guys opinion on a discussion I had on one of the Facebook Groups. A user there, who seems to be quite technically proficient if a little eccentric, was saying that the default charge & float voltages on the Sunsynk and DEYE inveters are set too high for most LifePO4 batteries and that they should be lowered so as to increase the battery life expectancy. Apparently the voltages can be dropped by switching the inverter to lead/acid batteries, adjusting the voltages down and then switching them back to Lithium. He maintained that the voltages should be set at Charge 55,2V, float 54V, shutdown so 48V so as to increase battery life expectancy. https://www.facebook.com/groups/664508601327065/posts/912503879860868 I was under the impression that it was the batteries BMS that controls the charge & float voltages being provided to the battery but I am no expert so though I would put it out there on the Forum for some opinions. So many questions! 1. Has anyone else ever heard of this? 2. Does changing the charge/float values on the lead battery screen actually make any differences to the charge/float voltages used when charging a battery with comms? 3. If it does make a difference, does changing the default charge voltage from 57V to 55.2V reduce the battery performance/charging ability at all? Or is this just a whole load of who knows what?
June 8, 20233 yr You only have to observe the inverter for a while to see those voltages dont do anything if you have working comms to the battery as confirmed by the LiBMS screen on inverter .
June 8, 20233 yr 1 hour ago, Sc00bs said: 2. Does changing the charge/float values on the lead battery screen actually make any differences to the charge/float voltages used when charging a battery with comms? @Sc00bs, if I remember correctly, Keith from Sunsynk mentioned this in one of the early videos explaining the setup. It went something like this: Set to AGM, change the voltage settings as required for the battery. Set back to Lithium and set required percentages. Our Sunsynk is set to Absorption=55.2V, Float=54V, Shutdown=48V, Grid Start=49V. Hope this helps.
June 8, 20233 yr 8 minutes ago, DeonBez said: @Sc00bs, if I remember correctly, Keith from Sunsynk mentioned this in one of the early videos explaining the setup. It went something like this: Set to AGM, change the voltage settings as required for the battery. Set back to Lithium and set required percentages. Our Sunsynk is set to Absorption=55.2V, Float=54V, Shutdown=48V, Grid Start=49V. Hope this helps. And what exactly will that do ? absolutely nothing . If comms to the battery somehow fails it will not continue working/charging it will throw an error (F58) and stop working. Even if somehow it were to continue charging those voltages would still destroy a 15 cell battery .
June 8, 20233 yr Author 2 hours ago, DeonBez said: @Sc00bs, if I remember correctly, Keith from Sunsynk mentioned this in one of the early videos explaining the setup. It went something like this: Set to AGM, change the voltage settings as required for the battery. Set back to Lithium and set required percentages. Our Sunsynk is set to Absorption=55.2V, Float=54V, Shutdown=48V, Grid Start=49V. Hope this helps. Thanks @DeonBez will go and have a look for the video
June 8, 20233 yr Author 3 hours ago, Nexuss said: You only have to observe the inverter for a while to see those voltages dont do anything if you have working comms to the battery as confirmed by the LiBMS screen on inverter . So @Nexuss are you are saying it doesn't make any difference and that voltages are decided by the battery BMS?
June 8, 20233 yr Author This video @Nexuss? Covers the restart voltage but I am assuming that the charge and float voltages work the same way
June 9, 20233 yr 8 hours ago, Sc00bs said: So @Nexuss are you are saying it doesn't make any difference and that voltages are decided by the battery BMS? Correct.
June 12, 20233 yr Author On 2023/06/09 at 7:44 AM, Nexuss said: Correct. @Nexuss Doesn't look like that from the Sunsynk video
June 12, 20233 yr 15 minutes ago, Sc00bs said: @Nexuss Doesn't look like that from the Sunsynk video That video does not say anything about it. On 2023/06/08 at 11:14 PM, Sc00bs said: This video @Nexuss? Covers the restart voltage but I am assuming that the charge and float voltages work the same way I think you are making the wrong assumptions . If upon a restart/losing comms the battery were to start charging at the set default AGM voltages there would be many batteries being fried constantly and it would of been a know problem.
August 20, 20232 yr 1. Yes. From Sunsynk & some battery manufacturers in their setup guides for Sunsynk. 2. Doesn't make any difference : charging voltage is limited by the BMS. - if Lithium mode selected (com between BMS & inverter then). Battery charging voltage = pack over-voltage setting of the BMS. There is no float. Battery reaches BMS OVP then charging stops. Batteries are kept @ BMS OVP V. At least for Seplos. - if AGM mode selected (no com) : max charging voltage = BMS OVP. If you set lower voltage, batteries get charged at that voltage. If you set higher voltage, batteries gets charged at BMS OVP max. This is also valid for float & equalization voltage if you choose to use them. Any voltage > BMS OVP = ignored ... 3. Endless debate. Some want to charge at 3.65v / cell, other @ 3.4v / cell. Typically you can charge < with automative / grade A cells which are all of a very close balance and capacity or you use an active balancer. Charge > with regular cells or passive balancer to give a chance for the running cells to get properly balanced ... IMO, setting up AGM voltage when using Lithium mode as per Sunsynk videos & some batteries instructions is more a backup if com fails (how come ?) and BMS fails (again, how come ?) And BMS com failure error disabled. As if no failure, BMS dictates charging voltage ... Edited August 20, 20232 yr by zivva
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