May 12, 20224 yr 3 hours ago, Beat said: I see that somewhat differently. The data sheet of the battery packs gives recommended and maximum limits for charging and de-charging currents, as well as for voltages. By setting the inverter/charger to these limits keeps the battery in shape. I.e. I set max utility charging to recommended limit, however no limit to PV charging, as I do not want to loose solar energy. That is anyway limited by the capacity of the PV panals total. And I set bulk and floating charge voltages to batteries datasheet recommendations. De-charging currents are dictated by the load anyway. I doubt that a BMS can do much better. Note that my system is off grid. Well I think that depends on the inverter and on the BMS. I know that since my comms were removed because of a BMS change by the manufacturer of my batteries, the BMS and the inverter have seldom been on the same page. Previously you could (if you had the time) see the BMS telling the inverter what it wanted. There's aspects to this beyond charge voltage & current and so on. My inverter has a feature called "SOC protection". This allows me to reserve a portion of the battery. If I set it to 60% it will allow the battery to discharge by 60% (IE to SOC 40%) whilst there is grid power. So if the grid drops for any reason, I always have at least 40% SOC. That's my safety margin, if you like. I can also set a similar figure for when there is no grid, to stop my batteries getting dangerously low and possibly sustaining damage. So it's a good facility to have. But it can only work if the inverter has a good idea of what the actual SOC is. When I had comms then it did and this mechanism was reliable. Now that I don't, the BMS may see a low SOC but the inverter doesn't, which means I am under-protected if the grid drops. Or the BMS may see a higher SOC than the inverter does, and so the mechanism kicks in too early, which costs me money as the house now runs from grid instead of using battery. So comms are desirable.
May 14, 20224 yr On 2022/05/12 at 5:10 PM, Bobster said: Well I think that depends on the inverter and on the BMS. I know that since my comms were removed because of a BMS change by the manufacturer of my batteries, the BMS and the inverter have seldom been on the same page. Previously you could (if you had the time) see the BMS telling the inverter what it wanted. There's aspects to this beyond charge voltage & current and so on. My inverter has a feature called "SOC protection". This allows me to reserve a portion of the battery. If I set it to 60% it will allow the battery to discharge by 60% (IE to SOC 40%) whilst there is grid power. So if the grid drops for any reason, I always have at least 40% SOC. That's my safety margin, if you like. I can also set a similar figure for when there is no grid, to stop my batteries getting dangerously low and possibly sustaining damage. So it's a good facility to have. But it can only work if the inverter has a good idea of what the actual SOC is. When I had comms then it did and this mechanism was reliable. Now that I don't, the BMS may see a low SOC but the inverter doesn't, which means I am under-protected if the grid drops. Or the BMS may see a higher SOC than the inverter does, and so the mechanism kicks in too early, which costs me money as the house now runs from grid instead of using battery. So comms are desirable. I do exactly what you do, but using volts and not SOC. This is on a Sunsynk. While I do have BMS communication between the Inverter and the battery bank I prefer not to have this enabled on the inverter. I also have a Victron BMV-712 voltage meter connected and it hardly ever reports a significantly different voltage compared to the inverter, so the voltage readings of the inverter is fairly accurate.
May 14, 20224 yr 1st Prize is BMS Comms. 2nd Prize is manual settings backed up with a Pi Module running ICC or Solar assistant. The 2nd prize depends on the operators understanding of his system. In other words rubbish in, rubbish out...The Sunsynk guys or any other guys for that matter can attest that with the Hubble issues recently one has to start to know how to get the best out of your system with manual settings. Those manual settings are different according to the chemistry used (LFP,NMC,AGM) and the configuration (15s/16s or 4cells AGM). A pi module that costs R3000 with software is a small price to pay for a system that cost you R300k. In fact it's like buying an expensive luxury car with no insurance and maintenance plan and no warranty. Does not matter your chosen equipment, or the equipment you have inherited, just know how to tune her up otherwise, you will be frustrated and not enjoy the experience.
July 9, 20224 yr Author Yes, will definitely get solar assistant, as even pylontech new batteries will first have to get a firmware rewrite on the phocos… and the pylontechs disappeared on landing to other dealers… so igot lithium battereries south africa 6.8kW battery, will use it fairly low and slow, with solar assistant, phocos still on the cards, but the availability is a bit of a letdown, if they cant firm up the delivery we will go sunsynk. There are setup features in the phocos that will work well for us.
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