Clivevan Posted January 30, 2020 Share Posted January 30, 2020 Finally after almost a year of struggles my Axpert 5Kw is installed with 4x180 Omni AGM batteries (48 volt). It is to operate as a UPS only. No panels. How do I set the Axpert to automatically cut out once the batteries have reached say 50% DOC? I tried to understand the manual but it is Greek. regards Quote Link to comment Share on other sites More sharing options...
Fazil Posted January 30, 2020 Share Posted January 30, 2020 set it to 48V but I prefer setting it to 49V just as a preference. Quote Link to comment Share on other sites More sharing options...
Coulomb Posted January 31, 2020 Share Posted January 31, 2020 I would change setting 29 (low DC cutoff voltage) to 50 V. Depending on loads, it might be acceptable to use 49 V (12.25V per 12 V module). 48 V is too low in my opinion, nearly dead flat. But take into account that I'm no lead acid expert. Quote Link to comment Share on other sites More sharing options...
viceroy Posted January 31, 2020 Share Posted January 31, 2020 If you want to do it properly, get a BMV702 (BMV 700 is slightly easier on the budget) Wonderful little device to monitor the SOH (state of health) of your batteries, and can be set to trigger a relay or alarm at whatever DOD you set. Otherwise what @Coulomb has suggested will work fine provided you aren't pulling big loads from the batteries which may trigger false positives when the voltage dips below the set threshold. Quote Link to comment Share on other sites More sharing options...
Clivevan Posted February 3, 2020 Author Share Posted February 3, 2020 thank you all so much - I will do as suggested. The BMV 702 and set at 49 volt. deeply appreciate the time and effort fellow humans devote to help fellow humans. Quote Link to comment Share on other sites More sharing options...
Clivevan Posted February 4, 2020 Author Share Posted February 4, 2020 OK now what? The programme only permits a Low DC cut-off range between 40 to 48 V (ie the custom setting for setting 29; the default is 42V!) How can the default be so low? Do batteries even go that low?? What to do if I want to select eg 49V as a low cut-off voltage? Or does it not matter much and 48V is OK? regards Quote Link to comment Share on other sites More sharing options...
Coulomb Posted February 4, 2020 Share Posted February 4, 2020 3 minutes ago, Clivevan said: OK now what? The programme only permits a Low DC cut-off range between 40 to 48 V (ie the custom setting for setting 29; the default is 42V!) Oops! I run patched LFP firmware, I forget what it's like for others. My bad. 3 minutes ago, Clivevan said: How can the default be so low? It was only intended as a last-resort emergency action, not an every day thing. Quote Do batteries even go that low?? Under extreme circumstances, sure. But it's not good for their long term health if it happens too often. Quote What to do if I want to select eg 49V as a low cut-off voltage? Or does it not matter much and 48V is OK? You can't. Even the lead acid flavour of patched firmware doesn't go above 48 V for this setting. So you need to find another way to achieve what you want. Which I believe is you want to turn off the loads when the battery voltage reaches a moderate SOC. Perhaps ICC can help, though it may try to switch your inverter into line (bypass) mode, but I think that with no AC-in, it will keep running from battery. Maybe you should consider patched firmware after all; see Can I update my firmware, and if so to what? If you can run 73.00e or 72.20e, either of those will let you set the low DC cutoff voltage to a maximum of 52.0 V. Warning: the LFP flavour is not intended for lead acid batteries, so this will not be ideal, and I haven't thought through the consequences. Quote Link to comment Share on other sites More sharing options...
Clivevan Posted February 4, 2020 Author Share Posted February 4, 2020 Ok - I follow. But if I should set it at 48 Volt that will equate to about 50% SOC? Surely that is OK? I noticed at the ICC page the following banner: Switch between grid and battery mode based on time setting or state of charge. My emphasis. I assume that means that ICC can assist? regards Quote Link to comment Share on other sites More sharing options...
Coulomb Posted February 4, 2020 Share Posted February 4, 2020 9 hours ago, Clivevan said: Ok - I follow. But if I should set it at 48 Volt that will equate to about 50% SOC? Surely that is OK? There seems to be disagreement. For example, from https://www.energymatters.com.au/components/battery-voltage-discharge/: State of Charge Sealed or Flooded Lead Acid battery voltage Gel battery voltage AGM battery voltage 100% 12.70+ 12.85+ 12.80+ 75% 12.40 12.65 12.60 50% 12.20 12.35 12.30 25% 12.00 12.00 12.00 0% 11.80 11.80 11.80 Others seem to say around 45% SOC. There is probably a large range depending on load and temperature. I guess it's better than nothing. 9 hours ago, Clivevan said: Switch between grid and battery mode based on time setting or state of charge. My emphasis. I assume that means that ICC can assist? Not necessarily, if you don't have AC-in connected. Quote Link to comment Share on other sites More sharing options...
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