What caused my low battery shutdown?

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graham-watkins asked May 9, '22

What caused my low battery shutdown?

I have a 5000va Multiplus running as an ESS on 48volt with 4 x 220Ah AGM batties running our house with mains power as backup. It has been running great for 18months but with recent bad weather and no sun we had a complete shutdown the other night. Admittedly the oven and hot plates were on at the time. It went ouit on low battery voltage and the mains would not come on. I had to bypass the whole system to get us through the night. Battery voltage was just above the low DC restart and the sun was shining so I turned it all back on and we have been fine since. I have checked 'dedicated ignore AC input' in the Vertual Switch tab, and in 'Ignore AC input', for my load I have selected 4000w for 30 seconds for if load is higher. Load lower than 2100 for 2 minutes for when load is lower than. In 'Battery Condition' I have Do not ignore when Vdc is lower than 47 V for 1.5 seconds or when state of charge is lower than 55%.

I am now thinking that the settings may be too high and/or the times I have set are too long for these conditions, please advice what you think.

shutdown

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nickdb ♦♦ commented · May 10, 2022 at 06:21 AM

That sort of load off 4 batteries like that will be putting them under tremendous stress, that is insufficient to run an oven/hotplate for any period without ruining them.

Compare the current you are pulling to their specs. It is not surprising they are dead, get yourself some LiFe batteries or a much larger bank of conventional batteries.

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Answer 1 · 2022-05-10T05:29:40Z

Alexandra answered · May 10, 2022 at 05:29 AM

@Graham Watkins

Your batteries will be weaker now because of age. So voltage collapse under load will be more of an issue.

Maybe lower your high connect down a bit so it connects sooner to grid on higher loads. As well as set higher the low DC voltage reconnect.

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graham-watkins commented · May 10, 2022 at 10:59 AM

As I said the battries are only about 18 months old and we don't usually load them up too hard, so hopefully I haven't damaged them too much but yes I have been thinking that I need to change those 2 settings. I have been looking at the original default settings and am thinking I will reinstall them. I might use more power from the mains but save the dollers on the cost of new batteries.

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