Shunt Discussion

AnOldUR · September 2023

Finally got around to (and over the fear of) completely draining my two 100Ah LiFePO4's to test the capacity. From full I was able to draw 196Ah before the system shut down, so I believe that's a pretty good indication that the batteries are good? After jump starting the battery with a NOCO Genius10 the SOC came up as 100% even though the batteries were still completely drained. In hindsight I should have reset it to zero before charging, but didn't so it's staying at 100% SOC while charging with the NOCO.

The shunt STATUS page is telling me that the NOCO is putting in up to 10 amps. My questions have to do with monitoring the charging cycle. On the STATUS page there is a Consumed Ah line, but no replaced Ah. The HISTORY page has a Charged Energy line displayed in Wh's, but I think it would be better to see Ah input displayed on the STATUS page for a quick comparison to what's been consumed. Is there a way to configure this? Am I missing something about how to read the display?

I'm assuming that the Charged energy on the HISTORY page will reach the Discharged energy of 2.5kWh's once fully charged. Any insight or suggestions would be appreciated.

Image: https://us.v-cdn.net/5021717/uploads/editor/eo/dvqs4cj2m91d.png

Image: https://us.v-cdn.net/5021717/uploads/editor/rk/ejf4ca9g3uu8.png

ColoradoJon · September 2023

The status page is not showing Consumed Ah because your monitor thinks that your battery is already at 100% SOC and you will not be able to monitor the actual charge status accurately enough because of it.

You can use the Voltage measure to guess where the charger is in it's charge cycle, though, if you know what voltages your NOCO charger uses on each phase.

The history page Charged Energy will never match the Discharged Energy. Power usage is not that precise, not even close. Here is a screenshot of my Victron 712 which is connected to my off-grid solar cabin in Colorado. Notice the Discharged Energy vs Charged Energy. Also, these screenshots were taken before sunrise so there is a load on the batteries. By 10:00am there will by 60-80amps inbound. This is a 12V system using 6V flooded lead acid batteries.

Image: https://us.v-cdn.net/5021717/uploads/editor/mh/5g3lw9gokw55.png

Image: https://us.v-cdn.net/5021717/uploads/editor/ru/rgy4g11239w1.png

KK1L · September 2023

As an aside it iw worthwhile to check the setting for 100% state of charge. By default it is set for lead acic...easy to overlook. Ask me how I know

AnOldUR · September 2023

Before this test I charged each battery independently then reconnected in parallel and again used the NOCO connected directly to the bank in hopes of assuring a full charge and balancing the cells. I then let the batteries rest over night. After that I reset the shunt.

I don't know if it makes any difference between our results @ColoradoJon, but there are a couple of thing that may be contributing factors. First, Your SmartBMV HQ2020XERIV's is not the same my SmartShunt HQ2226DE7Q7. Second, all the readings I'm posting are with the battery switch off, so nothing new has gone in or out after charging with the NOCO (and all my screen shots in this thread are from after the previously mentioned shunt reset).

I was under the impression that the displays percentage SOC was not always accurate, but that the displayed kWh's and current passing through the shunt was? After jump starting the batteries, the Energy readings were 2.5kWh Discharged energy and 2.6kWh Charged energy. I'm not sure if the difference is due to the batteries not actually being full charged. Maybe completely draining than charging balanced the cells better.

What confuses me most is that with no charging or discharging and no Consumed Ah's showing on the shunt's app, the voltage settles in at 13.32V overnight. The charts say this would be just above 90% SOC, yet I was able to draw 196Ah from the batteries before the BMS shut it down. Is it possibly just the characteristic of the brand of battery I've installed? Could the 13.32V rested voltage actually be 100% SOC (100Ah/battery)?

Battery specs are 12.8V Rated Voltage and 1280Wh's of energy.

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Yoshi_TAB · September 2023

. Is it possibly just the characteristic of the brand of battery I've installed?

Hi, Far from an an expert...but what I've read that is very possible. There are a bunch of components, such as the individual cells, BMS , internal wiring and components that all have to play together. How they work together would be dependent on their quality and assembly techniques.

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