Battery shunt not showing estimated time left

Cornishrooster

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May 20, 2022
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Hello all, I'm not really a beginner but I'm a hobbyist a best - first post here. Bought a Hiker trailer a year ago that has a fixed 100w panel and a cheap charge controller that went to a 100 agm battery. The port for the portable solar panel was wired directly to the battery, no fuses or charge controller present. I upgraded the batteries to two battle born lifepo4 75ah units. I also replaced the renogy controller with a victron mppt scc on each panel like in the drawing below. Reran some wrong sized wires according the bluesea systems chart and then fused it all. Everything works great but my battery shunt readings are all over the place. Right now I have a dometic 55L fridge on and a maxxfan on low - the shunt shows the amp draw around 3 amps and the expected life was about 2 days and some change. Then I plugged in the portable panel and the shunt jumped to 10days estimated life and then went blank. All the functions still work just not the battery life estimate. Anyone have and ideas?


Just realized I forgot to draw the positive lead from the shunt to the battery.
IMG_9233.jpg
 

Ampster

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Maybe it needs a reset. You can do that by charging the battery to full. Or it could have an incorrect battery setting
 

TacomaJoe

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Dec 8, 2021
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The shunt is giving you a report on the battery status. If you are drawing say 3A from the battery, it can check for how many are in it and divide by 3 to give you time. When you add the panel it is providing power that reduces the draw from the battery. Drawing less will last longer. Remember, the shunt is only giving battery numbers, not including the solar.
 

Cornishrooster

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May 20, 2022
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Maybe it needs a reset. You can do that by charging the battery to full. Or it could have an incorrect battery setting
Set all the battery settings to the battle born battery recommendations so I don't think it's that. I'll see what it does after the sun goes down. Thanks.
The shunt is giving you a report on the battery status. If you are drawing say 3A from the battery, it can check for how many are in it and divide by 3 to give you time. When you add the panel it is providing power that reduces the draw from the battery. Drawing less will last longer. Remember, the shunt is only giving battery numbers, not including the solar.
Hmm. Are you saying because there's power added it might be confusing the shunt? That would make sense in my mind. All the other numbers are on except battery charge estimated life on current draw.
 

TacomaJoe

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Here are some made up numbers to work into my imaginary example. Set the scene, your battery is fully charged (150Ah) and its night time (no solar). The loads in the trailer add up to 15A. Your meter will calculate a 10 hour life remaining (150Ah/15A). Five hours later you've pulled 75A (15A X 5) out of the battery and it should now show 5 hours left. Now the sun comes up and provides 5A, you plug in the other panel and get another 5A. At this time the sun is providing 10 of the amps and your battery is providing 5A. Your shunt sees the 5A, the meter would calculate life remaining based on the 5A so if you had 60Ah left in the battery it would show 12 hours of life.
 

rmaddy

Full-time Solar-powered Trailer Life
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Which shunt do you have? If it's the Victron SmartShunt or the Victron BMV-712 you should know that the "time remaining" value maxes out at 10 days so you will never see a value higher than that.

The time remaining is based on the battery's SOC and the assumption of the current load being applied until the battery is empty. As your loads change and as the battery is charged the time remaining will fluctuate.
 

Cornishrooster

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May 20, 2022
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Which shunt do you have? If it's the Victron SmartShunt or the Victron BMV-712 you should know that the "time remaining" value maxes out at 10 days so you will never see a value higher than that.

The time remaining is based on the battery's SOC and the assumption of the current load being applied until the battery is empty. As your loads change and as the battery is charged the time remaining will fluctuate.
I realize that but I'm confused as to why it would jump from 2 hours to 10 hours and then just go blank with only dashes instead of numbers. It is the victron smart shunt for the record.
 

rmaddy

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I'm not sure about the blank part but going from 2 hours to 10 hours makes perfect sense if the incoming charge is higher than your loads since the battery isn't being used at all and it would last forever in that state.
 
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