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bogeypro avatar image
bogeypro asked

Blue Solar Charge Controller MPPT 150/35, battery monitoring, how long until battery disconnect?

Hello, I have the Blue Solar MPPT 150/35, 2x12 volt AGM batteries, in an Airstream trailer. I just hooked up the Bluetooth Dongle, and I have the Victron Connect app up and running on my phone.

I see all the metrics, it is working as expected. But with this setup, can one ascertain how long the batteries will last until the battery disconnect kicks in? For example, I have the furnace on, the refrigerator on. I should be able to see the Amp Hours being sucked away from the batteries. But what I don't know is how long the batteries will continue to feed that load, before being shut down when it reaches the 50% threshold. Kind of like a reading that says "estimated time remaining".

Is that even possible?

Thank you

batterymonitoring
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3 Answers
snoobler avatar image
snoobler answered ·

The only thing the MPPT can see is the power being delivered TO the battery. It has no means of seeing what is being drawn from the battery as loads unless those loads happened to be powered by exactly the right amount of solar while in float mode. When there is no incoming solar, the unit can only see that the voltage is dropping.


You want a BMV-712 or Smartshunt to get the information you want including, % State of charge and time remaining.


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The time remaining is dependent on your desired depth of discharge. Since you generally don't want to discharge AGM below 50%. You specify a 50% discharge floor in settings, and the time remaining is when you'll hit that desired discharge floor, i.e., 50%.


Another fantastic feature of the BMV and Smartshunts is the ability to enter the Peukert factor. This is the name given to the phenomenon where batteries have lower capacity when pulling higher currents, e.g.,


A 100Ah battery is designed to deliver 5A for 20h - that's a pretty typical rating method.


However, if you use 10A, while you think you might get 10h out of it, you'll get less than that. You might get around 80Ah when pulling 10A. The Peukert exponent (default of 1.25 is pretty good) also factors this into the % charged and time remaining calc.




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bogeypro avatar image
bogeypro answered ·

@snoobler thank you so much for that excellent response. I appreciate that very much.

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snoobler avatar image
snoobler answered ·

My pleasure. If it addresses your concern, please "Accept" the answer for future visitors.

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