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ambientcoast asked

BlueSolar MPPT 75/15 New setup question.

Hey - I’ve just installed a BlueSolar MPPT 75/15 into a van along with 200w solar panels connected in series and a 105ah AGM battery. Everything *seems* to be working, but I just want to confirm a couple of things.

The controller is showing a steady flashing green LED and a steady flashing orange LED, which tells me that bulk charging is happening and that the controller is in BatteryLife mode. I haven’t switched away from factory settings.

I’m aware that the battery itself wasn’t fully charged when installed. When disconnected from the system, it reads around 12.3v.

Right now, the panels are generating around 30v or so. It’s a bit overcast and still early ish in the morning. I’m not expecting much from these conditions, tbh. However, the MPPT controller is turning this into a charging current of around 13.1v, tested with a multimeter with the battery disconnected.

With the battery connected to the charging circuit from the controller, I’m still seeing a voltage of around 12.3v on that circuit.

So, what I want to confirm is whether this overall voltage of 12.3v is expected on the charging circuit (given the battery voltage and the state of the weather), and whether this will increase in time as the controller brings the battery up to a full charge.

In other words, is the lower battery voltage pulling the overall charging circuit voltage down a little, as you’d expect if you connected two unequalised batteries in parallel?

Does that make sense?


MPPT Controllers
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1 Answer
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ambientcoast answered ·

I can probably answer this myself now... the voltage on the charging circuit is increasing as expected. Since I posted this question, it's now already up to 12.9v and we're still grey and overcast.

All good.

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