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lowredrt avatar image
lowredrt asked

Inconsistent wattage

Here’s a link to a screenshot video I took of my VictronConnect app.

https://youtu.be/N6MI9vRzVyQ

I have a SmartSolar MPPT 150/45. It is connected to (6) 100 watt 12v solar panels on my RV. I have the panels in two paralleled sets of three in series. The first day it was pretty consistent at 250 watts because it was a cloudy/gloomy day. The next day was intermittent clouds but mainly sunny. But my solar output was all over the place which makes me think I’m doing something wrong. Here are my battery settings:

12v; 43a max; 14.4 v absorption; 2 hr max; 13.5v float, 13.5v equilazation with automatic turned off; and -30.00mV/°C temp compensation. (All per my battery manufacture recommendation... Trojan T-105 AGM Deep Cycle... (4) 6v batteries in 12v series parallel)

I left every other setting alone.

So is that normal or am I doing something wrong?

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wkirby answered ·

This is not normal.
What I can see in your video is that your battery Voltage is all over the place. You are hitting 14.8V (absorb Voltage) which is causing the MPPT to throttle back but then the battery Voltage immediately falls away.
The battery Voltage should be a lot more stable than that.
Are you sure that all of the connections from the MPPT to your battery are sound?

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lowredrt avatar image lowredrt commented ·

All the connections are solid. One thing I forgot to mention is that the first day I had the MPPT connected directly to the battery with #4 welding cable. The second day I had the same #4 welding cable but with a 50A DC breaker installed. I was going to remove the breaker today to wire the MPPT back directly to the battery to see if the issue went away.... but there was no issue today. It is running great today and I haven’t removed the breaker. This has me scratching my head because I haven’t changed anything so I feel like the problem could come back and potentially harm my MPPT, or even worse, my batteries.

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wkirby avatar image wkirby ♦♦ lowredrt commented ·

Kind of cool that it's working, but a pity there is no answer as to why.
The Voltage of the battery can't physically jump around like that. Since you have checked all your connections, I'm out of ideas to what could be the problem. If it does it again I'd try eliminating the breaker just to test.

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