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cecirdr asked

Solar controller 100/30 not fully charging vmax slr155AGM

I have the controller set at the default 2 position on the dial. The first time I set it up, it got up to 14.4v and went to absorption, then to float. My battery was fully charged. The last two days (everything is new) my battery seems to get “stuck” at around 12.7 volts. I have 200 watts of solar. My battery is back up to 12.6 by noon, but it’s never getting higher Despite it being sunny. All afternoon I see anywhere from 70- 100 watts and 5-6 amps from my panels, but my battery voltage is refusing to rise.

FWIW, the battery and charger are in the same space and are the same temperature. Connections look tight. Things worked on my first charging run also, but not now. It was also in full Sun and got that day too. I’m stumped. Any ideas?

battery charging
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cecirdr avatar image cecirdr commented ·

Here are some screen shots from later in the afternoon. The battery has been at this voltage for hours and not increasing charge. I had run it way down over night for two nights because I had no choice due to needing cooling in my van. I realize it’ll shorten the battery life tremendously, but I don’t have a choice. The settings are at default, number 2 position. I haven’t edited anything. I’d really appreciate some help understanding what’s happening.

Thx so much!

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1 Answer
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pwfarnell answered ·

The minimum voltage on the last 2 days is very low at 10.03V, is this the voltage under load, or overnight without any loads. If the battery has been discharged to 10V then it may well be damaged and will not charge back up. Is the battery getting warm, a sign that there is damage. AGM batteries need to be fully charged every cycle to get good performance. I

However, as the battery is new then it may be that the solar is not large enough. Are there any loads on the system while it is charging, if the solar is producing 6.7A at 12.7V but you are using 5A then the battery will not charge. Have you cross checked the demand you are placing on the battery against the size of your loads, if the solar is less than your loads you are on a downward spiral. It may have charged fully when first set up because the battery was supplied close to fully charged. Some details on the load on the battery would be useful.

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