Optimal settings to keep 12V 9Ah AGM battery alive for a long time and safety

DIY
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1

Hello,

a few months ago I bought a “Victron Smartsolar MPPT 75/10”, a 30W solar panel, and a 12V 9Ah AGM battery to test out. I’m running some sensors in my garden 24/7. In the summer, I also run a small sprinkler system based on a timer and the weather. So far, it’s worked absolutely brilliantly. The load of the sensors is 0.1 amps, the sprinkler more but does not run all the time. Currently, a bulk charge is performed every morning to compensate for the losses from the night, but after that, the battery is essentially charged all day.

Questions:
1.) Are there any issues with “overcharging the battery” or similar, especially in summer when the battery is actually charged/full all the time? Should I adjust settings here? Are there any problems I should be aware of, including with the small AGM battery?
2.) What settings/measures should I take to extend the battery’s lifespan, if necessary? I would now assume that summer/winter should be treated differently

The "Victron Smartsolar MPPT 75/10 is currently more or less on standard settings.
I changed the following:
-The recommended charging current of the battery is 0.9 A, I set 1 Ampere in the Victron
-I selected the battery type “AGM Spiral Cell.” I don’t know if that’s the correct choice, it’s an AGM supply battery.
-The battery’s charging voltage according to the datasheet is 13.8 to 14.4 V. I set the absorption voltage in the Victron to 14.4 V and the float to 13.8 V. No other settings were made.
-The device is set to shut off the load output at 12V battery voltage, should it ever get that low. I’ll have to test it out in the winter. I treated the short-circuit plug according to the manual.

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Greetings

2

Show us a 24hr plot with battery current and voltage on so we get an idea of what load is being seen and the summary screen. Maybe the load output as well.

3

Hello pwfarnell,

Here are two diagrams:

1.) Diagram for the last 24 hours:
Exception: from approximately 5:00 PM to 7:00 AM today, no load wasconnected at all because I was remodeling something.*

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2.) Diagram for the last 3 days:
For the previous two days, only the garden sensors were connected 24/7, and the load according to the display was 0.1A.

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The sprinkler consumes only 0.5A and is switched on and off by the sensors depending on the weather and day of the week. I’d leave that out of the equation for now. It wasn’t switched on the last few days either, because I was on vacation.

The sensor network is the primary application and is intended to operate 24/7, year-round. It will be expanded somewhat, but the load profile won’t change. A low, constant load throughout the day.

Greetings

4

I would say that the system appears to be working well, you have a small load on and the MPPT goes into absorption for a short period and then goes to float for most of the day. The one thing I would suggest is reducing the float voltage down to 13.5V.

5

Thank you, that makes sense. After selecting the “AGM Spiral Cell” preset, I reduced the absorption voltage but didn’t give the float voltage a second thought. Selecting the preset probably didn’t make sense anyway.

In the summer, with a massive surplus of energy. If there are any settings I can fine-tune that might make even the slightest sense or even bring about a slight improvement regarding any aspect (mainly long battery life). I’m open to suggestions.

Thank you very much.