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Mercer SOL-I-AX-5P making the best of a bad install


Timbo_vb
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I'm trying to figure out the best way to figure out the best way to get a benefit out of a bad install at a relatives place. The inverter is a Mercer branded 5kw SOL-I-AX-5P with 4 * 105Ah non deep cycle batteries and 5 strings of 2 * 380w panels with panels are facing west (don't ask why). The inverter doesn't seem to blend power sources and jumps with a noticeable dip between sources, enough to turn off the HiFi, so I would prefer it not to bounce between sources

  • Inverter specs
    • DC input 48V 117A
  • AC Charger Mode
    • AC input 230V 50Hz 35A
    • DC Output 54V Max 60A Default 30A
  • Solar Mode
    • max current 80A
    • System voltage 48V DC
    • min voltage 40V
    • max voltage 145V VOC

I'm aiming for maximum battery runtime while load shedding then using offset some utility consumption when the panels get sun. I'm thinking of using the following settings to try force the batteries to stay as full as possible and use solar as much as possible when available.

  • 01: SOL Solar energy provides power to the loads as first priority. If solar energy is not sufficient to power all connected loads, battery energy will supply power the loads at the same time. Utility provides power to the loads only when any one condition happens:
    • - Solar energy is not available
    • - Battery voltage drops to either low-level warning voltage or the setting point in program 12
  • 12: 54v Setting voltage point back to utility source when selecting “SBU priority” or “Solar first” in program 01 (currently 50v)
  • 13: 54v Setting voltage point back to battery mode when selecting “SBU priority” or “Solar first” in program 01. (currently 54)
  • 16: CSO Solar energy will charge battery as first priority. Utility will charge battery only when solar energy is not available.

 

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21 hours ago, Timbo_vb said:

with 4 * 105Ah non deep cycle batteries

Eew. A bit slim for a 5 kW inverter.

I'm aiming for maximum battery runtime while load shedding then using offset some utility consumption when the panels get sun. I'm thinking of using the following settings to try force the batteries to stay as full as possible and use solar as much as possible when available.

  • Quote

    01: SOL

Yes. That will switch to utility powering loads at sundown. Can't avoid those two switches, sorry. Using setting 03 (AC input voltage range) will speed the switch-over. It will also reject mains when it's below 170 VAC, but that's a good thing. 

  • Quote

    12: 54v Setting voltage point back to utility source when selecting “SBU priority” or “Solar first” in program 01 (currently 50v)

Putting this setting as high as possible will switch to utility as soon as possible when the battery voltage drops. That will keep the battery as full as possible, but may start switching more often than strictly necessary.

  • Quote

    13: 54v Setting voltage point back to battery mode when selecting “SBU priority” or “Solar first” in program 01. (currently 54)

That's probably a reasonable compromise, keeping the battery fairly full, but making maximum use of solar.

  • Quote

    16: CSO Solar energy will charge battery as first priority. Utility will charge battery only when solar energy is not available.

Again, a good compromise for your goals. It will use solar power exclusively through the day, unless the battery drops below the voltage in setting 12, and will start utility charging at night to keep the battery full, but only if it wasn't fully charged during the day from solar.

If there is load shedding scheduled on a cloudy day, it might be necessary to temporarily change settings, e.g. to UTI output source priority, to get the battery charged from utility when you know that the sun can't do it.

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Thank you @Coulomb I think this is a useful setup for those who would like to conserve their lead-acid batteries.

The voltage dips between mode changes are causing the TV and HiFi to turn off and I have asked him to get the unit swapped with a 5kw King model, apparently they operate in a more smooth continuous mode without dips during mode changes.

 

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An axpert type with SUB mode works well with SLA batteries. SLA's should get you through a 2 hour load shedding just fine. The problem is when substations blow up and leave us without electricity for days killing our SLA's.

I'm going to try and see how many years I can get out of my SLA batteries if I keep my inverter in SUB mode. Please note I only have solar in charging source. So the batteries are getting cycled somewhat with around 60 watts x 12 hours.

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1 hour ago, Buyeye said:

60 watts x 12 hours.

I assume you meant 60 amps (at around 50 V, or 3 kW). You probably won't have the full 3 kW for early and late hours, so it's probably more like 3kW × 5 h ≅ 15 kWh, on a good day.

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Just now, Coulomb said:

I assume you meant 60 amps (at around 50 V, or 3 kW). You probably won't have the full 3 kW for early and late hours, so it's probably more like 3kW × 5 h ≅ 15 kWh, on a good day.

No I was talking about the 60 watts the inverter uses to power itself when the sun goes down till the sun comes up.

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2 minutes ago, Buyeye said:

No I was talking about the 60 watts the inverter uses to power itself when the sun goes down till the sun comes up.

Oops, my bad! I only skimmed your post. Sigh. I have a lot of posts to get through every day.

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  • 3 weeks later...
  • 6 months later...
On 2021/11/05 at 5:12 PM, Jojo2022 said:

What is the maximum solar value that can be connected to a Mecer SOL-I-AX-5P inverter

It's nominally 4 kW output (80 A @ 50 V). You can "overclock" that by about 20%, so about 4.8 kW of nominal PV power. More than that and the overshoots get big enough to start disconnecting batteries.

You also have to stay within the voltage rating of the inverter-charger, usually 145 absolute max (at your coldest likely temperature, often 0°C). That often means 2S max, with today's giant panels.

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Thanks Coulomb for the reply and heads up on the 20%. I'm busy sorting out an installation where they have installed 18x280W panels on one inverter and 18x275W on the other.  Both these values are well above the 4kW.  These values would be 5040W and 4950W respectively both above the 4800W overclock value. 

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