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hb-solar avatar image
hb-solar asked

MPPT Solar - 1800w

Hi Guys

I have 10 x 180w panels in parallel

Each panel is 43v VOC

I have an MPPT 150/100 TR regulator attached to a bank of 6 x 220ah batteries

Every day apart from the odd day in winter the battery bank goes to float. Batteries are only 2 year old.

In the past month, system fails after approx 200ah of use (4 hrs max) Batteries were tested and all 6 batteries are dead.

Is this Victron configuration wrong? The Victron MPPT calculator says this is Ok and the 150/100 reg is the correct unit. The Battery supplier is at a loss of what the issue may be.


Any thoughts welcome.


system design
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snoobler avatar image snoobler commented ·

Need more info.

  1. 220Ah battery type (6V, 12V, AGM, FLA, GEL, etc.)?
  2. Battery bank configuration (6 batteries are connected how)?
  3. MPPT charge settings (screen shot of victron connect)
  4. Size and length of wire between MPPT and battery.


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hb-solar avatar image hb-solar commented ·
Hi Snoobler


The batteries are AGM they are 6 x 12v connected in parallel 1320AH , 12v

Unfortunately stuck with 12v

MPPT 150/100 charge controller, with default settings. Battery type 2 i believe

Cabling is through a 30cm aluminium bus bar with 10 studs

Each battery has its own termination on the bus bar

Solar Reg has its own terminal central in the bus bar and does a 2000w multiplus inverter.

Cabling is 2 B&S around 30mm2. They are not all the same length. Vary from 300mm to 600mm

Overnight load unattended is approximately 50 AH from fridges.


All 6 batteries dead after 2 years ..

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3 Answers
Mike Dorsett avatar image
Mike Dorsett answered ·

If you are operating all panels in parallel into the MPPT, and your battery voltage is 12V, you are wasting a lot of solar 1800/12 = 150A - 1.5 times the MPPT rating of 100A. Operating the panels in 3 series x 3 parallel (1 spare) would be more efficient. Operating at 24V would also enable more of the solar to be utilised.

Depending on the quality of the batteries, and the cyclic load (depth of discharge) it is possible that the battery life is expired after 2 years. If you have 6 x 220Ah 12V batteries in parallel ( 1320Ah 12v) Then it may be possible that the 100A charge current is insufficient - leading to premature failure. Also, exact setting voltages, equalisations etc play a large part in battery health. As mentioned above more details are needed to indicate the cause of failure.


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bbmz avatar image bbmz commented ·
I agree to your suggestion of a higher voltage at battery side, to better use the available PV power.

Regarding the PV-side @HB_Solar need to comment on orientation and shading. If the panels are shaded and/or not all aligned in the same direction the parallel setup is way more effective. Otherwise your suggestion of 3x3 panels or 5 times 2 serial panels seems a good idea.

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kevgermany avatar image kevgermany ♦♦ commented ·
Not sure I follow the panel logic. The limit here is the output current. Input current will be much lower, even with a 24V battery configuration.
Three serial strings may be over the MPPT input limit in winter, so would need checking.
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hb-solar avatar image hb-solar commented ·
Hi Mike

The system is designed primarily for use over winter, I understand the wast of paower at times of full bulk charge (summer) . I am really interested in the comment of batteries expired after two years. I will look more deeply into the batterey cycle chart.

Question.

I am stuck with a 12v system so would two 150/100 regulators configured with 5 panels on each connected via the VE bus be a better option for utilising available solar yield and providing batteries a better charge.


Greg

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hb-solar avatar image hb-solar commented ·
I suppose the question is.

With 6 x 12v AGM in parallel and 10 x 180w of Solar panels at 43v

What victron regulator/s would you recommend.


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snoobler avatar image
snoobler answered ·

1800W / 12V = 150A

Your 150/100 can only provide 100A. If you split 600W of your array out to a 100/50A controller, that should suffice.


Factors that may have contributed to battery damage:

  1. Lead acid batteries need to be regularly charged to 100% - daily, and never discharged below 50% if it can be avoided.
  2. If this system performed such that the batteries were regularly at a less than 100% state of charge for days at a time due to poor solar performance, then they would deteriorate and lose capacity.
  3. If the MPPT was programmed to conduct equalization charges at elevated voltages, this damages AGM batteries. Type 2 should NOT do this, but I'm mentioning it in case it's not properly configured.
  4. Your bank is massive requiring a desired charge current of 10% capacity or 132A. Charging at lower current can encourage sulfation and capacity loss. AGM batteries are resistant to this compared to flooded cells, but low current charging over two years would not help.


Basic rules for happy AGM:

  1. Charge to 100% daily
  2. Charge at manufacturer specified current or 10-20% of rated capacity, 132-264A in your case.
  3. Charge to the manufacturer's specified absorption voltage, absorption duration, tail current and float voltage.
  4. Avoid discharging below 50%.


High quality AGM tend to only have about a 1200 cycle life before they reach their 70-80% rated capacity end of life.



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JohnC avatar image JohnC ♦ commented ·

@snoobler

The trouble with these "basic rules" is that most don't apply when you hook up a bank in multiple parallel strings. And makers currents are usually expressed as 'maximums', not necessarily what they recommend as optimum.

Having multiple parallel strings is the best way I know to destroy pb batts. Especially when pushed hard. Just to save me typing it again, some explanation here.. https://community.victronenergy.com/questions/115239/supercycle-battery-life-used-in-deep-cycle-mode.html?childToView=115259#answer-115259

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kevgermany avatar image
kevgermany answered ·

Getting messy.

What equipment do you have, what do you need to buy?

What's the temp compensation on the panels and how cold does it get in the coldest years. Without this there's no good way of suggesting a configuration.

If your DC loads are low, it might be worth wiring the batteries for 24V and adding a 24/12 DC DC converter. This would be cheaper than a second MPPT.

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