Best choice to increase run time ?

[GoldenNoodle]

I kind of inherited a wind/solar setup. It's got a 400 watt 12v 'Whisper' wind turbine, 480 watts of 12 vdc panels in a mix of 80 and 120 watts and 10 x 110 AH deep cycle 'renewable energy' batteries. The charge controller looks like it's an OEM/no brand name. Probably PWM ?

The battery bank was replaced in November 2019.

In the November-March time frame the system needs to be topped up with a generator at least once a week, in December it's 2x a week.

There's a constant 35 watt draw.

When I (try to ) do the math on that I get 10 x110 = 1,100 AH * 50% = 550 AH @ 12v = 6,600 Watts / 35 Watt draw = 188 hours (?) So even if there is almost no power from the PV or the wind it should still run about 7.8 days ?

Does that seem "right" ?

If so then what is the best option to increase run time ? In terms of a ratio is the PV/Turbine sized properly to the battery capacity ? Should I add PV or storage or both ?

If the numbers are whacky then where might I look for gains in the system (replacing the PWM controller?).

As well I have a 24 vdc 240 watt panel that came along with a different acquisition - what are some thoughts on adding that to this system ?

Thx
.

 

[boondox]

Yes, your math is correct. Just for clarity using watt/hours is betters so you have a net of 6,600 watt hours available and with a constant 35 watt load you use 840 watt hours a day and yes, it will last 188 hours or so. I would rather not draw down to 50% every cycle for longer life of the batteries.

I'd say add PV. Your storage is fine for your loads and even some more. I bet if you put a power monitor on the wind it won't add up to too much. PWM vs MPPT, you will get some extra juice but it won't rock your world.

One thing about mixed panels is that you aren't getting all the power they are rated for. Depending on how they are configured it might be much less. One route would be to get a couple of bigger panels and a charge controller to go with it. Leave the existing system as is and add a second. That way at least your new panels aren't taking a hit from playing mix and match and you are getting what you should out of the, If you are going to play mix and match the most important parameter to match is the current rating of the panels.

 

[fafrd]

I kind of inherited a wind/solar setup. It's got a 400 watt 12v 'Whisper' wind turbine, 480 watts of 12 vdc panels in a mix of 80 and 120 watts and 10 x 110 AH deep cycle 'renewable energy' batteries. The charge controller looks like it's an OEM/no brand name. Probably PWM ?

The battery bank was replaced in November 2019.

In the November-March time frame the system needs to be topped up with a generator at least once a week, in December it's 2x a week.

There's a constant 35 watt draw.

When I (try to ) do the math on that I get 10 x110 = 1,100 AH * 50% = 550 AH @ 12v = 6,600 Watts / 35 Watt draw = 188 hours (?) So even if there is almost no power from the PV or the wind it should still run about 7.8 days ?

Does that seem "right" ?

If so then what is the best option to increase run time ? In terms of a ratio is the PV/Turbine sized properly to the battery capacity ? Should I add PV or storage or both ?

If the numbers are whacky then where might I look for gains in the system (replacing the PWM controller?).

As well I have a 24 vdc 240 watt panel that came along with a different acquisition - what are some thoughts on adding that to this system ?

Thx
.

Until you figure out what your consumption is, (both during the day as well as when there is no sun) there is no way to answer your question .

Also what inverter do you have and what is its efficiency?

Oh, I see, you just have a constant 35W draw.

In there case your math is correct except for inverter efficiency.

80% efficiency (which is pretty poor) would effectively take your 35W load up to 44W and drop your 188 hours down to 150 (6-1/4 days).

Your batteries are big enough to get you through over 7 days with no input energy, so the issue is that your generation is below 850Wh (or 1050Wh) per day.

You need more PV, not more storage.

PV Watts will tell you what production you can expect month by month from your 480W array (and how much more PV you’ll need to keep up with the 35W load though the lowest-production month of December).

Also, how old are these panels?

 

[GoldenNoodle]

Until you figure out what your consumption is, (both during the day as well as when there is no sun) there is no way to answer your question .

Also what inverter do you have and what is its efficiency?

Oh, I see, you just have a constant 35W draw.

In there case your math is correct except for inverter efficiency.

80% efficiency (which is pretty poor) would effectively take your 35W load up to 44W and drop your 188 hours down to 150 (6-1/4 days).

Your batteries are big enough to get you through over 7 days with no input energy, so the issue is that your generation is below 850Wh (or 1050Wh) per day.

You need more PV, not more storage.

PV Watts will tell you what production you can expect month by month from your 480W array (and how much more PV you’ll need to keep up with the 35W load though the lowest-production month of December).

Also, how old are these panels?

Thanks. There is no invertor - it's a 12 volt draw.

I think the 80 watt panels are ~10 years. The 120 watt are maybe 3 years old - I'm not sure. The labels most stuff are blank from UV.

 

[GoldenNoodle]

Yes, your math is correct. Just for clarity using watt/hours is betters so you have a net of 6,600 watt hours available and with a constant 35 watt load you use 840 watt hours a day and yes, it will last 188 hours or so. I would rather not draw down to 50% every cycle for longer life of the batteries.

I'd say add PV. Your storage is fine for your loads and even some more. I bet if you put a power monitor on the wind it won't add up to too much. PWM vs MPPT, you will get some extra juice but it won't rock your world.

One thing about mixed panels is that you aren't getting all the power they are rated for. Depending on how they are configured it might be much less. One route would be to get a couple of bigger panels and a charge controller to go with it. Leave the existing system as is and add a second. That way at least your new panels aren't taking a hit from playing mix and match and you are getting what you should out of the, If you are going to play mix and match the most important parameter to match is the current rating of the panels.

So I could dump two sets of PV on two different controllers into the same battery bank ?

 

[boondox]

So I could dump two sets of PV on two different controllers into the same battery bank ?

Yup. And avoid the mix and match losses.

 

[fafrd]

Thanks. There is no invertor - it's a 12 volt draw.

I think the 80 watt panels are ~10 years. The 120 watt are maybe 3 years old - I'm not sure. The labels most stuff are blank from UV.

OK, for a DC load you calculations are about correct,

But after 10 years, your 80W panels are probably putting out no more than 90% of what they did when new: https://www.paradisesolarenergy.com/blog/solar-panel-degradation-and-the-lifespan-of-solar-panels

So figure 70W from your 80W panels and ~115W from your 120W panels and your 480W array is probably no more than a 430W effectively.

Here in the Bay Area, I get 11kWh per day out of my 4020W array in December, so if you had your 430W array in my area, you’d get 1176Wh/day on average in December (which should be more than enough to supply the 840W you need daily).

So something is not adding up…

 

[GoldenNoodle]

OK, for a DC load you calculations are about correct,

But after 10 years, your 80W panels are probably putting out no more than 90% of what they did when new: https://www.paradisesolarenergy.com/blog/solar-panel-degradation-and-the-lifespan-of-solar-panels

So figure 70W from your 80W panels and ~115W from your 120W panels and your 480W array is probably no more than a 430W effectively.

Here in the Bay Area, I get 11kWh per day out of my 4020W array in December, so if you had your 430W array in my area, you’d get 1176Wh/day on average in December (which should be more than enough to supply the 840W you need daily).

So something is not adding up…

The site is in "Northern" Ontario in Canada. Daylength is less than 8.75 hrs in December. Actual Daylight is probably 2.5 - 3 hours per day in December.

 

[fafrd]

The site is in "Northern" Ontario in Canada. Daylength is less than 8.75 hrs in December. Actual Daylight is probably 2.5 - 3 hours per day in December.

Use PV Watts to estimate your production in December: https://pvwatts.nrel.gov/

 

[GoldenNoodle]

Use PV Watts to estimate your production in December: https://pvwatts.nrel.gov/

Thanks for the link. It's 1.90 in December.

 

[Brett V]

Panels are cheaper than storage so the deck is stacked in your favor...provided you have the south facing real estate to do it.

 

[fafrd]

Thanks for the link. It's 1.90 in December.

In my case, my actual output is about 15% lower than the PV Watts simulation, but that should translate to at least 1.6kWh.

Again, should be more than enough for the 840W you need every 24 hours.

Unless you’ve got a few failing panels or a few failing batteries, you should be generating and storing sufficient power for your needs.

You may want to run a capacity test on your battery bank as well as an output test on your panels before deciding what’s next.

Again, something is not adding up…

 

[740GLE]

Do you know the history or life type deep cycle batteries have seen? Are the SLA or flooded, topped up on water? All manufactured in the same year/batch?

I’d imagine they are all wired in parallel?

If they’ve been used and abused they maybe short for this world, one bad battery may draw system capacity down. Might be worth testing each battery to verify their health.

 

[schmism]

Do you know the history or life type deep cycle batteries have seen? Are the SLA or flooded, topped up on water? All manufactured in the same year/batch?

As 740 is getting at... FLA battery pack is a weekly maintenance "nightmare". water levels, SG number, Equalization cycles.... its a real mess IMHO to keep a FLA pack running long term with normal use. (you are doing all those things right)

 

[fafrd]

As 740 is getting at... FLA battery pack is a weekly maintenance "nightmare". water levels, SG number, Equalization cycles.... its a real mess IMHO to keep a FLA pack running long term with normal use. (you are doing all those things right)

There are two solid counterarguments to the ‘faulty battery’ scenario.

First, he only has to top off weekly from ~Nov to March (and twice per week in December).

Battery capacity doesn’t change with season (while daily PV production does).

And second, he has 10 110Ah 12v batteries, or over 13kWh @ 100% or 6.5kWh @ 50% discharge.

Only needing to store 35W x 24h = 840 Wh to get through 24hours, his batteries would need to be have usable capacity under 7% of rated capacity before he’d have a problem (meaning the battery bank is essentially dead).

The OP started a constant ‘35W’ drain (<3A @ 12V) and I just want to make sure he did not mean a constant 34A drain…

 

[740GLE]

Over 13kwhr of theoretical storage, only if each battery is at peak condition ?.

One or two bad batteries or a couple batteries that are a few years older than others and it’s just a guess as to the storage capacity.

Increased PV production in summer would mask a weak/undersized battery but I also agreed that he could use more PV, just cause it’s always good to have more panels.

 

[GoldenNoodle]

There are two solid counterarguments to the ‘faulty battery’ scenario.

First, he only has to top off weekly from ~Nov to March (and twice per week in December).

Battery capacity doesn’t change with season (while daily PV production does).

And second, he has 10 110Ah 12v batteries, or over 13kWh @ 100% or 6.5kWh @ 50% discharge.

Only needing to store 35W x 24h = 840 Wh to get through 24hours, his batteries would need to be have usable capacity under 7% of rated capacity before he’d have a problem (meaning the battery bank is essentially dead).

The OP started a constant ‘35W’ drain (<3A @ 12V) and I just want to make sure he did not mean a constant 34A drain…

It is a 35 watt, 12 v constant drain. There's no invertor. The battery bank was replaced about 2 years ago. They used Sealed Lead Acid "renewable energy" deep cycle batteries. Not what I would consider professional grade (Surette, RR etc). but it is what it is.

 

[boondox]

Just FYI, here is a link you can use to calculate what you should get with mixed panels.

Mixing solar panels – Dos and Don’ts • SOLAR POWER SECRETS

Mixing Solar Panels: Discover Now Dos and Dont's of Mixing the Same Types or Different Types of Solar Panels. Act Now to Save Your Money!

solarpanelsvenue.com

That way you can see if they are performing as expected.

 

[fafrd]

It is a 35 watt, 12 v constant drain. There's no invertor. The battery bank was replaced about 2 years ago. They used Sealed Lead Acid "renewable energy" deep cycle batteries. Not what I would consider professional grade (Surette, RR etc). but it is what it is.

I would suggest you run a capacity test on those batteries.

Do you have an AC charger you can use to top them off?

I’d suggest to disconnect the SCC after the sun has gone down and top off the batteries with an AN AC charger overnight (any half-decent AC charger should have no problem keeping up with a 35W draw).

Then, with the battery ‘full’, disconnect the AC charger and see how long the battery is able to supply your 35W drain before they reach ~50% SOC.

New batteries ought to give you over 7 days (with no charging at all) to 50% SOC, but if your able to get anything over 2 days (48 hours), the batteries are not the issue.

 

[GoldenNoodle]

I would suggest you run a capacity test on those batteries.

Do you have an AC charger you can use to top them off?

I’d suggest to disconnect the SCC after the sun has gone down and top off the batteries with an AN AC charger overnight (any half-decent AC charger should have no problem keeping up with a 35W draw).

Then, with the battery ‘full’, disconnect the AC charger and see how long the battery is able to supply your 35W drain before they reach ~50% SOC.

New batteries ought to give you over 7 days (with no charging at all) to 50% SOC, but if your able to get anything over 2 days (48 hours), the batteries are not the issue.

When I look up 50% SOC I find all kinds of different ways to figure that value.

It looks like it could be any where from 12.9 ( https://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf if I use a value of C=30)

Down to 12.1 ( https://modernsurvivalblog.com/wp-content/uploads/2021/02/battery-state-of-charge-chart_v2.jpg )

Any suggestions on what an accurate value would be for this setup ?

Thanks for the help.