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solar power, would this combination make sense


Djuwenda

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Hello, 

 

After many years using a set of cheap AGM batteries, an 80w monocrystal panel and a 10a MPPT power charger, the time has now come to change the batteries. I guess the lesson I have learnt is that some solar input can do absolute wonders for the health and longevity of a set of batteries. Whilst I live aboard and CC, I am very often away for 5 days at a time. When before solar I would have to religiously charge my batteries before leaving, I can now forget about it and let the sun trickle charge for me.

My work requirements have now changed. If I am not travelling, I am working from home. So I will need a good bit more power than I did. I would also like to run a 12v fridge, which I never bothered with before.

Hence I am thinking about spending a (good) bit more this time, which should make investing in some good quality batteries a safer bet.

my understanding of electrickery is limited, please feel free to point out if you think i am mismatching and that these components would not be well suited to each other

61KR3E1zulL._SL1276_.jpg

https://www.amazon.co.uk/gp/product/B0779F3T4P/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=A246YAYJCIS7NJ

 

the only problem with going with three of these panels is I then have to get quite a meaty MPPT controller,  an 80a unit such as:

s-l640.jpg

https://www.ebay.co.uk/i/173018303294?chn=ps&adgroupid=50138193029&rlsatarget=pla-398785780940&abcId=1130076&adtype=pla&merchantid=101717088&poi=&googleloc=9041125&device=c&campaignid=1030309342&crdt=0

 

 

the battery bank will be made of 5 of these

xr5000_600x400px_1.jpg

https://www.alpha-batteries.co.uk/leoch-200ah-agm-leisure-battery/

 

 

 

Edited by Djuwenda
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Advice / Comments / Questions: 

1. If you are willing to invest "... a (good) bit more..." into your system, and are willing to buy a better quality battery, do not spend money on a cheap and (quite) possibly fake MPPT controller. Often, those Chinese made controllers are stated to be proper MPPT units. However, in reality, they are just PWM chargers. Do you really want a cheap controller looking after your 290 GBP (each) batteries?

Being in the UK, maybe have a look at a Steca MPPT Solar Controller. They are German technology, if you are not familiar with the brand. Here is a current catalog from Steca: https://1drv.ms/b/s!As8hSuMJ-Cwpvw4nxQBVcKqnw9IA (hosted on OneDrive)

If not Steca, have a look at Outback PowerMorningStar, Midnite Solar, or Rogue Engineering MPPT charge controllers. Any of those will be a much higher quality product. Although I haven't compared prices, Rogue will probably be the cheapest of those listed. All but MorningStar are manufactured in the US. I think MorningStar are manufactured in Taiwan.

2. If I may, why would you purchase 5 batteries?

Panel Specifications: Typical type: 330 W, Max-power (Pmax) W: 330 W Max-Power voltage (Vmp): 38.05 Max-Power current (Imp): 8.65 open circuit voltage (VOC): 47.28 short circuit current (ISC): 9.05

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Personally having found Stecca use a weird size of chocblock strip connector on their PWM controller that they can not supply as a spare part (mine burned out because of a loose connection) I would now avoid Stecca. There is no access to one set of chockblock screws without taking the thing apart.

Edited by Tony Brooks
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2 minutes ago, Tony Brooks said:

Personally having found Stecca use a weird size of chocblock strip connector on their PWM controller that they can not supply as a spare part (mine burned out because of a loose connection) I would now avoid Stecca

Thanks for the information. I will make note of that. Do you know if they are having issues with their MPPT controllers? 

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No, I do not. Until a month or so a go I would have said they were quality units. If I were buying one I would now want to see the cover off it first.

The    MPPT I bought from Solar Universe  to replace it at least seems to have better connectors for the cables. However as usual it seems to be of Far Eastern origin so may or may not be a true MPPT. What annoys me is that its display does not seem to give amps or Ah into the battery, only panel output figures.

Edited by Tony Brooks
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7 minutes ago, Tony Brooks said:

However as usual it seems to be of Far Eastern origin so may or may not be a true MPPT. What annoys me is that its display does not seem to give amps or Ah into the battery, only panel output figures.

Exactly why I am happy to pay international shipping costs (if no one is coming from the US to bring one with them), to have one shipped to me, here. At least I know what I am paying for, is exactly what I am getting. This is exactly why I hope the OP will consider buying a different controller for his system.

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3 hours ago, peterboat said:

80 AMP? why? reading the amazon site its just under 10 amps per panel which seems a bit low for a 330 watt panel maybe have a chat to bimble first?

Amazon seem to have gone a bit astray, these panels should produce a theoretical 27.5amps under ideal conditions, of course you would be lucky to get near that in our climes but it will be a lot more than 10 amps.

Phil 

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16 minutes ago, Phil Ambrose said:

Amazon seem to have gone a bit astray, these panels should produce a theoretical 27.5amps under ideal conditions, of course you would be lucky to get near that in our climes but it will be a lot more than 10 amps.

Phil 

They’re talking panel Amps I believe. 330W panel has a Vmp of 38.5V and Imp of 8.65A. 

38.5 x 8.65 = 330

At 14.4V approx 23A

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1 hour ago, Asia_Off_Grid said:

Advice / Comments / Questions: 

1. If you are willing to invest "... a (good) bit more..." into your system, and are willing to buy a better quality battery, do not spend money on a cheap and (quite) possibly fake MPPT controller. Often, those Chinese made controllers are stated to be proper MPPT units. However, in reality, they are just PWM chargers. Do you really want a cheap controller looking after your 290 GBP (each) batteries?

Being in the UK, maybe have a look at a Steca MPPT Solar Controller. They are German technology, if you are not familiar with the brand. Here is a current catalog from Steca: https://1drv.ms/b/s!As8hSuMJ-Cwpvw4nxQBVcKqnw9IA (hosted on OneDrive)

If not Steca, have a look at Outback PowerMorningStar, Midnite Solar, or Rogue Engineering MPPT charge controllers. Any of those will be a much higher quality product. Although I haven't compared prices, Rogue will probably be the cheapest of those listed. All but MorningStar are manufactured in the US. I think MorningStar are manufactured in Taiwan.

2. If I may, why would you purchase 5 batteries?

Panel Specifications: Typical type: 330 W, Max-power (Pmax) W: 330 W Max-Power voltage (Vmp): 38.05 Max-Power current (Imp): 8.65 open circuit voltage (VOC): 47.28 short circuit current (ISC): 9.05

I have the Midnite controller for my system it replaced some tracer units for me its a far better bit of kit than the chinese offerings?

When the bathtub is done it will have 2 KW of solar and a new midnite controller on it I like that you can monitor it on your laptop also you can set it correctly for different battery types, I am looking at Lithium for the electric bathtub or GTP powerblocks 

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With 1000 watts of solar and a good MPPT controller you will have loads of power in the summer, as AGM's don't like overcharging you may need to consider disconnecting the Solar in the summer when the batteries are full otherwise you could cook them maybe a immersion heater?. Most (All I have seen) MPPT controllers run in absorption mode for 2-4 hours at the beginning of the day when they wake up, that amount of solar could easily be pushing 30-40 amps by 9:00am, if the batteries are pretty full then?......

1000 Ah seems a lot for a battery bank, You could have a problem in winter as on poor dull wet day you will only get about 10% of solar size for about 6 hours say 45 Ah in a day, this is not going to fill your battery bank and so you will need alternative charging methods. As you know you need to fully charge your batteries to 100% at least once a week, the last few percent take ages as the batteries will only accept a few amps for several hours as they near full. With such a large bank if you are at 80% SOC in the morning even with a big generator / alternator the batteries are already beginning to limit the current (my agm's will accept about 10-12 amps per battery at 80%) with a max of 12 hours engine or generator running if you are not to annoy the neighbours, will you get those batteries to 100%?  if not they they will deteriorate fairly rapidly.

 

Do a power audit and size the battery bank accordingly. I have 600 watts of solar in 6 panels and I can switch 3 out of the circuit if I wish, usually from May to late August the 300 if more than enough.

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1 hour ago, Detling said:

With 1000 watts of solar and a good MPPT controller you will have loads of power in the summer, as AGM's don't like overcharging you may need to consider disconnecting the Solar in the summer when the batteries are full otherwise you could cook them maybe a immersion heater?. Most (All I have seen) MPPT controllers run in absorption mode for 2-4 hours at the beginning of the day when they wake up, that amount of solar could easily be pushing 30-40 amps by 9:00am, if the batteries are pretty full then?......

Now you have confused me. I was thinking that after finishing absorption, the MPPT switches to float mode and I can set the voltage on my float to anywhere between 13.0v (IIRC) and 14.something. My float is currently set to 13.2V so I was assuming that the solar could then not overcharge the battery bank.

I am just about to up my solar from 200W to 500W with battery bank of 6*110Ahrs so very interested to make sure I am not going to boil mine.

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1 hour ago, Detling said:

that amount of solar could easily be pushing 30-40 amps by 9:00am, if the batteries are pretty full then?.....

... then the batteries won’t be drawing anything like that current, will they?

The charge source doesn’t dictate the current flowing into the batteries, the batteries do. If they’re fully charged then they’ll demand little from the charge source. 

The only consideration is that the voltage be correct for the battery type being charged. 

11 minutes ago, Dr Bob said:

Now you have confused me

I’m not surprised. It’s nonsense. 

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Had me thinking as well 900 watts of solar and 1500 ah of full traction and yet my batteries still live after 12 years!! I watched a video of a PWM charger an oscilloscope was connected into it and it showed it charging for ever smaller times until it turned itself off

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7 minutes ago, peterboat said:

Had me thinking as well 900 watts of solar and 1500 ah of full traction and yet my batteries still live after 12 years!! I watched a video of a PWM charger an oscilloscope was connected into it and it showed it charging for ever smaller times until it turned itself off

Yup. And an MPPT would simply show an ever decreasing current until the voltage switched to float. 

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23 hours ago, Detling said:

1000 Ah seems a lot for a battery bank, You could have a problem in winter as on poor dull wet day you will only get about 10% of solar size for about 6 hours say 45 Ah in a day, this is not going to fill your battery bank and so you will need alternative charging methods. As you know you need to fully charge your batteries to 100% at least once a week, the last few percent take ages as the batteries will only accept a few amps for several hours as they near full. With such a large bank if you are at 80% SOC in the morning even with a big generator / alternator the batteries are already beginning to limit the current (my agm's will accept about 10-12 amps per battery at 80%) with a max of 12 hours engine or generator running if you are not to annoy the neighbours, will you get those batteries to 100%?  if not they they will deteriorate fairly rapidly.

Let me pick up something else in this post ….the optimum battery bank size. Detling seems to be saying that 1000Ahrs are too big because you will be charging in the 'difficult' part of the charge cycle for more of the time. This however ignores the benefits of a larger bank. In the example of going down to 80% SoC, that is down by 200Ahrs. If the bank was half the size (500Ahrs) then it would be down to 60% SoC. If you look at cycles to death for different DoDs, you get say 300 cycles at 50% DoD but 1500 cycles at 80% DoD. The larger bank would therefore last for more than double the cycles (hence balancing the cost) but the 'more than' could then make up for the charging issue in the last 20%.....particularly if you are running the engine anyway, or can get to shore power in the winter.

A further point is that I would rather have double the capacity for running for example a nespresso machine where you may be drawing 150-200A for a short period. Presumably there is less of an effect of a high discharge to the irreversible battery chemical/physical reactions.

Overall then, if the up front money is available, I would always go for a large bank rather than a smaller one.

Interested to hear if I've got it wrong.

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Not only but also... the time taken in absorption for a 1000Ah bank to go from say 85% to 100% is exactly the same time as a 500Ah bank would take. Bearing in mind that you’ll spend less (if any) time in bulk, using your example above, the 1000Ah bank will actually charge more quickly. 

Forgot to say, yes I agree with your post. 

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On 1/26/2018 at 01:10, Detling said:

... as AGM's don't like overcharging you may need to consider disconnecting the Solar in the summer when the batteries are full otherwise you could cook them

You probably need a new charge controller, as your quoted text makes no sense to me. The primary purpose for having a quality built controller is to control how your batteries are being charged. Not to mention, ANY quality controller will either have manual settings you can adjust, or a preset switched setting between FLA and sealed batteries. Once the controller detects the achieved battery voltage, it will go into float mode. Not to mention, numerous systems are commonly "over paneled" these days, simply due to the low costs associated with solar panels.

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On 1/26/2018 at 02:19, Dr Bob said:

Now you have confused me. I was thinking that after finishing absorption, the MPPT switches to float mode and I can set the voltage on my float to anywhere between 13.0v (IIRC) and 14.something. My float is currently set to 13.2V so I was assuming that the solar could then not overcharge the battery bank.

I am just about to up my solar from 200W to 500W with battery bank of 6*110Ahrs so very interested to make sure I am not going to boil mine.

Exactly. But, this does not only apply to MPPT controllers. PWM (quality) controllers have similar settings.

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16 minutes ago, Djuwenda said:

examples of 60a MPPT controllers at decent prices?

https://www.morningstarcorp.com/products/tristar-mppt/

http://www.outbackpower.com/outback-products/make-the-power/flexmax-series-charge-controllers/item/flexmax-6080

https://solar.schneider-electric.com/product/conext-mppt-60-150/

Below would probably be your best deal. Although, you would have to pay shipping from the east coast of the US:

https://www.ebay.com/itm/Xantrex-C60-Charge-Controller-60A-12-24V-Wind-Generator-Hydro-and-Solar-Panel-/251340237049 (~125 GBP)

Edited by Asia_Off_Grid
Added price.
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