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Advice On Solar Panel Technology Please


Blue Knight

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Hi All,

 

I'm not well versed with solar panel technology these days so I was wondering if you could help me please with regards to finding a suitable panel(s) that link with the following points:

 

1.  Our new-to-us boat (we collect it at the end of October) has 4 x wet 110Ah batteries (new in June 2019) so in theory I would have had 220 Amps available at 50% DOD when they were new. 

 

2.  My very basic power audit suggests a usage rate of 80 Amps per day. (I may need a bigger battery bank?).

 

3.  The boat has a Mastervolt 80A charger but I want to try and avoid using the engine to charge the batteries - where possible. It also has a Dometic 3.5 power pack too.

 

4.  Im also aiming to try and minimise the surface area of the roof which the panels occupy (so that we can walk on top safely).

 

5.  I like the look of the Victron Smart 100/50 MPPT Reg (700W limit) as in theory I could start with one panel before adding more if necessary. That being said, a bigger system would certainly help out during the dark months albeit not by much.

 

6.  I'm not sure about the health of the battery bank so I may even have to change-out the batteries for new ones at some point soon. 

 

My question to you fine folk is what would be the best solar panel units to choose and what are your experiences of using the various different technology types, i.e. solid, small, large, split, branded, directional etc.

 

I've seen a number of panels available at good price-points on the Midsummer Energy web site so that may be a good start without breaking the bank.

 

https://midsummerenergy.co.uk

 

Apologies for such a long post.

 

Many thanks in advance,

 

Andrew

 

 

 

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You've got several different ways of providing power, so thought needs to be given to

 

a) Providing power that's going to be used now - eg for large loads such as a washing machine, or other electric heating apparatus

b)  Providing power to be consumed later (and before the next opportunity to generate more)

 

The former is what the power pack is good for, the latter is for the charger and solar installation.  So, how much of the 80Ah is sporadic loads like a washing machine over which you have the choice of when to run it, and how much is continuous load such as refrigeration, pumps and the like (plus entertainment and communications like radio, internet & TV, which although under your control can't realistically be time-shifted) 

 

80Ah is near enough 1kWh.  To provide this for the warmer half of the year will require around 500w of solar panels, for the shoulder months (Feb, Oct) around 900w, and in the depths of Winter around 1600w.  This is all predicated on the panels being flat; if you are able to tilt them the winter requirement could be cut by 30%.  However, with only 400Ah of batteries you don't have much redundancy to cope with more than one dull, drizzly, damp, grey, overcast day in a row.

 

The number and type of panel is going to be a function of how much of your roof you want for other purposes such as storage and walking on (If you're not single-handing there isn't much need for the cabin top to be a walkable area).  Flexible ones don't have a great reputation for longevity or robustness, and can't be tilted.  Flat panels need housing  and apparatus to be able to tilt.  But 700w of flat panels is only 4.5m2 these days....

 

 

 

 

 

 

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Is this a holiday boat (mostly summer use) or an all  year round livaboard?

 

Solar looks to me to be a huge compromise between maximum power and retaining the ability to walk on the roof. If you plan to spend a lot of time moored up then lots of solar is good, if you plan a lot of boating through locks with possible single handing then walking on the roof is essential.

 

I would not trust stick down/walk on panels, maybe ok on a sailing boat with bare feet or deck shoes, but on the cut in winter you will be wearing boots with the soles full of towpath grit.

 

Its not easy, but is possible, to find panels of a shape that let you walk past them on the roof.

 

My compromise is to get just enough solar that I can go two full days without an engine run in the summer.

 

..............Dave

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3 hours ago, Blue Knight said:

I may need a bigger battery bank?

Bear in mind that it is the generation of the power used that needs to be the first consideration. There’s no point in having a bunch of batteries that you can’t fully charge. In general terms your battery bank capacity should be at least 3 times your average daily usage. Bigger is better but you firstly have to know that you can generate something like 120% of your daily usage. 

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Steel and walk on solar panels don't mix if fixed down due to the different thermal expansion rates of the materials. Some people have had them fitted in the marina, yet in the heatwave early in year, the panels cracked.  The rough surface of the flexable panels are a pig to keep clean inland. On sea going boats the only thing that drys on the panel is salt, which is easy to wash off. If you run the panels frames down the centre of the boat you have a two foot wide walkway either side. You can also fit the panels to the lids of roof boxs,   

Edited by nbfiresprite
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2 hours ago, DaveP said:

You've got several different ways of providing power, so thought needs to be given to

 

a) Providing power that's going to be used now - eg for large loads such as a washing machine, or other electric heating apparatus

b)  Providing power to be consumed later (and before the next opportunity to generate more)

 

The former is what the power pack is good for, the latter is for the charger and solar installation.  So, how much of the 80Ah is sporadic loads like a washing machine over which you have the choice of when to run it, and how much is continuous load such as refrigeration, pumps and the like (plus entertainment and communications like radio, internet & TV, which although under your control can't realistically be time-shifted) 

 

80Ah is near enough 1kWh.  To provide this for the warmer half of the year will require around 500w of solar panels, for the shoulder months (Feb, Oct) around 900w, and in the depths of Winter around 1600w.  This is all predicated on the panels being flat; if you are able to tilt them the winter requirement could be cut by 30%.  However, with only 400Ah of batteries you don't have much redundancy to cope with more than one dull, drizzly, damp, grey, overcast day in a row.

 

The number and type of panel is going to be a function of how much of your roof you want for other purposes such as storage and walking on (If you're not single-handing there isn't much need for the cabin top to be a walkable area).  Flexible ones don't have a great reputation for longevity or robustness, and can't be tilted.  Flat panels need housing  and apparatus to be able to tilt.  But 700w of flat panels is only 4.5m2 these days....

 

 

 

 

 

 

That's a really helpful set of points Dave - many thanks indeed.

 

As you say the main loads such as the washer-dryer will be supported by the Dometic PP so it's the 'power to be consumed later' bit that I need to focus on.

 

I've derived the 80Ah requirement from the compressor fridge, TV and the heating system and the rest solely down to the lighting/pump/phone charging requirements, beside other bits, as per your advice.

 

Your points on the seasonal variations is incredibly useful but what I find even more helpful is your explanation about 'redundancy' on those damp drizzly days when we don't want to move - which in theory should be quite often.

 

In light of what you've advised I best look at a suitable battery set-up first and then check to see if I can support its associated charging regime via both on and off-grid means.

 

Does this last bit sound correct to you?

 

Many thanks,

 

Andrew

 

 

 

 

 

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3 hours ago, dmr said:

Is this a holiday boat (mostly summer use) or an all  year round livaboard?

 

Solar looks to me to be a huge compromise between maximum power and retaining the ability to walk on the roof. If you plan to spend a lot of time moored up then lots of solar is good, if you plan a lot of boating through locks with possible single handing then walking on the roof is essential.

 

I would not trust stick down/walk on panels, maybe ok on a sailing boat with bare feet or deck shoes, but on the cut in winter you will be wearing boots with the soles full of towpath grit.

 

Its not easy, but is possible, to find panels of a shape that let you walk past them on the roof.

 

My compromise is to get just enough solar that I can go two full days without an engine run in the summer.

 

..............Dave

 

You'll be on the Xmas card list at this rate with all the advice you have given me ?

 

Nicky and I have left our jobs behind so we want to get into boating fulltime if possible but, via a build-up approach over the first-year of ownership.

 

This is just my waffling way of saying that I'm not exactly sure about our usage rates but what I would like to do is to buy a solar system where I can either a.) add bits as the need dictates, or better still, b.) get it right first time within an acceptable budget.

 

I've seen the following affordable panels on the Midsummer website which when coupled to a Victron Smart 100/50 MPPT should make for a good system albeit I need the likes of you guys to advise on the particular quality and performance of the panels.

 

I've been reading quite a bit on the subject but I'm now starting to get confused about which technology would be best. 

 

Here's a screenshot for reference.

782516568_Screenshot_20200917-232014_SamsungInternet.jpg.56ae17b8e7d87bab5d80ea3741148ac6.jpg

 

 

 

Edited by Blue Knight
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1 hour ago, WotEver said:

Bear in mind that it is the generation of the power used that needs to be the first consideration. There’s no point in having a bunch of batteries that you can’t fully charge. In general terms your battery bank capacity should be at least 3 times your average daily usage. Bigger is better but you firstly have to know that you can generate something like 120% of your daily usage. 

Many thanks indeed, now that makes perfect sense with the 120% and 3-times rules. 

 

.........so if I were to establish a charging regime that could maintain a usable 240Ah battery bank, minimum, then in theory I should be OK'ish.

 

My new-to-me batteries could already be destined for the knackers yard but at least it'll give me a chance to buy the right gear and start afresh.

 

All the best,

 

Andrew

 

 

 

 

34 minutes ago, David Mack said:

Single solar panel, set to one side, to avoid the Alde flue and to provide walk space down one side of the cabin top. Only 185W, but more than enough to keep the batteries topped up when not boating.

20200619_141459.jpg.4de57443531f667ca7457494c2f39b22.jpg

Which regulator have you fitted please David?

Edited by Blue Knight
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If you are thinking of using large domestic solar panels for the benefits of greater efficiency and state of technology, either...

1. Mount the pair at the front of the cabin roof with decent cables to reduce voltage drop (least likely to be needing to be walked on)...

Or..

2. Mount at the rear, and fit a retractable cabin side step just forward of the panels, so you can walk down the gunnels and then get on the roof easily.

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11 minutes ago, Blue Knight said:

Many thanks indeed, now that makes perfect sense with the 120% and 3-times rules. 

 

.........so if I were to establish a charging regime that could maintain a usable 240Ah battery bank, minimum, then in theory I should be OK'ish.

 

My new-to-me batteries could already be destined for the knackers yard but at least it'll give me a chance to buy the right gear and start afresh.

 

All the best,

 

Andrew

 

 

 

 

Which regulator have you fitted please David?

The David Mack offset panel looks like a practical approach to me though the asymmetry offends me a bit ?, I went for two long narrow panels but for various reasons it worked out out very expensive.

 

The Victron controllers are really good, I am not a fan of mobile phones and Bluetooth but it is really well done, and looking at a nice big display on an iphone is much nicer than built in little LCD displays and complicated button push sequences.  You can also go into advanced mode and mess about with all sorts of settings which keeps us engineer types happy.

 

We usually need to run the engine every third day to make hot water and work the washing machine (via TravelPower)  have about 700amp-hour of batteries and just 160w of solar but the solar is enough to eek out the three days, about 350w would be better but struggling to find roof space.

 

...............Dave

 

 

 

 

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51 minutes ago, dmr said:

The David Mack offset panel looks like a practical approach to me though the asymmetry offends me a bit ?, I went for two long narrow panels but for various reasons it worked out out very expensive.

 

The Victron controllers are really good, I am not a fan of mobile phones and Bluetooth but it is really well done, and looking at a nice big display on an iphone is much nicer than built in little LCD displays and complicated button push sequences.  You can also go into advanced mode and mess about with all sorts of settings which keeps us engineer types happy.

 

We usually need to run the engine every third day to make hot water and work the washing machine (via TravelPower)  have about 700amp-hour of batteries and just 160w of solar but the solar is enough to eek out the three days, about 350w would be better but struggling to find roof space.

 

...............Dave

 

 

 

 

Very useful sir.

 

I'm not a typical gadget bloke at home but for our off-grid motorhome adventures I always keep an eye on the power levels so the idea of the Smart Victron system App sounds really useful Dave.

 

May I ask if you are using wet batteries so your usable amps is 350 @ 50% DOD or do you have gels/AGM to go lower? I'm not a fan of AGMs but then again I only know how they work in motorhomes.

 

Thay said, I'm finding that my knowledge of narrowboat batteries is not good and needs help, lots of help?

 

Regards,

 

Andrew

 

 

Edited by Blue Knight
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59 minutes ago, matty40s said:

If you are thinking of using large domestic solar panels for the benefits of greater efficiency and state of technology, either...

1. Mount the pair at the front of the cabin roof with decent cables to reduce voltage drop (least likely to be needing to be walked on)...

Or..

2. Mount at the rear, and fit a retractable cabin side step just forward of the panels, so you can walk down the gunnels and then get on the roof easily.

Some good points but serial-2 would result in the certain death of my wife.

 

She trips up over a blade of grass so the fixing of a retractable step would only end in tears - or end in the local A&E ?

 

 

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1 hour ago, dmr said:

The David Mack offset panel looks like a practical approach to me though the asymmetry offends me a bit

If I'm honest it offends me a bit too. But the solar was installed as a bit of a trial, I wanted to maintain walk space on the roof, I wanted the panels as close as reasonably possible to the batteries, and the Alde flue was in the way.

And it isn't as if the bit of cabin behind is completely symmetrical!

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52 minutes ago, jonathanA said:

I wasn't impressed with bimble despite lots of people raving about them.

I only had room for a single panel and found Simon at runbythesun very knowledgeable and sensible. Prices were good too.

Bimble have offered very dubious advice on occasions, I have had to get customers to send stuff back and exchange it for a better fit which wont blow up the controller before now.

 

Bimble offer the best prices for what they stock. But dont buy the kits, buy what is best for you.

Edited by matty40s
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2 hours ago, Blue Knight said:

That's a really helpful set of points Dave - many thanks indeed.

 

As you say the main loads such as the washer-dryer will be supported by the Dometic PP so it's the 'power to be consumed later' bit that I need to focus on.

 

I've derived the 80Ah requirement from the compressor fridge, TV and the heating system and the rest solely down to the lighting/pump/phone charging requirements, beside other bits, as per your advice.

 

Your points on the seasonal variations is incredibly useful but what I find even more helpful is your explanation about 'redundancy' on those damp drizzly days when we don't want to move - which in theory should be quite often.

 

In light of what you've advised I best look at a suitable battery set-up first and then check to see if I can support its associated charging regime via both on and off-grid means.

 

Does this last bit sound correct to you?

 

Many thanks,

 

Andrew

 

 

 

 

 

 I've moved onto LiFePO4 batteries which are a completely different ballgame, but from my experiences with lead-acids; don't discharge below 50% (as you've already said), recharge to 100% asap after discharge.  They will wear out and should be considered consumables.  Don't buy expensive ones until you've wrecked at least one set of cheapo's and have feeling for how they behave.

 

The problem being that the recharging current the batteries will accept reduces approximately proportionally to their current state of charge (ie the closer you get to recharging them, the less input they'll take).  This means that running the engine to get them from 90% to 95% will take the same time as from 80% to 90%.  This means you're wasting diesel putting small currents in.  Solar though, will just sit there putting small charges in until you lose the light.

 

As to the panel from your screenshot - that's all marketing bollocks.  Look at; the efficíency (gives you power per area of panel), max voltages and currents ( to match different panels, and the controller), thickness and weight (for handling them).  Otherwise within a panel format, they're all alike.

 

Given the above, it's considered reasonable to carry a 2-day reserve of power ( don't forget that this can include going on a restricted diet for day 2!) and you need to be able to recharge them in the hours between returning to the boat and 8pm with the engine.  If you've got access to shorepower, use that; it will be an order of magnitude cheaper, quieter, and mechanically easier.

 

My solution over the last couple of years was 400ah (Pb) batteries, 1200w of solar, and fridge off between November and March. I'm looking forward to see how the lithiums perform in the coming winter....

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We and @trackman have had good experiences with stick on panels. We both bought ones from Midsummer Energy which were designed for use on standing seam industrial roofs ( sadly the company that made them are no more but there are alternatives). We have a Tracer MPPT controller not certain what Trackman has.

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1 hour ago, Blue Knight said:

Very useful sir.

 

I'm not a typical gadget bloke at home but for our off-grid motorhome adventures I always keep an eye on the power levels so the idea of the Smart Victron system App sounds really useful Dave.

 

May I ask if you are using wet batteries so your usable amps is 350 @ 50% DOD or do you have gels/AGM to go lower? I'm not a fan of AGMs but then again I only know how they work in motorhomes.

 

Thay said, I'm finding that my knowledge of narrowboat batteries is not good and needs help, lots of help?

 

Regards,

 

Andrew

 

 

OK, first it amp-hours rather than amps, and this forum can be a bit harsh if you get this wrong. We have Trojan T105/T125s which are wet lead acid. I am keeping a close eye on Lithiums but at present the Trojans make better economic sense. The 50% thing is a bit of a myth, though so deeply rooted its not worth arguing about. Proper lead acids go down to 20% though 40% to 50% is a good target as a safety margin is nice.

I try to keep the batteries above 50% but really don't stress if they go down to 40 or even 35.

 

Any more than about 800 amp-hour then 2v tractions are a better bet, and in the next few years it will swing in favour of Lithium, AGM is not a good option unless your boat design or personality makes topping up difficult.

 

..............Dave

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On mppt's, I found that  a 30A one was fine for 500W of panels even though you think you may need more. Last summer I think we only managed to hit 30A on two days!

I would avoid flexible panels. They are nowhere near as robust as the solid ones.

You seem to be using the figure of 50% SoC as a target rather than an absolute limit. The less discharge the longer your batteries will last and the easier to charge. Therefore If you have the space then I would certainly go for 5 or 6 batteries so you only discharge to 60 or 70% SoC. 

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1 hour ago, matty40s said:

Bimble offer the best prices for what they stock. But dont buy the kits, buy what is best for you.

 

But you can customise the Bimble kits. So it can be quite an easy way to work out all the bits and pieces you need by starting with a kit and then adding or substituting items as you wish (or even deleting the odd item if you can get something better/cheaper elsewhere). 

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