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How much Solar v Batteries? What do you have?


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Hi Everyone 

I've been trying to work out how much Solar and batteries I need, ideally to be able to use the panels for most electricity even through winter. I have lots of roof space and I budgeted for a lot of Solar so I'm ok with the finance side. 

I have done the usage calcs based on 'worst case' or maximum potential use, and overspeced the solar needs by 100% to account for winter. However, the Bimble solar calc seems to suggest I need a 1166 AH battery bank!?  I assume this is because I need double the AH I use so as not to run the batteries to 0. That's a lot of batteries though! Am I understanding this correctly?

What do other potentially power hungry users have?

Thanks 

Caitlin 

 

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We have 4 x 250w panels, & 8 x T150's + starter and BT batteries. (the T150's are 12 not 24)

We are power hungry though, washer, fridge, freezer, lg screen tv and all the other electronic gagets that most folks have, although we don't use a hair dryer.  I've limited myself to only having 4 electrical kitchen appliances...bread maker (in case we get froze in & I like homemade bread), slow cooker (which in hinesight I hardly ever use...we use the wood/coal stove as a slow cooker in the winter months), my food processer (I do a fair amount of cooking/baking), and of course my coffee machine

Heating is via the wood/coal stove and on occassion we turn on the central heating, but this is not a daily occurance just when it gets close to being proper cold :)

not that it shoud make any difference other then roof space, but we are a 10.10 WB

& yes we still need to run the engine daily in the winter months, but the solar saves a heck of a diesel in the summer months

Hope this helps

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27 minutes ago, Robbo said:

You’ll only get around 10% of solar in winter compared to summer.

I also think your over estimating your wattage in a lot of those items.  But this can be a good thing.

Fully agree with Robbo. To put it another way, you need 10 times the number of solar panels in the winter. To put it another way, dont expect to rely on solar panels in the UK in the winter.

We have 200 Watts of solar with 700 Ahrs of batteries and it is great in the summer putting in around 80Ahr/day - nearly our daily useage...but in the winter...we will need to run the engine.

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4 minutes ago, Dr Bob said:

Fully agree with Robbo. To put it another way, you need 10 times the number of solar panels in the winter. To put it another way, dont expect to rely on solar panels in the UK in the winter.

We have 200 Watts of solar with 700 Ahrs of batteries and it is great in the summer putting in around 80Ahr/day - nearly our daily useage...but in the winter...we will need to run the engine.

Thanks for your advice. I wonder if there's much point having that much then if it's not going to help in the winter. 

What do you class as Winter? I saw a boat blog which said they still got decent solar till about the end of October. Was Nov-Feb where they had to run engine. They had 500w. 

 

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Good to see you've done a power audit, but I'd question some of the figures. In particular, the phone charging looks nonsensical. And what is within "heating"? And why is it 70W? As for hairdryer.......hmmmmm.

Given the above inaccuracies, I can't see any forwards calculations based on these - for example solar amount needed, or battery bank capacity - being meaningful.

Also over-specifying by 100% is not an appropriate winter adjustment - basically during winter, the "average" factor is 10% of peak output, ie you'd need to ON AVERAGE overspecify 1000% (or maybe +900% depending on how the figures are interpreted) but during winter, there's some days where you'd basically not get any power off solar. Think, drizzly cloudy winter's day where it rains (or snows) most of the day, and is dull and cloudy when its not raining. And then there's some winter days when its about 12degC and sunshine. (Although of course, sunlight is weaker in winter than summer due to the seasonal effect).

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As said above, forget the winter for solar power, though the small charge will help to condition your batteries.

We have 260 watts of panels with 520ah of batteries. Mainly 12v usage, just HiFi and tv/dvd on 240 v when we use them. Washing machine on hot wash and vacuum cleaner powered by generator.  Solar keeps up great in summer, with more charging up via engine in the winter months.

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There is no rhyme or reason for our solar / battery set ups.

Boat 1) 170w of solar with a 6x 230ah battery bank.

Boat 2) 300w of solar with a 2x 110ah battery bank.

You cannot look at solar as a guaranteed supply to enable you to live a 'normal life' - as has been previously said - if you need 1000w of solar April to October then you will need 10,000 (or more) Nov to Feb.

I reckon that 10% of Summer output in those Nov-Feb months to be the max and more realistically somewhere above 5% is more achievable.

 

Treat Solar as a bonus but accept that you will need to generate by alternative methods for (probably) 50% of the year.

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10 minutes ago, Cpickle said:

Thanks for your advice. I wonder if there's much point having that much then if it's not going to help in the winter. 

What do you class as Winter? I saw a boat blog which said they still got decent solar till about the end of October. Was Nov-Feb where they had to run engine. They had 500w. 

 

Yes, that's about right. From Nov - Feb the sun is just too low in the sky to put much power in (if no clouds, rain etc) - and because we dont get blue sky often it is worse. Also think about all those trees and banks that the canals go through and there is not a lot of light. You really only get 6 hours of real light in the winter months (10am to 4pm) if you are lucky (for Scotland it is 11am to 2pm).

We have a lot of ocean sailing experience and here we found a wind genny very effective. If you are mooring in open spaces, then this could augment your power significantly BUT it can be noisey (and will be to your neighbours!!) and will not work if you are mooring in sheltered places (ie the sort of spaces we will be mooring).

Running the engine is the only answer, but if finance is not an issue, buy an alternator to battery charger. This fools the alternator into thinking the batteries need charging and thus the alternator puts out more charging voltage. We had a Sterling unit on our boat which worked great and you could see 50-60amps going into the batteries for many hours. I think Sterling claim that it charges the batteries 5 times fast which is what we saw.

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38 minutes ago, Paul C said:

Good to see you've done a power audit, but I'd question some of the figures. In particular, the phone charging looks nonsensical. And what is within "heating"? And why is it 70W? As for hairdryer.......hmmmmm.

Given the above inaccuracies, I can't see any forwards calculations based on these - for example solar amount needed, or battery bank capacity - being meaningful.

Also over-specifying by 100% is not an appropriate winter adjustment - basically during winter, the "average" factor is 10% of peak output, ie you'd need to ON AVERAGE overspecify 1000% (or maybe +900% depending on how the figures are interpreted) but during winter, there's some days where you'd basically not get any power off solar. Think, drizzly cloudy winter's day where it rains (or snows) most of the day, and is dull and cloudy when its not raining. And then there's some winter days when its about 12degC and sunshine. (Although of course, sunlight is weaker in winter than summer due to the seasonal effect).

Hi Paul, thanks for all your advice.. 

The phone charger is 5w, we have two of them, that's why I put 10w, what's wrong with that? I put 7hrs overnight because although we will be trying to ensure we just charge and turn off, I am allowing for forgetfulness. 

Hairdryer? Its 1900w, I use it for about 15mins twice a week. I've been told my 3000w can handle it. 

I overspecified by 100 as that is the advice on Bimble, overspec by 50-100.. but I understand what you've said. Perhaps Bimbles advice is more aimed at Spring and Autumn. 

 

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You should be able to reduce these figures by calculating your usage over 7 days, then divide by 7 to obtain average daily usage, as you  have said you only use hair drier twice a week, how about the washing machine?

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47 minutes ago, Dr Bob said:

Yes, that's about right. From Nov - Feb the sun is just too low in the sky to put much power in (if no clouds, rain etc) - and because we dont get blue sky often it is worse. Also think about all those trees and banks that the canals go through and there is not a lot of light. You really only get 6 hours of real light in the winter months (10am to 4pm) if you are lucky (for Scotland it is 11am to 2pm).

We have a lot of ocean sailing experience and here we found a wind genny very effective. If you are mooring in open spaces, then this could augment your power significantly BUT it can be noisey (and will be to your neighbours!!) and will not work if you are mooring in sheltered places (ie the sort of spaces we will be mooring).

Running the engine is the only answer, but if finance is not an issue, buy an alternator to battery charger. This fools the alternator into thinking the batteries need charging and thus the alternator puts out more charging voltage. We had a Sterling unit on our boat which worked great and you could see 50-60amps going into the batteries for many hours. I think Sterling claim that it charges the batteries 5 times fast which is what we saw.

Hi Bob 

Ok thanks, I had heard a little bit about the alternator thing before, although I think they guy said something like get a bigger alternator? Anyway your explanation makes more sense to me. I will have to wait a bit before getting one but I will try and get one of these Sterling units in October. 

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On 14/07/2017 at 20:53, Robbo said:

You’ll only get around 10% of solar in winter compared to summer.

I also think your over estimating your wattage in a lot of those items.  But this can be a good thing.

 

I disagree. My own solar setup delivers around 1-2% of summer output on a dull winter's day.

I can typically see 10.0A into my 24v battery bank on a day like today. On dull day in December I typically get 0.1A to 0.2A.

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9 hours ago, Dr Bob said:

... buy an alternator to battery charger. This fools the alternator into thinking the batteries need charging and thus the alternator puts out more charging voltage. We had a Sterling unit on our boat which worked great and you could see 50-60amps going into the batteries for many hours. I think Sterling claim that it charges the batteries 5 times fast

There's a fair bit wrong with the above paragraph. Taking the last bit first, 5 times faster than what? Up to 5 times faster than an old alternator with a low voltage regulator, poor wiring and split charge batteries? Maybe. 5 times faster than a modern alternator with a 14.6V regulator, correctly specced cables and no diodes in the charging circuit? No way. 

An AtoB charger doesn't 'fool' anything, it simply raises the charging voltage to the optimum for your batteries. If the alternator is already supplying the correct charging voltage at the batteries then an AtoB will do nothing. 

The last thing to bear in mind is that it's the batteries which determine the charging current, not the charge source. By way of example, a modern Beta with a 175A domestic alternator, correctly installed, will charge the batteries optimally with absolutely no external kit required. 

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10 hours ago, Cpickle said:

Hairdryer? Its 1900w

You will need a fair sized battery bank so as not to 'overload' the batteries.

Your hairdryer alone will draw about 190 amps - trying to run that discharge rate from a small battery bank for 15 minutes would be death for the batteries.

An engine starter motor may take those sort of currents but :

1) It is for maybe 10 or 20 seconds only

2) A engine start battery is normally a different internal construction to 'leisure' batteries.

 

Have you considered a gas powered hair dryer, or (perish the thought) let it dry au-natural

 

 

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I would suggest that you only ever use the hair drier when on shore power or with the engine running, that way you can ignore it.  If you were to get a newer, low power TV & laptop you would be able to greatly reduce those watts, and if you swap to LED lighting and only switch on what you need, that should come down to 10 to 20 watts.

A problem with winter solar is that the panels must be pointing towards the sun so you will need your panels almost vertical to get anything out of them.  Adjusting big panels , especially rotationally is not really possible, and getting them to say 70 degrees from horizontal (ie nearly upright) means they will have to have a very high pivot point.  So most people with big panels just accept that they will not get much in winter.

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Washing machine = 235 watts

Unless its a twin-tub, or an automatic running on cold water only, with the heating element disconnected then that figure is 'out' by a factor of 10.

When the water is being heated the power consumed will be (around) 2000 watts (depending on model - It may be 1700 w, or it may be 2500w) so around a 200 amp draw off the batteries.

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13 hours ago, Bettie Boo said:

We have 4 x 250w panels, & 8 x T150's + starter and BT batteries. (the T150's are 12 not 24)

We are power hungry though, washer, fridge, freezer, lg screen tv and all the other electronic gagets that most folks have, although we don't use a hair dryer.  I've limited myself to only having 4 electrical kitchen appliances...bread maker (in case we get froze in & I like homemade bread), slow cooker (which in hinesight I hardly ever use...we use the wood/coal stove as a slow cooker in the winter months), my food processer (I do a fair amount of cooking/baking), and of course my coffee machine

Heating is via the wood/coal stove and on occassion we turn on the central heating, but this is not a daily occurance just when it gets close to being proper cold :)

not that it shoud make any difference other then roof space, but we are a 10.10 WB

& yes we still need to run the engine daily in the winter months, but the solar saves a heck of a diesel in the summer months

Hope this helps

Bettie you have got the op wrong. He is talking about using/living on a BOAT not a bungalow!! With all that unnecessary electrical equipment that is all designed for mains electric useage by people attached to the national grid. For what its worth we have 4  110 ah leisure batteries and 160 watts of solar. The solar helps in the summer as it probably just about runs the fridge and in the winter its utterly useless. A typical uk winter being September to june :lol: we do the washing etc through the best bit of kit available to man, that being a travelpower and it probably cost less for one of those than your battery bank alone!! with the solar thingies. In short if anyone reading this post wants to live on a boat IT IS NOT a bungalow you DO NOT need all the crap people in bungalows need but for the occasional big power useage buy a travel power or if you have space a stand alone genie both items will prove CHEAPER in the long run and vastly better to use. But who am I to know. Get you facts from Bloggers and vloggers 99 percent of whom have only been living aboard for about ten minutes but feel the need to tell everybody how to do it :rolleyes:. The best ones are the ones who tell us its never a problem living aboard in the winter then you find they are so new to it that they havnt yet even done a cold winter. Last cold winter we had was 2010/11 when we were solid frozen in for 7/8 weks so less than 7 winters aboard you still have a shock to come :cheers: Just sayin like...................

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14 hours ago, Cpickle said:

Hi Everyone 

I've been trying to work out how much Solar and batteries I need, ideally to be able to use the panels for most electricity even through winter. I have lots of roof space and I budgeted for a lot of Solar so I'm ok with the finance side. 

I have done the usage calcs based on 'worst case' or maximum potential use, and overspeced the solar needs by 100% to account for winter. However, the Bimble solar calc seems to suggest I need a 1166 AH battery bank!?  I assume this is because I need double the AH I use so as not to run the batteries to 0. That's a lot of batteries though! Am I understanding this correctly?

What do other potentially power hungry users have?

Thanks 

Caitlin 

 

Solar.JPG

For less money than all that mularky fit a travelpower or whispergen for the heavy occasional work and cut way down on the cost of all those batteries which you will probably repeatedly kill.

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29 minutes ago, mrsmelly said:

Bettie you have got the op wrong. He is talking about using/living on a BOAT not a bungalow!! With all that unnecessary electrical equipment that is all designed for mains electric useage by people attached to the national grid. For what its worth we have 4  110 ah leisure batteries and 160 watts of solar. The solar helps in the summer as it probably just about runs the fridge and in the winter its utterly useless. A typical uk winter being September to june :lol: we do the washing etc through the best bit of kit available to man, that being a travelpower and it probably cost less for one of those than your battery bank alone!! with the solar thingies. In short if anyone reading this post wants to live on a boat IT IS NOT a bungalow you DO NOT need all the crap people in bungalows need but for the occasional big power useage buy a travel power or if you have space a stand alone genie both items will prove CHEAPER in the long run and vastly better to use. But who am I to know. Get you facts from Bloggers and vloggers 99 percent of whom have only been living aboard for about ten minutes but feel the need to tell everybody how to do it :rolleyes:. The best ones are the ones who tell us its never a problem living aboard in the winter then you find they are so new to it that they havnt yet even done a cold winter. Last cold winter we had was 2010/11 when we were solid frozen in for 7/8 weks so less than 7 winters aboard you still have a shock to come :cheers: Just sayin like...................

A harsh but very true post.

and....TravelPower is a superb machine but that comment is just a teensy weensy bit over the top.:D

Run the engine at least every third day, and to make best use of fuel whilst doing so you can go boating.

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

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@Cpickle It may be worth a while reading this book from Victron; https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

IMHO, the more solar the less likely you will have to run a generator/travelpower/engine and you the more you have the more you months you get from generator free power.  However do you want your boat to look like a solar farm?  You can get semi flexible panels which look much better and if your going to cover the roof in panels then these would look better, but they will perform worse especially in winter.  You can always start with a small solar setup of say 500watt, and then grow from there.

 

Edited by Robbo
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On 15/07/2017 at 09:35, Chewbacka said:

 

A problem with winter solar is that the panels must be pointing towards the sun so you will need your panels almost vertical to get anything out of them.  Adjusting big panels , especially rotationally is not really possible, and getting them to say 70 degrees from horizontal (ie nearly upright) means they will have to have a very high pivot point.  So most people with big panels just accept that they will not get much in winter.

 

There is of course a slight problem with the sentence I've highlighted. We don't get much sun in winter. 

Is there really any point in tilting panels towards one or another area of equally dull grey sky through the rain at 3pm on a December afternoon?

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