Solar panel advice

JENNY, I have, I think, explained my system many times on here.  I am one of those, in fact perhaps the only one, who uses a microwave through an inverter. Let me deal first with the OP. When I set my system up back in 2013, I had two brand new 110ah batteries (or so I thought) , a 2000w pure sine wave inverter and a 135w SP fixed to the roof. My SP is still there and working well. In the first couple of years the system worked very well and kept us in power at 100% virtually all the time but as with lead acid batteries, the capacity ie - the amount of power the battery can actually hold started to diminish and that affected the usefulness of the heavy draw items like the microwave and toaster and the inverter alarm came  on more frequently as the batteries became older. Now, it has to be said that the batteries I bought were  Elecsol- a defunct make and not a good battery at all as they were on their last legs as a company at that time and were producing nothing but starter batteries! However, they performed well for two years but then dived to little more than keeping the lights and pumps working. It was time to change. As I am a confirmed off gridder I changed the two heavy lead acids for a 100 Lithium and have had no issues since. If I were starting again, I would certainly look at the biggest power output SP it was  possible to fit and the comment by Boff regarding the ‘suitcase type’ certainly has gravity. 100w is OK for summer use I would say but winter use? I’m not sure I would want to go for more than a long weekend but then if the skies are bright and sunny, again, you  would get more power to the panel. The sun is low in the sky in winter so the capture of light is much less. And it’s not just the size of the SP- the capacity of the storage is just as important. That’s why batteries are so important to the success of the operation. It’s not good having a panel that is producing oodles of power if there’s nowhere to store it and the opposite is true- it’s no good having massive capacity if the SP is struggling to supply it- it’s a balancing act and it has to be thought about.  My general rule of thumb is that 120w is the absolute starting point for anyone seriously considering off grid camping. My next van will certainly be upgraded to at least 150w but more likely  200w.Having been to the show yesterday and seen RVs with 300w on the roof- now that’s getting somewhere!   Now to deal with the use of kit on board. A  DECENT leisure battery and more usefully, 2, are capable, without damage, of supplying large amps for short periods. I would never for instance, try to cook a meal in the microwave or heat something that took 20mins or so (not with a lead acid/s anyway) but I do use it successfully for things that take 3 mins or so. ie a toaster-3-4 mins, Vacuum 3- 4 mins etc. The television at 30w will hardly touch the battery and the ALDE pump at just over 1 amp will hardly put a drain on the battery.  The idea is not to kick the backside out of the battery but use it well within its capacity. I won’t talk about the Lithium as very few have them and they can’t be compared to a lead acid. But with the right setup, you can use microwave and toaster on an offgrid caravan. If you are saving anything between £10 and £25 a night on site fees, that money can be used to fund the equipment needed. So yes, install the correct equipment and offgrid caravanning can be perfectly possible in winter  but as in everything, don’t expect the world from a 100w SP and 1 battery as you can’t get a quart out of a pint pot. 

Footnote!  If anyone wants to know more about offgrid caravanning and Lithium batteries, which, although Initially expensive, can save you money over a longer period, Roadpro at Daventry have now produced a very good guide which covers all aspects of Caravanning offgrid. It answers all the questions that are usually asked about this subject. Called ‘The Roadpro Guide to Lithium Batteries for Motorhome, Campervans, Caravans, Specialist Vehicles and Boats’ I highly recommend you get a copy( if you’re going to the show, pick one up,) or if not, ask them to send you one,.

I have a lower tech approach to off grid than Merve. The caravan is fitted with a microwave.  At home our microwave is used 99% of the time for either heating milk for my wife’s coffee and cooking veg, maybe the occaional ready meal.  In the van off grid. The milk is heated in a pan that cost about £2. The veg is cooked in a steamer that cost me nothing. I do have an old inverter that I used to use for a camera battery and my laptop. I know have a 12v battery charger for the camera which leaves the laptop.  Phones, iPad (multiple) kindle are all charged from 12v usb.  

If there is an ehu I will plug in.  Unless it is raining or I, generally can’t be ar$ed for an overnight stay. 

"If you are saving anything between £10 and £25 a night on site fees, that money can be used to fund the equipment needed."

Something of a big "if" in savings, just for giving up an EHU. Using a totally different type of campsite is also needed. The more realistic saving without just taking an EHU, lays between £3>£5. 

We are very long term caravanning solar panel users, I think our first was in 1991 and involved making the suitable controller. We remain great fans of it, plus almost exclusively in the UK camp without an EHU but do so for the site options that brings.

“We remain great fans of it, plus almost exclusively in the UK camp without an EHU but do so for the site options that brings.”

I couldn’t agree more.  It is for us about options and choice  perhaps more than cost. 

Something of a big "if" in savings, just for giving up an EHU. Using a totally different type of campsite is also needed. The more realistic saving without just taking an EHU, lays between £3>£5.

Sorry Ocsid but I maintain that the savings on sites can be and are substantial. Sites I have visited have saved me at the very least £8 a night and many are saving me more than that. As for the sites , yes, that’s another draw for me- quiet, uncrowded CLs, grass pitches and peace! But it’s not all about saving and sites for me- it’s also about paddling my own canoe and the fun I find in doing it. As Boff says, one can do it in a low tech way and there’s nothing wrong with that but that extra margin of comfort now we are approaching our latter years is really helpful. The kit is bought and paid for and will soon be moved to my new ‘van (NEC 2019!). I have never said I won’t hook up again but I can’t see me doing so. The technology keeps improving and it offers opportunities to caravanning families only dreamt of before. 

The great thing about modern technology is that it offers opportunities that hitherto, have not been possible. Yes; most certainly one can go off grid at the ‘bucket and chuck it’ level or choose any level of comfort right up to being able to use microwave; toaster, virtually unlimited tele ( if that’s your bag) and being able to run the heating pump without much worry    of running out of power. The further you go or to put it another way, depending on what facilities you want, you have to match your kit to your requirements. Ocsid is absolutely right when he says it’s enthusiasts territory but what is an enthusiast? I would argue that you don’t have to be a massive enthusiast to get the pleasure of offgrid camping. I started very meagrely and it was good fun and very little difficulty. I have built up from there.  These days I want a little more comfort so I am prepared to align my system with that in mind. Modern tech allows you to do that. Quality Solar Panels, as not all of them fulfil the promises- I would always go for monocrystalline as they are better than their poly cousins: A search of the web will very quickly start to reveal what panels are worth having. Inverters are the same, always buy one well within the capacities you are going to ask of it. ie. if you are going to run something requiring 300w and that is the maximum you will ever ask of it the a 600w inverter will be excellent -then you have to decide Pure sine wave or Modified sine wave:  However, if like me you are wanting to run microwave and toaster, a 2000 or 3000w PSW inverter will do the business nicely. Going back to the 300w kit- and again, Boff is spot on with this, a decent size (90-110ah) in GOOD ORDER will be able to cope. However, with the larger amps 2 batteries will be required and even then, can only be used with care due to the tendency of plates to warp if you try to kick the backside out of them. So, we move to Lithium. This is a totally different animal to the lead acid and has so many advantages. It can produce massive amounts of power when asked without any danger of damaging the battery- unless of course you are not taking any notice of your battery monitor and run it down to nothing!! Then you could have a problem but the BMS (battery management system) will shut down the power before you get to that stage- technology again comes to the rescue. The one thing I always try to explain is the importance of a ‘balanced’ system. In other words, make sure your panels are capable of recharging your batteries fairly quickly or as fast as the weather will allow. Tiny Sp - big battery- no good as is large SP- small battery. Yes, I agree wholeheartedly with you Ocsid- it can be enthusiast territory but I’ve had so much fun doing it!! And I will, hopefully, well into the future, now the kit is there and with the battery having a life of 20 to 25yrs along with the SPs and the inverter- savings every year will pay for that kit well within 25 yrs. One thing is for certain, if I was in my 30s or 40s and I could afford it, I wouldn’t hesitate on finding out about the opportunities modern tech offers and installing a system whatever level that might be.

For the benefit of others Merve can you start putting some real numbers and costing up for this microwave powering solar system? 

• The price of that 3000 Watt PSW inverter?
• The size and pricing of that associated panel matching lithium technology battery installation, offering 25 years life?  [How many have achieved that 25 year life so far?]
• The size, pricing and weight of the solar array to quickly recharge the battery system?
• The price of the solar controller required?

Hi Ocsid. You ask a relevant question but you will know that there are dozens of different panels , inverters, batteries and controllers. Putting a price on it is difficult or well nigh impossible as it really depends on what one wants to get out of a system. My system I put in 6 yrs ago I remember the SP being around £550 for 135w. Massively cheaper now as you will see. The two lead acid batteries were £100 each and the controller came with the Panel. The inverter was £340. However, over the last 6 years, the system has paid for itself a couple of times over. I still have the panel working very well, the inverter, although not top quality, is OK for what I need. You live and learn and the more I have gone into this , the more I have learned about systems and what is on the market. 

Now, I have a new van arriving in April and part of the offer was for them to fit a 100w panel and supply a tow cover. Tow cover is fine but the 100w panel will have to be substituted for a 310w which they have agreed - the cost- £319.99! and that is for a panel that is almost 19% efficient. Such a massive difference- down to a quid a watt now!  The panel weighs 18kg but as I have taken 2 lead acids out weighing around 70kilos for the two, I am still way under where I was weight wise.  So, so far it hasn’t cost me anything you could argue. The Lithium Battery will be moved into the new van. That cost around 1k but they will become cheaper as more and more people start to use them. The inverter, although OK, will be changed for one that does what it says on the box. It will be pure sine wave and rated at 2000w- plenty big enough to do everything and handle everything I want to use.  (The old one will be sold.) The new inverter will be around £400 with a 350 watt MPPT controller with a Lithium cycle as is necessary. That is around £140. The only other bit of kit that I need to correctly charge the Lithium from the engine is the wildside Battery to Battery charger. Again with a Lithium cycle.  That’s another £180. So we have about £1,700 worth of kit that can be moved easily from van to van and that has a life expectancy of 25yrs. We tend not to change our vans very often so that helps- we won’t be reinstalling the system every 2or 3 years! The panel can be moved too but that is a little more difficult but certainly possible. So, we tend to do about 60 nights away a year at the moment and, I save on average about £9 -£10 a night on site fees. If we want to talk about CAMC sites, you can double that or more. But let’s stay with CLs and the £9. That’s £540 a year at the moment- we will be increasing our time away very shortly and as we increase, so do the savings. Not only that, I now have the freedom to go to any site I like on the network. I have the freedom to use equipment I could only dream of a few years ago. It all makes for a super easy time away. Don’t forget that this is only on the electric side of things. If you talk about LPG Safefill is another huge saving to caravanners like me but I had better be quiet about Safefill- some don’t like me mentioning it!  Now, if you extrapolate that figure by 25 you can see that it’s not what you pay at the beginning which I would be the first to admit is not for the faint hearted but I take the long view and the savings are massive. It’s the same as the Lithium- bloody expensive to start with but cheaper than lead acid in the end. It’s just how you view things I guess. I just like the idea of wild camping- I think it catches the essence of what caravanning is all about but being able to have a proper coffee or being able to use a toaster is just heaven! If I was to look for another reason, it’s greener than using  electricity created by burning the dinosaurs! I hope I have put some clarity to the question you ask. Speculate to accumulate- Yes, you can spend quite a bit but then you can save much more than you spend. 

Thanks Merve. So your solar system is a bit over £2000, but could answer the OP's request for powering a microwave. I notice you have not gone for the 3kW inverter settling for a 2kW, presumably this being adequate to power the microwave.

Item Price in £
Panel Array 320
Solar Controller 140
Battery 1000
Inverter 400
DC to DC converter 180
Total 2040

Without the need to power these very high demand units I suspect most needs at todays costings could be answered whilst retaining the van's typical £100 conventional battery, and adding a 100Watt £100ish panel and a £50 odd controller? Just a £150 additional investment.
The massive cost increase being predominantly driven by the likes of the microwave and because of the abuse of LA battery technology that brings, the desirability to adopt a Lithium technology there.

I do find the 25 year life arguments less than convincing, initially that they can only be predictions and secondly it needs an abuse free life. Any inadvertent running down to a low state of charge has a life limiting issues even here.

I suppose also I have reservations based on the poor real world life I have had with the lithium technology used in my laptops and smart phones. Here, a usable life of about three years, leaves me not to be over confident about the claims of 25 years, though I realise there are a spectrum of differing lithium technologies.

Without the abuse of say a microwave, my LA batteries have never given less than 8 years usable life, so spending on three of those consecutively to yield the 25 years, is much cheaper than going lithium for me, at today's prices.

Finally, in this time of fast advancing technology I am far from convinced I will be wanting to be "holding in" with my 25 year old today's best kit investment, that far ahead.

Getting another 25 years is for me an idle dream anyway, it would come caravanning with our letters from the Queen hanging up in the van though!