Solar questions - design, tilt, recharging e-bikes, etc (1 Viewer)

[Glas Robin]

The memsahib and I have this week "retired" at 48 and the tunnel is booked for 20th Sept with a vague plan to "turn left at the exit" and see where we end up. We'll be doing perhaps 3 long trips a year, followed by summer in the UK to top up the piggy bank.

This necessiates a few upgrades to the van, as we intend to be wild/off-grid a fair amount and I'd like to be able manage a week to 10 days if needed, without needing hookup/dumping.

I'm in the final stages of designing the solar system. Annoyingly although it's a 7.4m van, roof real-estate is a bit compromised as all the longitudinal gaps are a couple of cm short of the roughly 99cm width needed for large single panels. So I'm having to go for more but slimmer panels.

Usage and wishes
Our 12v usage is a bit of TV, lighting, recharging phones, laptops, tablets, aand the usual water pump/heating blower, etc. I'd like to reduce gas usage by converting extra solar to run the fridge when the batteries are full. Ideally I'd like to be able to charge 2 e-bike batteries/scooter as well - not every day, but I know they take quite a whack out of a battery.

Plans
I am planning 200ah of AGM batteries, 2x150w rigid panels probably with the voltronic MPP 350 Duo controller (if I can find one). I can't afford fancy lithium batteries. This would enable me to trickle charge the starter battery when the hab batteries were full, and send a signal to the fridge to use 12v too when the habs are full.

I think I probably need to have a separate 100ah deep cycle battery and smaller panel and cheap MPPT (or maybe really cheap PWM) controller to run the e-bike charging set up - as I can discharge it further without risk of damaging the main leisure bank. I'm planning to use a variable DC-DC converter rather than an inefficient inverter.

I've just about finished the engineering prototype for a simple motorised tilt system - using a linear actuator, remote control and an aluminium frame. Just need to get the panels to try it in anger.

Questions.

1. Does that plan sound reasonable? Any other suggestions?
2. Is it sensible to have the separate system for the e-bikes with a DC-DC converter? I reckon a 100w panel is probably enough.
3. Anyone know where I can get a MPP 350 Duo from? Global shortage it seems...
4. If I can get the motorised tilt system to somewhere between £50 and £100 - is this a price point that might make it viable to make/sell as a kit to others? There's nothing really on the UK market, unless you want a v expensive tracking system. I know it's as cheap to get a second panel at that price - but not everyone has the space or would perhaps also need to upgrade other components in the system for more panels.

Thanks as always for comments and suggestions.

Robin

 

[Wh05apk]

It sounds like you are wanting a solar system to use mainly during the winter, as you are heading back to the UK, for the summer? You also mention turning left at the tunnel, so presumably heading north? If so solar will provide very little power, you might do better with either b2b charger, or dare I suggest it a generator?

 

[Hagstrom]

A thorough and well thought out post. Something of a rarity these days?

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[The Wino]

Is it financially worth trying to get the fridge on 12 v?. We use about 70 p worth of gas a day off grid in the summer thats the fridge water heater (2 showers a day plus washing up etc) and cooking. The fridge can't be a huge cost and on 12 v works nowhere near as well as on gas .
Also is it worth having a separate system for the evokes? If you just use the main system you might have to watch the charge level so you don't go flat but it will happen a lot quicker on a separate battery and it would be easy to discharge it too far and knacker it.
Just my thoughts.

 

[Ivory55]

As it’s winter a diesel heater might be worth thinking about as wild camping and no ehu as a back up in case of no gas or heating failure

 

[Raul]

The only was to answer this correctly, is to know your daily necessary consumption. As a reference, 100w solar can harvest 3-5 times in Sumer 300wh to 500wh: that’s 25-40ah approximate. In the winter will be 0,4 to 1 max as 40wh to 100wh max: that’s 3-8ah for 12v of course. . Sometimes even worse. I would say strive for as much solar as you can, even if it’s to much in summer. Design for the worst case scenario, that’s winter, and have some overpaneling in summer. The gap you say is short of one meter. There are panels narrower than that, but better output. Number one choice for me would be the panasonic 250w and second victron 175w. Both are 800mm wide. The panasonic is a hibrid cell that’s tuned for a wider light spectrum and very efficient in low light compared to everything else. The tilt is nice, as you point to the sun. But, when it’s not sun, this is when you need it most, and best orientation when no sun is facing the sky, flat. That way you get all of the reflection and best performance. Tried and tested by many. The dc-dc converters are 85% efficient a good small pure sine wave inverter is 93% efficient. Now you need to find out the efficiency of the charger, and add up to the inverter efficiency, and see if it comes ahead of the dc-dc. Don’t take for granted single conversion will be better. Sometimes with a inverter you are ahead. Study the components you intend to use.
Fridge, absorption on electric is really bad efficiency. A absorbtion fridge will eat 3-4 times more energy than a compressor. In some cases as much as 7 times more. The only advantage absorbtion has, is ability to run on gas . And gas has 7kwh per litre. A compressor eats 300-400wh a day and any responsible off grider designs for 3-5 day reserve. This will take you into Li storage. It’s a tuff call with two agm’s , the shortest lifespan out of all leads, but the best charge rate and efficiency. If you don’t have big draws I would incline for GEL, as they fair better in partial state of charge. You will be spending lots of days with not enough charge.
As mentioned above, diesel heater is a must, your gas will not last long for heating as well.

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[Boringfrog]

Well done retiring at 48, me and SHMBO did similar in 2007 when I was 44 and she was 40, I did a bit part time work when back in the UK but have been fully retired for a couple of years. I prefer the Winter Months in Spain or Portugal so would always head South (maybe slowly) if leaving in September. I know you've already made a prototype for your adjustable panels but did you think about a solar briefcase when the sun's low? In Spain I did see a German chap with a solar panel mounted on the rear of his van that he could manually turn towards the Sun. Another tip I got many years ago, don't wee in your cassette, I've done this for years and also carry a spare cassette so can go weeks without the need for emptying.

Good luck, Frog.

 

[Wikky]

Perhaps look at flexible solar panels also. However if I was going North in the low sun times of the year I would look at diesel heating systems and refillable gas cylinders as back up to solar energy.

 

[Glas Robin]

It sounds like you are wanting a solar system to use mainly during the winter, as you are heading back to the UK, for the summer? You also mention turning left at the tunnel, so presumably heading north? If so solar will provide very little power, you might do better with either b2b charger, or dare I suggest it a generator?

Thanks.

“Turn left at the exit and see where we end up” is indicative of our state of mind, rather than a concrete plan. We may on the day turn right! We are intending to spend much of our time further south and east where there are more photons whizzing about .

Although having said that, our only real plans at this stage are to drive through Denmark/Norway in the spring to see the northern lights, and to ship the van to Canada the following spring and spend 6 months in Canada/US. Both trips will have lower sunlight at times, hence the desire for tilt to extract as much as I can at the shoulders of the day/year.

Generators are noisy tools of the devil, and not on the list - although are a useful solution for many I agree.

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[Glas Robin]

Is it financially worth trying to get the fridge on 12 v?. We use about 70 p worth of gas a day off grid in the summer thats the fridge water heater (2 showers a day plus washing up etc) and cooking. The fridge can't be a huge cost and on 12 v works nowhere near as well as on gas .
Also is it worth having a separate system for the evokes? If you just use the main system you might have to watch the charge level so you don't go flat but it will happen a lot quicker on a separate battery and it would be easy to discharge it too far and knacker it.
Just my thoughts.

Thanks. The running the fridge off solar, is perhaps a nice add on to reduce gas usage (and thus need to refill as often), rather than cost. One of the first upgrades a couple of years ago was to install a refillable GasIt system. I love it but am loathe to give up the space with a second cylinder. It seems daft not to use surplus solar once the batteries are full and I’ve followed Lenny HB ‘s threads on this. The benefit may be marginal I guess. And as I can’t get the required controller with 6 weeks til we leave, I may have to forgo it anyway.

The main reason for thinking of a separate system for the e-bikes/scooter is to avoid the risk of taking too much from the leisure batteries and damaging them. I figured a traditional deep cycle battery would take more of a hammering to much lower discharge.

But I’m open to guidance from more knowledgeable peeps (ie just about everyone!)

 

[Bobby-gg]

Get a gas level indicator for the single gasit cylinder so you can monitor your usage - just as an indication, I've got twin 6kg gaslow system that I topped up earlier this month and used a little for the fridge and water heating when required, cylinder was down to approx 65% until this weekend when we've had a cold and damp weekend at a festival and the cylinder is down to 5% as we've had the fridge on, the hob/cooker and the heating on to dry out wet clothing.

As, I'd do your research on AGM's and reconsider, look into EFB's instead if you can't afford lithiums

 

[Glas Robin]

The only was to answer this correctly, is to know your daily necessary consumption. As a reference, 100w solar can harvest 3-5 times in Sumer 300wh to 500wh: that’s 25-40ah approximate. In the winter will be 0,4 to 1 max as 40wh to 100wh max: that’s 3-8ah for 12v of course. . Sometimes even worse. I would say strive for as much solar as you can, even if it’s to much in summer. Design for the worst case scenario, that’s winter, and have some overpaneling in summer. The gap you say is short of one meter. There are panels narrower than that, but better output. Number one choice for me would be the panasonic 250w and second victron 175w. Both are 800mm wide. The panasonic is a hibrid cell that’s tuned for a wider light spectrum and very efficient in low light compared to everything else. The tilt is nice, as you point to the sun. But, when it’s not sun, this is when you need it most, and best orientation when no sun is facing the sky, flat. That way you get all of the reflection and best performance. Tried and tested by many. The dc-dc converters are 85% efficient a good small pure sine wave inverter is 93% efficient. Now you need to find out the efficiency of the charger, and add up to the inverter efficiency, and see if it comes ahead of the dc-dc. Don’t take for granted single conversion will be better. Sometimes with a inverter you are ahead. Study the components you intend to use.
Fridge, absorption on electric is really bad efficiency. A absorbtion fridge will eat 3-4 times more energy than a compressor. In some cases as much as 7 times more. The only advantage absorbtion has, is ability to run on gas . And gas has 7kwh per litre. A compressor eats 300-400wh a day and any responsible off grider designs for 3-5 day reserve. This will take you into Li storage. It’s a tuff call with two agm’s , the shortest lifespan out of all leads, but the best charge rate and efficiency. If you don’t have big draws I would incline for GEL, as they fair better in partial state of charge. You will be spending lots of days with not enough charge.
As mentioned above, diesel heater is a must, your gas will not last long for heating as well.

Thanks for such a detailed and helpful answer; it is very much appreciated Raul.

I’ve tried to do the usage calcs a number of times, including monitoring usage when we are away. But it’s difficult as we will be doing a different kind of trip in future to the current shorter holidays. My design is now basically to oversupply and see how we do.

Using your figures, 300w of panels should give me enough to replace in one day in summer the impact of fully discharging 200ah battery bank to 50%. In winter I will get much less, hence the tilt. But I haven’t factored in the charging gain from driving. Perhaps I should think about a third 150w main panel to take me to 450w.

The fridge is just an idea to make use of surplus free solar. I may leave it out initially and see how much of the time I’m actually fully charged when there is usable sun left.

Interesting re efficiencies. The isolated DCDC converters I’m looking at claim efficiency in the 90%+ range, whilst I always understood inverters to be 70-80% on the step up, then there is the loss from the step down in the charger. This is the bit of the system I haven’t fully thought out yet.

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[Lenny HB]

For a start forget about AGM batteries about the worst choice you could make for leisure use.

Using a seperate battery for charging the bikes makes it unnecessarily complicated far better to fit a decent battery monitor so yo are aware of the state of your batteries and your power usage.

A second gas bottle is essential if touring Norway there are either none or very few refilling points.

Running the fridge on 12v will only save a bit of gas, modern fridges run quite well on 12v to get any real advantage you need to be in the south of France or Spain.

Battery wise Gels or possibly Traction batteries would be your best bet.
With what you are looking at doing the extra cost of Lithium would be negligible you can now get 100ah ones for just over £400.

 

[Glas Robin]

Well done retiring at 48, me and SHMBO did similar in 2007 when I was 44 and she was 40, I did a bit part time work when back in the UK but have been fully retired for a couple of years. I prefer the Winter Months in Spain or Portugal so would always head South (maybe slowly) if leaving in September. I know you've already made a prototype for your adjustable panels but did you think about a solar briefcase when the sun's low? In Spain I did see a German chap with a solar panel mounted on the rear of his van that he could manually turn towards the Sun. Another tip I got many years ago, don't wee in your cassette, I've done this for years and also carry a spare cassette so can go weeks without the need for emptying.

Good luck, Frog.

We’ve been planning release for a couple of years now. The kids are off the books and paid for this summer (one graduated, one off to uni) and the mortgage is paid. So we’ve resigned employment and booked the tunnel. We are putting speech marks round “retired” as we plan to run a seasonal glamping site out of one of our fields over the summer - which will be quite a bit of work. Finally got planning permission this week.

I did think about briefcases - but I like the plan of rocking up, parking with nose south and pressing a button to tilt the roof panel. Plus I reckon the additional cost of the tilt is less than the cost of a briefcase per extra Wh.

Thanks for cassette tip. I’m about to install some compost loos for the glamping site - they all have a urine diverter. I wonder if you can fit a divertor to a Thetford toilet? It’s the urine that cause the smells. In any event I’ve been thinking hard about converting to black tank for a while, and posted about my plans on here a couple of years ago.

 

[eddie]

I have an automatic, tracking solar set up, and the daily yield is a few amps in Winter in Somerset, low enough to be insignificant.

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[Glas Robin]

Get a gas level indicator for the single gasit cylinder so you can monitor your usage - just as an indication, I've got twin 6kg gaslow system that I topped up earlier this month and used a little for the fridge and water heating when required, cylinder was down to approx 65% until this weekend when we've had a cold and damp weekend at a festival and the cylinder is down to 5% as we've had the fridge on, the hob/cooker and the heating on to dry out wet clothing.

As, I'd do your research on AGM's and reconsider, look into EFB's instead if you can't afford lithiums

Thanks. Got a Mopeka, but the battery never seems to last or the signal is too weak. Must try again.

AGMs was only because I’ve already got one at 100ah, so I thought the cheapest option initially was to chuck a second next to it. I don’t really understand battery tech enough. Maybe I need to read more on this - it’s a pretty fundamental part of the system!

 

[Raul]

Now with more input from your kind of usage, the tilt makes sense. Anything from 47-50deg north lat, the solar in winter is very low. The tilt is a must and sometimes vertical works well in morning and evening. I use 590w fixed flat on the roof, and 230w portable on a second controller. I take them out when needed. The portables are two panels hinged, resting on a stick. Simple and practical for my use. In the evenings and mornings, the 230w portable, overtakes the roof 590w on output. I do have hydraulic actuators and ball bearing industrial draw sliders and still working on how I can utilise this. The tilt involves heavy mechanism, moving parts in icy winter, water corrosion etc.

 

[Tombola]

All depends on budget Vs usage as usual.
Lithiums are the way to go budget allowing and B2B certainly a plus.
12v fridge then yes 400+ solar, and as much lithium as you can fit, maybe a quick few days trial with X amount of ah, then add to it if required.
Future proof the mppt etc by making sure the voltage will take the extra panels/batteries if needed.

Good luck, whether you turn left or right, sounds great

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[Glas Robin]

For a start forget about AGM batteries about the worst choice you could make for leisure use.

Using a seperate battery for charging the bikes makes it unnecessarily complicated far better to fit a decent battery monitor so yo are aware of the state of your batteries and your power usage.

A second gas bottle is essential if touring Norway there are either none or very few refilling points.

Running the fridge on 12v will only save a bit of gas, modern fridges run quite well on 12v to get any real advantage you need to be in the south of France or Spain.

Battery wise Gels or possibly Traction batteries would be your best bet.
With what you are looking at doing the extra cost of Lithium would be negligible you can now get 100ah ones for just over £400.

Thanks Lenny - I was hoping you might comment even though it’s *yet another* solar thread!

I need to read and understand more about batteries. I have 100ah AGM at present, so my starting point was to double that as an inexpensive option.

Thanks for fridge tip. Given I can’t get the dual Bluetooth controller with AES signal that I want for love nor money, I may forgo it anyway.

Sounds like I need to reconcile myself to finding somewhere else to stow the BBQ as I need to put a second cylinder back in the gas locker!

 

[Raul]

Like for like a agm vs traction flooded, agm 500 cycles, traction 1200 cycles, and more robust in deep discharge, and desulphate equalising charge. The agm is good on fast charge/ discharge, a choice for large loads with a penalty in cycle count. The flooded is less capable on fast charge discharge, copes well with C/10 rate. The GEL even slight less than flooded rate, but, copes well with partial state of charge. This is a bonus when you can’t charge to full every day. Trojan has a industrial line flooded traction with graphene that copes with partial state of charge. If you go with lead, allow for maintenance.

 

[paddymcc]

We recharge our ebike from a small pure sine wave inverter (300W). We tend to move on fairly regularly so tend to recharge when we are on the move and know that the B2B will ensure a plentiful supply.
I like the idea of tiltable panels and am thinking of something similar but am aware that in the far north in summer ( Norway, Yukon etc) that the sun is always lowish and so a panel that only tilts south may not be any better than one that is horizontal. In Norway in June I know you could get some solar gain for 20+ hours a day so that may be more important. As Raul says winter in the UK (or Romania) they are likely to be more useful. But I'd like to see what you have in mind anyway! Pictures please!
I think I would go for lithium if I were in your position. You should try to match batteries so adding a second newer AGM wouldn't be sensible anyway.

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[wfdTamar]

As Lenny says forget AGM batteries and adding a new one to the one you have is not good. Better to replace it with something new and better than AGM. I looked into it a few years ago and couldn't quite spring for Lithium either (not at UK prices), but found a lead carbon Leoch battery which seems a good option.

12v 100AH Leoch Pure AGM Lead Carbon PLH+ C100 Deep Cycle Leisure Battery NCC Class A - Alpha Batteries

12V 100Ah Ultra Deep Cycle battery for multiple applications – from Leoch’s Pure Lead Carbon series. Features • Pure Lead […]

www.alpha-batteries.co.uk

I wouldn't have a separate setup for the bikes. Just use the main one. B2B charger too and a proper shunt based battery monitor (not just voltage).

You can get a Votronic 350 here and he might send to the UK. He's in New Zealand and sends them to Australia. Having said that I had a not very good experience with him when I needed one replacing.

Votronic Duo MPP MPPT Solar Regulator Charge Controller LiFePo4 Lithium Lead 350 | eBay

Votronic Duo MPPT Solar Regulator 350W. Made in Germany by Votronic. LiFePO4 Batteries: Battery protection in case of high temperatures and particularly in case of low temperatures. Battery Type adjustable Acid/Lead-Acid, Gel, AGM, LiFePO4.

www.ebay.com.au

Have a look at the AandNCaravanServices site, some good info.

 

[cyberyacht]

You're young enough to make any investment worthwhile. Definitely go for Lithium. It save payload too. Diesel heater gives flexibility and ease of supply. Plus as much solar as will fit.

 

[Carado]

Hi Robin
I have the same van as you Carado T449 and have two 150 Watt solar panels on the roof with room to fit another 150 watt panel also I have two leisure batteries under the. Drivers seat both are 95 amp and have had no problems with being off grid the Victronic unit takes care of all that is required however I only run the fridge on 12 volt when the engine is running the rest of the time I have it on gas as have in the gas locker two 11 kg Gaslow refillable bottles which last a long time as to charging the electric bike I either put it on charge when the engine is started via the Victronic inverter or if stationary the solar panels will give enough power to charge the bike ,
have a great trip

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[Lenny HB]

AGMs was only because I’ve already got one at 100ah, so I thought the cheapest option initially was to chuck a second next to it.

If they fail in Norway it will be a very expensive option everthing in Norway cost 6 arms & legs.

 

[Lenny HB]

As Lenny says forget AGM batteries and adding a new one to the one you have is not good. Better to replace it with something new and better than AGM. I looked into it a few years ago and couldn't quite spring for Lithium either (not at UK prices), but found a lead carbon Leoch battery which seems a good option.

But they are AGM.

 

[ChrisL]

You might like to consider lead carbon gel batteries, as opposed to agm, i'm about to have 3 105 ah's fitted this week, they have the advantage of normal gel regarding cold weather charging and design life but charge quicker then regular gel's and should suffer less sulphation at partial states of charge. I got mine from alpha batteries.

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[Glas Robin]

Hi Robin
I have the same van as you Carado T449 and have two 150 Watt solar panels on the roof with room to fit another 150 watt panel also I have two leisure batteries under the. Drivers seat both are 95 amp and have had no problems with being off grid the Victronic unit takes care of all that is required however I only run the fridge on 12 volt when the engine is running the rest of the time I have it on gas as have in the gas locker two 11 kg Gaslow refillable bottles which last a long time as to charging the electric bike I either put it on charge when the engine is started via the Victronic inverter or if stationary the solar panels will give enough power to charge the bike ,
have a great trip

Thanks - that's really helpful. It's a great van isn'it? I love the large garage. I've installed a slide out plaform on decent drawer runners and we can get 4 bikes plus paraphernalia loaded in 60 secs.

We're just coming up on 3 years. Have you found any niggles with it?

 

[Carado]

Yes Robin they are a good van and no have not had any niggles with it yet but have only owned it since last November mine is the 9 speed automatic and as you said the garage is fantastic

 

[MitchandJenny]

2 X 11kg refillable gas system is a must.!!
Reference pee, get a10ltr plastic can ( with
a large neck ) and a “ She wee “ it’s then a simple trip to the bushes for an empty. !! ( you do need some liquid in the cassette) also use bio clothes washing liquid in cassette to keep it spotless. (1€/ltr)
Use fridge on gas !!
100w suitcase solar panel will give you 3 times what 100w flat on the roof will give,
particularly in Winter, and can be orientated regularly @ 90deg to get optimum charge. I fitted a plug on the side of the van adjacent to the battery box and, as the panel has its own mppt controller, just plug panel straight in. “KISS”.
Keeping things simple IS, in my opinion, best and is easy to repair / replace if any probs occur.
We have used this set-up for 5 years now
and, with 2 X 100ah lead acid deep cycle batts from Varta, we watch a couple of hours TV nightly and spend 3 months off grid during Dec, Jan, Feb with Campsites for loo emptying and Launderettes for washing. But not tried this as far North as you plan to go.
Good luck with your trip and plans.
Mitch.
PS. Batteries £100 each, Solar panel £100.

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