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Last edited by sallytrafic on Fri Mar 13, 2009 8:27 am; edited 2 times in total ______________________________________________________________ Regards Frank - - please follow me on twitter @FrankieBryant
Denn wir haben nichts in die Welt gebracht; darum offenbar ist, wir werden auch nichts hinausbringen.
RIP Peter and Fiona Our thoughts are with you Chris and Graham. Fighting with Mavis and Ray
Plusnet, Safari 5, G5 PowerPC iMac running OSX 10.5.8, Salisbury UK : Get behind early - it gives you more time to catch up.
Some thoughts on the issue of presentation, since I would not dream of putting forward technical advice to the 'master of solar' (or should that be PV?).
The section on regulators is quite hard to get your head around and might benefit from a simpler explanation of the benefits. For example, I am not sure what "deliver more power to the battery at the top of the charge" means.
Also, following the paragraph on regulators, the phrase "They come in three flavours monocrystalline, polycrystalline and amorphous" suggests that it is the regulators that come in three flavours, not the panels.
I think it might be worth including a statement about what PV panels can actually achieve. Something along the lines of: "They are not an effective replacement for mains charging, perhaps other than in high summer in southern latitudes. But by topping up the batteries with a little bit of power each day, they can postpone the time when you have to hook-up, connect a generator or drive.
Last edited by sallytrafic on Mon Mar 09, 2009 9:16 pm; edited 1 time in total ______________________________________________________________ Regards Frank - - please follow me on twitter @FrankieBryant
Denn wir haben nichts in die Welt gebracht; darum offenbar ist, wir werden auch nichts hinausbringen.
RIP Peter and Fiona Our thoughts are with you Chris and Graham. Fighting with Mavis and Ray
Plusnet, Safari 5, G5 PowerPC iMac running OSX 10.5.8, Salisbury UK : Get behind early - it gives you more time to catch up.
I'm looking at buying a charge regulator at the moment and I find it all very confusing, I understand most of the connections and the basics of what it does, IE Solar in put, and output to the battery, but I'm struggling to find anything on the "load" connection at all, why is it there and what is it used for generally, and what are the possible uses.
also is it better to go with a controller with a LCD readout, or or are LED's really enough.
If you are thinking of the Large battery Small solar panel and no Regulator idea, make sure that the solar panel has a blocking diode fitted so that it doesn't drain power from your battery overnight.
We have seen a van with this type of set up and although the solar panels were charging the battery wonderfully during the daytime, the battery went very flat very fast as soon as it got dark. The solar panal acting like a large storage heater on the roof of the van all night
Thats a good point Tina I'll have a think and include something about blocking diodes and their near relative the bypass diode. The two do completely different thinks but are often confused.
______________________________________________________________ Regards Frank - - please follow me on twitter @FrankieBryant
Denn wir haben nichts in die Welt gebracht; darum offenbar ist, wir werden auch nichts hinausbringen.
RIP Peter and Fiona Our thoughts are with you Chris and Graham. Fighting with Mavis and Ray
Plusnet, Safari 5, G5 PowerPC iMac running OSX 10.5.8, Salisbury UK : Get behind early - it gives you more time to catch up.
This is about solar photovoltaic (PV) panels, ie the sort that use sunlight to give you free electricity. Free that is once you’ve bought them, they are expensive and not as efficient as you might like them to be. Expect to pay between £4 to £5 per Watt (more in the smaller sizes). Panels come in three flavours monocrystalline, polycrystalline and amorphous. Of these the amorphous is the less common needing far more space for the equivalent wattage they are cheaper though and very flexible so can be stuck directly to the curving roof of a motorhome or boat. They also produce a good output in dull conditions.
If you see a panel marked as 100 Watts what does it actually mean? Well it means that if irradiated with sunlight at or above 1,000 Watts per square meter you will get more or less 100 Watts of power.
So this 1,000 Watts per square meter how much sunlight is that? Its about as bright as it gets at the earths surface. You don’t really have to worry about that though. What the Met Office does is take actual measurements averaged out over ten years or so and quote a number of sun hours per day. Each sun hour is equivalent to an hour at 1,000 Watts per square meter. So for argument’s sake if it was sunny for 8 hours but only at 500W per square meter they would say 4 sun hours. I can only quote for UK but for example on the South coast in June and July if your panel is lying horizontally you get 5 sun hours per day on average.
Just to put some figures to that then if you had a 100W panel then it would produce 500 Watt hours in a day in June on the Isle of Wight. Dividing by 12 Volts gives 42 Ampere hours of charge That sounds quite good doesn’t it? Except that well its not really 12V is it? Your battery on charge needs abut 14V so divide the 500 by 14 instead and you get 36 Ampere hours. The next recalculation has to take account of what voltage the panel is working at when it delivers its maximum 100W, unfortunately its not 14V but about 17V. How much less than maximum power it is at 14V depends on design.
There is another way to extract more power, this is by using a regulator. When solar power was first experimented with it was thought that you didn’t need a regulator at all (and that is still true if you have a big battery and a small panel). This is because although the panel 'wants' to deliver its power at 17V the battery whilst it is charging will hold the voltage down, unfortunately as the battery charges this effect becomes less and the panel voltage rises to a point where the battery will gas profusely leading to loss of electrolyte. The 'surface effect' in the battery chemistry plays its part too. It takes time for the charge to move from the surface of the battery plates. So the battery voltage on charge does not accurately reflect the amount of charge the battery has received. Then regulators were produced that avoided damaging batteries but wasted energy by just disconnecting the panel as the voltage went too high. The problem with disconnecting the panel at this point is that although you avoid producing a lot of gas the battery is not fully charged. Pulse Width Modulated (PWM) regulators deliver more power to the battery at the top of the charge (say above 80% charged) by effectively matching the incoming power to the correct charging voltage, ie just keeping the battery at the gas producing threshold. Maximum Power Point Tracking (MPPT) regulators go a stage further by allowing the panel to always work at its maximum power point whilst giving three or four stage charging to the battery. Both PWM and MPPT regulators have temperature compensation, as the final charging voltage at 25°C might be 14.4V whereas at 0°C its over 15V. A good PWM regulator might cost £70 a MPPT regulator twice as much.
I hope that has lowered your expectation of what a panel can produce. We can do better than that though. For a start 5 sun hours was with the panel lying horizontally stuck to your motorhome roof. I happen to know that the sun hour figure rises if you arrange to point it at the sun as the sun tracks across the sky. This effect is marginal in summer but much better in the other three seasons. However automatic tracking systems are more expensive still perhaps £20 per Watt and beware of results that show a 5 times improvement that is only valid at the extremes of the day, likewise percentage improvements quoted for February are only good in February. That said the further North you travel and the more you venture out in late Autumn, Winter or early Spring the more benefit they will bring. They nearly always include MPPT regulators. It is up to you and the space you have whether you go for the efficiency of a tracking system or just add more panels.
There is one more component of your solar system, that is the blocking diode. This diode, which is often included within the regulator, prevents your battery discharging at night back through the solar panel. It is in series with the cable from the panel and acts to only allow electricity to flow one way, from panel to battery. There can be some confusion with the bypass diode which is often fitted into the terminal box of the panel for a completely different purpose. The specification of the panel and regulator will need to be consulted if you are unsure if a blocking diode has been supplied. Note some pundits say that the blocking diode is unnecessary* and some regulators achieve the requirements of the blocking diode without actually using a diode. (* argument is beyond the scope of this FAQ)
So there you have it, free energy ... at a price. Even if they are not able to replace all the power you used last night they will extend your stay, postponing the moment when you have to hook-up, connect a generator or drive. They are also very very very quiet.
There is a MHF detailed guide to solar systems here >click here for part 1< Note that it does not yet cover some more modern aspects such as MPPT regulators.
Last edited by sallytrafic on Wed Mar 11, 2009 1:58 pm; edited 1 time in total ______________________________________________________________ Regards Frank - - please follow me on twitter @FrankieBryant
Denn wir haben nichts in die Welt gebracht; darum offenbar ist, wir werden auch nichts hinausbringen.
RIP Peter and Fiona Our thoughts are with you Chris and Graham. Fighting with Mavis and Ray
Plusnet, Safari 5, G5 PowerPC iMac running OSX 10.5.8, Salisbury UK : Get behind early - it gives you more time to catch up.
I'm looking at buying a charge regulator at the moment and I find it all very confusing, I understand most of the connections and the basics of what it does, IE Solar in put, and output to the battery, but I'm struggling to find anything on the "load" connection at all, why is it there and what is it used for generally, and what are the possible uses.
also is it better to go with a controller with a LCD readout, or or are LED's really enough.
Kev.
Kev, If you are adding a panel and regulator to an existing battery system you can if you wish ignore the load connection.
After all, all the loads of your system lighting, pumps etc are already connected to your battery probably via a distribution fuse box.
If you are starting afresh then connecting all the loads to the regulator, may depending on the design of the regulator have advantages.
For example some regulators have load disconnect. This automatically disconnects your loads at a low voltage giving protection from too deeply discharging your battery.
I recently fitted a regulator like that to an existing system. What I did was transfer the loads that I could most easily do without, to the load disconnect line via a fused distribution whilst leaving others connected to the original fused distribution connected directly to the battery.
Here is a diagram of my system
So now if my battery voltage falls too low then my fridge (12V compressor) TV and 12V socket are automatically disconnected (my diesel heating system has its own low voltage disconnect.
If I was designing from scratch I would have added most of the lighting to the new distribution as well.
Some regulators are able to calculate how much charge remains in the battery by sampling how much has been put in by the various charging systems and how much drawn by the loads. In that case all the charging methods and loads must be connected to the regulator or the regulator must have a methods of sampling the current remotely using shunts.
Does this help? I could go further to talk about multi panel multi battery installations etc.
As to your LED versus LCD display. Mine has LEDS but I can't even see them easily. Once your regulator is up and running and you have got used to its performance IMO there is either going to be enough solar energy going into the batteries of there isn't, you are going to know without having a complicated display. Mind you for £100 there is a smart meter that I could add on that requires only a shunt fitted to the negative lead of my battery..............
______________________________________________________________ Regards Frank - - please follow me on twitter @FrankieBryant
Denn wir haben nichts in die Welt gebracht; darum offenbar ist, wir werden auch nichts hinausbringen.
RIP Peter and Fiona Our thoughts are with you Chris and Graham. Fighting with Mavis and Ray
Plusnet, Safari 5, G5 PowerPC iMac running OSX 10.5.8, Salisbury UK : Get behind early - it gives you more time to catch up.
Frank,
I think your 'final edit' is very clear, instructive and pitched at the right level for anyone looking for an introduction to Solar / PV Panels (like me for example - I now understand a bit more about regulators).
I think it might be worth including a statement about what PV panels can actually achieve. Something along the lines of: "They are not an effective replacement for mains charging, perhaps other than in high summer in southern latitudes. But by topping up the batteries with a little bit of power each day, they can postpone the time when you have to hook-up, connect a generator or drive.
Hope this is constructive.
Philip
I hope you will forgive me for pinching part of your post JeanLuc,but what you say is very important to those who are about to spend hundreds of pounds on a solar panel system which will only ever (in this country)be able to top up their batterys and NOT be able to cope with the demand made on the batterys in a average size coach built MH
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Our thoughts are with you Chris and Graham. Fighting with Mavis and Ray 
