Expensive or cheap Solar Panels?

AGM will take a fast charge and should not vent. Don't buy a wet cell deep cycle, they are a joke, only take a trickle charge and unless you are driving 500km a day are usless! We have had friends hire vehicle's with these fitted and they had to drive all day, yes, ALL day to charge them. I'm sure they did the the job in their day (1970's). As for solar I cant help you as I run a noisy generator :)

AGM's are the best way to go.

Measure your roof and see what you can fit on top before ordering something because it is cheap.

Regards

Derek

John,
The numbers used to nominate the capacity of solar panels is the Maximum Watts which in many cases won't even be attainable unless in reasonable conditions.
The numbers you need to know are the reasonably expected Watts in reasonable light conditions, however they are never quoted.

Some cheaper solar panels will not work efficiently in low light, so the number of AH per day is reduced even in good conditions.

Don't expect to get 120 watt performance from a 120 watt panel all the time, it just won't happen.

I did a 'test' with my 200+ watt solar system, with no cleaning and having it laying horizontal in part overcast conditions, it only returned dismal performance numbers on the day, however on a good day it shows >12 Amps @ the gauge, not the extremely dismal (7 to 8 Amp) numbers I've shown below.

With my SÖLAR system laying horizontal on the roof it starts recharging the AGM battery system at dawn, even in these real life conditions, and with the panel NOT cleaned of bird dung & dust etc.

@ 7 am
SÖLAR system is collecting 3.8 Amps
(I know this only because I checked)
Battery is showing 14.2v (charging Voltage)

@ 9 am
SÖLAR system is collecting 7.5 Amps
Charging 2.3 Amps into the AGM's
in previous 2 hours has collected 10ah

@ 11 am
SÖLAR system is collecting 8.5 Amps
Charging 1.2 Amps into the AGM's
in previous 4 hours has collected 13ah

@ 1 pm
SÖLAR system is collecting 8.6 Amps
Charging O.4 Amps into the AGM's
in previous 6 hours has collected 20ah

@ 3 pm
in previous 8 hours has collected 26ah
(can't fib, lost notes with other numbers)

@ 7 pm
SÖLAR system is collecting Zero Amps
Charging Zero Amps into the AGM's
in previous 12 hours has collected only 29ah

During the day there were times when almost nil Amps were showing, hence the extremely low 29ah total for the 12 hours, instead of a realistic 50+ Amphours.

The 25 year warranty on solar panels is not worth the paper it's written on if you don't know the manufacturer of the panel, as it's only based on panel performance, not the panel failing because the wiring has cracked or solder breaks because the panel has vibrated them loose, which is usually given a lesser 12 month quality warranty.

I would only use AGM Deep Cycle batteries.

Maîneÿ . . .

My take on the panels fwiw is that you are simply wasting your money on top brand panels.

Sure if you are using them to power a remote telecommunication station supporting fibre optic and mobile that is 900km away and where down time costs $40,000 per hour, pay the premium for the insurance of brands.

But if you are using them for a RV, I am sure you will find that many people here have had good "ebay panel" experiences. Just be careful and do your research.

Solar panels are commoditising rapidly, and getting better technically. The ebay ones are often back door brand units.

Also despite what other people tell you, cheaper ones generally aren't much less efficient, or shade intolerant, if at all. ( except when comparing diffent construction technologies.)

Here is the killer IMHO. You could probably get 3 or 4 decent "ebay" 80 watt panels for the price of 2 BP ones. So you have one or two spares that would give you 50 to 100% more capacity most of the time, and probably all the time. In addition by having more panels you are building more shade tolerance into your system so you could reasonably expect to get somewhere between 1.5 and 3 times the power using cheapies given the same expenditure and realistic, partly tree shaded conditions. ( if mounted on your camper)

There are a couple of people on Exploroz selling panels and have had good reports. I would rather have follow up from them than from an OIL executive in the UK :-)

The other thing widely misunderstood on this forum is the current output you can expect. Panels are rated at their Maximum Power Point. In other words the voltage and current that they are most efficient at. Unfortunately for 12v users, this is usually about 18V. So a 100w panel for example will generally output 100/18=5.5A. Not 100/12 ( which would equal 8.3A). This is because the power is lost in most regulators. A rule of thumb is that you will only get 70% of the rated solar power as usable power - under ideal sun conditions. So you will need to buy 30% more power in the panels than you need. ( Another good reason not to pay a premium).

Batteries - Strongly recommend avoiding wet cell types - cheap, but not suitable for enclosed living spaces due to free acid and possibility of hydrogen buildup. Gel or AGM types are expensive but the only way to go. They are commonly used in big computer backup systems and routinely replaced long before end-of-life. These used ones are often on ebay and can save you a lot of money.

Panels - I use one BP one and one ebay cheapy. The BP has a stronger, bigger aluminium frame, but the ebay one performs better, and I've no doubt that both will die prematurely due to corrugations rather than manufacturing quality issues. I'd go with the lowest dollar per watt solution.

Controller - I agree with your plan to have excess capacity here.

A few general considerations - In my experience, excess solar capacity is very useful, but still doesn't make the sun shine. How long do you want to run from the batteries? Have you done an energy budget? I agree with 200 Ah storage, but you will need more than a 120W panel to get the best out of that storage. If you mount the panels horizontally, the angle of incidence is a long way from ideal. You cannot actually use all of that 120 watts since that figure relates to the panel's optimum operation - at a voltage too high for charging your batteries. To complement 200 Ah of battery capacity, I'd suggest at least 160W of solar capacity, more if the panels are mounted horizontally. Another very desirable item is a smart 12V charger to boost the alternator output.

Final note - you may find our blog Electricity for Camping useful. Also there is a new solar article on this site that's well worth a look here

Steve,
your doing my head in mate LOL! is the 140 still for 12 volt setup or is it 24volt setup ?
and how long have you been selling this actual panel, are they a new brand that you have brought in or is it the same that you have sold before ?

Cheers mate and thanks ,I will chat with the MOF later :)

why use old technology. All living in the dark ages of solar on this forum.
24v solar panel with Morningstar MPPT controller about $350 incl meter from US delivered to charge 1 150Ah VRLA like DC series Fullriver battery. Dont put batteries in parallel. Dont hook up the vehicle to the battery. Power the fridge from the vehicle while travelling. 170w panel with MPPT regulator because of efficiency is like having 230w panel in winter and 200w panel in summer. If you run TV lights and laptop 120w is not sufficient panel capacity. Best advice ever given to me when first bought my solar system was spend the money once, do the job once and do it properly.

John,
Not sure where your located but it may be worth your while chatting to Glen Broadhurst from http://www.powertobefree.com.au/index.html. He installed the panels & solar regulator on our van and did a wonderful job. I found him extremely knowledgable and easy to understand. Ous system works a treat even though it's only a reasonably small system on our 15'6" Supreme Getaway van.