Solar Panel Question?

[CAPTAIN FANTASTIC]

I had a Rutland 913 wind charger working non stop, easily charging my 4 x 110 amps batteries for over 9 years. I removed it this winter with view to change the bearings. But I did not put it back, I bought a 100w solar panel; semi flexible, polycrystaline (monocrystalines are no good with shades) for £101.

So far I have been very impressed, very thin, robust, no frame, it charges the batteries quicker than the wind charger even during cloudy days. Solar technology has moved on in the last few years. I will not go back to wind generation for my type of sailing.

 

[Slow_boat]

So polycristaline is the way to go?

I saw a Japanese ketch in Brittany that had two 100w panels, one each side in the mizzen rigging. May be the way I go.

 

[rbmatthews]

For solar panels you have a choice of:

• A simple on/off regulator that disconnects the panel from the battery when the battery voltage reaches a certain figure and reconnects when the volts fall to some lower figure. ( actual values should be in the spec)
• A pulse width modulated (PWM) regulator which breaks the charging into a series of pulses of diminishing duration as the battery becomes charged. Better because the battery is always maintained at max state of charge.
• A maximum power point tracking regulator (MPPT) that maintains the panel volts at the voltage corresponding max power output during the charging stage but then uses PWM control as the battery becomes charged. Better still because it is maximising the power output from the solar panel

Does anyone know how to tell the difference between these three types? I recently ordered what claims to be an MPPT controller for £5.50 (free P&P) but I have heard that most of these are actually PWM ones. Are there simple tests that you can do to determine whether it is really an MPPT, or one of the other two? I know the price is one indicator, on which basis this one is probably not an MPPT, but it is claimed these are factory seconds, so they could be. Whatever it is, it does seem to work, and is hardly going to break the bank.

And if they really are PWM, how do they get away with advertising and selling them as MPPT?

 

[JumbleDuck]

Does anyone know how to tell the difference between these three types? I recently ordered what claims to be an MPPT controller for £5.50 (free P&P) but I have heard that most of these are actually PWM ones. Are there simple tests that you can do to determine whether it is really an MPPT, or one of the other two? I know the price is one indicator, on which basis this one is probably not an MPPT, but it is claimed these are factory seconds, so they could be. Whatever it is, it does seem to work, and is hardly going to break the bank.

My surefire method is "Find the part number on alibaba and check what the manufacturer says".

 

[VicS]

Does anyone know how to tell the difference between these three types? I recently ordered what claims to be an MPPT controller for £5.50 (free P&P) but I have heard that most of these are actually PWM ones. Are there simple tests that you can do to determine whether it is really an MPPT, or one of the other two? I know the price is one indicator, on which basis this one is probably not an MPPT, but it is claimed these are factory seconds, so they could be. Whatever it is, it does seem to work, and is hardly going to break the bank.

I suppose check that it controls the panel output voltage to what the panel manufacturer states V_PMAX to be.

And if they really are PWM, how do they get away with advertising and selling them as MPPT?

because people will buy cheap tat on ebay

 

[GrahamM376]

I was informed (maybe unreliably) that having two regs feeding the same bank can reduce charge rate as each reg sees the input from the other - any truth in that? I have an Aerogen split charge reg with a 25w solar panel alsoconnected to it and, other regs for the gantry mounted p[anels feeding 2 x banks, one reg to each bank.

 

[sailinglegend420]

So polycristaline is the way to go?.......

There really is no intrinsic difference between modern polycrystalline or monocrystalline panels in their performance or shade tolerance. Any differences depend entirely on the manufacturers of the panels.

 

[ostra4]

On the last boat we had we fitted a 90 watt high quality panel six years ago which we paid 450 euro for bought in Greece,the regulator was another 120 euro .Panel mounted on tilt able and swivelling pole , we saw around 4.8 amps as a max feeding 120 amp battery .Most of time that was enough to run the fridge although other power requirements were low .After changing boat we boat a year or so ago we bough an eBay special 100 watt panel for £100 , so far I really can't tell the difference quality wise and the best output I saw last year was 5.8 amps , the regulator off eBay for £20 shows same information as the expensive one on last boat .The expensive regulator just before we sold boat tended to freeze on certain functions showing battery 99 % full even first thing in morning .Bearing in mind the large difference in cost of the two systems Im not convinced the expense of supposed better quality panels and regulators are worth the extra .Time will tell but I can buy nearly four panels now for price of my first one .

 

[vyv_cox]

I'm surprised if the regulator gets that hot, pretty warm maybe but not as hot as it would if all the excess energy is dumped and dissipated as heat.

In Greek midday sun in June the controller becomes very warm. The LED display on our unit, exactly the same as the one shown here http://www.sunworks.co.uk/ disappears completely. I know the unit is OK as it was returned to the manufacturers last year to correct another fault.

 

[Redfox226]

Does anyone know how to tell the difference between these three types? I recently ordered what claims to be an MPPT controller for £5.50 (free P&P) but I have heard that most of these are actually PWM ones. Are there simple tests that you can do to determine whether it is really an MPPT, or one of the other two? I know the price is one indicator, on which basis this one is probably not an MPPT, but it is claimed these are factory seconds, so they could be. Whatever it is, it does seem to work, and is hardly going to break the bank.

And if they really are PWM, how do they get away with advertising and selling them as MPPT?

I was having the same problem with an eBay controller said to be MPPT - felt it wasn't doing the 140aH battery justice with an 80W panel despite flashing an LED earlier today to tell me it was 'over voltage' (I assume 100%).

Bit the (fiscal) bullet, and installed a Victron 75/15 MPPT today - immediately this went into bulk charge mode - so battery definitely not 100% then... I'll see what charge level tomorrow brings....

 

[LadyInBed]

So polycristaline is the way to go?

I saw a Japanese ketch in Brittany that had two 100w panels, one each side in the mizzen rigging. May be the way I go.

What, like this?

 

[Tropical Kitt]

I use two 20w thin flexi Nasa solar panels fixed to the cabin top of my 19' Prelude. They are my only electrical input for my 75AH leisure battery. (My outboards are too small to have charging coils.) When sailing in Scotland each summer the solar panels just cope with my careful demands, although the voltage does drop rather low sometimes. The electronic gear seems to be tolerant enough to cope, so far. All bulbs are LED. Tiller pilot and chart plotter use most. I use a wind vane to steer when on the wind which saves a lot.
Good luck but there is no way that solar will compare favorably against wind generation which will work up to 24 hrs a day, unless you have a huge array.
Jerry in Cumbria.

 

[sailinglegend420]

....despite flashing an LED earlier today to tell me it was 'over voltage' (I assume 100%)....

"Over voltage" probably means some kind of fault - not that it is 100% charged. Possibly a fault in the charge controller itself not limiting the voltage to 14.4v as it charges up.

....Bit the (fiscal) bullet, and installed a Victron 75/15 MPPT today - immediately this went into bulk charge mode - so battery definitely not 100% then...

All chargers go straight into Bulk mode when connected because they can't possibly tell just from seeing the battery voltage what state of charge they are unless they can also measure the current actually going into the battery, or being discharged from the battery. They may detect how quickly it takes to get to say 14.4v and then stay there for a timed period based on this, or they just stay at 14.4v for say three hours and switch to Float even if the batteries are fully charged. This is the fundamental problem with most chargers!

 

[Slow_boat]

What, like this?

No, it was u-bolted to the inner (lower) and outer (main) shrouds. Seemed like a good out of the way arrangement.

 

[Triassic]

My boat came with a solar panel fitted horizontally across the aft deck behind the cockpit. It's a rigid affair in a frame measuring about 3'x4' and I believe it's rated in the region of 65w, and it looks quite old. I have a fairly modest power need, running just a radio, chart plotter and a small Waeco fridge box plus occasionally the tiller pilot and LED lighting. I've yet to have a problem with the single 100a/hr battery running down although I have just fitted a BM1 meter to see how close I am cutting things..... I do have the capability of charging from the outboard if I really have to, but I don't generally as it interferes with the instruments (something else I must get round to sorting some time!).

It's my first experience of solar panels and I must say to date I've been really impressed, however I'm aware I'm not sailing right around the clock (I've done the odd night passage but then I've not been draining the battery during the day). My rationale for getting the meter was to see how marginal things are so that I can consider fitting a second battery and additional panel if needed. Some great advice and links on here, thanks.

Well I can now report after a 10 day period staying on the boat that the lowest my battery got to was 75% according to the BM1, and that was after a couple of days in a marina when I wasn't running the radio or chart plotter! The reason for the drop was because my cockpit tent is immediately in front of the panel and I was moored facing south, so the panel was in the shade most of the day. There were five full days sailing in there during which the tiller pilot was in use about 75% of the time, and about ten hours at night. I ran the fridge for the whole ten days. Three of the days sailing were in less than ten knots of wind so I don't think I would have got much from a wind generator, one was completely overcast and I didn't see the sun all day, and two of the mornings were spent in thick fog where it only appeared as a dull haze. Overall I'm quite pleased with the performance of the solar panel.

 

[Trundlebug]

I fitted a 150w semi flexible panel to our sliding sunroof on the boat over the winter.
It was fitted to help compensate for the usage of a new 85L fridge, also fitted over the winter to replace the old gas one.
I expected 24h usage of the fridge to be around 35 Ah, and I wanted to try and be able to stay independent for a few days if required if we didn't go anywhere.
Boat is a twin engined 33ft mobo.
Lighting now converted to LED throughout so fridge is the main regular electrical consumer, but there are also creature comforts of shower, heating, radio / CD, 12v vacuum cleaner (uses 9A) SWMBO's hair dryer and hair straighteners to consider too.

After returning from a shakedown 10 day holiday on Sunday, I can report as follows.

Because of my optimised fridge installation (Isotherm with Smart energy control, plus an extra 25mm Kingspan fitted all round the fridge) the consumption overnight was only around 5 Ah, much to my delight.
One morning after showers & cleaning etc and using most or all of the above appliances we were 15Ah discharged from arrival the previous evening. By about 2pm the solar panel had put it all back in and we were back to zero discharge / charge.
And that's in early spring.

So I'm very impressed with what the solar panel can do.

Note, in view of comments about short life of semi flexible panels through delamination I have sealed all round the edges with grab adhesive / sealant.
I'm hoping this will help extend its life.

 

[Dougal]

Another question please...?
I know I'm going to need a 'dual bank' regulator, but how will that work, considering I also have a high output 3 stage battery charger running when using shore power? Will a regulator deal with this just as if the engine alternator kicked in?

 

[Trundlebug]

Your solar regulator will work independently of any other charging systems you have.
Wire up the solar regulator to the batteries you want charged and it will sense and control everything automatically.

With the proviso that you will only really want to charge the domestic bank from the solar panels, as that's the bank that will get used during "at rest" periods.
The starter battery will cope on its own, as soon as it's used the engine is started so will recharge the starter battery again.

 

[Dougal]

Your solar regulator will work independently of any other charging systems you have.
Wire up the solar regulator to the batteries you want charged and it will sense and control everything automatically.

With the proviso that you will only really want to charge the domestic bank from the solar panels, as that's the bank that will get used during "at rest" periods.
The starter battery will cope on its own, as soon as it's used the engine is started so will recharge the starter battery again.

So are you saying i shouldn't bother with a 'dual' regulator? Just hookup the solar panel to the domestic bank?

 

[vyv_cox]

So are you saying i shouldn't bother with a 'dual' regulator? Just hookup the solar panel to the domestic bank?

I have a dual bank solar panel regulator and a multi-stage mains charger that is connected directly to the domestic bank. The regulator keeps both banks well charged, particularly in winter when the boat is laid up. For the small extra charge for a dual bank regulator it makes far more sense to have one, especially if it's a good one that shows the voltage in each bank. When the battery charger is running on mains all the solar power is directed to the starter battery and the same thing happens when the engine is running, charging domestic bank only.