Solar Charging

[Mitchellmoxo]

Afternoon,

 

Came back to my boat last night and reading my volt meter (11.4) I have never seen it that low, I assumed there would be something wrong with the solar panels.

 

Today I brought a new controller and I am still only getting about 12.5V even in direct sunlight when I would usually be getting 13V minimum. I checked the 2 leads coming from the solars and the voltage is 13.2V but this is not going to the batteries for some reason?

When I do disconnect the charge controller the battery voltage does drop to around 12.1 so the solars are doing something?

 

Is there anything this could be?

 

Thanks

[MtB]

Afternoon,

 

Came back to my boat last night and reading my volt meter (11.4) I have never seen it that low, I assumed there would be something wrong with the solar panels.

 

Today I brought a new controller and I am still only getting about 12.5V even in direct sunlight when I would usually be getting 13V minimum. I checked the 2 leads coming from the solars and the voltage is 13.2V but this is not going to the batteries for some reason?

When I do disconnect the charge controller the battery voltage does drop to around 12.1 so the solars are doing something?

 

Is there anything this could be?

 

Thanks

 

 

Do you mean sunshine or just sunlight?

 

If the latter this could just be down to the reducing amount of energy radiating from the sky this time of year. My own panels are down to about only 25% of peak summer output already!

[Electronics]

Like Mike said above, if sunlight you could be down to 25% already on the panels showing 13.2V. Your battery is taking charge (slowly, just ) but is loading the solar panels

hence your seeing 12.5V, I would return the controller I dont think you have a fault there , your just short of current and to correct that you need more sunlight. At 12.5 volts that shows the battery

is at about 80% capacity (12.75V approx = fully charged)

[Mitchellmoxo]

great thanks for the replies so nothing wrong with my panels then as I was worried. thanks - time to look for a generator as backup lol

[Alan de Enfield]

great thanks for the replies so nothing wrong with my panels then as I was worried. thanks - time to look for a generator as backup lol

 

A generator as 'main source' (if not using the engine),

 

In Autumn & Winter Solar panels become the (very poor) back-up system

[Electronics]

great thanks for the replies so nothing wrong with my panels then as I was worried. thanks - time to look for a generator as backup lol

Personally I hate generators , Petrol - fire risk, storage problem and then theres the noise, you could buy a generator to run off your engine I dont think

you will need to run that long to make up the solar short fall ? or think about buying another solar panel and running it in parallel with the panel you have.

[WotEver]

Personally I hate generators , Petrol - fire risk, storage problem and then theres the noise, you could buy a generator to run off your engine I dont think

you will need to run that long to make up the solar short fall ? or think about buying another solar panel and running it in parallel with the panel you have.

 

"Solar shortfall"? Bit of a euphemism that. There will effectively be no solar for the next 5 months or so. Whether a standalone genny, built-in genny, or Travelpower or other engine-mounted genny, they'll all need to be running for many hours a day over those months.

[Chewbacka]

.......................................... At 12.5 volts that shows the battery is at about 80% capacity (12.75V approx = fully charged)

Probably not as the 12.5V is with a charging current going into the batteries. After the sun goes down I would expect the battery volts to drop.

[Crow]

Well the shorter days aren't helping,that's where a percentage of power is lost,it's only getting worse,but them frosty mornings with a clear sky are just as good as a summers day,

Some times better ,as too much heat on them the power drops off

[ditchcrawler]

If the batteries were down to 11.4 volts with no lot he has quite a bit to put in unless its just one small battery

[Alan de Enfield]

If the batteries were down to 11.4 volts with no lot he has quite a bit to put in unless its just one small battery

 

If the batteries were down to 11.4v then they may well be 'knackered.'

[ditchcrawler]

 

If the batteries were down to 11.4v then they may well be 'knackered.'

Which is why they have come up to 12.5V with only about 10Ah going into them

[Gareth E]

Well the shorter days aren't helping,that's where a percentage of power is lost,it's only getting worse,but them frosty mornings with a clear sky are just as good as a summers day,

Some times better ,as too much heat on them the power drops off

 

Really? I've found with mine that I get far more on a cloudy summer day than I do on a brilliantly clear winter day.

[WotEver]

 

Really? I've found with mine that I get far more on a cloudy summer day than I do on a brilliantly clear winter day.

Well yes, Summer will always be better than winter - the solar rays have much less atmosphere to go through. However Panels love to be cool and if they're both cool and receiving sunshine they usually give a really good output. Edited September 20, 2016 by WotEver

[FORTUNATA]

I was hoping the prices of the panels would drop the same as LED lights. After all, the solar market is becoming a bit like double glazing. Later I may have a go at building a DIY wind turbine or even acquire one. Wind should soon be more in supply than sun.

[MtB]

Well yes, Summer will always be better than winter - the solar rays have much less atmosphere to go through. However Panels love to be cool and if they're both cool and receiving sunshine they usually give a really good output.

 

Despite figures demonstrating panels still deliver 10% of their summer output in winter, my empirical experience says otherwise. In mid winter I get about 5% of the peak current I see in summer, for about 30% of the time.

 

It occurs to me that this low harvest is possibly due to me having my panels flat on the roof though. In summer when the sun is high I find tipping them towards the sun makes no difference to their output at all but I've yet to try this in winter. In winter the sun is low near the horizon all day so maybe tilting and turning devices come into their own in winter. But they are a right faff. Less trouble to just run the genny!

[Arthur Brown]

Solar that was sufficient in the summer may well not be sufficient by now in the season. An MPPT controller will get about 20% extra electricity out of the same sunlight over a PWM controller, More panels will help too, as you struggle with solar harvest the tilting the panels to face directly to the lower sun will be a help. BUT you will run to a period in deeper winter when solar doesn't cover live aboard usage.

 

If your battery has reached below 12v (rested) then it's flat, essentially recharge it asap using petrol, diesel or mains.

[Guest]

I was hoping the prices of the panels would drop the same as LED lights. After all, the solar market is becoming a bit like double glazing. Later I may have a go at building a DIY wind turbine or even acquire one. Wind should soon be more in supply than sun.

Loads of examples of home made wind gennys on the net, you tube etc. Many use stepper motors, DC motors off treadmills, door closers etc Even battery drill internals. Some just wind their own coils then add permanent magnets off ebay. Seems car alternators are not good unless converted to permanent magnet, but radiator fan motors work OK.

[WotEver]

 

Despite figures demonstrating panels still deliver 10% of their summer output in winter, my empirical experience says otherwise. In mid winter I get about 5% of the peak current I see in summer, for about 30% of the time.

 

It occurs to me that this low harvest is possibly due to me having my panels flat on the roof though. In summer when the sun is high I find tipping them towards the sun makes no difference to their output at all but I've yet to try this in winter. In winter the sun is low near the horizon all day so maybe tilting and turning devices come into their own in winter. But they are a right faff. Less trouble to just run the genny!

Yes, tilting the panels lower will make a huge difference in winter. It could easily double the output.

[MtB]

Yes, tilting the panels lower will make a huge difference in winter. It could easily double the output.

 

 

Yes but feck all x 2 still equals feck all...

[WotEver]

 

 

Yes but feck all x 2 still equals feck all...

There's always that...

[Electronics]

Measured my old Sanyo 200 watt panel today (200 watts in full sun i.e 100,000 lux light level) Light reading today on the cut was just over 3500 lux (no shade)

so maths wise panel should generate 7 watts and the meter says its delivering 6.8W so not bad from an old panel. OK so lets say I generate from 9 this morning until

about 6 tonight so I get a total of approx 60 watts. That will power my fridge for about 20 minutes, not a lot !, but on the plus side thats 60 watts still in the battery bank.

 

Thinking about adding another 3 panels next year but from the above at this time of year that still gives only 1hr 20 min of fridge time per day. I might work out tonight

that if prices dropped on panels and I covered a bigger boat 70' how much could you generate with dual Amp/Cry panels fitted across the whole roof area.

[MtB]

I now have 560w of solar, lying flat on the roof.

 

Charge current now at 5pm on a bright but cloudy evening in September is 1.2A into my 24v battery bank currently at 70% SoC. The solar is just about keeping up with the fridge now, so from shortly I'll be needing to run the engine or genny on a regular basis until Spring.

 

Just to illustrate how far the performance falls 'out of season'.

 

 

 

(Edit to get the SoC right!)

Edited September 21, 2016 by Mike the Boilerman

[Jess--]

Measured my old Sanyo 200 watt panel today (200 watts in full sun i.e 100,000 lux light level) Light reading today on the cut was just over 3500 lux (no shade)

so maths wise panel should generate 7 watts and the meter says its delivering 6.8W so not bad from an old panel. OK so lets say I generate from 9 this morning until

about 6 tonight so I get a total of approx 60 watts. That will power my fridge for about 20 minutes, not a lot !, but on the plus side thats 60 watts still in the battery bank.

 

Thinking about adding another 3 panels next year but from the above at this time of year that still gives only 1hr 20 min of fridge time per day. I might work out tonight

that if prices dropped on panels and I covered a bigger boat 70' how much could you generate with dual Amp/Cry panels fitted across the whole roof area.

you would find that adding an extra panel in series will dramatically improve your output in low light, this is because in low light a single panel may well be outputting below the voltage needed to put anything at all into the batteries (say 10v for argument from the panel) where 2 panels will be nearer 20v and will easily put something into the batteries.

[DaveP]

I might work out tonight

that if prices dropped on panels and I covered a bigger boat 70' how much could you generate with dual Amp/Cry panels fitted across the whole roof area.

I reckon you could get 2 x 11 standard 250w panels on a 70' boat - 5.5kW. About 260Ah/day in the depths of winter (about 2000Ah in high summer). But no space then for logs, coal or planting...

 

I've got a pair of 250w panels on my boat and they're now starting not to cover my consumption. I'm considering another pair to be stored underneath the current ones and pulled out for the darker part of the year. Would save about 170 hours of engine run time, so there's definitely potential (sorry).