150W monocrystalline with PWM vs 200W polycrystalline with MPPT

[Johann]

I am completely new to solar power and I am considering buying a solar panel system for an off-grid hut in Wales, where I will be staying during the month of February. I require roughly 100 to 200 daily Watt-hours to power an LED light and a laptop on which I will be working. I have found two solar panels on ebay that seem to fit my needs, but as I have zero experience in buying solar panels, I thought I'd ask here before going ahead with the purchase.

Here are the two panels:

http://www.ebay.co.uk/itm/150W-solar-panel-kit-folding-monocrystalline-battery-charger-150W-caravan-12v-/301459750815?pt=UK_Gadgets&hash=item463066bf9f

http://www.ebay.co.uk/itm/2-100Watt-solar-panel-W-20A-MPPT-complete-Kit-for-RV-Boat-Home-System-12V-24V/390980292475?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28111%26meid%3D018cd0a05ec24dbf876daf13696ac444%26pid%3D100009%26prg%3D11472%26rk%3D8%26rkt%3D10%26sd%3D301459750815

My main question is: Would it be better to buy the 150W monocrystalline panel with its included PWM charge controller, or the 200W polycrystalline panel with its MPPT charge controller? (Both controllers are rated at 20Ah). I know that monocrystalline panels are slightly more efficient, but I assume the extra 50W of panel would counter this. I've also heard that MPPT charge controllers are more efficient in systems of 150W and higher, and also in cold conditions (I will be using the panel in British winter at a reasonably high altitude). Taking this into consideration, which panel would be more suitable?

Any help would be much appreciated.

Antony

I got this from somewhere else, so this is not my work and credit needs to go to the creator.


Price

Monocrystalline solar cells cost more than polycrystalline for the same size.

Efficiency

Monocrystalline cells have a higher efficiency than polycrystalline cells due to the structure being made from one large crystal as opposed to many small ones. In addition to having an overall better efficiency, monocrystalline panels can perform up to 10% better than polycrystalline panels in high ambient temperatures.

Size

Since monocrystalline panels are more efficient per area, the size of the solar panel is less than a polycrystalline solar panel for the same wattage. If you are limited on size and want to get the most energy possible, monocrystalline panels are the better choice.

Looks

In terms of looks, monocrystalline panels have a nice uniform color and have a more circular cell shape. Polycrystalline cells are in squares and have inconsistencies in the color sort of like granite.

Longevity

Even though a monocrystalline panel has the potential to last up to 50 years, most warranties only go up to 25 years which polycrystalline panels are able to reach just fine.

Overall, the production process for monocrystalline silicon is mature, and the process for polycrystalline in still maturing. As purity and process tolerances for polycrystalline Si improves, the performance gaps between the two are narrowing.

[foo1bar]

That comes at quite a shock, I didn't realise the inverter would use so much power. In order to charge my laptop, I really do need to be using AC power (it's the only way I can plug my laptop in) - I assume I should use modified square wave in order to prevent the inverter from leeching all of my power?

It's very very likely that you don't need an inverter to power your laptop.
Without knowing the make/model of laptop can't guarantee, but many laptops have ability to be charged from a car charger. (and I think you were talking a 12V system, so a car charger would work)

I *can* guarantee that you can buy a laptop which has a car charger - and ones that have DC to DC power adapters.

Using your existing AC power adapter is probably the cheapest way to go - assuming you have to have AC power for other reasons anyhow.

[antobag]

Thanks everyone. Looks like I'll definitely be going for the poly panels (I don't mind about the slightly larger size) and a small 150W PSW inverter that I'll use as rarely as possible.

It's very very likely that you don't need an inverter to power your laptop.
Without knowing the make/model of laptop can't guarantee, but many laptops have ability to be charged from a car charger. (and I think you were talking a 12V system, so a car charger would work)

I *can* guarantee that you can buy a laptop which has a car charger - and ones that have DC to DC power adapters.

In terms of using a DC-DC adapter, I can't seem to find anything that goes directly from the battery (ie. crocodile clips) to a laptop charger. Could/should I use the following?:
[My 12V Battery connected to:]
1) A battery to car charger adapter: http://www.amazon.co.uk/TRIXES-Batte.../dp/B005G39HLY
[connected to:]
2) An in-car laptop charger: http://www.amazon.co.uk/In-Car-Charg...laptop+charger
[connected to my laptop.]

If this is okay, would it also be possible to place a car charger splitter between the two (eg. http://www.amazon.co.uk/Ring-volt-In...cessory+socket) so that I can use multiple DC appliances on one battery? I know that the splitter is rated at 10A maximum (so 120W on 12V), but this should be enough for my needs. However, I'm just a bit concerned that adding so many different car-charger connections could end up causing some adverse effects.

Any more of your fantastic advice would be much appreciated!

[foo1bar]

If this is okay, would it also be possible to place a car charger splitter between the two

That particular one has a USB output - which means it has electronics in it which would be drawing some amount of power.
Instead of that, I'd just wire in two car cigarette sockets.
And I'd probably get something that's direct wired, rather than clip-on. And with a built-in fuse.

[antobag]

That particular one has a USB output - which means it has electronics in it which would be drawing some amount of power.
Instead of that, I'd just wire in two car cigarette sockets.
And I'd probably get something that's direct wired, rather than clip-on. And with a built-in fuse.

Thanks foo1bar. What are the benefits it being direct wired over clip-on? Also, would it be dangerous to use one without a built-in fuse?

The best thing I've found on the internet in the UK is this: http://www.amazon.co.uk/Waterproof-C...ref=pd_cp_ce_1

Would I be able to wire 2 or 3 of these to the same battery?

An Amazon reviewer has mentioned that the cables are too small to be used with anything more than the supplied 2A fuse. How true is this? I would most likely need to have at least 5A going through (in order to get 60W to power my laptop (which runs at 90W max)).

[foo1bar]

Thanks foo1bar. What are the benefits it being direct wired over clip-on? Also, would it be dangerous to use one without a built-in fuse?

The best thing I've found on the internet in the UK is this: http://www.amazon.co.uk/Waterproof-C...ref=pd_cp_ce_1

Would I be able to wire 2 or 3 of these to the same battery?

An Amazon reviewer has mentioned that the cables are too small to be used with anything more than the supplied 2A fuse. How true is this? I would most likely need to have at least 5A going through (in order to get 60W to power my laptop (which runs at 90W max)).

searching for 'cigarette socket' i saw this:

http://www.amazon.co.uk/Practical-Motorbike-Tractor-Cigarette-Lighter/dp/B00C7MXQAU/

Doesn't have a fuse - but has a link to buy a fuse holder. And together they'd still be cheaper than the one you found.

I don't see a problem with wiring 2 or 3 sockets to the same battery. My car has 3 sockets, plus all the normal car things (lights, radio, etc)

I do think you need to be careful about not using so much power that you drain the battery. Especially since I think you're talking about only charging it from the sun - so you won't have a lot of power to recharge it.

My reasoning for a hard-wired solution is that then everything is solidly put together - I don't have to worry about spring loaded clips that aren't working as well as I want. I haven't used these clips - but I know from jumper cables that getting a good connection to a battery via spring-loaded clips can be a PITA. Maybe it won't be as bad with cleaner things to connect to (not dirty from years of being under the hood of a car)

[jimindenver]

To show how direct wiring can make a difference.

Long ago we bought a small 12v 200w auto drip coffee maker. Trying to use it plugged into a cigarette lighter while on the road took so long that we deemed it a failure and it was stashed away. When I was testing our 230w portable while camping a few years ago it was all I had that could put a big enough load to push the system. I didn't expect much and was blown away when it made it's pot in about the same time a regular auto drip does while pushing the system to over 16a.

So hooking up something properly with ample wire, the shortest distance and fewest connections makes a difference.

[antobag]

searching for 'cigarette socket' i saw this:

http://www.amazon.co.uk/Practical-Motorbike-Tractor-Cigarette-Lighter/dp/B00C7MXQAU/

Doesn't have a fuse - but has a link to buy a fuse holder. And together they'd still be cheaper than the one you found.

I don't see a problem with wiring 2 or 3 sockets to the same battery. My car has 3 sockets, plus all the normal car things (lights, radio, etc)

I do think you need to be careful about not using so much power that you drain the battery. Especially since I think you're talking about only charging it from the sun - so you won't have a lot of power to recharge it.

My reasoning for a hard-wired solution is that then everything is solidly put together - I don't have to worry about spring loaded clips that aren't working as well as I want. I haven't used these clips - but I know from jumper cables that getting a good connection to a battery via spring-loaded clips can be a PITA. Maybe it won't be as bad with cleaner things to connect to (not dirty from years of being under the hood of a car)

I was originally avoiding that socket as it is shipped from China (just me being impatient!) but I just noticed that they have a UK distributor for only a few quid more AND there's two supplied, so I've gone ahead and bought it. Much cheaper than the single £9.99 one I found!

You're right, I think I'll stick to two sockets for now. I assume it'd be fine to go ahead and stick 5A fuses in them?

[antobag]

To show how direct wiring can make a difference.

Long ago we bought a small 12v 200w auto drip coffee maker. Trying to use it plugged into a cigarette lighter while on the road took so long that we deemed it a failure and it was stashed away. When I was testing our 230w portable while camping a few years ago it was all I had that could put a big enough load to push the system. I didn't expect much and was blown away when it made it's pot in about the same time a regular auto drip does while pushing the system to over 16a.

So hooking up something properly with ample wire, the shortest distance and fewest connections makes a difference.

Thanks jimindenver. So would you recommend that I go directly from my battery to a DC-DC 12V-19V step-up adapter (ie. this: http://www.amazon.co.uk/In-Car-Charg...ptop+charger)? If so, I assume I'd have to cut the cable of the adapter in order to attach it directly to the 12V battery?

[jimindenver]

Isn't the plug in on that the power source itself, best you can do is make sure the wiring and receiver is up to snuff.

[antobag]

Isn't the plug in on that the power source itself, best you can do is make sure the wiring and receiver is up to snuff.

You're absolutely right. I guess I'll stick to the car charger for now - the company (Lavolta) have some pretty good reviews, so hopefully the adapter will work well with my system.

Thanks again for all the help.

[Bucho]

You're absolutely right. I guess I'll stick to the car charger for now - the company (Lavolta) have some pretty good reviews, so hopefully the adapter will work well with my system.
Thanks again for all the help.

Good luck, a DC charger for the laptop sounds like a great idea, but I think you still need to have a conversation about generators.

[antobag]

Good luck, a DC charger for the laptop sounds like a great idea, but I think you still need to have a conversation about generators.

Thanks for the luck, I'm sure I'll need it! I'm prepared to have a few unproductive laptop-free days and a few candlelit evenings if I need to give my battery time to recharge, so hopefully I won't be needing a generator. Although I'll probably be eating my words when I'm stuck in a dark hut on a Welsh winter's night with nothing but a few books to keep me occupied... on second thoughts, anyone know of any good "cabin fever preparedness" forums?

[Mike90250]

... I'm prepared to have a few unproductive laptop-free days and a few candlelit evenings if I need to give my battery time to recharge, so hopefully I won't be needing a generator. Although I'll probably be eating my words ....

When you have several cloudy days, the batteries are low, and you can't run anything, they (batteries) are well on their way to the grave. sitting for 48 hours, nearly completely discharged, the batteries will sulfate and die. Day 2, is when I run my genset to re-bulk the batteries, because this last Nov & Dec, we had 5 weeks of solid clouds. The choice is to, on the first day of clouds, shut your batteries off while they are still full, or continue to use the system and recharge with the generator.
weather-rain.jpg
The third option, run the batteries flat, and then buy new ones.

[antobag]

When you have several cloudy days, the batteries are low, and you can't run anything, they (batteries) are well on their way to the grave. sitting for 48 hours, nearly completely discharged, the batteries will sulfate and die. Day 2, is when I run my genset to re-bulk the batteries, because this last Nov & Dec, we had 5 weeks of solid clouds. The choice is to, on the first day of clouds, shut your batteries off while they are still full, or continue to use the system and recharge with the generator.
[ATTACH=CONFIG]5527[/ATTACH]
The third option, run the batteries flat, and then buy new ones.

I'm planning to run my battery down by only 30% D.O.D each day, and by 50% max. I'll shut it off if it gets near this amount. Would leaving it at around 40% D.O.D for more than two days cause a lot of long-term damage? Definitely don't want to be running them flat and buying new ones!