450w 12v system or 380w 24v?

[Khoogyra]

I posted this in the 'newbie' section, but I noticed the replies are in the 0-2 range on average and I'm not sure it was the greatest place for such a post. So here we go!

I am moving to a farm in the near future where all electricity is coming form solar panels. The more I researched, the more I realised their systems were very minimal for what they wanted to be doing. They picked up some 2 x '2 x 15w' panels on sale for $60 in total or something, which is a decent $1/w deal, but they're using it to power a 110ah battery... They say it takes 4-5 days to fully charge it and it gives them 2 full laptop charges and 2 or 3 cell charges.

So, that got me to thinking... I found a local dealer who seems to sell good quality panels, chargers, etc. I have already purchased:

1 x 125w Qixin QSE panel (backed by nuenergy) (Ningbo Qixin Solar Appliance Co.)
1 x 45a Juta CMP45
1 x 110ah AGM from MCA model #fcd12-110

I also have some weatherproof connectors that he cut and connected for me. Anyway, I've contacted him in regards to exchanging a few things in for some heavier duty panels. The plan was to upgrade the 125w to a 150 and add 2-3 more 150's and 2 or 3 more 110ah batteries.

So that's a total system of:

3/4 x 150w Mono panels
3/4 x 110ah agms
1 x 45a charger, possibly upgraded to a Tracer-4215RN 45a MPPT

And for an inverter I'm looking at the

Univ-1000 or 1500

I'm not quite so sure about those inverters, but at 200 or 300 for a true sine inverter, i may have to cheap out and upgrade to something else later. He's got something called a xantrex and a few other things, but they're all in the $400+ range and I'd rather have a bigger array, or battery bank for now.

Now... here's the new question.... I was calculating my costs out and the higher end (the 4's) would end up in the 3k range after I got all the cabling and if I decided I wanted a dc circuit breaker vs a fuse (with which I hold a petty dispute). That would include a uni-T meter and a few other things I'm looking at as well.

But... I wonder. What if I decided to upgrade the 125w to a 190w 24v panel and purchased a second. The other realistic choice was picking the 3's and shaving it to 2200+tax... approximately at least. But with 2 190's I could shave off the cost of upgrading to an mppt and still have room in my budget for a 4th battery... If people think I can take it on a 380w 24v system on a 45a MPPT.

My thinking is that because the losses in wiring are lowered by upping the voltage, as well as having less wiring than 3 or 4 panels, maybe it'd run more like a 450w, even though it's 380? I'm unsure about all this. But I'm taking another stab and understanding this all a bit further than last go... 4 days where I'd wake up multiple times per night with PV math spinning in my head.

I am also looking at picking up a Sun Danzer 50l DC refridgerator. I hear it uses up only 8ah/day and would be of great help to the people I'll be staying with, as well as myself if I move my RV elsewhere later on. This is not going on my RV. It's going near a communal space in a field where people will be working on a progressing permaculture.

The sorts of loads I see using... These aren't necessarily often, and especially at the same time.
Music: 200w sub + 200w amp on a self powered laptop.
Power tools/battery charging: drill press, etc. I hear I need a lot for this kind of thing. I guess we'll see.
Cooking: 50l fridge, maybe a crockpot or something for sunny days.
computer: an hour or two of gaming?

This brings up another question. Is my understanding currently wrong that:

In the day, if my batteries are full, then I can run, say an inverter with my music system running without draining my battery (unless the draw is greater than the energy being produced by the solar panels)? That might change my perspective in some aspects, if that doesn't pan out.

Anyway, thanks for any help you can provide. Please let me know if you need any other info. For the record, the 150w panels are $405+tax and the 190's $520 at 17.4 and 17.8 efficiency.

[Mike90250]

Welcome. It helps us to fillow threads if you don't post dupes. We see a listing of all the "new" ones, and replies happen as folks can reply.

First, give up the idea of cooking, with solar PV electric . If you have sun, get a solar oven - many brands exist.

Second, if you have loads, (chargers and such) that have been running on Mod-Sine inverters, then you are OK. There is some percentage of plug-in do-dads, that die quickly on mod-sine inverters, and some that don't. Just warning ya.

Fridge - Most of the "mini" fridiges, consume as much as energy efficient full size models. Count on 1KWh usage a day for it. Thats going to need several panels, or more, depending on how many useable "solar" hours (10 am - 2pm roughly) you hae in your region.

You get what you pay for. Buy good gear, you generally get good results. Cheap gear from fleabay, you get uncertain results. What will ruined batteries cost you ?

Large tools - run them from a generator, they need lots of power, and you will need a very large inverter to power them.

[Khoogyra]

Hi,

Thanks for the reply!

I'll go delete my old thread after posting this.

So as far as cooking goes... I was looking at a friend's crockpot (slow cooking over 8+ hours with chili etc) and it took something like 1.5a, which didn't seem like it was too bad if used during the day.

Next up, the inverter. I have not been running anything on PV yet. This is my first setup. The inverters I'm looking at are all Prosine/Pure Sine inverters. The upgraded model, which is under $100 to upgrade to would be a Xabntrex ProWatt 1000 or 2000... Likely the 1000.

Also, nothing is coming from ebay. There's a local dealer who says he goes straight to China, buys say $100,000 in panels and comes back here, cutting out a middle man in the process and allowing him to sells Mono Crystalline panels for 50% of what other local retail stores sell for. I looked up the panels he sells (QSE) and they're backed by Nuenergy in Europe, where they've been sold for something like 8 years. I hear Europe has high standards in goods that are imported from anywhere.

Next we have the fridge. This fellow says you can run this 50 litre fridge on a 125w panel and a 110ah battery without any problem at all as it only uses 8ah/day. It has 4" of insulation. I've looked this thing up on a few sites and it seems highly recommended.

I hope this provides better quality info for the next response.

[Khoogyra]

This was posted by Naptown in the other thread that I've now edited.
Naptown:
If you are going to buy an MPPT inverter then I would suggest going for 3 60 cell grid tie panels and wiring them in series. A couple things happen then. The cost of the panels for the wattage you will get is substantially less as grid tie panels are much more common and less expensive. That 45A Mppt charger will handle 1000W of PV @24v Heck you might save enough to get a real inverter. Don't worry or concern yourself with panel efficiency. It really makes no difference in output other than the physical size of the panel will be slightly smaller.

[Khoogyra]

Grid-tie eh?

I'll look into it, but it sounds like it's meant for being in the city. This system is meant to be portable enough that I can pack it up in the RV and move ANYWHERE and have at least some electricity. This is definitely off-grid. I'm paying under $3/w from this guy. The other retailers want $7-9/w in my city. If I add HUGE shipping, etc from online, it seems I'm still paying more than $3/w for Poly Chrystalline, which I'm still not sure is worse/better than Mono Crystalline.

What I was wondering was whether I'd receive better results with 3 150w on PWM or MPPT or if the conversion of the 24v system into 12v with MPPT would would be worth the larger 190 panels.

I'm unsure if I should provide his website. The fellow in question has been running his company for 24 years now. He does automotive engineering and sells panels on the side. He also welds his own stands, etc. Seemed like a really cool guy and only carries pure sine inverters, and from my research, only high quality goods.

[Sunking]

So as far as cooking goes... I was looking at a friend's crockpot (slow cooking over with chili etc) and it took something like 1.5a, which didn't seem like it was too bad if used during the day.

That is one Hell of a load for solar 1.5 amps @ 120 volts is 180 watts and @ 8 hours is 1440 watt hours which takes in your area around 500 watts of solar panels and 450 pounds of a battery.

FWIW most crock pots use 300 watts so I think you have underestimated by some 40%. So if that is correct you can just about double the numbers I quoted.

[Khoogyra]

One last thought before I take off to work.

The reason I've gone with the largest panels I can find is that the more I looked into this whole thing the more I realised that every cable, connectorconverter, etc is going to cost me efficiency in the entire system. So if I go with 3 60w grid-ties with micro inverters, I am going to lose a bunch in the extra wiring to make it a higher input system (more panels) You're suggesting a 180w system, which seems rather lacking.

Also, I'm planning on learning more about DC powered objects and running more of them. I've got a 12w 'soft white' LED floodlamp which is DC and the fridge I mentioned above is DC as well. There's a lot of really intelligent people on this farm and the likelihood of finding more DC loads seems rather likely. The inverter is likely to be used for all this in the tech world (PC, Laptop, amp/sub). These types of activities would be done in the day, whilst the floodlamp and dc fridge would be draining the night use.

The battery bank would be around 440ah at a standard 20h drain. And when I do the math, it seems like even my pc or music setup is drawing only 6-7amps/hour. Considering I only want to play an hour or two of games in a day, and I can't be running crazy speakers blasting dubstep, 20's jazz and Romanian Gypsy music, I'd say that it seems feasible with the system I'm currently designing.

So all that said, I've been looking at the 2 x 190 24v panels with Volt to Amp conversion in the MPPT to deliver a more constant voltage to the controller. I do this so that (theoretically) when I'm running a 6amp load in the middle of the day with sun shining, the system provides higher voltage to the controller, so that it can send (rather hypothetically) a high enough voltage, after losses in the wiring, to the inverter without having to dip into the battery storage.

That's probably going out on a rather large limb. But I've been reading about voltage drops, etc and it seems like having a higher voltage output would provide a more even 'lower' voltage from the MPPT to whatever I'd be running.

Maybe I'm WAY off. Please let me know.

So the largest panels I can buy with the smallest amount of wiring possible, to avoid as many losses as I can. I understand 24v from the panel to the MPPT avoids losses rather substantially. Am I wrong in this understanding?

[Naptown]

Grid-tie eh?

I'll look into it, but it sounds like it's meant for being in the city. This system is meant to be portable enough that I can pack it up in the RV and move ANYWHERE and have at least some electricity. This is definitely off-grid. I'm paying under $3/w from this guy. The other retailers want $7-9/w in my city. If I add HUGE shipping, etc from online, it seems I'm still paying more than $3/w for Poly Chrystalline, which I'm still not sure is worse/better than Mono Crystalline.

What I was wondering was whether I'd receive better results with 3 150w on PWM or MPPT or if the conversion of the 24v system into 12v with MPPT would would be worth the larger 190 panels.

I'm unsure if I should provide his website. The fellow in question has been running his company for 24 years now. He does automotive engineering and sells panels on the side. He also welds his own stands, etc. Seemed like a really cool guy and only carries pure sine inverters, and from my research, only high quality goods.

No grid tie generally refers to the output voltage. they are not necessarily compatable with batteries and PWM charge controllers.

What town do you live in where modules are $7-$9 a watt? I would be happy to ship there and include shipping for half that cost. (just kidding but those prices are a rip off. even the $3.00 is high. )

Take a look at our sponser Solartown they have a Canadian CS6P 230P 230 watt panel for $1.56 a watt. These are good quality modules. They will require an Mppt charge controller.

[Naptown]

One last thought before I take off to work.

The reason I've gone with the largest panels I can find is that the more I looked into this whole thing the more I realised that every cable, connectorconverter, etc is going to cost me efficiency in the entire system. So if I go with 3 60w grid-ties with micro inverters, I am going to lose a bunch in the extra wiring to make it a higher input system (more panels) You're suggesting a 180w system, which seems rather lacking.

Also, I'm planning on learning more about DC powered objects and running more of them. I've got a 12w 'soft white' LED floodlamp which is DC and the fridge I mentioned above is DC as well. There's a lot of really intelligent people on this farm and the likelihood of finding more DC loads seems rather likely. The inverter is likely to be used for all this in the tech world (PC, Laptop, amp/sub). These types of activities would be done in the day, whilst the floodlamp and dc fridge would be draining the night use.

The battery bank would be around 440ah at a standard 20h drain. And when I do the math, it seems like even my pc or music setup is drawing only 6-7amps/hour. Considering I only want to play an hour or two of games in a day, and I can't be running crazy speakers blasting dubstep, 20's jazz and Romanian Gypsy music, I'd say that it seems feasible with the system I'm currently designing.

So all that said, I've been looking at the 2 x 190 24v panels with Volt to Amp conversion in the MPPT to deliver a more constant voltage to the controller. I do this so that (theoretically) when I'm running a 6amp load in the middle of the day with sun shining, the system provides higher voltage to the controller, so that it can send (rather hypothetically) a high enough voltage, after losses in the wiring, to the inverter without having to dip into the battery storage.

That's probably going out on a rather large limb. But I've been reading about voltage drops, etc and it seems like having a higher voltage output would provide a more even 'lower' voltage from the MPPT to whatever I'd be running.

Maybe I'm WAY off. Please let me know.

So the largest panels I can buy with the smallest amount of wiring possible, to avoid as many losses as I can. I understand 24v from the panel to the MPPT avoids losses rather substantially. Am I wrong in this understanding?

No 100V+ to the Mppt charge controller will reduce the losses to a minimum.

[Khoogyra]

W00t!!

Thanks for the reply Sunking. I've read some of your posts and looked forward to meeting you.

So I see your point. That IS a HEAVY load. And my PC/Music system would require a much heavier system than I'm looking at from the looks of things. Do you think a 3rd 190w might help? It seems like I may be able to run my PC for an hour or so though. So it still seems feasible, considering I don't plan on gaming much.

... Wait, there's another post...

And I live in Vancouver Canada. I've called a couple of retailers and they all wanted $700+ for 150w panels... which I guess is still under $7... but after taxes it's still rather high.

I'm looking at Solartown. I wonder if they have a spot to pick up locally.

[Khoogyra]

Oi, those seem like nice prices, but I don't see any local pickup, which makes me think the prices in shipping must be astronomical. I really must head to work now, but I'll check out what it'd cost me when I get back.

If the shipping cost is right, I may trade the 125w panel in for an MPPT + xantrex 1000w inverter. And then I'd probably pick up 4 of those panels and a few batteries. But then... I still have to research into this company. I spent 8 hours looking up the last one and came out feeling pretty decent about it.

[noone]

I do not understand why people always say this.

First, give up the idea of cooking, with solar PV electric . If you have sun, get a solar oven - many brands exist.

Fridge - Most of the "mini" fridiges, consume as much as energy efficient full size models. Count on 1KWh usage a day for it. Thats going to need several panels, or more, depending on how many useable "solar" hours (10 am - 2pm roughly) you hae in your region.

Hi

OK I do agree for grid type cooking aplliances with an inverter but 12 volt cooking appliances can be great from PV and batteries.

Maybe not if you want to cook for hours but for simple cooking needs 12 volt and PV may be the thing many are looking for.

A 12 volt slow cooker uses around 10 amps so even that will only use around 30Ah for 3 hours ...that would be a bit much for many but might be ok for others.

Other 12 volt appliances use FAR less, as little as 10-20 watt hours and can even be used from a small battery as samll as 7 to 10 Ah with a small solar panel.
Yes I will kill a 7 Ah battery doing this but it is not as quick as many would think and will probably still be very economical.

I have also been experimenting with directly cooking form PV without a battery and it works very well so far (a bit more to do but i think it will be good pretty soon).

Armour on now!

[Khoogyra]

Woot! More discussion!

Thanks for the input. Indeed, the fridge I'm looking at is 12v. The crockpot, well... I haven't looked into it, but you make a good point that DC 12v is what I should be looking into for that solution. I'll look into more 12v appliances for things I want to run.

I mean, cooking is not the most important thing to run on electricity. We shouldn't get too hung up on that I think. I know how to make a woodgas stove. I've done it with cans and clay and had... scary, but inspiring results. 12' flames makes one realise why you don't want your air intakes to be a full soup can size wide...

So truth be told, running an inverter is going to be hard on a 380w 24v or 450-600w 12v, running at 500w or 750w AC. Is this correct? I'm still going to look into it more, but some friends have purchased a VIP ticket to 'The Avengers' and I got off work to see it.

I'll be back later on to see if anyone has any more input to this. I'm also looking into a Reverse Osmosis system. Does anyone have any good input for a 12v RO unit?

[Naptown]

So truth be told, running an inverter is going to be hard on a 380w 24v or 450-600w 12v, running at 500w or 750w AC. Is this correct? I'm still going to look into it more, but some friends have purchased a VIP ticket to 'The Avengers' and I got off work to see it.

I'll be back later on to see if anyone has any more input to this. I'm also looking into a Reverse Osmosis system. Does anyone have any good input for a 12v RO unit?

The higher the AC wattage the higher voltage the system should be.
As far as an RO system look into the marine ones. expensive but durable.

[russ]

The higher the AC wattage the higher voltage the system should be.
As far as an RO system look into the marine ones. expensive but durable.

For 12V the marine ones are probably the only option available.