Two "free" solar panels

[SunEagle]

Just took a look on Amazon on the recommended controller, i.e. a MS TS 45 MMPT. Pricey little booger! I accept the advice already given that I need an MMPT controller, but was just wondering if a more economical controller might be available? Especially given the fact that this is kind of an experimental project. (looks like Mike's prediction is coming true regarding the "free sheep")

It comes down to which is less costly.

A cheaper PWM CC will only use about 67% of the panel wattage once you get above 200 watts. So you end up purchasing more solar panels to get the wattage you need.

A cheaper MPPT CC may use a higher percentage but may also not have the ability to set the proper charging voltage for all types of batteries. There are also fake MPPT CC which are very cheap and should be avoided.

A quality MPPT gives you both the usage of about 98% of your panel wattage, along with multiple charging setups. They are also built better and will last a lot longer.

So yes that MS TS 45A is not cheap but it is also much better in quality then a non name brand.

The choice is up to you.

[smily03]

Out of random curiosity, what's the expected lifetime of a TS-MPPT-45 vs like a PWM TS-45? (Assuming, of course, that they're kept in good environmental conditions, etc.)

[Cajun Bill]

It comes down to which is less costly.

A cheaper PWM CC will only use about 67% of the panel wattage once you get above 200 watts. So you end up purchasing more solar panels to get the wattage you need.

A cheaper MPPT CC may use a higher percentage but may also not have the ability to set the proper charging voltage for all types of batteries. There are also fake MPPT CC which are very cheap and should be avoided.

A quality MPPT gives you both the usage of about 98% of your panel wattage, along with multiple charging setups. They are also built better and will last a lot longer.

So yes that MS TS 45A is not cheap but it is also much better in quality then a non name brand.

The choice is up to you.

Good info Sun Eagle. Here is my dilemma: I don't know what I don't know, but I am learning fast. Even so, I'm guessing that I will not be enlarging this system so can I get by with a "chevrolet", at least for a little while, or should I go with the "cadillac" from the get-go? I know that quality costs and I don't mind paying for quality if it is the best route to go. Guessing that the cheapo MPPT controllers are Chinese junk, but not sure. Thinking of going with something like this just to start with and if everything works well, upgrading asap to the "cadillac". Found this at Amazon, but only two reviews https://www.amazon.com/Y-SOLAR-Solar...op?ie=UTF8#Ask

LittleHarbor, the inverter is a PSW Xantrex (don't remember the wattage, but I think it's 1500W), so I'd like to stay with a 12V system. I will look at the Midnight Solar Kid you recommended.

All good info so keep them coming.

[Cajun Bill]

It comes down to which is less costly.

A cheaper PWM CC will only use about 67% of the panel wattage once you get above 200 watts. So you end up purchasing more solar panels to get the wattage you need.

A cheaper MPPT CC may use a higher percentage but may also not have the ability to set the proper charging voltage for all types of batteries. There are also fake MPPT CC which are very cheap and should be avoided.

A quality MPPT gives you both the usage of about 98% of your panel wattage, along with multiple charging setups. They are also built better and will last a lot longer.

So yes that MS TS 45A is not cheap but it is also much better in quality then a non name brand.

The choice is up to you.

Good advice Sun Eagle. Was just wondering if I got get by with a "chevrolet", at least for awhile, rather than a "cadillac" until I see if this system will work in the way I want it to work. I found this on Amazon https://www.amazon.com/Y-SOLAR-Solar...op?ie=UTF8#Ask. I realize it is probably a Chinese cheapo, but might give me an idea if I want to go forward.

Little Harbor: I'll take a look at the one you suggested and as an FYI, my inverter is a PSW Xantrex, 1500W I think.

Once again, until I can get back to my camper, I can't get finalized info to see if it works out on paper.

[SunEagle]

Good info Sun Eagle. Here is my dilemma: I don't know what I don't know, but I am learning fast. Even so, I'm guessing that I will not be enlarging this system so can I get by with a "chevrolet", at least for a little while, or should I go with the "cadillac" from the get-go? I know that quality costs and I don't mind paying for quality if it is the best route to go. Guessing that the cheapo MPPT controllers are Chinese junk, but not sure. Thinking of going with something like this just to start with and if everything works well, upgrading asap to the "cadillac". Found this at Amazon, but only two reviews https://www.amazon.com/Y-SOLAR-Solar...op?ie=UTF8#Ask

LittleHarbor, the inverter is a PSW Xantrex (don't remember the wattage, but I think it's 1500W), so I'd like to stay with a 12V system. I will look at the Midnight Solar Kid you recommended.

All good info so keep them coming.

I understand your feelings. What I am trying to do is keep you from wasting your money like I did.

I built a small 420 watt solar/battery system using 3 x 80w & 2 x 90 watt panels along with a low cost 30A PWM charge controller. If I had made the right decision it would have been to get 2 x 200watt panels and a 30Amp MPPT CC. Just doing that I would have saved at least $300.

The reason is that my PWM is turning that 420 watts system to less than a 300watt based on how it works. So I ended up buying more panel wattage at $2/watt and pretty much throwing it away due to the inefficiency of my PWM CC

[Sunking]

Thanks for the encouragement Sunking. Just a clarification, this will be connected in my shop, not my RV. The batts, power monitor and inverter will be taken out of my fifth wheel as I am planning on selling it soon anyway and downsizing, The panels are not RV panels, they were intended for a residential installation. Additionally, I have four 6V GC batts, not two so that should be even better I'm sure.

Does not matter what kind of panels they are. The only thing it changes in my answer is to leave out the RV part. You need to run 24 volts, then you can use a less expensive 15 to 20 amp controller. MPPT Controllers has power input limitations based on battery voltage. So let say you have a 20 amp MPPT controller. Power Input vs Battery Voltage are.

48 volts @ 1200 watts
24 volts @ 600 watts
12 volts @ 300 watts

A good 20 amp MPPT Controller cost roughly $175 to $225. A good 40 amp unit cost around $350 to $400. So hopefully you can tell running 24 volts is a lot less expensive than 12 volt. Run 24 volts. You already have the batteries to do it.

I just saved you $200

[Cajun Bill]

Okay, that makes sense, but will I be able to use my Xantrex PSW inverter or do I have to purchase another one?

[SunEagle]

Okay, that makes sense, but will I be able to use my Xantrex PSW inverter or do I have to purchase another one?

If you keep the battery system voltage the same as the Xantrex you should be ok. Unfortunately if you decide to enlarge your system then going to a higher battery voltage is the right thing to do. But then you would have to replace that Xantrex with a different one.

By the way my inverter is a 12v Xantrex PSW rated 600watts which is a nice unit.

[Cajun Bill]

If you keep the battery system voltage the same as the Xantrex you should be ok. Unfortunately if you decide to enlarge your system then going to a higher battery voltage is the right thing to do. But then you would have to replace that Xantrex with a different one.

By the way my inverter is a 12v Xantrex PSW rated 600watts which is a nice unit.

That's what I was thinking, but as Sun King pointed out, then I've got to buy a more expensive controller. That's why once I figure out the load (I have a Kill-a-Watt in the RV, but can't get to it now), if the inefficiencies of the cheaper PWM won't affect the outcome i.e. they produce enough charging capacity anyway, I may try to get by with a cheapo temporarily and then upgrade later. The panels are what they are and I don't plan to buy more, the batts are what they are and I don't plan to buy more, the inverter is what it is and I'd rather not replace it, so the only "wild card" that I can control is the controller IMHO (pun intended).

[Sunking]

Your panels and batteries are just fine. Keep in mind at 12 volts takes twice as much current as 24 volts.

At 560 watts of panels requires a 40 amp Controller operating into a 12 volt battery, and only 20 amps into a 24 volt battery. A 40 amp MPPT is $400, a 20 amp is $200 which can pay for a new higher voltage inverter. Just something to think about.

[Cajun Bill]

Your panels and batteries are just fine. Keep in mind at 12 volts takes twice as much current as 24 volts.

At 560 watts of panels requires a 40 amp Controller operating into a 12 volt battery, and only 20 amps into a 24 volt battery. A 40 amp MPPT is $400, a 20 amp is $200 which can pay for a new higher voltage inverter. Just something to think about.

Good point! Now I need to start thinking about the actual wiring and how to mount the panels on my shop roof. While I have to mount them on the opposite slope of the roof because of trees behind my shop, the pitch of the roof is only about 1 on 12. Should be easy to mount them so they are flat, facing straight up, but I can't point them in a southerly direction due to the trees. I'm sure that will limit the amount of sun exposure during the fall/winter, but is that a deal killer? Gonna research mounting and wiring next.

[SunEagle]

Good point! Now I need to start thinking about the actual wiring and how to mount the panels on my shop roof. While I have to mount them on the opposite slope of the roof because of trees behind my shop, the pitch of the roof is only about 1 on 12. Should be easy to mount them so they are flat, facing straight up, but I can't point them in a southerly direction due to the trees. I'm sure that will limit the amount of sun exposure during the fall/winter, but is that a deal killer? Gonna research mounting and wiring next.

The direction of the panels is not a deal breaker except if that is North. The best is usually directly South but West does work especially if you have a good view of the sunset.

What it comes down to is the amount of good sunlight your harvest. Anything but South is less than the 100% you hope to get.

[Logan5]

If you go with a 24 volt system you can obtain an extremely efficient chest type refrigerator/freezer that runs directly from the 24 volt bank, w/o the need to run an inverter at all. If you run an inverter only to maintain a refrigeration load, your inverter waste a moderate to large amount of energy wile waiting to supply the actual load. If the refrigeration only engages for 15min's per hour, your inverter burns 10 to 30 wh the other 45 min's of the hour. If you are already cool with the top load freezer, top load refrigerator is easy to adapt to as well.

[Cajun Bill]

Actually, the whole point of this exercise is to see if I can use these "free" panels to run my existing freezer and/or fridge that are presently in my shop already so I'm not interesting in buying a new freezer and/or fridge. If I can't keep the costs down to the point that I can get payback in as few months/years as possible, I probably won't even start the project. At this point, it's a paper exercise that, so far, is only going to cost me for a controller and possibly a new inverter. Can someone give me a source for mounts? I'm interested in one's made for metal roofs. I suspect that I can fabricate something myself, but would help to get some ideas from viewing products made for that.

[Logan5]

Actually, the whole point of this exercise is to see if I can use these "free" panels to run my existing freezer and/or fridge that are presently in my shop already so I'm not interesting in buying a new freezer and/or fridge. If I can't keep the costs down to the point that I can get payback in as few months/years as possible, I probably won't even start the project. At this point, it's a paper exercise that, so far, is only going to cost me for a controller and possibly a new inverter. Can someone give me a source for mounts? I'm interested in one's made for metal roofs. I suspect that I can fabricate something myself, but would help to get some ideas from viewing products made for that.

With batteries payback will never happen, regardless of inverterless system. Even with free panels. battery systems will always cost more than PoCo in most of the US. running a mains powered chest freezer and or refrigerator from an inverter can use nearly 2X the watts or more than running a native DC refrigeration appliance, If your inverter uses 10 watts just to make AC power avail, yet freezer only cycles on for 12 min's every hour or so, you waste a huge amount of energy just waiting for the actual load. If you do plan to do this, make sure you run a 24 volt battery bank so you can take advantage of a 24 volt inverter. You will also want an MPPT charge controller to take advantage of your full array. Although Refrigeration is possible at 12 volts it only starts to becomes practical at 24 volts. Unless a quality LVD is employed you will be replacing the battery bank annually or worse.