Newbie system questions

[Particle]

Hello. It’s great to see that there is a community out there for off-grid energy. In my case, I only plan to experiment with it on a small scale as a hobby since I’m a renter. By contrast I see that many of you I see are quite invested.

When selecting components that I should buy, I had a few questions. I’m hoping that you guys might be able to shed some light in the form of answers to those questions I have.

1) Respected Inverter Manufacturers
I was surprised that there isn’t an easier to find list of inverter brands that are considered to be reliable in this world. I’ve gathered some brands from context during my research such as OutBack, ExelTech, and Xantrex. Other brands like Samlex, Go Power!, and Cotek appear to be a bit more affordable and perhaps exist as a second tier after the very expensive brands listed first. Can you guys list inverter brands along with how confident you feel in that brand name? It would also be good if you could list brands to absolutely stay away from (such as Power Jack, right?) or other generic buying tips. I’m trying to establish a gradient of affordability versus perceived reliability.

2) Respected Solar Charger Manufacturers
This is similar to the point above. There seem to be many inexpensive MPPT chargers on eBay. Charge controllers from the likes of Morningstar are many times more expensive for the same current capability. I suspect the danger is largely the same—cheaper controllers double as magic smoke shows. What brands of controllers are reliable? I’ve got a Steca 10A PWM controller right now that I’ve commandeered from my father. It seems to be a passable choice but I may want something MPPT later if this turns out to be fun.

3) Inverter?
Is there any particular reason to buy a traditional inverter as opposed to using a quality UPS if your goals are small? A $500 budget seems to be able to get a true sine inverter in the range of 1000W while that same budget could fetch a 3000 VA APC SmartUPS. They’re designed for prolonged usage, have true sine output, have load & battery indicators, and feature higher conversion efficiency (95%) than most of the inverters I’ve looked at. I’d just not plug it into the wall and use external batteries if I went that way. I’d probably get a 1500 or whatever the largest model that still features a 24V inverter inside would be and apply the saved money elsewhere.

4) MPPT vs PWM
As I understand it, MPPT is really only of a significant benefit when panels aren’t at peak production (shadowing, winter, clouds, etc). Is this correct?

5) Load Connection Point
Small charge controllers are fairly limited in terms of how much load current they can supply. Why is it that the load is usually connected to the charge controller instead of to the batteries directly? Is it just to be able to provide statistics and low battery voltage cutoff?

[waynefromnscanada]

Welcome to the form "Particle"
First, we need some info on you're proposed system. What to you, does "small hobby" mean? A 1000 watt inverter is not what most of us would consider small, or hobby.
What are you're planned, or expected loads?
That old saw: "Ready, Fire, Aim" comes to mind. It applies to many, many new solar projects who's owners make that mistake.
Re the controllers: Many of the cheap "junk" so-called controllers are not controllers at all, rather they are just voltage regulators. If you value you're batteris, get enough panel wattage to properly change them, and a proper controller to look after them.
MPPT controllers shine in cold weather, when they turn extra panel voltage into extra charging amps. They also allow the use of higher voltage, or non-standard voltage panels to be used to max advantage, and they allow higher voltages from the panels to be used for long wire runs with min power loss as they down-convert those higher voltages and turn those higher voltages into higher charging voltages. Nothing to do with non-peak production, or cloud cover etc.
Charge controllers and loads, inverters etc are normally connected to the same battery terminals, not different ones, and there is good reason for that.
Hope this helps, it's a start anyway and I'm sure others will join in.

[Cariboocoot]

1) Respected Inverter Manufacturers

You're on the right track, in my opinion. Ones that don't have recognizable brand names (or are "store brands") tend to be fly-by-night outfits that change models/specs/manufacturers more often than they change their socks. Within the "good" brands it's a matter of price/features/quality: for any given price weigh up the features in the different offerings. Some of that $ goes to value. For instance the small Samlex inverters have practically no surge time. Not important if you don't start motors.

2) Respected Solar Charger Manufacturers

As you suspect; same as with inverters. In my opinion the best MPPT controllers are MidNite and Outback. Morningstar makes the best PWM controllers. I am not keen on Xantrex products due to poor customer service/support and products that seem to be excessively "buggy", but they still have their place.

3) Inverter?
Is there any particular reason to buy a traditional inverter as opposed to using a quality UPS if your goals are small? A $500 budget seems to be able to get a true sine inverter in the range of 1000W while that same budget could fetch a 3000 VA APC SmartUPS. They’re designed for prolonged usage, have true sine output, have load & battery indicators, and feature higher conversion efficiency (95%) than most of the inverters I’ve looked at. I’d just not plug it into the wall and use external batteries if I went that way. I’d probably get a 1500 or whatever the largest model that still features a 24V inverter inside would be and apply the saved money elsewhere.

Make sure you are getting exactly what you think you are getting. As far as I know $500 UPS is not true sine nor designed for continuous use.

4) MPPT vs PWM
As I understand it, MPPT is really only of a significant benefit when panels aren’t at peak production (shadowing, winter, clouds, etc). Is this correct?

No. MPPT controllers offer these advantages: 1). greater flexibility in array design; 2). higher current output from any additional array Voltage. They can not make up for clouds, shading, et cetera. They can make up for "oddball" panels (Vmp not ideal for the battery Voltage) and long wire runs from array to controller (by utilizing higher array Voltage to reduce V-drop). In addition, when temps are cold panel Voltage rises and the MPPT controller can turn this into additional charge current. This also comes with a downside: the Voc will rise in cold temps too, and can exceed the controller's maximum input Voltage.

5) Load Connection Point
Small charge controllers are fairly limited in terms of how much load current they can supply. Why is it that the load is usually connected to the charge controller instead of to the batteries directly? Is it just to be able to provide statistics and low battery voltage cutoff?

Only light loads can be connected to the LOAD terminals on a charge controller. You see these chiefly on small PWM type controllers. This is designed to facilitate DC only systems where the load may be nighttime lighting (indeed Morningstar makes units that can detect dark and automatically turn the loads on). Never connect an inverter to these terminals. Larger charge controllers do not have "LOAD" connections. You can connect any size load to the batteries directly, providing the batteries can handle it, despite having a small charge controller (which may/may not be able to recharge the batteries). The rule in most cases is: batteries run the loads, charge controllers replenish the batteries (even though it may appear the loads are running off the controller and it may actually be supplying the full current need at the time).

[niel]

in general the old adage that, you get what you pay for, kind of holds true. there are other manufacturers that are good such as magnum and rogue. some others may be out there that are good, but we have focused on certain ones as are mostly applicable to the north american continent. europe does produce products that may be little known to us that could be applicable and of quality and china is slowly realizing garbage won't get them anywhere in our marketplace.

your steca is such a european product if i remember correctly and it will function fine. it is a pwm design that is of the shunt style. this can be bad as excess power is shunted to ground rather than series regulated that just feeds through that which it calls for. this means you don't want to put it at its max or more as it will heat it up and possibly blow it out.

as to mppt, in 90% of cases this is the best to have for battery run systems, but if you factor in costs this figure can be brought down further. oversimplifying it, an mppt controller is a dc to dc converter that adjusts itself to optimize the given input current and volts to better match up with that required for an output current and volts. now the drawbacks are the mppt will cost more and it will add a bit more power lost in self consumption to operate, but is usually a no brainer trade-off as you gain so much more in current compared to that consumed.

another avenue to take could be the grid tied way of solar which is more efficient (no batteries), but does nothing for periods of power outages. there are also a few hybrid inverters that will allow both gt and battery backup and this could allow smaller pv voltages and thereby allow smaller costs for pv strings. this means it may have some growth potential as well as being more versatile, but won't be as efficient as the batteryless gt system. sma and outback have some of these hybrids as does xantrex.

another gt inverter allows each pv to be separately inverted and tied to the grid (batteryless) like enphase and is often easy to expand upon even though reinspection of the installation may be required in each expansion. yes, inspections are often required for gt systems and are technically required for off grid systems too in many cases.

you need to get a better feel for what you want and what equipment can get you there. this is not always an easy task as it requires much learning. even we old farts constantly learn and as you start reading you'll come to know just how involved something like solar can get.

[Particle]

We're off to a good start, thank you both. As for "Ready, Fire, Aim", no worries. That's why I've posted here. I've only been researching and have so far spent exactly $0 on equipment.

First, we need some info on you're proposed system. What to you, does "small hobby" mean? A 1000 watt inverter is not what most of us would consider small, or hobby.

In my case, I consider this a hobbyist project since I have no plans to depend on it for anything. It's a project that will be done purely for the fun of seeing cool technology at work. I wouldn't need to store charge at the rate I'm using it at since using it will be infrequent.

What are you're planned, or expected loads?

Off most of the time. When on, less than 100W. I'd like to oversize it so that I at least have the option to play with larger loads stretching into the 750W range at times if desired.

Charge controllers and loads, inverters etc are normally connected to the same battery terminals, not different ones, and there is good reason for that.

Only light loads can be connected to the LOAD terminals on a charge controller.

This is good news because that's exactly what I would have preferred to do (and why I asked if it's safe). I thought it was kind of strange that the charge controllers would be involved in the discharge cycle, but coming from the outside that's just how things appeared to be.

---

Further notes: I'm planning on going with AGM batteries. A brand I've used in the past for other projects is Univeral Battery and I've come to like their products. I'd want to get a pair of 12V 55 Ah or 75 Ah batteries to run as a 24V bank to start with. Their 12V products run about $2/Ah. I'd probably need two series of them (as in 2S2P) to do 750W well. I gather that marine duplex cable works well for connecting to panels since it's UV resistant, double insulated, etc. I've also gathered that only authentic MC4 connectors should be used as knock-offs tend to suffer problems.

[Cariboocoot]

Further notes: I'm planning on going with AGM batteries. A brand I've used in the past for other projects is Univeral Battery and I've come to like their products. I'd want to get a pair of 12V 55 Ah or 75 Ah batteries to run as a 24V bank to start with. Their 12V products run about $2/Ah. I'd probably need two series of them (as in 2S2P) to do 750W well. I gather that marine duplex cable works well for connecting to panels since it's UV resistant, double insulated, etc. I've also gathered that only authentic MC4 connectors should be used as knock-offs tend to suffer problems.

Whoa on the AGM's. There's nothing wrong with them (or Universal Battery) but; they cost more per Amp hour and are unforgiving of mistakes. Very easy to make mistakes first time out with solar. Way too easy. This forum is full of posts about such mistakes!

Odd that you want to start out with 24 Volts, especially for such small power demands. 12 Volt can handle 750 Watts continuous without difficulty. (And I can't believe I'm suggesting someone go down to 12 V from 24!)

Anyway. What you can expect from 75 Amp hours @ 24 VDC: about 750 to 800 Watts hours @ 120 VAC. You won't need too much panel to recharge that either: perhaps as little as 60 Watts.

You will then immediately become addicted and want to build a bigger system. Just thought you should be warned.

[Particle]

I like the idea of a sealed battery, especially in a situation where I'll be living in the same space and won't be building a fume vent. A 24V system seemed desirable so that I could reduce system current. It will let me use smaller wire and should also help me get more capacity out of my batteries since the discharge curves will be much stiffer at the lower current. It does really throw a monkey wrench into inverter selection, however.

I was looking at panels and found a 190W Astroenergy module at affordable-solar.com for $230. It's just small enough to where it can be shipped FedEx for $25 which is convenient. Shipping via a commercial freight carrier would be expensive when it's just one panel. Does that seem like a reasonable choice?

[icarus]

Of all the "no name brand" charge controllers, the only one worth a darn IMHO is the Rogue. For the price it is a great controller, and a good value. a pretty god controller with good display function,which is important to a newbie.

as for inverters, the Morningstar Suresine 300 is very hard to beat. Very efficient, not very expensive, and very rugged. For a small battery system, there is little chance with few watts of panels and few ah of batteries that you are going to be powering anything bigger than 300 watts. The biggest (or nearly the biggest) mistakes that newbies make, is assuming that because they have a 1500 watt inverter, they should be able to power a 1500 watt load.

PV systems need to be balanced between the loads, the PV input potential, the battery size etc, and all calcs begin with the loads. Define the loads, and work backward to size the battery, PV , the inverter, charge controller and line voltge battery charger. Any other strategy is bassackwards?

Good luck and keep in touch.

Tony

[waynefromnscanada]

I too was going to recommend the Morningstar 300. as did Icarus, but since you plan on going 24 volts, that one is out :(
Too bad, as it's one of the best little inverters ever.

[Cariboocoot]

Both Exeltech and Samlex have small 24 Volt inverters. Of the two the Exeltech units are better in my opinion. Guess what; they cost more.

As Tony and Wayne said, the Morningstar 300 can't be beat for quality/price/performance. But it it 12 Volt only.