A simple, inexpensive, yet powerful solar storage system

[NW-Bound]

Generally, when wiring panels in parallel, you want a close match in voltage.

When wiring in series, you want a close match in current.

The question of course is when you have a bad mismatch, what will the penalty be.

I'm new to this, but I found this article explaining different setups of panels and how adding a low watt panel to existing panels can actually lower the total output.

https://solarpanelsvenue.com/mixing-solar-panels/

I just glanced through the article. Some of the combinations that he shows will not be quite as simple as he explains. It depends on how the MPPT controller looks for the optimal operating point. Many just latch on to a local maximum point of I vs V, while a few do a complete sweep.

 

[Sunset]

I'm testing out my Bluetti with the 12V cooler , just running off the Bluetti after fully charging it via the house outlet adapter.

Want to have an idea does it last 1 day or maybe 2 days without any solar input. So far after 6 hours it doesn't register any drop on the battery picture.

Also wondering, should I put a fuse between solar panels when I'm running four 100W panels in series, and how do I know the size of the fuse ?

I was also wondering does order matter, as in put my best (mono crystalline) panels first in the series, and then the poly ones ?

 

[travelover]

I'm testing out my Bluetti with the 12V cooler , just running off the Bluetti after fully charging it via the house outlet adapter.

Want to have an idea does it last 1 day or maybe 2 days without any solar input. So far after 6 hours it doesn't register any drop on the battery picture.

It is hard to determine charge level using voltage on a lithium battery, so I suspect the gauge will plunge suddenly as it nears full discharge.

Also wondering, should I put a fuse between solar panels when I'm running four 100W panels in series, and how do I know the size of the fuse ?

Normally solar panels don't need to be fused as their current is finite. Batteries need to be fused because they can deliver hundreds of amps and start a fire.

I was also wondering does order matter, as in put my best (mono crystalline) panels first in the series, and then the poly ones ?

Being in series, I don't think it would matter.

 

[meierlde]

I'm testing out my Bluetti with the 12V cooler , just running off the Bluetti after fully charging it via the house outlet adapter.

Want to have an idea does it last 1 day or maybe 2 days without any solar input. So far after 6 hours it doesn't register any drop on the battery picture.

Also wondering, should I put a fuse between solar panels when I'm running four 100W panels in series, and how do I know the size of the fuse ?

I was also wondering does order matter, as in put my best (mono crystalline) panels first in the series, and then the poly ones ?

The answer to the fuse size question is assuming depends on the voltages of the panels which once you sum them up divide 1000 by the voltage, and then allow 10 amps or so of overage, since the main reason is to prevent a short .

To the question of order it really should not make any difference as the resistances of the panels are all summed in this case.

 

[NW-Bound]

Different battery chemistries have different voltage characteristics. NMC or NCA cells have their voltage drop more linearly with the state of charge. LFP cells have a discharge voltage curve that is very flat in the center, with the drop getting accelerated near the end of charge.

Regarding the fuse size, you know the short-circuit current rating of the panels. That is the highest ever that the panels can put out under ideal conditions. An additional 25% margin is plenty.


Regarding the panel connection order, it does not matter as earlier posters pointed out. Nor does it matter if you wire them in parallel.

 

[NW-Bound]

Normally solar panels don't need to be fused as their current is finite...

It is true that the current output of solar panels is limited.

The only thing that a fuse at the PV input protects is the hazard of a short circuit in the line going from the panel string to the Bluetti.

With many MPPT chargers, shorting their PV input terminals while being connected to the battery will cause a very high current to flow from the battery through the charger and through the shorted terminals.

Also, if the panels are connected backwards, their series diodes will conduct and short out the path of this backdrive voltage.

Again, this depends on the design of the charging circuits.

One can test this as follows. Take a small 12V auto incandescent light bulb. Stick the wires to the PV input of the Bluetti to see if the bulb lights up.

 

[travelover]

It is true that the current output of solar panels is limited.

The only thing that a fuse at the PV input protects is the hazard of a short circuit in the line going from the panel string to the Bluetti.

........

I would expect the battery to be fused, as that is where the power needs to be disconnected if a short occurs.

 

[NW-Bound]

I would expect the battery to be fused, as that is where the power needs to be disconnected if a short occurs.

True. But, but, but...

As I recounted in an earlier post, two summers ago, I wanted to do a makeshift installation of some solar panels to get more power. And in the middle of the summer, the easiest way was to lay them down on the pool deck, and run long wires to the charge controller.

I miswired a panel with backward polarity. And I had no circuit breaker nor fuse in the line. It's 10-gauge wire, of 100 ft long (counting both + and - wires). The current flowing from the charge controller was high enough to cause the 10-gauge wires to be hot to touch when I was tidying them up to prevent tripping when I walked around the pool. And when I rushed to disconnect the panel, its 3 diodes had already been blown and shorted out.

The charge controller was connected to the battery with a 100A breaker. It did not trip. The long wires apparently had enough resistance to limit the current to under 100A, but it was still high enough to burn out the 10A diodes in the panel.

I have up to 8 panels connected to a charge controller, which pools the power to the battery. Hence the controller-to-battery circuit carries a much higher current than the individual circuit from the panels to the 80-A controller. In my permanent installation, I used 10-A circuit breakers for panels with a 7-A current rating.

So, YMMV. I agree that a fuse or circuit breaker may not be needed, but if you install one, know what fault it will serve to protect against.


PS. Right after I disconnected the miswired panel, I worried about the charge controller. This was an expensive Outback unit. Thanks goodness, it was OK. I was able to order the right diodes and replaced the burnt ones in the panel. Everything was honky dory afterwards.

 

[travelover]

......
The charge controller was connected to the battery with a 100A breaker........

I curious why you chose a 100 amp breaker. Generally the fuse or breaker is sized to protect the smallest gauge wire in the circuit.

 

[NW-Bound]

I curious why you chose a 100 amp breaker. Generally the fuse or breaker is sized to protect the smallest gauge wire in the circuit.

The output of the Outback controller is 80A. The output wires are big and only 4 in. long to reach the big DC system bus bars. There are 8 panels connected to this controller, and each panel is rated at 327W.

I have a total of 8 MPPT controllers in my system, but not all are 80A. Each is fused according to their rating.


PS. The ratings of my 8 controllers are as follows: 80A, 60A, 60A, 60A, 60A, 60A, 40A, 40A.

Not all of them are loaded to their ratings. I want to underload them for longevity. The outdoor ambient is hot at 120F. One of my 2400W inverters complained of overheating when delivering only 2000W. No overheat damage, but it turned itself off, and transferred the load over to the grid.

 

[travelover]

The output of the Outback controller is 80A. The output wires are big and only 4 in. long to reach the big bus bars. There are 8 panels connected to this controller, and each panel is rated at 327W.

I have a total of 8 MPPT controllers in my system, but not all are 80A. Each is fused according to their rating.


PS. The ratings of my 8 controllers are as follows: 80A, 60A, 60A, 60A, 60A, 60A, 40A, 40A.

Not all of them are loaded to their ratings. I want to underload them for longevity. The outdoor ambient is hot at 120F. One of my 2400W inverters complained of overheating when delivering only 2000W.

OK, I can see where you'd want a second fuse to protect the smaller wire.

 

[Sunset]

At my cabin in the woods.

I'm now running my 4 solar panels with the Bluetti to power a Massimo E-Kooler. It's been 2 weeks and all is good.

At first I had the panels on a roof, but could only get 2 hours of direct full sun. So I moved them to a spot where I get 4 hours.

We also use it to power cell phones and tablets and a couple of flashlights.

A 2 day stretch of rain got us nervous as the battery went to 2 bars.

I have the E-Kooler set at 35F.

I've seen the charging display peak at 390 watts, for brief periods.

This fun solar experiment is saving us 3 hours per week .

 

[ncbill]

Another limited option to power a room, including A/C & heat:

 

[Sunset]

My Bluetti 150 was a lot cheaper than the video guys.
I paid $800 and it's like this
Doing on my phone so may mess it up.
https://m.media-amazon.com/images/I/41745iJYxqS._AC_SY580_.jpg

 

[ncbill]

My Bluetti 150 was a lot cheaper than the video guys.
I paid $800 and it's like this
Doing on my phone so may mess it up.
https://m.media-amazon.com/images/I/41745iJYxqS._AC_SY580_.jpg

Yep, the guy in the video had to buy a high-capacity power station with 240VAC output given the mini-split he installed uses 240VAC.

As he notes had he known he could have put in a 120VAC mini-split, or just used a 120VAC window A/C instead, which is probably what I'd do.

 

[Chuckanut]

My Bluetti 150 was a lot cheaper than the video guys.
I paid $800 and it's like this
Doing on my phone so may mess it up.
https://m.media-amazon.com/images/I/41745iJYxqS._AC_SY580_.jpg

I notice that solar panels are not included. Does anybody know what that setup cost?

 

[travelover]

I notice that solar panels are not included. Does anybody know what that setup cost?

You could back out the cost by itemizing the individual components, but my take is that he spend more than necessary as he doesn't know much about electricity.
A cheaper and better approach would be the way NW has done it - buy some big a$$ used solar panels, a controller, inverter and some less expensive Chinese lithium batteries. That high efficiency window AC was a good find.

 

[ncbill]

You could back out the cost by itemizing the individual components, but my take is that he spend more than necessary as he doesn't know much about electricity.
A cheaper and better approach would be the way NW has done it - buy some big a$$ used solar panels, a controller, inverter and some less expensive Chinese lithium batteries. That high efficiency window AC was a good find.

The guy in the video I posted was already buying $60 used solar panels.

Using a power station eliminates all the wiring/fuses/etc. required by the above approach, and is portable.

I'm sure NW's system is much more powerful, but also more expensive and more hassle.

For just a room I'd use a cheaper window-mount A/C instead and just plug loads into the power station directly (no hardwiring, sub-panels, etc.)

When I win the lottery I'm putting this unit in between my meter & panel:

Plus buying 30kWh of rack-mount LFP batteries for the ultimate whole-house UPS.

 

[travelover]

..........Using a power station eliminates all the wiring/fuses/etc. required by the above approach, and is portable...........

I said it was less expensive not more convenient. And the guy in the video wasn't looking for portability.

 

[pb4uski]

Just charge phones in the car. No need to go someplace or even run the engine while you're doing it. Heating water with electricity generated with solar sounds unnecessarily complicated. Why not solve that issue with a simple propane burner ($29.99) and old fashioned percolator?
A 20# propane cylinder will last a long, long time just used for that.

I'm not suggesting that getting involved with solar is a bad idea. Just saying that the reasons you mention are really easy and convenient to solve using your car and propane.

When we're dry camping (I'm assuming this would be similar to your remote, off-grid cabin) we don't bother with solar despite many of our friends going to elaborate systems. We run the fridge, furnace and stove on propane. We power the the lights, furnace blower, vent fans and computer/phone charging off the house battery. When the house battery runs low, we charge it from the truck via jumper cables. If we aren't using the furnace, once a week does it. The furnace blower does have a significant draw, so in cold weather we might need to charge the house battery every other day.

I'm likely going to get some solar going before we leave for Florida next January just for the experience of learning the ins and outs. But we don't expect to be able to do anything with it we don't do without it now, at least as far as dry camping goes.

Great information in this thread!

I'm with you... sort of... in fact I just ordered a percolator for use on the propane stoves today. Back in February we went to the Everglades camping. DW made the reservation. So we get to our site and the first thing that I always do is find the water and electrical posts so I make sure to put the trailer far enough away so the slideout doesn't hit anything. So I'm looking and looking and guess what... no water or electrical hookup! It was just for a few days and I had water in the onboard water tank so we limped along on one 12v marine battery for a few days and I recharged the battery by plugging it into the truck a few times. Lesson learned though.

We're planning another trip to a number of national parks so I'm now looking into using solar to keep the batteries charged. Today, I also ordered a two battery box and a set of cables to wire them in series. I already have a one-year old 24DC EverStart Marine battery that is doing good and will probably just get another one.

Our travel trailer is already wired for solar via a Zamp sideplug (and I know that the Zamp plugs are "backwards")... from what I read the pre-wiring is just basically wiring from the side plug to the battery.

I'd like to get a solar panel, controller and wiring to keep the two marine batteries charged for lights, water pump, slide, awning, electric jack, etc. We'll use propane for the fridge, hot water and cooking and go without tv (we are camping after all). From what I read somewhere 140W would be the most that I would likely need.

One option I'm looking at is a 100w panel kit from Harbor Freight on sale for $170 but I'm very open to buying a higher quality kit or a panel, controller and wiring separately if I can get better quality even if I end up spending more. OTOH, I'm not interested in spending the $800 for a Zamp 140W kit. Another posibility is a $400 120w kit from Northern Tool that includes a Zamp connector so it would be pretty much plug and play.

https://www.harborfreight.com/100-watt-amorphous-solar-panel-kit-63585.html?_br_psugg_q=solar+panel
https://www.northerntool.com/shop/tools/product_200854290_200854290


Any suggestions?

I'm not planning on having an inverter as I don't care to mess around with my trailer wiring.

Sugggestions?

 

[ncbill]

I said it was less expensive not more convenient. And the guy in the video wasn't looking for portability.

Here's what the approach you mentioned entails:

Complete 48V Offgrid Solar Power System

More powerful, but a lot more hassle.

 

[travelover]

Here's what the approach you mentioned entails:........

More powerful, but a lot more hassle.

You don't need anything nearly that extensive to duplicate what the guy in the video did. All you need is a lithium battery, a controller and an inverter, plus the solar panels. All of which would fit in a box the size of a cooler (except the panels)


Example

https://www.amazon.com/LiFePO4-Battery-2000-5000-battery-Off-Grid/dp/B08Y7PN36G/ref=sr_1_1_sspa?

https://www.amazon.com/Renogy-Charge-Controller-Compatible-batteries/dp/B07G1PL1B9/ref=sr_1_3?

https://www.amazon.com/Renogy-1000W-Solar-Inverter-Cabin/dp/B07JMQ27WJ/ref=sr_1_5?

 

[pb4uski]

Question that will show that I have no idea what I am doing and just winging it.

I stopped in at Walmart to buy a second battery to convert my one-battery RV set-up to a 2-battery set-up.. Unfortunately, I hadn't noted the detail specs of the Walmart battery that I already had before going to the store.

The battery that already have that I bought about a year ago was 24MS, 675 MCA similar to this:

The one I bought today that I intend to use with the one that I already have is (actually it says 24XMS but same 1000 MCA):

Is using these together in parallell going to work ok?

 

[NW-Bound]

Even when the battery sizes are mismatched, they will still work OK when wired in parallel for applications with low drain currents.

However, an older battery may have a higher self-discharge, and it may end up draining the newer battery and ruining it. You may want to keep an eye on this.

Before wiring them together, charge them up independently. Then after a rest period of a few hours, measure their voltage and see if they are the same.

 

[Sunset]

Just charge phones in the car. No need to go someplace or even run the engine while you're doing it. Heating water with electricity generated with solar sounds unnecessarily complicated. Why not solve that issue with a simple propane burner ($29.99) and old fashioned percolator?
A 20# propane cylinder will last a long, long time just used for that.

I'm not suggesting that getting involved with solar is a bad idea. Just saying that the reasons you mention are really easy and convenient to solve using your car and propane.

When we're dry camping (I'm assuming this would be similar to your remote, off-grid cabin) we don't bother with solar despite many of our friends going to elaborate systems. We run the fridge, furnace and stove on propane. We power the the lights, furnace blower, vent fans and computer/phone charging off the house battery. When the house battery runs low, we charge it from the truck via jumper cables. If we aren't using the furnace, once a week does it. The furnace blower does have a significant draw, so in cold weather we might need to charge the house battery every other day.

I'm likely going to get some solar going before we leave for Florida next January just for the experience of learning the ins and outs. But we don't expect to be able to do anything with it we don't do without it now, at least as far as dry camping goes.

Great information in this thread!

[/QUOTE]I have found a faster way to percolate my coffee, since my solar system is too weak to cook coffee and do the other stuff.

I put the coffee pot on the burner full blast without the guts. Once it is boiling in about 5 minutes, I take it off the heat and drop in the pipe add the prefilled basket and top.
Put it back on the stove at low heat and coffee is ready in 5 more minutes .