Portable solar setup

[whoaru99]

Is anyone considering 24/36/48 volt systems instead of the more common 12V? My little charge controller can handle up to a 24V panel array and 12v or 24v battery, but 24V battery and 24v @ 10 amps from panel(s) is probably overkill for my little bubbly fountain project.

Most of it comes down to how much capacity you intend for the system to have. And, bear in mind, the panel side voltage and output/battery side voltage don't necessarily (and probably often) don't match.

For a small setup as you describe, there is not much pracical reason to go up in voltage.

But, if you're building a big system, then going higher in voltage helps a lot with the cabling as higher voltage means you can use smaller gauge, less expensive cables. For big systems drawing lots of current and/or having long runs not needing huge cables adds up to meaninful savings.

I have an installed 24V battery backup power system primarily for sump pumps, but it's not solar powered although the Samlex 2200W (EVO-2224 charger/inverter) has external DC input capability that could come from a solar setup.

I stay with 12V battery side for much of my stuff because I already had quality 1000W and 1500W pure sine inverters that run on 12V. In a pinch 12V batteries are all over and I don't need to scrounge up multiples to make 24V or 48V on the battery side if push comes to shove.

But, even though for now I'll be staying with 12V battery voltage, I'll probably be at ~48V panel input to charge controller with a series/parallel arrangement of the four 200W panels I have.

If I were installing or building out a bigger system several kW or bigger it only makes sense to go up in voltage on both panel and battery sides. But, again, for small system, not really.

 

[whoaru99]

Is anyone considering 24/36/48 volt systems instead of the more common 12V? My little charge controller can handle up to a 24V panel array and 12v or 24v battery, but 24V battery and 24v @ 10 amps from panel(s) is probably overkill for my little bubbly fountain project.

On another directly related note, have you figured out the actual power draw of the fountain and know the solar panel watt rating?

The whole basis of self sustaining is power in has to be more than power out. If one doesn't really know where it's at in that regard then the opportunity is ripe to miss the boat and/or throw parts at it.

 

[RickeyM]

A coupe of things working here. Considering the size of the original solar panel and the low cost of the set up I'd be amazed if the panel has more than a 10 or 15 watt output. Same thing with the pump. Not likely the setup having a high watt draw pump. That would necessitate a higher output solar panel upping the system cost. I've seen smaller pumps that draw between 4 to 10 watts. It's pretty much a given that a panel output of 40 to 50 watts (or higher) would be needed to run the pump and charge a partially discharged battery. Next, forgoing using the small power station which really isn't designed for continueous use, a battery connected to that panel through the solar charge controller I already have would be used for continueous pump pumping. So, for the project a modest panel and battery need to be sourced. In the meantime, coming up with a budget friendly DIY fountain

 

[hjames]

My neighbor put a pair of small panels on his shed-roof with a small portable battery pack inside. He said the only fear is to not let the battery get below freezing, so he brought it indoors during the coldest stretch of winter. I believe he said the battery pack is 1500 watts - to run his fridge for a day or so if we get a power outage.
I think he is at under $500, overall.

 

[whoaru99]

My neighbor put a pair of small panels on his shed-roof with a small portable battery pack inside. He said the only fear is to not let the battery get below freezing.

If it's a LiFePO4 battery then, yeah, they have some cautions in cold weather. They can be used cold but they do not like to be charged cold. A good BMS will cut off charging below a certain temp to preclude battery damage.

There are versions with internal heaters for those cold weather use cases. May not be important enough is this case, but just mentioning as FYI/FWIW.

If it's lead acid battery, a long as it stays fully charged they don't freeze until like -70f. Fully discharged, yeah, freeze about the same temp as water.

 

[hjames]

If it's a LiFePO4 battery then, yeah, they have some cautions in cold weather. They can be used cold but they do not like to be charged cold. A good BMS will cut off charging below a certain temp to preclude battery damage.

There are versions with internal heaters for those cold weather use cases. May not be important enough is this case, but just mentioning as FYI/FWIW.

If it's lead acid battery, a long as it stays fully charged they don't freeze until like -70f. Fully discharged, yeah, freeze about the same temp as water.

He explained it was a lithium battery, but not the same as the ones in our cordless yard gear that have the fire hazard if overcharged ...
It all sounded very positive -

I'd love to go with some cells on our roof, arranged around and between the skylights, but until that 80' tall tree in our front yard ages out
and we have it removed, there isn't enough full sun to help match the expense of panels.

 

[RickeyM]

The swell thing about solar power is, as long as you can get sunlight to your panels, you can start small and scale up.

 

[egellings]

It is just an idea. Using diodes to wire OR the controller outputs will ensure isolation of the controller from each other and still work together in charging the battery.

Use Schottky diodes for minimum forward voltage drop, if you can find them with the required forward current rating.

 

[whoaru99]

The swell thing about solar power is, as long as you can get sunlight to your panels, you can start small and scale up.

Yes and no. Whilst it's not inherently a show stopper to mix and match stuff, there are some practical implications/limitations of doing that with different panel ratings of current and voltage.

The ultimate in flexibility could be a microinverter type system where each panel sorta works as an independent contributor to the collective. But, then there are different twists and turns to have battery backup with microinverter systems.

End of the day, establishing what the big picture might look like in a way to accomodate updates/expansion would be the ideal way rather than try to piece it along and hope it plays nice together.

 

[RickeyM]

Yes and no. Whilst it's not inherently a show stopper to mix and match stuff, there are some practical implications/limitations of doing that with different panel ratings of current and voltage.

The ultimate in flexibility could be a microinverter type system where each panel sorta works as an independent contributor to the collective. But, then there are different twists and turns to have battery backup with microinverter systems.

End of the day, establishing what the big picture might look like in a way to accomodate updates/expansion would be the ideal way rather than try to piece it along and hope it plays nice together.

If I were doing a supplimental type solar power system I'd stick with multiples of the same panel. Sticking with established brands so more likely the same model panels would still be available down the road. With an inverter/charge controller of sufficient capacity without having to replace expensive components down the road.

 

[whoaru99]

Got one of the 305Ah batteries finished and on the charger. Not really much to look at from the outside.

Pretty good cell balance though for Grade B cells that haven't been touched in a year or two.





That battery box worked out pretty well. Think I'll go with another like it for the other 305Ah.

 

[Te-Te]

Interesting thread, thanks for starting it.

We were talking about portable panels yesterday. As a possible was to slow down the electric meter.
My wife saw some news about availability, there was also a quote from Eversource that their meters are not equipped to handle the back feed and will actually charge you for the power you generate. Hmmmm...it's either sour grapes or they designed it that way on purpose.

I wouldn't mind a temporary set up to power my inflatable hot tub all summer.

I always wondered about the back feeding aspect as far as safety to line workers go.
If there is work being done on the street and they think the power is cut, but someone is back feeding them?
If the homeowner knows to shut the main breaker off it's fine. But what if they don't?
I wonder if this is why Eversource isn't keen on doing that.

 

[whoaru99]

I always wondered about the back feeding aspect as far as safety to line workers go.
If there is work being done on the street and they think the power is cut, but someone is back feeding them?
If the homeowner knows to shut the main breaker off it's fine. But what if they don't?
I wonder if this is why Eversource isn't keen on doing that.

There are regulations/rules that dictate equipment and lockouts to prevent that from happening.

But, of course, it all relies on people doing it the right way. None of the right ways rely only on someone remembering to shut of a breaker/switch to prevent backfeed.

The very simple form of interlock installs in the breaker panel. It physically blocks the backfeed breaker from being switched on until the main breaker is first turned off. Then, conversely, it blocks the main breaker from being turned on until the backfeed breaker is first turned off.

Then it gets fancier from there with other forms of transfer switches that allow one or the other input but not both, can be manual, can be automatic, grid tie inverters, etc., etc..

 

[Te-Te]

There are regulations/rules that dictate equipment and lockouts to prevent that from happening.

But, of course, it all relies on people doing it the right way. None of the right ways rely only on someone remembering to shut of a breaker/switch to prevent backfeed.

The very simple form of interlock installs in the breaker panel. It physically blocks the backfeed breaker from being switched on until the main breaker is first turned off. Then, conversely, it blocks the main breaker from being turned on until the backfeed breaker is first turned off.

Then it gets fancier from there with other forms of transfer switches that allow one or the other input but not both, can be manual, can be automatic, grid tie inverters, etc., etc..

Thank You for that information. I never had to deal with such a situation, so I always wondered what would need to be properly and legally done.