Extending time between recharges for my Delta Pro. Help please!

[melimelo]

I have a small 2 season off-grid cabin and one DP. I don't have the money to invest in a full PV system, but I am saving to buy a couple of panels to power the DP. Power consumption is basic at roughly 1 KWH per day (solar fridge, lightbulbs and laptop). I have been charging the DP with a generator every 3 days. All I want to do is up it to every 5 days so I don't have to empty the fridge in between weekends this summer. I am looking to buy 1 or maybe 2 solar panels for my east facing roof. No south facing available. Wondering what I should get (amps/volts) and configuration: 2s1p, 1s2p? Input would be greatly appreciated. Thank you community!!

 

[sunshine_eggo]

It depends on how much sun you get.

Your goal is to generate 1kWh/day.

For this, you need to determine your available solar at your exact location using the PVWatts link in line #1 of my signature. I ran it for North Bay, Canada:



1kW of panels facing due south tilted to 45°. No shade from sunrise to sunset.

You're interested in the Solar Radiation column.

That number is the average number of daily "solar hours" you get. You would divide your 1kWh of daily energy by these hours, so for April, 1000Wh/5.36 = 186W.

The site takes into account average weather, but it's still only looking at an average daily number. Some will be horrible and some will be notably better.

If the panels are shaded for part of the day, then that reduces your production. The bulk of production is from 9a-3p, so shade outside that time will be less harmful. Generally speaking, shade is as desirable as an incurable STD. It should be avoided at all costs when possible.

Let's plan for the worst case:

Jan is 2.21h

1000/2.21 = 452W

Assuming this unit:

https://websiteoss.ecoflow.com/cms/upload/2022/10/12/1312845623_1665543468829.pdf

Using typical 100W panels (22Voc, 6A Isc), you could arrange them in a 6S3P arrangement and stay under the 150V input limit (panel/string Voc) and the input current limit of 15A - the 15A can be exceeded. The unit will only draw a max of 15A even if more is available.

Based on MY analysis and your stated needs, I would choose at least a 600W array arranged in either 6S or 3S2P.

This should give you enough oomph to fully recharge your battery with a single good day of sun after 1-2 crap days.

It will be marginal in the coldest/worst weather months.

You don't have to use small 100W panels, but they seem to be more readily available to most. Larger panels can be used, you just need to respect the 150V (never exceed) and 15A (can exceed, but extra is wasted) limits.

 

[melimelo]

It depends on how much sun you get.

Your goal is to generate 1kWh/day.

For this, you need to determine your available solar at your exact location using the PVWatts link in line #1 of my signature. I ran it for North Bay, Canada:

View attachment 206484

1kW of panels facing due south tilted to 45°. No shade from sunrise to sunset.

You're interested in the Solar Radiation column.

That number is the average number of daily "solar hours" you get. You would divide your 1kWh of daily energy by these hours, so for April, 1000Wh/5.36 = 186W.

The site takes into account average weather, but it's still only looking at an average daily number. Some will be horrible and some will be notably better.

If the panels are shaded for part of the day, then that reduces your production. The bulk of production is from 9a-3p, so shade outside that time will be less harmful. Generally speaking, shade is as desirable as an incurable STD. It should be avoided at all costs when possible.

Let's plan for the worst case:

Jan is 2.21h

1000/2.21 = 452W

Assuming this unit:

https://websiteoss.ecoflow.com/cms/upload/2022/10/12/1312845623_1665543468829.pdf

View attachment 206486

Using typical 100W panels (22Voc, 6A Isc), you could arrange them in a 6S3P arrangement and stay under the 150V input limit (panel/string Voc) and the input current limit of 15A - the 15A can be exceeded. The unit will only draw a max of 15A even if more is available.

Based on MY analysis and your stated needs, I would choose at least a 600W array arranged in either 6S or 3S2P.

This should give you enough oomph to fully recharge your battery with a single good day of sun after 1-2 crap days.

It will be marginal in the coldest/worst weather months.

You don't have to use small 100W panels, but they seem to be more readily available to most. Larger panels can be used, you just need to respect the 150V (never exceed) and 15A (can exceed, but extra is wasted) limits.

Thanks for this detailed reply! I only use the cabin from April to October, so thw winter months don't matter so much. I used the PVWatts link years ago to calculate what I would need. My location and positioning of roof/shading are not ideal, for sure! I would have to cut down my whole wooded area to get unadulterated sun year round because the cabin sits at the base of a hill, with the trees to the south. That said, summer allows for direct and unfettered sunlight from 8am to 4pm, so that's something. I can only afford 2 panels at the moment, unless I buy second hand. Not sure if it is worth putting 2 panels up, seeing as they won't fully meet charging needs, but thought I'd try as an experiment. Thanks again for all the info. I really appreciate it!

 

[sunshine_eggo]

If 2 panels are 100W each, then you might fall short of 1000Wh/day of production; however, if you only generated 500Wh every day, that would extend your time between generator charging to 5-6 days.

500Wh EVERY DAY this time of year is very conservative, i.e., 200W * 5h = 1000Wh, so it's only the strings of inclement weather that will get you. Sunny days with 200W are almost certain to get the better part of 1000Wh with clear skies.

Money might be better spent looking for large used panels in your area. 100W panels typically cost about $100 each. You can often get 250W+ in larger used panels for about $100.

If you go 2X 100W panels, I recommend 2S.

 

[Brucey]

Add a couple cheap 12V batteries for poormans expansion? Ecoflow 12V 280Ah will give you 3.5kWh for $519:

https://www.amazon.com/ECO-WORTHY-280Ah-LiFePO4-Lithium-Off-Grid/dp/B0CJY4413M/

 

[melimelo]

Add a couple cheap 12V batteries for poormans expansion?

Thanks Brucey! Just so I understand, how would I "add" batteries to the ecoflow? The link you shared is for "ECO-WORTHY 12V 280Ah LiFePO4." Is this attachable to the Ecoflow?

Thanks again!

​

 

[Brucey]

Thanks Brucey! Just so I understand, how would I "add" batteries to the ecoflow? The link you shared is for "ECO-WORTHY 12V 280Ah LiFePO4." Is this attachable to the Ecoflow?

Thanks again!

​

Yes you would use something like this to connect the 12V battery to the ecoflow solar charger port.

Loading…

www.amazon.com

You would need to charge the 12V battery with an external charger, I like the Victron IP22 12/30 which can charge at up to 30A (completely user programmable via Bluetooth).

The downside is that you are going to be charging the Delta pro slowly from the 12V battery at 15A. However over many hours you can transfer a decent amount of power. You could use 24V batteries or two of those 12V 280Ah in series to double your charging speed (would need 24v version of the ip22 or another charger).

That's what I did with my Delta 2 max (two xt60i ports and max of 500W). Two 24V 100Ah batteries giving an additional 5kWh.

 

[melimelo]

Yes you would use something like this to connect the 12V battery to the ecoflow solar charger port.

Loading…

www.amazon.com

You would need to charge the 12V battery with an external charger, I like the Victron IP22 12/30 which can charge at up to 30A (completely user programmable via Bluetooth).

The downside is that you are going to be charging the Delta pro slowly from the 12V battery at 15A. However over many hours you can transfer a decent amount of power. You could use 24V batteries or two of those 12V 280Ah in series to double your charging speed (would need 24v version of the ip22 or another charger).

That's what I did with my Delta 2 max (two xt60i ports and max of 500W). Two 24V 100Ah batteries giving an additional 5kWh.

View attachment 206611

View attachment 206612

Nice setup! I think I understand. Just to be sure, where does the (victron) battery charger get its power to charge the battery in an off-grid situation? Do the solar panels plug into the battery charger? Now that I am writing this, I am not sure I really understand. Sorry, noob over here.

 

[sunshine_eggo]

If you have $700 to spend on battery/charger that still requires charging with generator, I would suggest that money would be WAY better spent on PV.

 

[melimelo]

If you have $700 to spend on battery/charger that still requires charging with generator, I would suggest that money would be WAY better spent on PV.

Of course, the generator powers the charger. That makes sense. I agree with going the PV route. I just want to get a few more days out of the DP that I already have. 5 would be great. I will look into second hand panels as suggested. I don't have $700 to spend at the moment, and most of the budget it will be eaten up by mounting hardware, cords etc.

 

[melimelo]

If 2 panels are 100W each, then you might fall short of 1000Wh/day of production; however, if you only generated 500Wh every day, that would extend your time between generator charging to 5-6 days.

500Wh EVERY DAY this time of year is very conservative, i.e., 200W * 5h = 1000Wh, so it's only the strings of inclement weather that will get you. Sunny days with 200W are almost certain to get the better part of 1000Wh with clear skies.

Money might be better spent looking for large used panels in your area. 100W panels typically cost about $100 each. You can often get 250W+ in larger used panels for about $100.

If you go 2X 100W panels, I recommend 2S.

Thanks! That is so clear.

 

[Brucey]

If you have $700 to spend on battery/charger that still requires charging with generator, I would suggest that money would be WAY better spent on PV.

Well his goal is to get from three days/3kWh to 5 days/5kWh between generator runs. This would get him to 6 days/6kWh of capacity. I would agree panels as well to reduce generator run time.

 

[Brucey]

Nice setup! I think I understand. Just to be sure, where does the (victron) battery charger get its power to charge the battery in an off-grid situation? Do the solar panels plug into the battery charger? Now that I am writing this, I am not sure I really understand. Sorry, noob over here.

I have a couple of Victron 150/35 chargers that I use with some Hyundai 300W panels.

 

[sunshine_eggo]

Well his goal is to get from three days/3kWh to 5 days/5kWh between generator runs. This would get him to 6 days/6kWh of capacity. I would agree panels as well to reduce generator run time.

I focused on this in the OP:

I have a small 2 season off-grid cabin and one DP. I don't have the money to invest in a full PV system, but I am saving to buy a couple of panels to power the DP. Power consumption is basic at roughly 1 KWH per day (solar fridge, lightbulbs and laptop). I have been charging the DP with a generator every 3 days. All I want to do is up it to every 5 days so I don't have to empty the fridge in between weekends this summer.

And I also missed this:

I am looking to buy 1 or maybe 2 solar panels for my east facing roof. No south facing available. Wondering what I should get (amps/volts) and configuration: 2s1p, 1s2p? Input would be greatly appreciated. Thank you community!!

That changes the math quite a bit.

@melimelo I would encourage you to look into ground mounting. Flat panels on the ground will perform better than East facing.

200W flat on the ground will get you the benefit you need April through August. Sep and Oct will fall short. However, if you can double it to 400W before September, that should get you through 1kWh/day in October.

400W and especially the 600W of solar I mentioned earlier has a high probability to significantly reduce the amount of generator running you need unless you start utilizing more power while you're on site.

Consider that if you eliminate a large portion of your generator fuel expense, you may pay for the panels very quickly and experience ongoing savings.

 

[melimelo]

Well his goal is to get from three days/3kWh to 5 days/5kWh between generator runs. This would get him to 6 days/6kWh of capacity. I would agree panels as well to reduce generator run time.

I'm a her by the way. But thanks for the ideas and input nonetheless.

 

[sunshine_eggo]

I'm a her by the way. But thanks for the ideas and input nonetheless.

Are you offended?

 

[Brucey]

I'm a her by the way. But thanks for the ideas and input nonetheless.

My apologies for the assumption

 

[Brucey]

Are you offended?

Did you send an inappropriate pic already?

 

[melimelo]

Did you send an inappropriate pic already?

Doesn't my "profile" pic give it away?