Panel Placement and Wiring Options

Hi there,

We are in the midst of planning our DIY solar build at our northern ontario camp this summer. We have already purchased a battery (Kedron 24v 300a) and inverter (SRNE 24v All-in One). We are now looking at panels, mounting options, and wiring and have some questions.

System size is small. No electric heat, propane fridge and stove. LED lights, and occasional TV/Microwave/toaster use. We do have a 3/4 1ph jet pump that pumps water up from the lake, that is our only large draw. We also have a generator (firman open frame) that will be hooked up to the inverter/charge controller, provided it doesnt have too dirty of power to trip the switch. If it does we will be looking into inverters.

The panels I am looking at are 2, maybe 3 Q Cell 480w panels. My though here is that they have a High Voc (53.6) so I will have plenty of room on shady days to get over 24v for the battery.

As for orientation, we had thought to mount them on the south east facing roof of the cottage. I have attached a screenshot from SunCalc of the property. It is a large treed hill to the south which is going to limit our efficiency. We had though that we could split the panels between different sides of the roof, but that may end up doing more harm then good with the shadier panel drawing from the sunnier one if I understand my reading correctly. The other option is to put the panels on some sort of ground mount in the north east corner of the lake-side lawn. I am starting to think this may be the best option, though digging a trench for the wire would be a handfull.

As I take it, Wiring 2 panels in series, would be the best option if they are in similar lighting conditions? Am I right in assuming that these panels in series would overpower my inverter, which has a 100V limit?

So if I use the Q Cell, any amount would need to be in series?

Thanks in advance,

Jordan

Whitty21 said:

As I take it, Wiring 2 panels in series, would be the best option if they are in similar lighting conditions? Am I right in assuming that these panels in series would overpower my inverter, which has a 100V limit?

Click to expand...

You are right. Two panel in serie will blow the MPPT of the inverter.
You can put 2 or 3 panels in parallel and that will work fine. This will give you more power in case of shade.
With all the trees on the picture I guess shade could be an issue.

We have already purchased a battery (Kedron 24v 300a)

Click to expand...

Ouch! 3500$ really? That near 500$/kWh.
Many LFP batteries are now available at 150-250$/kWh

Whitty21 said:

We had though that we could split the panels between different sides of the roof, but that may end up doing more harm then good with the shadier panel drawing from the sunnier one if I understand my reading correctly. The other option is to put the panels on some sort of ground mount in the north east corner of the lake-side lawn.

Click to expand...

Putting panels in parallel will be fine. I have four different arrays that do this. The contractors for my solar build set up 4S4P.

If you want, you can look at blocking diodes which prevent a "backload" to parallel strings in an array. It may actually use more energy for the diode than you save in parallel. I would feel safe in saying not using a blocking diode for parallel array is an accepted practice.

yabert said:

You are right. Two panel in serie will blow the MPPT of the inverter.
You can put 2 or 3 panels in parallel and that will work fine. This will give you more power in case of shade.
With all the trees on the picture I guess shade could be an issue.

Ouch! 3500$ really? That near 500$/kWh.
Many LFP batteries are now available at 150-250$/kWh

Click to expand...

They have yet to ship the battery so I may have some discourse still. When we planned this back in october, Kedron seemed like the best deal at 24v. We had planned to do 24v batteries for expandability if we wanted, as for as I understand, I would be capped at 2 12v batteries as you can't run multiple groups of batteries in parallel. Do you have a recommendation? I see renology has 12v 300 on sale right now, as well as victron.

Whitty21 said:

Do you have a recommendation? I see renology has 12v 300 on sale right now, as well as victron.

Click to expand...

I don't see how Renogy can suggest to put 12V batteries in series as there is no communication between batteries. So I suggest you yo stay with a 24V battery for your 24V inverter.
Other people will probably have better recommendation for new 24V battery as I usually play with used EV battery I paid 40-80$ / kWh.
But simply look at Li time of Redodo and compare with Kedron.
1x Kedron 300Ah = 7.68 kwh for 3500$
2x Redodo 200Ah = 10.24 kWh for 3000$

Edit. Still 2x Renogy 24V 200Ah are 10.24kWh for 3800$

My next question would be regarding wiring them to the panel. As I understand, 10g panel wire is good for 30 amps. the open current of the Q Cell panel is 11.26, meaning I could only have 2 per strand. I imagine this would stop me from using 2-1 or 3-1 connectors and force me to use a combiner box? or am I wrong?

Whitty21 said:

My next question would be regarding wiring them to the panel. As I understand, 10g panel wire is good for 30 amps. the open current of the Q Cell panel is 11.26, meaning I could only have 2 per strand. I imagine this would stop me from using 2-1 or 3-1 connectors and force me to use a combiner box? or am I wrong?

Click to expand...

Yes. It stopped me from doing that and have a combined box.

You can get 3 to 1 connectors that will do that, but im doubtful it’s properly rated. If it is, getting a MC4 rated above 30 amps to connect to it and then the SCC could be hard.

yabert said:

I don't see how Renogy can suggest to put 12V batteries in series as there is no communication between batteries. So I suggest you yo stay with a 24V battery for your 24V inverter.
Other people will probably have better recommendation for new 24V battery as I usually play with used EV battery I paid 40-80$ / kWh.
But simply look at Li time of Redodo and compare with Kedron.
1x Kedron 300Ah = 7.68 kwh for 3500$
2x Redodo 200Ah = 10.24 kWh for 3000$

Edit. Still 2x Renogy 24V 200Ah are 10.24kWh for 3800$

Click to expand...

Not to mention 2x EG4 LifePower4 200Ah = 10.24kWh for $2600

AZ Solar Junkie said:

Not to mention 2x EG4 LifePower4 200Ah = 10.24kWh for $2600

Click to expand...

We are talking Canadian monopoly money. Even if they shipped to canada the EG4 batteries would cost $3490 before customs and shipping. Thanks for the input though

Whitty21 said:

We are talking Canadian monopoly money. Even if they shipped to canada the EG4 batteries would cost $3490 before customs and shipping. Thanks for the input though

Click to expand...

Gotcha - gulp

Whitty21 said:

My next question would be regarding wiring them to the panel. As I understand, 10g panel wire is good for 30 amps. the open current of the Q Cell panel is 11.26, meaning I could only have 2 per strand. I imagine this would stop me from using 2-1 or 3-1 connectors and force me to use a combiner box?

Click to expand...

Another option for you is to use panels with lower Voc.
Some panels have around 36-40Voc, so you can put them in series and reduce Amps.
At you place I would consider 4 panels in a 2S2P arrangement .... you will never have enough panels
Panel are really cheap now. As example I had a quote for Trina 470W for 300$ each. But you have to search because some seller still sell at high price (like 0.8$ to 1.0$ / W)

You will see anywhere on this forum price of 0.20-0.25$ / W, but it's in US and for complet pallet at discount.

yabert said:

Another option for you is to use panels with lower Voc.
Some panels have around 36-40Voc, so you can put them in series and reduce Amps.
At you place I would consider 4 panels in a 2S2P arrangement .... you will never have enough panels
Panel are really cheap now. As example I had a quote for Trina 470W for 300$ each. But you have to search because some seller still sell at high price (like 0.8$ to 1.0$ / W)

You will see anywhere on this forum price of 0.20-0.25$ / W, but it's in US and for complet pallet at discount.

Click to expand...

Its looking like we are likey going to do just this. 2 ~500w panels at ~38Voc.

Also want to thank you for noting the battery price. Ended up canceling the Kedron order and ordering 2 200ah 24v Redodo batteries, already have them at home. Saved us $700 and got us an extra 100ah.

Why are people still using low voltage MPPT when high voltage MPPT gives such superior performance- especially in poor generating conditions (which I suspect Canada would count lol)

A good high voltage system would run rings around a PWM or low voltage MPPT system...

If you were wedded to using a particular hybrid inverter with inbuilt low voltage MPPT controllers, then simply adding external high voltage MPPT controllers will allow charging in poor lighting conditions that the inbuilt ones simply won't function in...

Whitty21 said:

Also want to thank you for noting the battery price.

Click to expand...

You are welcome. Let us know if they work great for you. I never used Redodo battery.

Its looking like we are likey going to do just this. 2 ~500w panels at ~38Voc.

Click to expand...

1kW to charge a 10 kWh battery. That will be really long and probably take 2-3 sunny days to charge during october to march period.
I have 1.5kW to charge 3 kWh battery at home and despite during summer the battery is almost always fully charge before noon, in the winter it need more than a sunny day to charge.
Simply keep that in mind.

yabert said:

You are welcome. Let us know if they work great for you. I never used Redodo battery.

1kW to charge a 10 kWh battery. That will be really long and probably take 2-3 sunny days to charge during october to march period.
I have 1.5kW to charge 3 kWh battery at home and despite during summer the battery is almost always fully charge before noon, in the winter it need more than a sunny day to charge.
Simply keep that in mind.

Click to expand...

This is just our hunt camp. Longest we stay up there is a week at a time max, and like I said there really isnt much draw on the power side. Mostly we are just up there thursday to tuesday over the long weekends from spring to fall. If we go up in the winter it is just a short weekend and we likely wouldnt use the power as the batteries will be in an unheated space.

I am safe to assume the lithium batteries are fine being left up there through the winter provided they have a full charge correct?

Bop said:

Why are people still using low voltage MPPT when high voltage MPPT gives such superior performance- especially in poor generating conditions (which I suspect Canada would count lol)

Click to expand...

Because high voltage SCC's are high amperage are high cost. Even in Monopoly money.

Whitty21 said:

I am safe to assume the lithium batteries are fine being left up there through the winter provided they have a full charge correct?

Click to expand...

Yes. You will have to disconnect them from solar and from load. LFP battery should not be charge below freezing temp.
As you can probably not disconnect the internal BMS load, I suggest you to contact the supplier to know her suggestion for winter storage.

This is what I got back from Redodo.

"For longer storage of the batteries, it is recommended to charge/diacharge them to 50% level and every 3 months to charge once to 50% level.
The storage temperature for 24V200Ah battery is -10℃ to 50℃ / 14℉ to 122 ℉"

So it looks like if I am to play it safe I should bring them home over the winter, as they will be exposed to temps below -10. Also they will be on their own up there from late october to may, so ~7 months.

How does one go about cycling a battery in storage and testing for 50% SOC?

Whitty21 said:

This is what I got back from Redodo.

"For longer storage of the batteries, it is recommended to charge/diacharge them to 50% level and every 3 months to charge once to 50% level.
The storage temperature for 24V200Ah battery is -10℃ to 50℃ / 14℉ to 122 ℉"

So it looks like if I am to play it safe I should bring them home over the winter, as they will be exposed to temps below -10. Also they will be on their own up there from late october to may, so ~7 months.

How does one go about cycling a battery in storage and testing for 50% SOC?

Click to expand...

Which is why I am surprised that the use of LYP (LiFeYPO4) cells instead of LFP ones isn't more widespread- their operating temperatures go from -45C to 85C (-49F to 185F) with charge rate tapering only happening in the top and bottom 25C (so can be charged or discharged at full charge rates from -20C up to 60C (-4F to 140F) and reduced rates below/above those right to the end of their operating temperature band...

(their heat handling abilities is why I chose them for my own battery bank, with summer temps in excess off 40C for weeks on end...)
Specs for my own 400Ah cells...

It shows the difference- your 'storage' values, my LYPs haven't even started charge tapering yet....

Whitty21 said:

How does one go about cycling a battery in storage and testing for 50% SOC?

Click to expand...

It can be a lot of trouble for nothing, because the voltage of a LFP battery is almost the same from 30% to 70%.
If you are interested, you can buy tool to monitor SOC fairly accurately, but to me, charge them at 27V with low end of charge current* (1A to 20A) and after consider them at around 70-90%.

By the way, if that happen to you to read 0V at battery terminals, this is simply because the BMS shut down it self.
There is some chance that simply hook 24V at terminals could restart the BMS.

*considering 200Ah battery, 20A represent 0.1C charge rate