Poor solar performance

[Ryang]

Hi there

I could really use some advice on my current solar setup

I was very green 6 months ago, purchased 2x250 panels, a Renogy 40amp mppt charger , chucked them on the roof of the caravan and though life would be perfect.

Unfortunately these panels never produced more than 190w combined. Got burned by cheap eBay panels that sounded like quality.

Next, I purchased a 200w panel, seemed better quality. Before installing I disconnected the other panels and connected directly to the Renogy, angled it at the sun and saw 160w without trying, thought, beauty, whacked it on the roof (flat roof mount that is).

Reality is that it doesn’t produce more than about 100w once installed.


So I am at a quandary. Is this ‘normal’ output. Is it a controller issue, cabling issue? A. User Issue or something simple.

So I’ll clear up the install a little. I ran 8awg cable from controller to roof, I thought it easiest to just crimp ring connectors on the end, and use a bolt n nut style connection shrink wrapped. thsts how the 3 panels on their standard cable terminate together. Is this okay? I thought this would be fine. My crimps are nice and strong.

Anyone have experience with the Renogy controller? Are they good?

Where should I go from here?

Cheers

Ryan

 

[Ped]

What type of battery? the average soc in morning?

 

[upnorthandpersonal]

What type of battery? the average soc in morning?

And which solar panel(s) exactly?

 

[Ryang]

The battery is 2x 120 lithium. Soc is skewed as I turn on the generator to ensure battery in the morning.

The panels were sunraiser 250w mono panels.
The 3rd i don’t remember

 

[MichaelK]

It's not an equipment issue, it's a design/implementation issue. Un-mount your panels and point them directly at the sun at noon and see what happens. Because your panels are mounted flat, they are picking up only a fraction of the sun's output. Here's a trick you can do. Take a short scrap of PVC pipe, maybe 12" long, and position it so it's exactly perpendicular to the panel surface. When you can see the spot of sunlight from the center of the pipe shining on the panel's surface, you have the panel oriented perfectly perpendicular to the sun. Be carefull though. At full output, all your panels outputting together might exceed the 40amp limit of your controller.

 

[Ped]

Well 500w even flat mounted should produce more than 190w. And running generator doesnt change anything since theyre lifepo4. The battery will accept max current until about 97% full.

Unless panels are very expensive or specially made theyre all the same asian built things in general. As far as I've ever seen anyway. The controllers are also fine. I use one.

Do you have a shunt based battery monitor?

Heres my theory...by the time youre getting to peak sun the batteries are damn near full and the controller is intentionally blocking anymore current to the batteries.

You can confirm without a monitor by voltage reading of 14.6v or whatever your max voltage setpoint is....which should be about 14.6v.

 

[MichaelK]

Heres my theory...by the time youre getting to peak sun the batteries are damn near full and the controller is intentionally blocking anymore current to the batteries.

You can confirm without a monitor by voltage reading of 14.6v or whatever your max voltage setpoint is....which should be about 14.6v.

That may be what's occurring. Here's how I check that. I put a heavy load on the inverter that's greater than what I think the output is. Say a toaster for example. Check what the solar output is on the charge controller while the load is running. That will tell you exactly what the max output is. Once the toaster pops, you'll see the amperage drop back down to baseline.

 

[Ryang]

It's not an equipment issue, it's a design/implementation issue. Un-mount your panels and point them directly at the sun at noon and see what happens. Because your panels are mounted flat, they are picking up only a fraction of the sun's output. Here's a trick you can do. Take a short scrap of PVC pipe, maybe 12" long, and position it so it's exactly perpendicular to the panel surface. When you can see the spot of sunlight from the center of the pipe shining on the panel's surface, you have the panel oriented perfectly perpendicular to the sun. Be carefull though. At full output, all your panels outputting together might exceed the 40amp limit of your controller.

Unfortunately these are on top of a caravan so mounting anything but flat is not super practical. I could test the pael outputs using the pipe. great little trick.

 

[Ryang]

Well 500w even flat mounted should produce more than 190w. And running generator doesnt change anything since theyre lifepo4. The battery will accept max current until about 97% full.

Unless panels are very expensive or specially made theyre all the same asian built things in general. As far as I've ever seen anyway. The controllers are also fine. I use one.

Do you have a shunt based battery monitor?

Heres my theory...by the time youre getting to peak sun the batteries are damn near full and the controller is intentionally blocking anymore current to the batteries.

You can confirm without a monitor by voltage reading of 14.6v or whatever your max voltage setpoint is....which should be about 14.6v.

i do have a shunt based monitor, but the lead cable is too short so i havent the cable yet to extend it. Trying to source something suitable without heading into any major shops at the moment.

As for full batteries - this is not whats happening. I am running a 220 12v waeco fridge and a 12v engel 40l fridge. Plus all the usual phone chargers, lights etc, we are VERY power hungry. Hence the need to maximise solar input.

total daily solar is maxing at about 70amps at the moment. we use about 120amps a day in useage.

I've not seen the batteries hit about 13.7 (atleast on the renogy controller battery monitor - which i dont trust).

I did feel like it may of been blocking current originally, but even when the batteries are dead flat i have the same issue. so i ruled that out. OR the controller is faulty.

 

[Ryang]

That may be what's occurring. Here's how I check that. I put a heavy load on the inverter that's greater than what I think the output is. Say a toaster for example. Check what the solar output is on the charge controller while the load is running. That will tell you exactly what the max output is. Once the toaster pops, you'll see the amperage drop back down to baseline.

we dont run an inverter. Have setup the van to survive on 12v to maximise power efficiency.

 

[Ped]

Well not saying youre wrong BUT you are also generator charging, no? I run a dorm fridge off inverter myself on 120Ah lifepo4. All apliances 120v. I only use about 35-40ah by morning. Thats also tv, lights, phones, water pump, my vaporizer, until midnight or so. With 390w on a good sunny morning im full by 11:30am just on solar. AND you have double the battery.

 

[Ryang]

Well not saying youre wrong BUT you are also generator charging, no? I run a dorm fridge off inverter myself on 120Ah lifepo4. All apliances 120v. I only use about 35-40ah by morning. Thats also tv, lights, phones, water pump, my vaporizer, until midnight or so. With 390w on a good sunny morning im full by 11:30am just on solar. AND you have double the battery.

Yes but the question is, how much is your controller actually producing in terms of amps back into the battery.
I have very poor 700w of solar, i only get a max of 250w in (and thats a good day), down to 235w PEEK now.

 

[Ryang]

can anyone explain this to me. This is the renogy app, the battery section shows the battery voltage. My concern is it says (for example) 13.1v is 98%, 13.2 is 99% 13.3 is 100%. Now we know this isnt correct. A thought i have is that, is the mppt controller not utilizing the full sun as it thing the battery is 100%, but the voltage is far to low for it to be 100%.

Am I missing something here?

 

[nosys70]

for 12v LFP , 13.8 is ok. you have to configure your charger to use LFP profile.
look if it is using lead acid profile or LFP if you have real lithium.

 

[Ryang]

its configured for LFP.

ill show you the settings. Thats what i find strange. Does anyone else use a renogy mppt charger?


i did drop a battery to make sure things werent going weird. so back to 120 at the moment for testing.

 

[Ryang]

The manual does say this
-
**Default charging parameters in LI mode are programmed for 12.8V LFP battery. Before using Rover to charge other types of lithium battery, set the parameters according to the suggestions from battery manufacturer
-
Battery clearly states 12.8v as well.

Thats a funny number isn't it?

 

[monty]

LiFePO4 cells are 3.2 V nominal x 4 = 12.8 V.

 

[Ryang]

12.8 is only 17% charge? so its a strange number to me.

when the controller says 13.1 is 98%, but the voltage chart says thats 40%.

I am a little confused. Is the renogy controller just saying the wrong info?

 

[monty]

17 % ??? Where does that come from ??

What voltage chart ?? Anyway here are some generic numbers for LFP for you to ponder (multiply by four for 12 V system):

Minimum discharge voltage = 2.5 V
Working voltage = 3.0 ~ 3.2 V
Maximum charge voltage = 3.65 V

 

[Ryang]

 

[Ped]

Ok first and foremost your settings are extremely wrong. Is that a default for lithium? You cannot be charging above 14.6v (setting 14.7v - voltage drop). You cannot equalize either. That will destroy a lifepo4.

 

[Ped]

Its actually 3.25 nominal, 3.65 full. Try doing user setting and match mine. Set limits at 14.7v if it lets you, if not 14.8v.

 

[upnorthandpersonal]

Not even necessary to charge them to 100% max capacity - assume 3.5 to 3.6 per cell is very full (don't push to 3.65 if not needed).

 

[Ped]

As an aside remember I told you I use 35-40ah over night running 120v/inverter. Heres my morning % and thats with clouds yesterday eve, tv to 1am, 1.22A idle.

As well Im in constant "debates" that dorm fridge supposedly "use WAY more energy" than 12v fridges. If you got 2x fridges using half the energy, 100% 12v with no idle current, and 2x the battery you should be around 85-90%.

 

[Ped]

Not even necessary to charge them to 100% max capacity - assume 3.5 to 3.6 per cell is very full (don't push to 3.65 if not needed).

See battleborns interview about charging to 100% and why they recommmend it. This topic starts around the 9 min mark.