Is this a proper amount of amps for 200w of panels?

glassroots · Sep 3, 2020

I've got 2 100w renogy panels for a 12v system. I'm in Portland, OR where the solar radiation isn't great (currently around 4kWhr/m²/day). On average my system throughout the day is bringing in 1.5-3.5 amps, during peak hours 2.5-3.5 amps at most.

In east Texas where I installed the system I was definitely getting more power, and as far as I've been able to tell everything is still working fine.

[font=Tahoma, Verdana, Arial, sans-serif]Is this normal? It's become problematic to where I have to be careful about how much I get on my laptop (a gaming laptop that admittedly pulls 140w when running at max performance). I'm concerned about the winter because it drops down to a wopping 1[size=small][font=Tahoma, Verdana, Arial, sans-serif]kWhr/m²/day at best.[/font][/font][/size]

[font=Tahoma, Verdana, Arial, sans-serif][size=small][font=Tahoma, Verdana, Arial, sans-serif]Any advice appreciated. :huh:[/font][/font][/size]

bullfrog · Sep 3, 2020

Have you tried changing the angle of the panels? We had one member that was forced to use a generator that stayed in that area over winter due to the number of low sunlight days I believe.

highdesertranger · Sep 3, 2020

do the math it's easy,

V x A =W

V = volts
A = amps
W = watts

so you can change this around so that watts divided by volts = amps. so 200 watts divided by 12v = 16.6a. now remember this is under lab conditions and you will not see this in real life. so yes according to the math you are way low.

now how are you measuring the amp output and where?
what type of battery(S)?
how are you measuring your battery State Of Charge(SOC)?

highdesertranger

glassroots · Sep 3, 2020

bullfrog said:
Have you tried changing the angle of the panels?...

It's mounted on my van roof so it's flat, I don't want to invest into one of those adjustable stands.

glassroots · Sep 3, 2020

highdesertranger said:
do the math it's easy,

V x A =W

V = volts
A = amps
W = watts

so you can change this around so that watts divided by volts = amps. so 200 watts divided by 12v = 16.6a. now remember this is under lab conditions and you will not see this in real life. so yes according to the math you are way low.

now how are you measuring the amp output and where?
what type of battery(S)?
how are you measuring your battery State Of Charge(SOC)?

highdesertranger

Yea I've seen the calculated max output of the panels, but was unsure if my area with its low solar radiation would be enough for such a drastic difference.

I've got a 100ah lithium battery, essentially new. I've been using the charge controller (20a renogy mppt) to check the incoming voltage/amps.

I haven't measured the stage of charge other than by seeing what the current voltage is of the battery compared to the range it operates in (roughly 12.5-14.2V). I know that it's not linear compared to the charge but it gives me a rough estimate.

jacqueg · Sep 3, 2020

Seems like it's in the ballpark to me. I hang out in the PNW too, and the first thing I bought energy-wise was a generator. I just recently bought a portable solar panel kit, but I will use it as a supplemental source up here - anything I get is great, but I'm not relying on it.

I expect to get my money's worth out of the panel using it down in Arizona.

I'm pretty sure 200w of solar will not come close to cutting it during the winter in the PNW, although you might do better east of the Cascades.

There's a couple things to note here -

Shortening day length is more noticeable here than further south.

Sunlight is less intense here, regardless of time of year.

And of course, cloudy skies will really get in your way, no matter where you are.

glassroots · Sep 3, 2020

With how slowly my battery charges, it does correlate with the readings on the charge controller. My battery died the other day, and after jumpstarting it back to 12.5'ish volts, it's been 1.5 days of charging with almost no load on it to only be sitting at 13.3V

glassroots · Sep 3, 2020

jacqueg said:
Seems like it's in the ballpark to me. I hang out in the PNW too, and the first thing I bought energy-wise was a generator. I just recently bought a portable solar panel kit, but I will use it as a supplemental source up here - anything I get is great, but I'm not relying on it.

I expect to get my money's worth out of the panel using it down in Arizona.

I'm pretty sure 200w of solar will not come close to cutting it during the winter in the PNW, although you might do better east of the Cascades.

There's a couple things to note here -

Shortening day length is more noticeable here than further south.

Sunlight is less intense here, regardless of time of year.

And of course, cloudy skies will really get in your way, no matter where you are.

And like you I've got an e-150, so the roof space is minimal. With my roof vent I could probably only fit another 100w panel up there. I might just hold out until I get into something bigger to improve my electrical situation. I do have a battery isolator I could use to pull from my alternator, unfortunately the alternator only goes up to 13.5V or so though I think. May be my only saving grace in 2 months though.

tx2sturgis · Sep 3, 2020

glassroots said:
I've got a 100ah lithium battery, essentially new. I've been using the charge controller (20a renogy mppt) to check the incoming voltage/amps.

Gotta ask this question: Is the charge controller a LI-compatible unit?

jonyjoe303 · Sep 3, 2020

rule of thumb you should get about 1 amp for every 20 watt of panel, for 200 watts you should see a max of 10 amps if the sun is overhead, even in cloudy days you should get at least 4 to 5 amps. (200 watts / 14.6 volts = 13.6 amps the max you would ever see in the best conditions)

Are your panels connected in series or parallel? in parallel you might max out at 5 amps, the voltage won't be high enough for the mppt to work, in series you should get the full 10 amps. Mppt need the higher voltage to increase your amps.

If your panels are in series and your only getting 4 amps, you might have voltage drop from the controller to the battery. The controller might think your battery is full and will lower the amps.

I have voltage drop on my system. Its a 240 watt 36 volt panel, 20 amp ecoworthy mppt controller, and 220ah lifepo4 battery. My panel is flat on the roof. If I set the bulk setting on the controller to 14.6 volts (recommended for lifepo4) it charges at 4 to 5 amps even in bright sunlight. But I found out if I raised the bulk setting to 15.5 volts, It charges the battery at 12 amps and sometimes maxes out at 15 amps. Because of voltage drop the bulk setting of 15.5 volts barely gets the battery to 14.6 volts.

In this picture the lcd screen on the controller (not shown) reads 15.5 volts, the LED meter (shown) reading directly from the battery reads 14.6 volts. Note the 15.1 amps the panel is putting out. The only problem with raising the bulk setting too high on lifepo4 is what happens if the bms activates, some controllers will creates voltage surges, it won't damage the battery but it destroys devices connected to the battery. You would need to use a 12 volt voltage stabilizer and connect all your 12 volt devices to the stabilizer, it will protect from voltage surges.

If you checked everything else, check the voltage at the battery terminals and bounce that with what the controller is reading. In my estimation your not getting full output from your 200 watts. Even when its overcast I get at least 3 to 4 amps from my 240 watts.

glassroots · Sep 3, 2020

They are run in parallel not series. So I should try running them in series to see if that resolves my issue?

glassroots · Sep 3, 2020

tx2sturgis said:
Gotta ask this question: Is the charge controller a LI-compatible unit?

It is.

jonyjoe303 · Sep 3, 2020

They are run in parallel not series. So I should try running them in series to see if that resolves my issue?

Yes I would connect them in series, that would raise your panel voltage to 42 volts, mppt will definitely increase your amps. You should at least double what your getting now.

DLTooley · Sep 4, 2020

At this time of year you should have mostly sunny skies, though not for much longer. As such if those are current numbers you have an issue.

The advantage of going to series is in low light conditions such as clouds or near dusk. It would also help with voltage drop, but you’ll want to fix that anyway.

maki2 · Sep 4, 2020

Sometimes it looks like my amp reading is horribly low until I remember that my battery is already at or near 100 percent and the controller itself has reduced how many amps are being sent into the battery. Be sure you understand what you are looking at on your readout before you go into worry mode.

glassroots · Sep 4, 2020

jonyjoe303 said:
Yes I would connect them in series, that would raise your panel voltage to 42 volts, mppt will definitely increase your amps. You should at least double what your getting now.

So when in parrellel my panel would roughly be around 16-18ish volts and 1.5-3.5 amps. Now that I've switched it to series, during the morning it's running at 32.5V and .6 amps. It seems like the voltage doubled and the amps halved, but nothing else. I'll continue to monitor throughout the day, but if I'm understanding this right it didn't help?

Sent from my SM-G988U using Tapatalk

glassroots · Sep 4, 2020

maki2 said:
Sometimes it looks like my amp reading is horribly low until I remember that my battery is already at or near 100 percent and the controller itself has reduced how many amps are being sent into the battery. Be sure you understand what you are looking at on your readout before you go into worry mode.

Well my battery is currently at 13.3V and the charge controller doesn't change from bulk charging to boost charging until around 14.4V, then switching to bulk at 12.6V.

Sent from my SM-G988U using Tapatalk

glassroots · Sep 4, 2020

It's noon now and sitting at 7.3a, a pretty huge improvement. Thanks for the tip on switching to series.

Sent from my SM-G988U using Tapatalk

technerd88 · Sep 4, 2020

Now grab yourself two more panels and put them in series and then put the two sets of series in parallel....then youll be really rockin. That was the best config for my setup....well similar. I have 3x 3 series of 100w and I regularly pull in 60+ amps from my epever 80a mppt.

theBest · Sep 4, 2020

@glassroots
List the model numbers of your panels.
Provide links to the items you bought.
What are the manufacturers specs for your systems components?

What is the type of photovoltaic material the panels are constructed with?

What is the angle of the sun in Texas?
What are the average number of days with full sunshine in Texas?
What is the angle of the sun in Oregon?
What are the average number of days with full sunshine in Oregon?
Are these numbers different between Texas and Oregon?
What adjustments can you make to improve your panels energy gathering in Oregon compared to Texas?

Is this a proper amount of amps for 200w of panels?

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