Report your peak amps from your panels, curiosity...
- Thread starter Bbasso
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jonyjoe101
Adventurer
with a sharp 240 watt 36 volt panel lying flat on my van roof and connected to a ecoworthy 20 amp mppt controller, the most i have seen is 15 amps in the summer, in winter its about 11 amps.
dwh
Tail-End Charlie
An MPPT controller does 3 things.
A) Operate the solar at its Vmp to get the most watts.
B) Down-convert the incoming higher-voltage to a lower-voltage that is more efficient for battery charging.
C) Use that lower voltage to do a PWM charge on the battery.
Step B is where the amps boost happens. By lowering the voltage, the amps goes up. It's essentially an electrical transmission that down-shifts to get more torque..
So while your panel's sticker says 5.29 amps at 18.9v, with MPPT that just means that's what is coming into the controller:
5.29a x 18.9v = 99.9w
But that is not what is going out to the battery after it runs through the transmission. Under the right conditions - say it's doing bulk stage and the battery is at 12.5v - you could theoretically see a lot more amps on the output side:
99.9w / 12.5v = 8a
Most of the time you won't see that much of an improvement, but it can happen
228B
Observer
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Thank you dwh. Always enjoy reading your posts. I learn something new almost every time. Thanks too to LeishaShannon.
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There's (lol) VM&P Naphtha, a refined petroleum product (the key component in liquid camp fuel), then there's "Vne" in aviation pertaining to airframe performance (velocity never exceed?)...
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And could someone explain "Optimum Operating Current" in relation to panel output? Is that strictly a silicon PV cell internal temperature thing? or...
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Regardless of the curious details, I realize that "it is what it is" when one's home-built solar electric power system is up and running. We cannot modify a panel's output. Yes, there are things we can do to best manage PV output (keeping panels out of partial shade), using the appropriate conductor to achieve 3% or less losses from resistance, and having/editing internal software for the best possible charge profile voltage setpoints in our controllers for optimum "energy density" when charging our specific battery type... and so on and so forth, as well as using a good-quality PV panel.
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I cannot speak for the solar power veterans, but for this no0b this hardly gets old, this "tweaking" of things as best we can in order to achieve the highest efficiency available for our individual means...
Thank you dwh. Always enjoy reading your posts. I learn something new almost every time. Thanks too to LeishaShannon.
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I suppose I could research this on my own, but what is "Vmp" or "lmp" as it pertains to electricity?
There's (lol) VM&P Naphtha, a refined petroleum product (the key component in liquid camp fuel), then there's "Vne" in aviation pertaining to airframe performance (velocity never exceed?)...
.
And could someone explain "Optimum Operating Current" in relation to panel output? Is that strictly a silicon PV cell internal temperature thing? or...
.
Regardless of the curious details, I realize that "it is what it is" when one's home-built solar electric power system is up and running. We cannot modify a panel's output. Yes, there are things we can do to best manage PV output (keeping panels out of partial shade), using the appropriate conductor to achieve 3% or less losses from resistance, and having/editing internal software for the best possible charge profile voltage setpoints in our controllers for optimum "energy density" when charging our specific battery type... and so on and so forth, as well as using a good-quality PV panel.
.
I cannot speak for the solar power veterans, but for this no0b this hardly gets old, this "tweaking" of things as best we can in order to achieve the highest efficiency available for our individual means...
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dwh
Tail-End Charlie
Vmp is "Voltage (at) Max Power". That is the operating voltage that will get the most efficiency (watts) out of the solar at the moment. It's a moving target which depends on the heat of the cells and the angle of incidence of the photons.
Without the MPPT, the solar is just connected directly to the battery, so it will operate at whatever the battery's voltage is at the moment, and that is going to be a lot less than the Vmp and thus less efficient.
With MPPT, the solar is separated from the battery, and the MPPT controller will regulate the solar's voltage to keep it operating at the whatever the Vmp of the moment is (most MPPT samples and adjusts the load on the solar every 60 seconds to regulate the voltage the solar operates at).
Imp is the "Current (at) Max Power". In the case of your panel, under Standard Test Conditions (STC), if it is operating at 18.9v (the Vmp), then it will produce 5.29a (the Imp). Imp is a.k.a, "Optimum Operating Current" - the current you'll get under optimum operating conditions.
And yea...there's also a lot of V* stuff in aviation.
Without the MPPT, the solar is just connected directly to the battery, so it will operate at whatever the battery's voltage is at the moment, and that is going to be a lot less than the Vmp and thus less efficient.
With MPPT, the solar is separated from the battery, and the MPPT controller will regulate the solar's voltage to keep it operating at the whatever the Vmp of the moment is (most MPPT samples and adjusts the load on the solar every 60 seconds to regulate the voltage the solar operates at).
Imp is the "Current (at) Max Power". In the case of your panel, under Standard Test Conditions (STC), if it is operating at 18.9v (the Vmp), then it will produce 5.29a (the Imp). Imp is a.k.a, "Optimum Operating Current" - the current you'll get under optimum operating conditions.
And yea...there's also a lot of V* stuff in aviation.
MINO
Adventurer
I was just wondering about this myself and trying to research it. Still learning as I go.
I'm running 2 Unisolar 68W Amorphous panels (Vmp 16.5) and 2 100w "eBay" Flex panels (Vmp 17.8). My Camper came with one Unisolar panel. I upgraded to 2. When that wasn't enough, I decided to go with the eBay panels to keep the weight down on my already heavy pop-up roof.
Vmp is a little off from the mismatched panels. Also there's no ventilation behind the panels so I may be losing a bit of potential due to heat.
Controlled via BlueSky 3000i MPPT. 10AWG cables. 215AH Fullriver battery.
During peak SoCal summer sun these past few weeks, I've seen up to 19-20A @ 14.9V.
I'm running 2 Unisolar 68W Amorphous panels (Vmp 16.5) and 2 100w "eBay" Flex panels (Vmp 17.8). My Camper came with one Unisolar panel. I upgraded to 2. When that wasn't enough, I decided to go with the eBay panels to keep the weight down on my already heavy pop-up roof.
Vmp is a little off from the mismatched panels. Also there's no ventilation behind the panels so I may be losing a bit of potential due to heat.
Controlled via BlueSky 3000i MPPT. 10AWG cables. 215AH Fullriver battery.
During peak SoCal summer sun these past few weeks, I've seen up to 19-20A @ 14.9V.
IdaSHO
IDACAMPER
Interestingly, it actually looks like most all of Florida is roughly the same as North Idaho.
Also, what voltage are you seeing that 14.9 amp reading at?
The voltage you see your max amps at makes a big difference as well with regards to testing panel efficiency.
Also plays a big part in just how usable that power is to charging a depleted battery bank
100 watts @ 14V = 7.14 amps
100 watts @ 13V = 7.69 amps
100 watts @ 12V = 8.33 amps
Also, what voltage are you seeing that 14.9 amp reading at?
The voltage you see your max amps at makes a big difference as well with regards to testing panel efficiency.
Also plays a big part in just how usable that power is to charging a depleted battery bank
100 watts @ 14V = 7.14 amps
100 watts @ 13V = 7.69 amps
100 watts @ 12V = 8.33 amps
Joe917
Explorer
All conductors from panels to controller, and controller to battery bank, 10G PV cable
See here.
Nice clean install, however, you may well be underwired. 10 G is not large wire.
How long are your runs? The run between the charge controller and the battery bank is critical.
Anything over 1% drop here is unacceptable.
http://www.rapidtables.com/calc/wire/voltage-drop-calculator.htm
FWIW I have run 10 G from the panels to the charge controller but as the panel voltage is 48v nominal voltage drop is minimized.
35 amps is the most I've noticed off my 2X315 amp panels. Battery state of charge also affects acceptance and therefore amps.