Solar question.

[Smitty716]

If the most you can get is 8 amps with pwm or 11.7 amps with mppt why buy more watts ? I don’t understand if all you can get out of a 100 watt panel is 11.7 Andy all you can get out of a 300 watt panel is 11.7 why buy a 300 ?

 

[Weight]

where did you read that? Power is measured by watts. amps times volts. If the charge controller puts out 10 amps at 14 volts that is 140 watts. Panels in parellel put more amps. Panels in series put out more volts. Higher rated panels put out more voltage or more amps or both. The combination of volts and amps make the watts. More of either, more watts. Up to the limits of the controller, more watts more charge amps.

 

[jimindenver]

I do not think you have this correct. 300 watts can provide over 20 amps with a MPPT controller. 200 watts will provide over over 11a and there are other things to consider like what panels. Personally I have 1185 watts and can get as much as 80 amps. PWM is limited by the battery voltage but even there more watts means more amps.

 

[Smitty716]

So what’s how do you read the numbers on a controller? If it’s a 40 amp where are those amps going ? And are you getting 40 amps ?

 

[Smitty716]

And I bought. 175 watt panel and am going to have 2 universal 100 ah batteries so what mppt controller would work ? I plan on adding one more panel later

 

[Master Mechanic]

specs are on back of panel would need them. off hand 30 or 40 amp so u can expand array

 

[frater secessus]

So what’s how do you read the numbers on a controller?

If you are asking what a 40a rating means on a controller, it means the controller can output 40a into battery charging and/or loads.

If it’s a 40 amp where are those amps going ? And are you getting 40 amps ?

Battery and loads.

The better question is:  where are the Amps coming from?  A charge controller stands between the power source (usually solar panels) and the 12v system (batteries and loads).  Installing a 40 controller does not magically produce 40a out of nothing.

Here is a gentle introduction to how solar works.

 

[jonyjoe303]

for a 1x 175 watt panel, a 20 amp mppt will work. The ecoworthy 20 amp mppt (about 100 dollars) will work good, it has an lcd screen and tells you how much amps its putting out. You can program everything from the buttons on the unit. Some controllers require a bluetooth connection addon cost extra. You don't have that item, you can't program your controller.  

For 2 x 175 watt panels, then you need a 30 amp mppt. But you also have to make sure the controller can handle the voltage of 2 panels hooked together. A 175 panel will probably be rated 36 volts. 36 volts x 2 = 72 volts. Some controllers can only handle a max of 50 volts panel input some more expensive ones can go as high as 150 volts input. 

With panels flat on your roof, you never going to get the rated output of the panel except the 2 or 3 hours the sun is overhead in the summer. Thats why its always best to get the biggest panels available that can get every bit of sunlight.

This is the ecoworthy 20 amp mppt controller I been using with my 240 watt panel, it been running 24/7 for almost 5 years straight. I used it with lead acid and now I'm using it to charge my lifepo4, never let me down. Only drawback it can only handle a max 45 volt panel input. Good for up to a 1x 260 watt panel.

 

[John61CT]

The amps rating of the controller can be much higher than the panel max rated output.

This allows you to add more panels later.

It can also be a bit lower, aka over-panelling, since it is very rare that panels actually put out their max rating.