Low current

CALLD wrote: »

Hi,

I assume you are hoping to see approximately 28Amps under direct perpendicular sun conditions (AM 1.5, 1000w/m2).

Many things affect current:

Battery SoC (a fully charged battery will only take what it needs to maintain the set voltage.

Charge controller - a PWM or MPPT? There is a difference!

Wiring - Amps = Volts over Ohms. There is an inevitable voltage drop from the panels to the charge controller. Use ohms law to figure out if the wiring can carry the current while still maintaining the required voltage at the charge controller/battery/load.

Sun intensity plays a big role, it drops off dramatically when the sun is lower than 30° from the horizon. At low altitudes things like clouds, mist, haze, pollution etc. have a huge effect.

Shading, with your setup if any of the PVs are shaded the diodes will not be enough to compensate, you just don't have enough "reserve voltage"

As I pointed out in the last point, your PV voltage is very close to your battery voltage, meaning that under certain conditions it will struggle to overcome resistive losses. Unless you have very heavy gauge wiring or very short distances you could find that ohms law is "stealing your amps"...

D

CALLD wrote: »

I think you need a pro to come and look at your system for you. There are at least several problems with your set-up.

1) the batteries. Even with two "Big" car batteries you have far to little storage for your PV! I'm also assuming you live somewhere where you can't get proper deep cycle batteries and that's why you ended up using car batteries? Sad thing is they are probably going to fail long before you figure out what is wrong with your system:(

2) if you have an MPPT charge controller why did you not opt for the highest possible voltage from your array? Most MPPT controllers can accept up to 150volts?

3) I could go on about your loads, inverter etc but I'd rather let the boffins jump in from here.
My advice would be to get someone who knows what they are doing to come and help you before you ruin your equipment...

D

Photowhit wrote: »

Several things,

The Tristar comes in 2 types of controllers that look pretty much the same, are you sure you purchased the MPPT type? It tends to run 3x and much as the PWM type.

The panels I assume of these grape flex panels? I'm not a huge fan of flexible panels, they don't tend to last as long and tend to discolor over time, but initially they should be fine.

I would expect amps at 24 volts on a sunny day to be around 90-95% of the panel rating for PWM, or 5.68 x 5(strings for 24v) x .9 = @26 amps for a PWM and about 1000 / 24 x .77 = about 32 Max for a 24 volt system.

Many things can limit your charging current. First would be do your batteries need the current, as others have pointed out, car type batteries do not have a lot of capacity, their goal in life is to produce a lot of current over a short period of time for starting a car. Deep cycle batteries produce a small amount of current over a long period of time. Your charge controllers will see the rise in voltage and limit the voltage so the batteries don't over heat. The batteries will begin not needing the current/amps rapidly and you will see a reduction.

Did you check to see how much current the charge controllers were passing through when you were running the air conditioner? When a heavy load is applied, the maximum amps should be passing through the charge controller. If you were only seeing a voltage drop to 24.7 you should be seeing more amperage than 12 amps or you should see additional voltage drop somewhat quickly.

If you do indeed have a MPPT type charge controller the input voltage should be around 2x the output voltage to be most efficient. How far is your array/panel from your charge controller? Long runs over the wrong gauge wire can drop your voltage, and you will loose some power there.

Trouble shooting, do these with a heavy load so you know you have the demand for maximum current;

Do you have breakers for each string? If you turn off each breaker, one at a time you may find that some strings have problems, perhaps even wired backwards. Do NOT do this is you have fuses!

You could use a clamp meter to measure the current while in use, this would tell you if you have other issues, bad wiring past the breaker or fuse or perhaps even a bad fuse or breaker.