Solar install on our Cruise Lite TT

[larry2c]

Thanks for the reply Babock

I'm sort of ignorant on electrical so I'm having a hard time seeing in the Renogy spec sheets for the panels and the CC where the limitations you mentioned come in to play. The spec for the CC says max input watts of 400 and max voltage of of 25V. With our two 100W panels we never get anywhere near that limit (max open circuit readings I got was 18.2V and 9.8A). So does your info still apply?

I'm not trying to be argumentative on this, I'm just trying to understand...

[babock]

The max spec for the controller doesn't have anything to do with what limits the power in your case. PWM controllers will only output the same current that is input to them. The PWM only reduces the voltage that the panels produce down to the battery charge voltage. For that reason, the 9.8A that you measured going into the charge controller is going to be the exact current that is fed to the batteries but at a lower charge voltage.

Do a search for how a PWM controller works might help you understand more.

You are not alone. A lot of people get disappointed when they see their real numbers. There is a guy on here that will lead you to believe that he gets 7A out of his one lone 100W panel with a PWM controller which is basically impossible. I have a 700W system with an MPPT controller and I have see a little over 500W in late summer as my peak power output. My controller displays the peak power output every day it is on.

[larry2c]

OK, I'll do some readin' - thanks

[rk06382]

Originally Posted by babock

The max spec for the controller doesn't have anything to do with what limits the power in your case. PWM controllers will only output the same current that is input to them. The PWM only reduces the voltage that the panels produce down to the battery charge voltage. For that reason, the 9.8A that you measured going into the charge controller is going to be the exact current that is fed to the batteries but at a lower charge voltage.
.......

Originally Posted by larry2c

OK, I'll do some readin' - thanks

A MPPT controller will raise the amperage as it lowers the voltage. This was the output from my old Epever 40a MPPT solar charge controller. It was at 6 pm.


This from my current Victron 50a MPPT solar charge controller:


In each case the MPPT charge controller raised the amperage as they lowered the battery charging voltage. They will also shut off when the battery is fully charged.

Also you will notice that the solar voltage was from six Renogy 100 Watt 12 Volt Monocrystalline Solar Panel (Slim Design) in parallel.
My roof last summer: (I am going to add more solar panels.)

[babock]

While you are at it, notice how low the voltage of those panels are in parallel. If you really want to take advantage of MPPT, you want at least 2 in series. Better to have them in a series parallel config than all in parallel. If you are going to use the Renogy low voltage panels like that, they need to be in series especially to take advantage of early morning sun. The Victron MPPT won't even start until the panels are at 5V over battery voltage!

[rk06382]

Originally Posted by babock

While you are at it, notice how low the voltage of those panels are in parallel. If you really want to take advantage of MPPT, you want at least 2 in series. Better to have them in a series parallel config than all in parallel. If you are going to use the Renogy low voltage panels like that, they need to be in series especially to take advantage of early morning sun. The Victron MPPT won't even start until the panels are at 5V over battery voltage!

I may do that this summer but snow is still on the ground, but it maybe easier to just add more panels in parallel.

I forgot I had this MPPT vs PWM chart:


PWM can only output 81 of 100 the watts.

[babock]

Originally Posted by rk06382

PWM can only output 81 of 100 the watts.

That actually depends on the panel voltage. Your 16V panels are actually made for PWM so you get a larger percentage of the power since you are wasting less of the voltage above charge voltage.

For example, a 20V 100W panel will ouput 5A. A 16V 100W panel will output 6.2A.

Originally Posted by rk06382

I may do that this summer but snow is still on the ground, but it maybe easier to just add more panels in parallel.

If I were you, I would put the ones on the right side in series and then in parallel with the ones on the left side in series. Do you know if your panels have bypass diodes for the 3 columns that you have? It is possible that your panels aren't the best for shading if it can't bypass columns. Most panels have an even number of columns so if you get shading, you only lose half of the panel.

[larry2c]

OK, I've been doing my homework and as far as I can figure, I will likely be missing out on maybe 20 amps a day by having the PWM CC vs. the MPPT. Not insignificant but we are low power users - no inverter or large power drainers. We have several progressively longer trips coming up so I'll be checking to see how well we can maintain our batteries. I understand that what I have installed may not be perfect for everyone, but if it works for us, then we have accomplished what we set out to do.

[aeblank]

My dad has pwm. It works just fine...
Get this, he doesn't even have lithium.
Somehow he survives 2 months in the boonies of Arizona.

[nayther]

I'm about ready to pull the trigger, how does this "kit" look to you seasoned veterans?


https://www.ebay.com/itm/Renogy-300W...0AAOSwxupbGKAR


I have two Costco 6v batteries, generator back up and usually camp in the wide open desert. Heavy load would be coffee maker in the morning before the solar comes up to speed or start the generator. In the evenings like to watch TV via satellite and would like to keep the sattelite receiver on all the time so don't have to reconnect each time its powered up. Will this one allow me to connect series/parallel to bump the voltage? I know its more efficient to transfer higher voltage than lower and been debating on where to put charge controller, trailer is "pre-wired" for solar with jack on the roof and sticker inside for controller location but reading that it would be more efficient if mounted nearer the batteries so the 12v conductors are shorter.

[unyalli]

Originally Posted by nayther

Will this one allow me to connect series/parallel to bump the voltage? I know its more efficient to transfer higher voltage

This kit has a PWM power waster charge controller. All panels will have to be connected in parallel with this controller no series. I only see enough Y connectors to connect two of the three panels.

- Jeff

[nayther]

Originally Posted by unyalli

This kit has a PWM power waster charge controller. All panels will have to be connected in parallel with this controller no series. I only see enough Y connectors to connect two of the three panels.

- Jeff

OOPS! thought linked to a MPPT controller, thanks for pointing that out.


here's one with MPPT:
https://www.ebay.com/itm/Renogy-300W...frcectupt=true

[babock]

Originally Posted by nayther

OOPS! thought linked to a MPPT controller, thanks for pointing that out.


here's one with MPPT:
https://www.ebay.com/itm/Renogy-300W...frcectupt=true

Not a fan of installing 100w panels. You can buy 200w panels for $185. Half of the mounting brackets and half the wiring. Install 2 of those and buy a Victron solar controller.

[unyalli]

Originally Posted by nayther

OOPS! thought linked to a MPPT controller, thanks for pointing that out.


here's one with MPPT:
https://www.ebay.com/itm/Renogy-300W...frcectupt=true

This his would do all in series. Try to mount all three panels so orientation is the same. Slight difference in angle to the sun won't be a big deal but if all panels are oriented at the same angle to the sun the MPPT sweep will be maximized. Remember, in series, the charge controller sees this as one 300 watt panel.

Has a battery monitor been discussed? The only way to know real battery state of charge (SOC) is with a battery monitor watching a shunt in the negative connection to the batteries.



- Jeff

[babock]

Originally Posted by unyalli

This his would do all in series. Try to mount all three panels so orientation is the same. Slight difference in angle to the sun won't be a big deal but if all panels are oriented at the same angle to the sun the MPPT sweep will be maximized. Remember, in series, the charge controller sees this as one 300 watt panel.

Has a battery monitor been discussed? The only way to know real battery state of charge (SOC) is with a battery monitor watching a shunt in the negative connection to the batteries.



- Jeff

Doesn't matter one bit what the orientation of the panels are.

The controller sure doesn't know or care.

[unyalli]

Originally Posted by babock

Doesn't matter one bit what the orientation of the panels are.

Wow! Need I say more?


- Jeff

[aeblank]

@Unyalli...

Go Pack go.