How to connect 48V panels to 24V installation

[Louis]

Good day,
I've installed a 24V solar system consisting of 5 solar panels, a battery bank with 8 x 102Ah deep cycle batteries, 2 x 5 - 30A solar charger controllers and 3000W x 24V pure sine wave inverter. Solar power is generated with 5 panels (2 x 120W x 12V connected in parallel to deliver 24V and 3 x 300W x 24V panels.) This is a manual switch-over system and is in use from 6pm to 6am daily.
Unfortunately 2 of the 300W x 24V panels were stolen. The only panels available to me are 300W x 48V panels and I'm not sure if it is possible to connect them to my existing 24V system.
Needless to say apart from being a total novice I'm not in a financial position to upgrade my system to a 48V one.
Could someone please assist/guide me how to go about to step-down the 48V to 24V and salvage my existing installation?
Many thanks!

[SunEagle]

Hello Louis. I am not sure what you wanted to post but just about all of it did not come through.

[Louis]

Hello Louis. I am not sure what you wanted to post but just about all of it did not come through.

Sorry, I've tried to copy and paste the text, but it did not show all of it. I've re-typed it and trust it is readable now. Thanks.

[sensij]

I've never heard of 48 V panels. Most panels available today follow these guidelines:

36 cells = 12 V = Vmp around 17-18 V
60 cells = 20 V = Vmp around 31 V
72 cells = 24 V = Vmp around 37 V

What do you really have?

[Mike90250]

The only easy way to add the higher voltage panels, is with a additional MPPT controller just for them, or add them parallel and accept the power mismatch losses
(150 w from your 300w panel)

[SunEagle]

I have not heard about 48V panels. So can you provide the specifications (Vmp, Voc, Imp) of those.

Also how did you have your original 3 x 300W panels wired to the CC and what is the make and model of that CC?

[littleharbor]

Sounds like 96 cell modules like these Panasonic 325 watt HIT , https://www.wholesalesolar.com/19419...ck-solar-panel

[SunEagle]

Sounds like 96 cell modules like these Panasonic 325 watt HIT , https://www.wholesalesolar.com/19419...ck-solar-panel

Ok. I had not seen those before.

So wouldn't a quality MPPT CC convert that higher panel voltage and still be able to charge a 24volt battery system?

[Louis]

Sounds like 96 cell modules like these Panasonic 325 watt HIT , https://www.wholesalesolar.com/19419...ck-solar-panel

It is given as a 72 cell with the attached specs.

[sensij]

It is given as a 72 cell with the attached specs.

Yes, that is a true "24 V" panel. It can be hooked up to a 24 V battery through a PWM (or mppt) controller. What are the specs of your other panels?

[SunEagle]

It is given as a 72 cell with the attached specs.

Those are grid tie panels which are pretty common. Again it will depend on the type of CC you are using for those panels. I am still not sure how you wired the original 3 x 300w panels to a 30A CC.

A quality MPPT could convert that ~ 900 watts to ~ 37.5amp of charging for a 24volt battery system but the system Ah rating may have to go up.

I am still not sure how your 2 systems are wired and if they both go to the same 8 battery system. Sounds like a mess to me and a great chance of something going boom.

[Louis]

Yes, that is a true "24 V" panel. It can be hooked up to a 24 V battery through a PWM (or mppt) controller. What are the specs of your other panels?

This is the other one.

[littleharbor]

Had you posted this info originally we wouldn't be talking about 48 volt panels. The devil is in the details. Those are 24 volt panels. If anybody told you otherwise you best stop taking advice from them because they haven't got a clue about solar.

[SunEagle]

Had you posted this info originally we wouldn't be talking about 48 volt panels. The devil is in the details. Those are 24 volt panels. If anybody told you otherwise you best stop taking advice from them because they haven't got a clue about solar.

Yep. both of those 300W panels have pretty much the same Vmp ~ 35.6v and Imp ~ 8.3amps. So I don't see any issue.

[sensij]

This is the other one.

Those specs are nearly identical, so that panel can be safely put in parallel with the new one.

Assuming you mean that your 120 W panels were put in *series*, then that combined 240 W can also be safely put in parallel with the two 300 W panels. If all three panel circuits are in parallel to the same charge controller, each of the three must be individually protect with a fuse or circuit breaker, no more than 20 A.

It sounds like you have more than one charge controller. What models? Which panels are wired to which controller?