Clear blue water, pwm solar voltage

[SamDeleted]

I have a question if you all don't mind pls


I am about to buy panels, 410w Canadian solar. 8 is the most I can fit on the roof, we're on a 48v AGM battery bank and a Morningstar ts-60 pwm

Panel specs:
Vmp: 31.2
Voc: 37.2

Was planning 2s4p so vmp 62.4v...

the batteries need 55v~ to charge, that's only 7.4v of clear blue water

Am I cutting it too close ? In the real world am I going to see lower voltages than the vmp?

Regards

 

[SamDeleted]

I could go 9 panels , 3s3p , but that would mean a 2 foot overhang off the flat roof .

It's a bit more complicated woodwork wise but it could be done


But I'm concerned that 3s would over volt the charge controller (max125v) . An online max solar volts calculator puts it at 125.48v @ -5c (23f)

 

[sunshine_eggo]

I could go 9 panels , 3s3p , but that would mean a 2 foot overhang off the flat roof .

Absolutely not. you would completely waste the 3rd panel in all cases. PWM works by shorting the panels to the battery forcing them to work at battery voltage.

It's a bit more complicated woodwork wise but it could be done

But I'm concerned that 3s would over volt the charge controller (max125v) . An online max solar volts calculator puts it at 125.48v @ -5c (23f)

Those are 60 cell panels. In hot conditions, they may not yield sufficient voltage to completely charge.

55V seems VERY low unless you're running standby-type batteries, which may be a mistake. Most AGM get full charged between 57.6 and 59.2V.

You need two 24V panels in series. 24V panels are 72 cells. with a typical Voc around 47 and a Vmp around 40.

 

[timselectric]

Definitely don't over voltage.
I generally shoot for 85% or less.

 

[SamDeleted]

Absolutely not. you would completely waste the 3rd panel in all cases. PWM works by shorting the panels to the battery forcing them to work at battery voltage.



Those are 60 cell panels. In hot conditions, they may not yield sufficient voltage to completely charge.

55V seems VERY low unless you're running standby-type batteries, which may be a mistake. Most AGM get full charged between 57.6 and 59.2V.

You need two 24V panels in series. 24V panels are 72 cells. with a typical Voc around 47 and a Vmp around 40.

Yes you are correct I've looked at the batteries data sheet again,

55v float, up to 60v bulk.


This is a bit of a spanner in the works for me then ... Those Canadian solars are going very cheap ... £138 delivered Inc tax .

I could get this sorted with a different by using charge controller but the morning star is bought and paid for

 

[sunshine_eggo]

Yes you are correct I've looked at the batteries data sheet again,

55v float, up to 60v bulk.


This is a bit of a spanner in the works for me then ... Those Canadian solars are going very cheap ... £138 delivered Inc tax .

I could get this sorted with a different by using charge controller but the morning star is bought and paid for

A cheap panel that doesn't do what you need isn't worth anything.

 

[SamDeleted]

Are

A cheap panel that doesn't do what you need isn't worth anything.

Are 72cell panels hard to find/ expensive do you know




Appreciate the help ?

 

[sunshine_eggo]

Are


Are 72cell panels hard to find/ expensive do you know




Appreciate the help ?

No. Quite common. They're "24V" panels.

 

[SamDeleted]

No. Quite common. They're "24V" panels.

Trina Vertex S 425W Black White Mono

High-power mono panels with half-cell technology for optimal energy production with minimal loss.

midsummerwholesale.co.uk

 

[sunshine_eggo]

Trina Vertex S 425W Black White Mono

High-power mono panels with half-cell technology for optimal energy production with minimal loss.

midsummerwholesale.co.uk

Yep.

Up to 2S5P would work.

 

[SamDeleted]

Brilliant

It might cost me a few pennies extra but at least I'll have a working system

Thanks again