@ 20Hr rating vs label 100 amp rate

[AHC]

Hi I’m new to solar and learning... I have 2 Trojan SPRE 12 volt 225. Recently I was advice by a friend to use the @ 20Hr rating instead of the 100 ah for programming the capacity on my Renogy Rover charge controller. The question is if I use the 225 x 2 (550) or the 204 x 2 (408) that is the @ 20Hr. Please any clarity on this subject is appreciated.

 

[fratermus]

instead of the 100 ah for programming the capacity on my Renogy Rover

Where is 100Ah coming from? The default in the controller?

The rated 20hr capacity of the batt is 204Ah per the specs (225Ah is the 100hr rating). If the batts are in series I'd plug 204Ah into the controller. If they are parallel I'd enter 408Ah.

 

[MichaelK]

The standard for capacity is almost always the 20hr rate. Trojan recommends a charge density of 1/8C. So, the math works out to be 225Ah X 2 batteries X 0.125C = 56.25A.

If you want a honest 56A out of your panels you need a fudge-factor to compensate for panel inefficiency. I usually recommend 85%. That is, you can realistically expect your panels to put out 85% of nameplate wattage.

So, to get an honest 56A you need (56.25A X 13V charging)/0.85 = 860W. You could get that with three 285W grid-tie panels.

Which Rover model do you have? Is it the 40A? Can it be exchanged for the 60A model? That's what you really need for an optimal system.

 

[AHC]

Thanks for the info. The 100 is in the upper label. It says 12 225 ah @100 hr. So I will use the @20 rating as advised. The controller is the Rover 60A model.

 

[fratermus]

The 100 is in the upper label. It says 12 225 ah @100 hr

Ahh. The thread title is a typo for "20Hr rating vs label 100hr amp rate"

 

[AHC]

Ahh Thanks