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Old 28-03-2016, 13:30   #31
noelex 77's Avatar

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Re: 12v vs 24v Solar

Originally Posted by Texlan View Post

In my installation I switched from parallel to series because at elevated cell temperatures the maximum power point voltage would fall below my LiFeP04's set float voltage of 27.2v. I would still charge, but lower and lower current the warmer the cells were.
Yes you did the right thing. A single "24v" panel (or multiple panels in parallel) is not suitable for charging 24v battery systems. The voltage is too low. You must have at least two panels in series.

This confuses a lot of people. "12v" panels are fine for 12v batteries their voltages are high enough. Vmp is typically around 17.5v. Unfortunately due to silly labelling "24v" panels do not have double the voltage of "12v" panels.

The Vmp of the panels quoted is 27.5v. The Vmp drops with increasing temperature and in practice this voltage is much to low for a 24v battery system. The panels are ok for a 12v battery system, but at least two must be connected in series for a 24v system.

I am not surprised they did not work well when connected in parrallel.

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