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Compass Marine How To | all galleries >> Welcome To >> Installing A Small Marine Solar System > Do I Need A Controller ?
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Do I Need A Controller ?

I get asked this question quite often and the answer is almost always a resounding yes.

In this photo I have two group 27 batteries, in parallel, consisting of 160 Ah's at the 20 hour rate. The batteries were fully charged then went into float mode.

As we can see on the digital volt meter the current accepted / needed to maintain a float condition, on these two parallel group 27 batteries, is just 0.08A or eight one hundredths of an amp. EIGHT HUNDREDTHS OF AN AMP!

A rather diminutive 10W panel can produce about 0.51A. Even with a small panel if the bank is left on charge for multiple days at a time, with no loads as is the case with many boats, you can over charge your batteries. While that difference may not sound like much the difference between the 0.08A the batteries want to accept at float voltage and what a 10W panel can produce, about 0.51A, is a 537% increase in current.

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