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"constant current" ?


Adri
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The phrase 'constant current'  (CC) (regarding the bulk mode of charging most batteries), when is it "constant"?  Do you NEED  to charge batteries at THIS current, and no less?  Or can we charge said batteries at lower value current but not exceed this value?  (Ex.: Ni-Cads must be charged at CC for a fixed time to be fully charged.)

Or do they/we mean "current limit"? (meaning to limit the maximum current.) 

As I read it if I have PV rated less than the required/specified CC I will never meet the CC rating of the particular type/size of the battery with my particular setup.  In theory therefore I should never expect to reach beyond the bulk charge point to charge this (or any) particular battery.

On the contrary, if my PV can only produce (some) less Amps than the CC rating I should still be able to reach the bulk voltage point, but it will take a while longer.  If this is true then it should in theory be called "current limit" (meaning in effect "Do not / cannot exceed CC rating") and not "current control".

Some would call this nit-picking, but I prefer to know what "they" mean correctly, to better understand "them" and what "they" are saying.

(Perhaps it's a shade of "fake news" we're bombarded with daily...)

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1 hour ago, Adri said:

The phrase 'constant current'  (CC) (regarding the bulk mode of charging most batteries), when is it "constant"?  Do you NEED  to charge batteries at THIS current, and no less? 

"Constant current" is an old term from the lead acid days, way before PV charging was common. You charged from the mains, and in the bulk stage, you charged at either the maximum current the charger could provide, or the maximum current that the battery can handle. In either case, it was a constant, hence "constant current".

1 hour ago, Adri said:

On the contrary, if my PV can only produce (some) less Amps than the CC rating I should still be able to reach the bulk voltage point, but it will take a while longer. 

That's correct. But generally, you want to size your panels and/or charger such that it can usually charge the battery from empty to full in something like 8 hours. Otherwise, it won't be able to keep the battery full, and the battery will eventually just run out of charge, possibly to the point of damaging the battery. You also don't need charge hardware that can charge the battery in one hour, even if the battery could handle that. So in reality, there isn't a huge range of charge currents that make sense for a given battery capacity.

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To you and me that makes perfect sense. 

I just wonder how a beginner/novice will understand the concept correctly. Hence my query.  What makes sense?  How will these folk interpret CC / CL?       (Spoken or written science, interpretation, etc....)

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