[RE-wrenches] BZ Products Charge Controllers

[Larry Crutcher, Starlight Solar Power Systems]

Hi Mark,

I am a real stickler about terms and I hope to always further understanding about batteries so consider this: No charge controller "tapers" charge current. The reduction in current is due to the slowing of the electrochemical process as the battery is saturated. At constant voltage, you can provide any amount of amperage to the battery but it will only absorb what it can. This is a common misconception that I hear regularly.

Once the battery reaches equilibrium, that is, current into the battery equals the self discharge rate, then it is in float. The process to reach float stage is called absorption stage. So I suppose we could call the two stages Bulk and Absorb/Float.

Larry Crutcher
Starlight Solar Power Systems





On Apr 11, 2013, at 9:43 AM, mark at hurshtown.com wrote:

I see what you mean by no float/3rd stage.  Indeed the MPPT500 just tapers off the amps once it reaches the "float" voltage.

The MPPT250 however does have an undocumented(?) mode where once it thinks the battery is thoroughly charged, it only puts a brief burst of charge into the battery when the voltage sags to something like 13.8V.  The first time I encountered this I thought I had a bad controller.  This really does represent a form of float charge.

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