[RE-wrenches] Walking back my error re: charge regulation methods

[Mick Abraham]

Hi, Wrenchies~

I've been remiss in failing to send "props" to Larry Crutcher regarding his
clarification on how battery charge regulation really works. See his post
copied below. I see my error in that current is not directly reduced by the
charge device, but the controller pulses get shorter and shorter to keep
from exceeding the absorption voltage as the battery's internal resistance
rises. The internal resistance presents a sort of "back pressure" so the
amperage does diminish, but the reduced amperage is more of an effect than
a cause.

I'll try to reprogram my remarks along those lines in future. I'm sorry for
any mis-explaining from my side. Thanks, Larry, & again I say: The Wrench
List is the Bomb!

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675

---------- Forwarded message ----------
From: "Larry Crutcher, Starlight Solar Power Systems" <larry@
starlightsolar.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Cc:
Date: Mon, 15 Oct 2012 16:56:40 -0700
Subject: Re: [RE-wrenches] Off-grid non-inverter battery charger
recommendations?
Hi MIck,

I often see your explanation for absorption charge phase. Consider this:
While charging, current is applied without voltage regulation (CC). At the
charge set point, PWM control (CV) takes place to regulate voltage. There
is no control over current as the battery internal resistance dictates
this. For example, if you have a pure DC source at a constant voltage
attached to a battery, once the battery reaches that voltage, charge
current will naturally start to decrease.

I find it interesting that many people, including some manufacturers,
believe a PV charge controller or AC battery charger is adjusting or
tapering the current supplied to a battery when it is the other way around.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103
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