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

[Dan Fink]

I agree that this list is *the bomb*.
I think back to the old days of PV, where arrays and gennys were either
mostly on or off, and the "Absorb" phase was mythical....but really it is
the only thing that actually brings a battery bank to 100% SOC, and the
controller just lets it happen, rather than causing it.
Most batteries don't just die, they are murdered!
-- 
Dan Fink,
Executive Director;
Otherpower
Buckville Energy Consulting
Buckville Publications LLC
NABCEP / IREC accredited Continuing Education Providers
970.672.4342 (voicemail)



On Thu, Nov 1, 2012 at 7:40 PM, Mick Abraham <mick at abrahamsolar.com> wrote:

> 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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