[RE-wrenches] PV excellent battery charger

[R Ray Walters]

On Mar 25, 2010, at 5:55 AM, Warren Lauzon wrote:

> Actually, PV is not a particularly excellent battery charger,

What is better than a properly sized array with the latest controllers?

> 
> Everything else mentioned can be done by any decent AC battery charger.

True, but at great expense. The traditional AC chargers like the ones made by Lester are industry standards, and are archaic in comparison.
Now chargers that come with say an Outback Inverter, that was installed as part of a solar system, do have everything as you mentioned except I'm not sure about the PWM.
We'd need to hear from Chris Frietas or some other Manu rep to further explain the charge regulation on the Outback inverters, and whether it uses PWM.
Outside of the solar industry, batteries are not treated near as well.

Ray

> 
> 
>> My understanding is that the voltage, in excess of battery voltage, from
>> the array, represents energy that is dissipated as heat in the batteries.
>> This extra voltage, multiplied by the amperage is wattage. This extra
>> power can produce more amps at a reduced voltage.  It is amperage that
>> charges the battery.
>> 
>> Thanks,
>> 
>> Drake
>> 
>>> MPPT doesn't really do that much for the battery, it just makes the PV
>>> modules more effective.
>>> The real magic is:
>>> A) the 3 stage charging (compared to traditional single stage AC chargers)
>>> B) Temperature compensation
>>> C) PWM that helps pulse off sulfation
>>> D) Slower charge rates let batteries charge more fully without damage from
>>> overheating.
>>> 
>>> R. Walters
>>> ray at solarray.com
>>> Solar Engineer
>>> 
>>> 
>>> 
>>> 
>>> On Mar 24, 2010, at 7:04 PM, drake.chamberlin at redwoodalliance.org wrote:
>>> 
>>>> Can anyone tell me why PV is considered an excellent battery charger? I
>>>> think it is, only after the addition of a MPPT charge control.
>>>> Otherwise,
>>>> the battery drags the PV voltage below Vmp.
>>>> 
>>>> One of the NABCEP objectives for the entry level class is to explain why
>>>> PV modules make excellent battery chargers and show this through the IV
>>>> curve.
>>>> 
>>>> Thank you,
>>>> 
>>>> Drake
>>>> 
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