[RE-wrenches] PV excellent battery charger

[Warren Lauzon]

Actually, PV is not a particularly excellent battery charger, except for the 
single fact that it runs from sunlight.

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

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Northern Arizona Wind & Sun - Electricity From The Sun Since 1979
Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
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----- Original Message ----- 
From: <drake.chamberlin at redwoodalliance.org>
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Sent: Thursday, March 25, 2010 3:40 AM
Subject: Re: [RE-wrenches] PV excellent battery charger


> 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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