[RE-wrenches] PV excellent battery charger

R Ray Walters ray at solarray.com
Thu Mar 25 14:49:52 PDT 2010


Of course, the MPPT makes the PV array behave like a larger array, but that's comparing MPPT to non- MPPT, I thought you were comparing PV to a regular AC charger.

R. Walters
ray at solarray.com
Solar Engineer




On Mar 25, 2010, at 4:40 AM, drake.chamberlin at redwoodalliance.org wrote:

> 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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