Down-sizing battery systems [RE-wrenches]

[Doug Pratt]

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No doubt about it, battery packs are getting smaller. Mostly because 98% of systems are grid-tied now, and for those few that elect to go with battery backup, 4 to 8 hours of runtime is fine. For the off-grid systems, as Jeff has noted, electrical loads have increased, plus, battery costs have skyrocketed, and where I used to always aim for 4-5 days of storage (@ 60% DOD), costs are often forcing me down to 2.5-3 days. I warn dealers that this is going to impact battery life expectancy, but it's a tough sell for dealers who do a battery-based system once every year or two, and really don't understand batteries at all. Hey, but on the other hand, generators are getting better, and cheaper, so maybe this isn't such a bad thing.

Cheers,
Doug Pratt
DC Power Systems



> ----- Original Message ----- 
> From: "Jeff Yago"
>>
>> Over the years I have noticed we are designing smaller and smaller
>> battery
> banks for both grid-connected and total off-grid applications.
>>
>> I think this may have come from the pre-90's solar design goals that
> off-grid applications should have 4 to 5 day of autonomy.  This was easy
> to
> do when the only electrical loads were a refrigerator, a few lights, and a
> small television.  However, this is harder and harder to achieve these
> days
> as more and more homeowners consider multiple computers, a satellite
> receiver, high-speed Internet, recessed lighting, a 60" television with
> theater-sound, and a dish-washer as must-have  necessities.
>>
>> To reduce battery space requirements and costs, we are starting to
>> install
> off-grid systems with fewer days of battery-only capacity, and relying on
> a
> back-up generator to re-charge when solar is not available. I also think
> since it is now easier to sell back to the grid, perhaps there is less
> need
> for huge battery banks in battery back-up type solar systems to absorb all
> that excess power when installing a large solar array.
>>
>> Anybody out there doing battery based systems that are starting to notice
> these market trends?
>>
>> Jeff Yago
>>


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