flooded v. sealed batteries [RE-wrenches]

[Joel Davidson]

Bruce,

No argument here. PV systems with good forklift batteries that are properly
sized to start with and well maintained last 10 to 15 years as compared to T105s
and L16s maintained just as well that last 6 to 12 years.

Bob Hammond's battery survey at http://www.sandia.gov/pv/docs/PDF/IEEE2.pdf is a
little dated but shows what batteries U.S. PV integrators were buying and
selling.

Best regards,
Joel Davidson

Bruce Geddes wrote:

> Hi All,
>
> Joel wrote:
>
> > Hi Matt,
> >
> > In general, L16s and forklift batteries are just big golf cart batteries.
>
> I disagree.  L16's yes, they are big golf cart types but traction cells are
> a different story.  I use T105's in mobile homes due to the weight but in
> off grid houses exclusively traction cells.  Down here (New Zealand) I deal
> with Exide for their Powerlift traction batts.
>
> To prove the point look at the cycle ratings.
>
> Trojan L16 600-700  cycles to 80% D.O.D.
> Trojan T105 500-600 cycles to 80%
> Exide Powerlift 1500 cycles to 80%
>
> The thing to watch out for is the capacity specs.  Most renewable power
> batteries are rated at C20.  Traction cells are rated at C5.  Golf cart
> batteries are C20.  BP Solar rate their PVstor at C100.
>
> C5 x 1.295 = C20 (close enough).
>
> Most "purpose built" renewable batteries are variations of the traction
> cell.  The antimony content of the grid is reduced to reduce gassing and
> this is not too bad as the renewable battery is not expected to cycle
> anything like the traction battery.  I don't find the extra cost for purpose
> built batteries justifies the difference.  Downside for traction batteries
> in difficult locations is that they link with big lead straps that are
> sweated on to the posts.  A bit tricky to apply but boy does it make for a
> great, trouble free intercell connection!  No corrosion or volt drop.
> Purpose built types have a different post, usually with leads and bolts.
>
> In temperate climates the flooded lead acid battery is the best compromise
> in cost, performance and lifespan.  If the ambient temperature is around 30
> degrees celcius or higher industrial NiCd will give better life for the
> cost.  Downside is that NiCd is less charge efficient and higher self
> discharge.  Some of you may be able to use NiFe which is less efficient
> again than NiCd and has self discharge in the order of 3% per day.
>
> Sealed lead acid has its place also.  A flooded battery has greater ability
> to dissipate heat as electrolyte is in contact with the case over a large
> area and will generally outlast a sealed battery in equal installations.
> They can also be pushed a bit harder on charging and discharging.  A sealed
> battery will outlast a poorly maintained flooded battery though.  I use
> sealed batteries in places where maintenance is likely to be overlooked or
> at extended intervals (holiday homes).  Of course with the encapsulated
> electrolyte a sealed battery can be installed indoors more easily than a
> flooded.  This may be an advantage in very low temperature environments.
>
> So what is the "best" battery?  That depends on a number of factors like
> environment (temperature), cost priority, skill of the installer (welding
> versus bolts), acess to different types, etc.  No one battery is ideal for
> all situations.  Everything is a compromise and it depends on what weighting
> you give to each factor.
>
> Bruce Geddes
> PowerOn
> info at poweron.net.nz
> www.poweron.net.nz

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