L-16 "cycling" requirements? [RE-wrenches]

[bbassett at rockisland.com]

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Some of what I've heard about batteries:

That lead acid batteries require some cycling to form the plates, unless 
the battery has tank formed plates, which means that the plates have 
already been formed before they were installed in the battery case. This 
also allows the manufacturer to match plates for more equal performance 
and a better battery too. 

I've also heard, I think from Ralph Heisie (sp?) of Bogart. That it 
might be possible that the total cycle life is pretty closly related to 
the total number of AHr's discharged form the battery over it's life 
regardless fo depth of discharge. Maybe if you talk to him you could ask 
if he still thinks that might be true.

A battery can be brought to a full state of charge by either charging 
for a shorter time at a higher voltage or for a longer time at a lower 
voltage, within limits. Even a NiCd battery can be fully charged at a 
lower voltage than normal if left long enough. This is also why 
batteries show thet signs fo being overcharged if they are left on float 
24/7, unless the voltage is fairly low.

Brad
AEE Solar



 	One thing to remember is that with flooded batteries like the L-16,
especially if they are constantly on float as in a grid tie
application, they should be cycled 5-10 times when they are new to
form the plates. If not, you will see a permanent reduction in
capacity. I learned this the hard way when I installed my own grid
tie system ablut 10 years ago and never cycled the batteries, only
to see a reduced capacity much later when it was too late.
Jon Hill, Sierra Solar Systems
Doug Pratt wrote:
> 
> Ya know Todd, now that you ask, I can't point to a definitive source 
> that
> says "cycle your deep-cycle batteries periodically or lose capacity", 
> but
> that's been my understanding for lead-antimony cells. They tend to get
> "stiff" chemically and won't go as deep without dropping voltage. My 
> years
> of driving an EV certainly support this. Need to do a long trip? There's
> nothing like a modest warm-up cycle or two to make your batteries 
> deliver
> more kWhrs without voltage sag.
> 
> Lead-calcium is a different critter, and loves to just float and float 
> with
> most cycles no deeper than 10-15%. But as you've found, since Ma Bell 
> quit
> using 48-volt relay-based switches (in the '80s), which required 
> monstrous
> banks of cells, lead-calcium wet-cells have become rare. 
> 
> Given my druthers with sealed batteries, I prefer gels. They've got more
> moisture in them initially, so they're a bit more tolerant of abuses. 
> But
> they're harder to manufacture, therefore more expensive, and not always
> worth the higher cost. My own Outback grid-tie system has a set of 550 
> Ah
> Yuasa industrial gels on it ($$$!!!), and I'd sure like to see 20 years 
> out
> of them. (Ask me again in 15 years...)
> 
> My biggest beef with wet-cells on grid-tie systems is that folks will 
> forget
> to water them. Since they're used infrequently they sorta slip from 
> memory
> and the next thing you know it's been 8 to 30 months since the last
> watering. I've yet to visit a grid-tie system with wet cells that didn't
> have plates showing (other than brand-new). It's just inviting trouble.
> 
> Thanks for the $/kWh/yr calcs. Good info!
> 
> Cheers,
> Doug Pratt
> 
> 
> -----Original Message-----
> From: Todd Cory, Mt. Shasta Energy Services
> [mailto:toddcory at finestplanet.com] 
> Sent: Friday, May 20, 2005 11:45 AM
> To: RE-wrenches at topica.com
> Subject: Re: L-16 "cycling" requirements? [RE-wrenches]
> 
> 
> I would also like to know where this idea came from that "batteries need
> exercise to stay healthy"? Trojan discounts that notion. They have also
> suggested that EQing a floating battery is unnecessary... the stir the
> electrolyte myth doesn't wash.
> 
> As I understand it, batteries have two "clocks working toward their end 
> of
> life.
> Once clock is a chemical clock... that even floated with no cycling, 
> they
> will
> only last so long. The other is a cycle clock... that counts the number 
> of
> charge / discharge cycles. Also of consideration is the length of time 
> they
> are
> left discharged due to the resulting sulfation that happens to the 
> plates.
> 
> We can talk all day about optimal bulk, float and EQ voltage settings, 
> but
> evidence suggests it is best to err on the side of slightly overcharging 
> wet
> cells rather than chronically undercharging.
> 
> I have found lead antimony wet cells are really not all that horrible in
> grid
> intertied applications, especially as with modern inverters like the
> Outback,
> float current losses are minimized. With hydrocaps watering is also
> minimized
> and a "cheapo" like a Trojan L-16 will typically last a good 10 to 12
> years...
> similar to their life expectancy in an off grid system. Plus, they are 
> very
> cost
> effective. Yes, a better wet cell would be a lead calcium configuration 
> but
> for
> some reason (probably manufacturing quantities?) they are horribly
> expensive.
> 
> As I understand it, lead calcium's are best for shallow cycling and 
> float
> service. (Perfect for battery back up grid ties.) I suppose the reason 
> for
> the
> price differential is that they are not mass produced as lead antimony 
> cells
> are. Last year I did some research about the price to replace those lead
> calcium
> wet cells at the hydro plant I work at since their "rated life" is 
> nearly
> up.
> (Guess who gets to take them home!)
> I believe the cost is going to be around $9K for 12 kW.
> 10 kWh of AGM's are about $1.2K
> By comparison 20 kW of L-16's were about $1.3K.
> 
> Price per kWh:
> Wet cell lead antimony: $65.00; life span ~10 years = $6.50/kWh/year 
> (deep
> cycle)
> Wet cell lead calcium: $750.00; life span ~20 years = $37.50/kWh/year
> (shallow
> cycle)
> AGM lead calcium: $120.00; life spam ~10 years = $12.00/kWh/year 
> (shallow
> cycle)
> 
> If labor is included in the above numbers wet cell lead calciums are 
> more
> price
> competitive.
> 
> 
> I agree that each application needs the proper battery configuration and
> chemistry. Grid ties with battery backup optimally need a different 
> battery
> chemistry than off grid. The problem seems to find a cost effective 
> approach
> to
> this application.
> 
> So Doug what do you use? AGM's?
> 
> This is a pertinent topic for the list, as with Outback GFX inverters, 
> grid
> intertied systems with backup power with no longer have to pay the
> inefficiency
> penalty we had with brand X's old SW design.
> 
> Todd
> 
> 
> 
> 

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