[RE-wrenches] Battery Experience

R Ray Walters ray at solarray.com
Sat Jul 14 13:32:23 PDT 2012 

The cycling I referred to is just the normal load cycling of the charge controller raising the voltage each day to the absorption voltage and then the voltage slowly dropping over the night, along with the battery's self discharge. It's not a lot, so the 5% side includes an inverter in search mode and metering loads.  Don't forget the charge controller itself takes a couple of watts.  The DOD % is low, but it still results in some long term sulfation.  No matter what we do the battery won't last indefinitely.

As for your experiences, yes, the charge controller not coming back on because the battery voltage is too low has been a real battery destroyer.  The C40 definitely had that problem.
In cold country, add freezing and cracking all the cells, and it's game over for the entire bank.
As for 5 yr old L16s?  A shorted out (dead cell) is pretty much par for the course at that life span.  My own set of L16s had a dead cell at 4-1/2 yrs.  They're not a great deep cycle battery IMHO, except maybe the new high cycle life models from Trojan.  The old L16 had a cycle life of about 550 to 600 cycles to 80% DOD.  The old T105 golf cart battery was rated at 750 cycles, and was much cheaper per AH.

Ray


On Jul 14, 2012, at 1:58 PM, Jason Lerner wrote:

> Hi Ray,
> 
> With no inverter in the system and all the loads turned off do you think the batteries are really cycling that much?  Yes your scenario's sound familiar.  My favorite is a load is left on, the charge controller turns off most, but maybe not all the loads with the LVD,  but the battery keeps discharging until the battery Voltage gets to low so that Charge controller turns itself off so that now no PV charging can occur.
> 
> Speaking of battery cell explosions, this spring I had my first.  A customer with 8 L16's and 600 watts of PV came to his vacation cabin and found one cell had blown up,  with scorch marks on the inside lid of the battery box.  There is plenty of ventilation in there,  the owner was meticulous about maintaing this 5 year old battery bank.  All cables were bright and tight with no sign of corrosion or electrolyte sheen on top of the batteries.  I took it back to the manufacturer who shrugged their shoulders and said, "internal short,  it happens...."
> 
> Have I been lucky not to experience this before?  They made it sound like it happens fairly often.
> 
> Thanks,
> 
> Jason
> On Jul 14, 2012, at 10:33 AM, R Ray Walters wrote:
> 
>> The batteries in your scenario are actually being cycled daily probably somewhere in the 2 to 5% range.  Looking at a chart for # of cycles vs. DOD, you see the most efficient use of the battery is usually from 20% to 80% DOD,  an FLA battery in perpetual float just doesn't last as long you might think. Depending on the brand of golf car battery, I would give this system a maximum life span of 10 years.
>> Maintenance will eventually be the issue; sometime in the battery's life, it will be over charged, left for weeks under charged, or let the water go dry.
>> A typical scenario I've seen many times: charge controller fails because of lightning, small load is left on, and the battery gets fully discharged.  Since no one is there, it sits for weeks and becomes permanently damaged.  Scenario 2 is similar:  a load is left on (light in a closet) fridge or pump stays on and malfunctions,  and the system crashes.
>> Scenario 3 no temp compensation, battery gets over charged in the heat, boils its H20 off a couple of cells, the dead cells pull the rest of the bank down in spiraling failure that can actually do damage to the house: acid spills, corrosion, and exploding cells.
>> I find my off grid systems that fare the best are well designed full time use with one or two people who are very consistent in their use, and maintenance.
>> I've replaced batteries every couple of years on some part time systems, because simple problems are not caught for weeks or months.  I have a couple of higher end part time systems that the owner can monitor and contact us, if for instance the power goes out.  This keeps it from leading to permanent damage.
>> 
>> Ray Walters
>> 
>> On Jul 14, 2012, at 8:58 AM, Jason Lerner wrote:
>> 
>>> Hello John,
>>> 
>>> Thank you for your helpful explanation.  I wonder if there should be a "six" life,  that being time.
>>> 
>>> Lets use the small summer cabin analogy that gets used for one month a year.  Let's say the system has Four T105 -RE's,  500 watts of PV, 4 average daily sun hours. They do one discharge/charge cycle down to 20% DOD and then fully charge again the same day for a 2 hour absorb.  That would be 30 discharge cycles a year x 8 years = 240 discharge/charge cycles.
>>> 
>>> If one was to design and instal a proper battery based system using the guidelines presented in this email thread with plenty of PV for daily charging,  periodic EQ's, 20% or less DOD, no electrolyte on the battery tops to cause corrosion, never letting the plates go dry from low electrolyte level and having them at a cool 60º F year round would you expect this summer cabin system to last 4000 cycles?  In a perfect world would that be 4000 cycles ÷ summer cabin 30 discharge/charge cycles a year = 133 years ??
>>> 
>>> Of course I am not expecting that,  but am just trying to squeeze the longest life span possible out of batteries that mostly just sit.
>>> 
>>> Best,
>>> 
>>> Jason Lerner
>>> 
>>> Waldron Power and Light Co.
>>> On Jul 13, 2012, at 10:33 AM, John DeBoever wrote:
>>> 
>>>> Wrenches,
>>>>  
>>>> Forcing a lead acid battery to cycle for the fun of it reduces its cycle life.
>>>>  
>>>> In a nutshell, lead acid batteries have “five lives”, each varying depending their specific intrinsic technology attributes developed by the battery OEM:
>>>> o   Cycle life
>>>> o   Corrosion life
>>>> o   Stratification life
>>>> o   Shorting life
>>>> o   And… Temperature life
>>>>  
>>>> These lives are all inter-connected and temperature is the one that is the most influent to all of them. The interesting part is that all of these “5 lives” are 90% of the time exacerbated by the system sizing (cyclic/non-cyclic, loads, insollation, PV array, battery bank size, wiring and power conditioning losses, etc.), the install, the setting points commissioning, the maintenance, not to forget the load patterns (perceived vs. reality dynamics and growth of the load).  Cycling for cycling does not increase the battery life. Adequate cycling based on adequate full recharge keep the battery in good health.
>>>>  
>>>> John
>>>>  
>>>> John F. DeBoever
>>>> Global Technical & Projects Director – Renewable Energy
>>>> Trojan Battery Company
>>>>  
>>>> 12380 Clark Street
>>>> Santa Fe Springs, CA 90670
>>>> Tel: +1-562-236-3000 Ext. 3139
>>>> Cell: +1-845-514-7600 – NY office time zone: USA EST (GMT-5)
>>>> Skype: john.f.deboever
>>>> Fax: +1-562-236-3239
>>>> jdeboever at trojanbattery.com
>>>> www.trojanbattery.com
>>>>  
>>>>  
>>>> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of larry at starlightsolar.com
>>>> Sent: Friday, July 13, 2012 12:18 PM
>>>> To: RE-wrenches
>>>> Subject: Re: [RE-wrenches] Battery Experience
>>>>  
>>>> Jason,
>>>>  
>>>> Forcing a lead acid battery to deeply discharge does not increase capacity or life of the battery. It only shortens battery life and may damage the battery. This is one of many battery myths. 
>>>>  
>>>> Larry Crutcher
>>>> Starlight Solar Power Systems
>>>> -------- Original Message --------
>>>> Subject: Re: [RE-wrenches] Battery Experience
>>>> From: Jason Lerner <wapalco at rockisland.com>
>>>> Date: Fri, July 13, 2012 7:28 am
>>>> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>>>> 
>>>> Hello John,
>>>>  
>>>> This time of year I service off grid summer cabins where people come up once a year for a few weeks.  The batteries in these systems generally do not die from over cycling,  but from over/under watering,  acid stratification, corrosion,  and generally being ignored.  The more savvy customers I will recommend they turn off the PV's when they are there to get a deep discharge in.
>>>>  
>>>> Could you recommend any thing else they could do to lengthen their battery bank lifespan? These systems generally have a small PV charging capability,  and float charge 350 days a year. It seems ironic that these systems that really never get used,  and my battery bank at home that gets used (but not abused) and cycled daily, will last the same number of years.
>>>>  
>>>> Thanks very much,
>>>>  
>>>> Jason Lerner
>>>>  
>>>> Waldron Power and Light Co.
>>>>  
>>>> 
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