[RE-wrenches] Tri-Star MPPT

[Ray Walters]

Did you look for dead cells?   I've seen many L 16 sets  (including my 
own) only last 4-1/2 years, so that set was already almost done.  If she 
started mixing new batteries in before, she knew she already had a 
problem.  Did this system change from 12 v to 24 v?  The rule of thumb 
for eons  (or at least the long history of lead acid batteries) is that 
a mixed set of new and old batteries will only last as long as the 
oldest battery.   The new batteries will be chronically undercharged, 
while the old ones will be chronically over charged.
My guess is the higher charging rate available  caused some already 
heavily sulfated cells to go ahead and short out.
It's like giving a gasping man some oxygen, and then he goes into 
cardiac arrest.  You did what you could, but those batteries were on 
their way out already.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 7/23/2013 3:36 PM, William wrote:
> Brian:
>
> I don't have the PV details handy but I will provide them.
>
> Question:  will a sulfated cell exhibit a SG of 1.26?  I thought a 
> sulfated cell locked the acid onto the plates, minimizing the SG 
> readings below that of a healthy cell. 1.26 is a relatively high reading.
>
> William
>
> On Jul 23, 2013, at 1:28 PM, Brian Teitelbaum 
> <bteitelbaum at aeesolar.com <mailto:bteitelbaum at aeesolar.com>> wrote:
>
>> William,
>>
>> What does the PV array consist of? What size and type, and how many, 
>> modules?
>>
>> Which TriStar? 45 or 60A?
>>
>> What controller did she have before the upgrade?
>>
>> The high charging voltage might be a sign of sulfation. Depending on 
>> her load profile, that 8A charge rate might have caused chronic 
>> undercharging. In a 5 peak sun-hour location, that's only 40Ah/day of 
>> charging capacity.
>>
>> Brian Teitelbaum
>>
>> AEE Solar
>>
>> *From:*re-wrenches-bounces at lists.re-wrenches.org 
>> <mailto:re-wrenches-bounces at lists.re-wrenches.org> 
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of 
>> *William Miller
>> *Sent:* Tuesday, July 23, 2013 1:13 PM
>> *To:* RE-wrenches
>> *Subject:* [RE-wrenches] Tri-Star MPPT
>>
>> Friends:
>>
>> I have a customer with a new Tristar MPPT controller. The customer 
>> has some older L-16 batteries mixed with new and she thinks the 
>> controller has damaged her batteries.  I am trying to convince her 
>> that the batteries were already damaged and mixing old with new is a 
>> bad idea.
>>
>> I removed the worst batteries from the array, leaving one string of 
>> older batteries with reasonable SG readings.  The CC still acts 
>> strangely:  When programmed to charge the L-16 batteries, the battery 
>> voltage shoots up to 30.2 volts and the batteries boil a lot.  The 
>> green light on the controller blinks at variable rates, at one moment 
>> fast, the next slow, the next solid.
>>
>> I believe the client started with bad batteries, 6 are 4 years old, 2 
>> are 1 year old.  She is convinced that the CC damaged her batteries.  
>> She replaced panels and CC recently, installing the Tristar.  I 
>> believe the old PV system charged at such a slow rate (8 amps) that 
>> the battery deficiency was not apparent.  The higher charging rate 
>> has emphasized the problem.
>>
>> Any one have any thing to add to my theory?
>>
>> Thanks in advance.
>>
>> William Miller
>>
>> <image002.jpg>
>>
>> 17395 Oak Rd. Atascadero, CA 93422
>>
>> www.millersolar.com <http://www.millersolar.com/>
>>
>> 805-438-5600 voice*
>>
>> *Note: above number replaces cell number
>>
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