[RE-wrenches] Electrolyte Dilution vs Voltage

[Ray]

I'm sure part of the problem is no load current circulation, but much of 
the problem can be seen with a clamp on meter while charging.  I've seen 
parallel strings pulling 10 amps on one string and 1 amp on the far 
end.  Not subtle at all, and very easy to understand why it would lead 
to unequal battery charging.  Let us know William what you find out with 
your extra shunts; we always appreciate your keen mind and desire to get 
to the root of the problem in a no nonsense manner.  I think resistance 
checks of the batteries and arranging the batteries into strings of 
equal resistance might help too, but yes, less parallel strings is better.

Ray Walters
Remote Solar
303 505-8760

On 7/18/18 7:33 PM, William Miller wrote:
>
> Colleagues:
>
> I believe that circulating currents in multi-string battery 
> installations are a major cause of premature failure of such a 
> system.  I think it is important to monitor these currents.  Most 
> telling would be checking these currents in an at-rest scenario.  It 
> would be helpful to have a baseline at install and then check 
> periodically.
>
> Measuring these currents with any type of DC clamp-on meter can be 
> inaccurate at best.  In a conversation with Steve Higgins at a recent 
> trade show I came up with this idea that may have some merit:  If an 
> install has more than one string of batteries, install an 
> appropriately sized shunt in the negative lead of each string.  At any 
> later date you can apply any decent voltmeter with a millivolt scale 
> and check for battery string imbalance with some degree of accuracy. 
> Shunts are cheap and readily available and if you avoid the brand that 
> Outback uses in the Radian GSLC cabinets, they are relatively rugged.
>
> We will be trying this in any future install with multiple strings, 
> although we avoid this if at all possible.
>
> William Miller
>
> Gradient Cap_mini
> Lic 773985
> millersolar.com <http://www.millersolar.com/>
> 805-438-5600
>
> *From:*RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org 
> <mailto:re-wrenches-bounces at lists.re-wrenches.org>] *On Behalf Of 
> *John Blittersdorf
> *Sent:* Wednesday, July 18, 2018 6:24 PM
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] Electrolyte Dilution vs Voltage
>
> Mac,
>
>   I was about to ditto Ray with his more common than I would like 
> scenario of battery death when I saw your mention of the 2nd string 
> not connected. It is always nice to see
>
> a solution that is simple and should have been considered, but wasn't. 
> The assumption with battery issues usually is that they are actually 
> hooked up!  I often thought that it would be worth the money to supply 
> a cheap AC/DC clamp meter with every installation so that a phone 
> consultation could quickly determine if the strings were unbalanced 
> and what might be the reason. Bad cells and bad connection  will 
> usually show up in a current check and then a quick voltage check of 
> each battery with a load on the system will show the culprit if a bad 
> cell and corrosion present might find the bad connection.  I use 
> Interstate L16's most of the time and find that the life is typically 
> 6 years.  I used to call them a 7 to 10 year battery but kept 
> racheting back the claim until I now call them a 5 to 7 year battery 
> with more if properly maintained.  I have seen 10 years but it is rare.
>
> John Blittersdorf
>
>
>
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