Battery strings [RE-wrenches]

[Kurt Albershardt]

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One thing to consider with paralleling the individual cells/batteries inside the string is the increased difficulty of isolating a string for maintenance or testing.  We connect individual strings (typically of large AGM telecom cells) through pullout fuses to a central busbar system on which all the load fuses also terminate.  *Every* connection to the central busbar is through a fuse or breaker, allowing for isolation when needed.




--On Monday, September 18, 2006 4:17 AM -0700 Darryl Thayer <daryl_solar at yahoo.com> wrote:

>
> Hello all
> It seems that all of these configurations get into
> trouble over time.  Reverse return is clearly better
> than just paralleling.  I have a two parrellel set
> that is OK todate, (3 years old, lead calcium flooded,
> 6 volt batteries, 48 volt string) it uses parralled
> batteries between the two strings.  I hope it reduces
> the chances of battery fires or problems if one cell
> goes bad.  Next time I am at the site I will force a
> charge or discharge and check if there is any current
> in the paralleling connections.
>
> The differences between sets of paralleled batteries
> can develope by slight temperature differences between
> the batteries.  And if a set gets warmer it will
> accept more power and get warmer. Sources of this
> tempature difference are suttle, and can be do to just
> ramdom nature.
>
> Darryl
> --- Bob Ellison <ellison at gisco.net> wrote:
>
>>
>> Todd,
>> I have thought about that but I am afraid if a high
>> resistance connection
>> developed in a couple strings it might just cause
>> the power to run in a zig
>> zag pattern through the battery following the lowest
>> resistance path.
>>
>> The best cure is still a single string, but unusable
>> in this case.
>>
>> Thanks,
>> Bob
>>
>> -----Original Message-----
>> From: Todd Cory, Mt. Shasta Energy Services
>> [mailto:toddcory at finestplanet.com]
>> Sent: Sunday, September 17, 2006 12:30 PM
>> To: RE-wrenches at topica.com
>> Subject: Re: Battery strings [RE-wrenches]
>>
>>
>> Has anyone ever tried a center of series string,
>> parallel intertie to the
>> same point on another series string? It might be a
>> wacky idea, but it would
>> help balance the strings to each other not just on
>> the ends but in the
>> middle of the string as well...
>>
>> Or another option would be to try paralleling every
>> battery in a series
>> string with the ones in the other string. That would
>> help insure the two
>> strings were balanced with each other. It'd make for
>> lots of battery cables,
>> but has anyone tried this?
>>
>> Todd
>>
>>
>> Drake Chamberlin wrote:
>>
>> > Although bus bars seem to be a better solution, I
>> don't think they are an
>> adequate solution.  According to veteran solar and
>> battery distributor,  the
>> different strings will develop variations in
>> internal resistance.  The
>> currents, and therefore the charging through the
>> individual strings will be
>> uneven. His solution is to stick with one string and
>> get bigger batteries
>> for bigger systems.












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