Just how good are those used, sealed lead-acid batteries? [RE-wrenches]

[Jeff Clearwater]

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Hi Mick,

Bravo Mick - best answer yet IMHO.  The quick and dirty methods just 
won't tell you for sure what you got.  My method was labor intensive 
- Micks' does true amphours with less labor - this is the way to go.

Jeff C.
Village Power Design



>Hi, Bob~
>
>For real world battery testing, I suggest actual amp-hour measurement
>during discharge. The results from this approach are neither instant nor
>stress free to the battery, but they are reliable.
>
>I built a gizmo that I affectionately call the "Battery Hammer". My rig
>uses a Tri-Star 60 controller with digital meter option, but a Trace
>C-series controller with DVM would also work. The integrated meter
>avoids the need for a separate amp-hour meter with shunt.
>
>If you configure the controller as a "low voltage disconnect", it will
>automatically terminate the discharge for you. The meter will tell you
>how many amp-hours the battery string delivered before reaching the low
>voltage cutoff point. Add a couple of breakers, cable, and a suitable
>load. The "suitable load" is the tricky part...I could post further on
>that if list members are interested.
>
>With a rig like this, you can "set it & forget it", then come back later
>to see the results. However, I often spot check the voltage for the
>weakest segment in the string. If one segment is low by .5 volts when
>the string is at rest, that "delta V" typically becomes much wider when
>you impose a load. If the voltage drops precipitously on one segment of
>the string, the LVD switch stops the discharge while there is still
>usable energy in the other segments. 
>
>(If you observe this problem, contact me off list about a battery
>balancer which can prop up the weak segments of the string by robbing
>energy from the stronger ones, thereby enabling higher amp-hour delivery
>before the LVD point is reached. You could replicate my own experiments
>with the balancer and post your findings to the List.)
>
>The "Battery Hammer" has proven useful to me and to my clients. With all
>the used C-40 controllers that are in circulation, a similiar test rig
>could be built for relatively low cost. Considering all the times that
>I've looked at a battery bank and wondered about its capacity, it's
>great to now have a tool that can answer that question in genuine
>amp-hours.
>
>Mick Abraham
>Abraham Solar Equipment
>Pagosa Springs, CO
>www.abrahamsolar.com
>
>Bob Clark wrote:
>
>how do I know how "good" a used, sealed battery is?...how do I determine
>its condition (and capacity to hold a charge)?
>
>
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com
NABCEP (tm) Certified Solar PV Installer

530-470-9166
877-SOLARVillage
877-765-2784
65 Schoolhouse Rd
Amherst, MA 01002
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~


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