L-16s like higher voltages [RE-wrenches]

[Joel Davidson]

Good discussion. Running a fossil fuel generator to equalize PV system
batteries and criticizing utility companies and other polluters is like
driving a car or truck and hating Arab oil but that's another topic.
Arco Solar did a disservice to the PV industry promoting so-called
self-regulating 30-cell modules that almost never equalized batteries.
Even 33-cell modules can be too low voltage. 36-cell modules can
equalize batteries nicely. 14.8 volts terminal charge voltage works
nicely. I've shied away from BP grooved grid modules because the extra
voltage was higher than equalization. Other opinions?

"David Palumbo, Independent Power & Light" wrote:
> 
> >2. The report's conclusion that its necessary to EQ at 15.3 v (2.55v/cell)
> >for up to 20 hours on a regular basis ( weekly or less) is totally
> >impractical offgrid. They mentioned using a generator to do this, but that
> >would totally negate any  environmental or cost benefits from going solar
> >in the first place.
> 
> <<I am puzzled when I read of this practice too.  It sounds as if some
> people do this.  They use a charge controller to deliberately limit
> the voltage of the batteries when running on solar power (or wind)
> and then burn fossil fuels to wildly overcharge them from time to
> time.  It makes more sense to me to use a higher voltage setting on
> the controller, or no controller at all, if the batteries need more
> charging.  Equalisation should then only be needed as a last resort
> if some cells are getting low.  Hugh>>
> 
> I agree with Hugh.
> I have working with L-16's, and similar batteries for over seventeen years
> and have seen various people and systems get good results (equivalent of 900
> to 1,000 deep cycles, or 8 to 12+ years of useful life in a properly sized
> system )by following some simple basic rules.
> 1.) Make sure batteries are fully charged (100% on a accurate amp hour meter
> or hydrometer) at least once per week.
> 2.) Check each cell to make sure they are relatively equal (within .010 on a
> hydrometer, or .05 on a voltmeter). If some, or one cell, is out of wack
> then charge the battery bank (with an RE source if possible) until it comes
> up with the others. If it does not come up "exactly" equal to the other
> cells do not worry about it. Close is good enough in this game. Just make
> sure that you keep up with the checking so they do not drift apart too much.
> There are a few reasons why some cells will not catch up all the way with
> others in the same bank. Such as unequal sulfuric acid in the electrolyte.
> Upon shipping some cells spill a little; or when they were first filled they
> were shorted a bit. I also suspect that internal resistance may vary
> slightly from cell to cell as battery manufacturers tolerances are not as
> tight as facilities that work on electronics.
> 3.) Rotate the batteries within the pack (especially true with larger cell
> batteries where you are expecting a very long service life). Get the
> batteries that are on the + and - ends rotated into the middle every year or
> two.
> 
> I have also found that the recommended high voltages (above 15v) are not
> necessary to completely charge (what an equalization charge really is) lead
> acids if you follow the above rules. The length of the charge at 14.6 to
> 14.8v (at 78F) is what accomplishes the complete charge (all cells
> relatively equal). What's the point in heating up your cells if you don't
> have to?
> For instance you can tell when your batteries are well charged when charging
> with a Trace SW by the amps charging into to your batteries. After you have
> been in the absorption stage of charging for a while (1 hr more or less) at
> 14.6 to 14.8 at 78F you should notice your amps tapering off as the cells
> become fully charged. The amps will get lower the longer you charge. The
> cells should be equal (again, relatively) when the AC amps on the Trace
> meter read below 4 amps. You can also follow this on a good amp hr meter
> with a correspondingly higher DC amp number depending on system voltage.
> A good three stage PV charge controller and ammeter work the same way.
> 
> Best,
> Dave

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