Chuck,
those numbers don't make a lot of sense.
I have not followed this thread, but the least aggressive float charge regime
for any SLA (can float indefintely) is 2.25V/cell near end of charge , so 13.5V
for a "12V battery" . A more typical still conservative charger can float
for long periods at 2.3V/cell near end of charge, or 13.8V for your battery.
If you want to have any hope of recovering sulphated cells and for cyclic
applications,rejuvenation etc 2.45V/cell or 14.4V, which is about what a car
alternator is set to charge at. A smart charger may charge at higher
voltage (2.45/cell) until current drops to a certain level and then drop back
to a less agressive long float regime, so it is possible that one of your
chargers does that, but you are reading the lower voltage in float mode when it
has already throttled back
The cutoff voltage where the inverter stops operating is typically set to
somewhere between 1.5 and 2V a cell, depending on expected max current of load,
with 1.8V being a common value for moderate load (10.8V cut off V for battery).
12.3V is way too high. I think what may be happening is you have a sulphated
battery and the internal battery impedance is now so high, the voltage drops
out at peak load to below the cutoff point immediately, even though the battery
is fully charged. When you read voltage, it is oscillatiing between switching
invertor on and off giving a misleadingly V value.
If you had a battery cycler with an aggressive charge regime and fully
discharged and charged the battery 10 or 20 times, you likely could reduce
impedance quite a bit and might get your bees flying a bit more.
At 2.3V/cell it takes more than 20 hrs to fully charge most SLA's,if you want
to prevent your battery from slowly cycling down.
There are a number of slightly different SLA technologies and some have much
higher self discharge than others (not good for occoasional use) and also some
have better recovery from abuse. Try cycling the batteries using a light load
like an 8W car indicator light. Be very careful to set an alarm clock or
something to be sure you don't overdischarge.
Tim Hughes
--- On Wed, 9/16/09, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Subject: Re: [OM] More on the 12 volt SLA battery
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Date: Wednesday, September 16, 2009, 7:48 PM
Recall that this is just a little battery, only 12 amp hours. And the
inverter starts complaining about low voltage when the battery gets to
12.6 volts. It can still keep on for quite a while but the chirping
from the inverter gets bothersome.
Looking back on my 5 year old test notes I see that the Schumacher 1.5
amp battery charger/maintainer never got the battery over 12.85 volts.
The 6 amp auto charger, however, it running them up to 13.5. That
should probably give me a lot of extra shooting life.
Chuck Norcutt
Ken Norton wrote:
> Chuck, that number of full-dump flashes just doesn't seem right to me. I
> know those inverters are pigs when it comes to "overhead" current draw, so
> maybe you might be running into a time-based discharge pattern when using
> the AB 800s.
> Of course, this is referring to "normal" usage, not your current problem
> with a battery on life support.
>
> I do plan on seeing how much oomph my deep cycle marine battery gives when
> powering a pair of monolights. I know it will keep a laptop computer alive
> for 20+ hours. Hmm... Actually, now that I think of it, we got at least 24
> computer hours (sometimes with two computers) and six hours of 18w compact
> florescent runtime and the battery voltage was still about 10V
>
> AG
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