Death of a battery
5-14-06
75 amp hour EverStart battery
test done, see below.
This page is about how I revived two weak
batteries that I use at the cabin.
Sunnyway 20 amp hour AGM battery. This was the original battery in my
Xantrex 400 plus. Since I really never used the
spotlight or the air compressor (I can just use a
power cord for it anyway), while I was taking the
Xpower inverter out of the unit, I also grabbed
the battery. An interesting aside about the
battery: The manufacturer is Sunnyway and this is
a 20 amp hour battery. Sunnyway is an Indian
battery company and while they have batteries that
look exactly like mine, none are 20 amp hour.
Xantrex says to order replacement batteries from
Enersys, but that is now Exide batteries and don't
support Xantrex units. So I'm on my own.
Anyways, this battery was used
for about 2 years in the Powerpack and I noticed
that it was getting weak. I figured that was it,
in the words of Scotty on Star Trek, "Aye
laddie, she's dead for sure!"
Exide EverStart (Wal-Mart) 75 amp hour deep
cycle battery. This battery was
part of my original bank and is about a year old.
Recently while at the cabin, I rewired the bank so
all the batteries are connected to one central
point (known as a combiner) rather than wiring
them as one big 'ol battery. That's when I notice
while testing them individually that this one was
weaker than the rest. It's always been a problem
child but it seemed to perform well. So out it
came from the bank and into my electric boat as
the power source.
20 amp hour AGM revival:
This battery is pretty cool. Small, nice wire
connectors and a decent power capacity for running
small stuff. I noticed that while it would take a
charge, the thing would hold it under load for
oh......a minute! Alas I thought it was a goner,
so with nothing to lose:
Using a battery charger from my days in RC
planes, I connected the battery to it. The charger
is for Lith-ion batteries which can 'splode if not
charged right. It puts out 17.6 volts at 1.12 amps
shorted and 14.6 volts under load (varies the
power output to the battery).
The initial charge on the AGM was 12.45
volts. While it would go to 14.8 volts,
it would not hold the charge.
First, I connected the charger to the battery
for 10 hours. The charged voltage was 12.90
volts. So, I disconnected the charger and let
the battery sit overnight.
I then connected the charger again for another 10
hours. Now the battery was at 13.60 volts.
So I let it sit again.
Next I did the charge thing again and after 10
hours, the voltage was now 14.8 volts and
at rest it was 12.80 volts. With a load, it
worked well.
So, I repeated the process. Then, as a test, I
ran one of the 12 inch/12 volt circulation fans
at the cabin and a 12 volt CF light for 2 days.
Not a problem. Next, while I'm here at the house,
I'm going to connect a 6 amp load and go
from there.
75 amp hour deep cycle:
update: after using the
method outlined below, I ran 10 watts 6 hours a
day off this battery with a 6 amp draw for 1 hour
for a total of about 30% of the capacity used.
Final charge was 70% so all is good.
This battery has always been a little bit of a
problem, so I decided to solve this once and for
all with a combination of equalizing and slow
steady charging.
First, I measured the capacity. For a 75 amp
hour battery, running my 6 amp test load
for just an hour before pooping out was not good.
Okay, so I used my Vector smartcharger
at the 10 amp rate and let it charge for
several hours until the battery temp. went up as
measured from the side of the case. Now I used
the dirty little secret of wet cells. I shook it.
This releases the bubbles trapped between the
plates and mixes the electrolyte in the battery.
After letting it rest, I did the same process
at 6 amps but for half the time.
Next, I let the charger do an automatic charge
which starts at bulk, goes to absorption and then
hits a trickle charge.
The battery is now been running a 12 volt
light (5 watts). Starting at 12.81 volts,
it is at 12.67 volts and dropping slowly.
Next, it's a full charge and a test with my ye'
olde 6 amp test draw.
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