[KYHAM] Battery Lesson Learned...help needed

[Cecil E Ferguson]

Tyler,

I've noted with deep interest, all the responses you have received thus
far and they are creditable.  One thing no one has touched on, however,
is that when two batteries are parelled and float charged, a small
resistor placed in series with the charging lead for each of the two
batteries will serve a very good function.  They will tend to keep the
charging levels equal for the two batteries and each will tend to keep
that particular battery from being over charged.  If you use a 1 ohm
resistor in series with each battery, and you attempted to charge the
battery(ies) with say, three amps, you would expect the resistor to drop
three volts, thereby forcing the charging current back to a trickle
charge.  When the battery approached a full charge condition, the voltage
differential between the charger and battery would be reduced and the
battery would demand less charging current - also the resistor would no
longer need to, nor would it, drop as much voltage as before, a very good
protector..

The wattage of the resistor(s)  (for a one ohm device) would need to be
twice the rated current of the charger. If a 6 amp charger is being used,
I recommend a 12 watt, 1 ohm resister or even a 6 watt, one-half ohm
resistor for each battery.  These high wattage, low ohmic resistors are
easy to find.  One could parallel two or more resistors to gain the ohmic
value and power rating desired.  If a resistor is uses as described, the
load should be taken directly from the batteries, not through the
resistors, of course.

I would also recommend these resistors if using a solar panel with
parallel batteries.  You'll have far fewer problems.   

Oh, lead acid batteries used for starting, do take a float charge pretty
good.  I've used them with satisfactory results for many years of
service, exposed to varying temperatures, annually..  Too, the entire
time the engine is running on a vehicle, for exmple, the battery is
getting a "float charge."  I, too, recommend a deep charge battery,
however.  For your application, I believe the AGM type to be better
suited than the Gel type.  The Gel type requries a much more controlled
charging level.

Gene, KE4NNA.  (Formerly Transmission and Protection, telco; then Comm
Engineer with state of Florida, now retired) 
**********
On Mon, 14 Jun 2004 11:54:18 -0400 (GMT-04:00) wa4qal at ix.netcom.com
writes:
> Tyler Allison wrote:
> 
> > First the story...it's long.
> > 
> > I've been running a 12VDC battery system for about a year. It 
> powers my
> > ham radio equipment, my weather station and my home network (cable 
> modem,
> > hubs, wireless routers, etc).  It ran off (2) two 12V Everstart 
> Deep Cycle
> > Marine Trolling motors I purchased at Walmart.  I was very 
> careful, I
> > thought, about reading as much as I could about proper wiring, 
> wire size,
> > etc.  I hooked them up with black and red 6 gauge wire. Thicker 
> that it
> > needs be..I think. Everything was hooked up to an Everstart 
> 2/10/20 amp AC
> > charger that has auto-shutoff (green light) when everything is 
> fully
> > charged. I put the batteries in the garage since I'd read some 
> conflicting
> > stories about the risk of non-sealed batteries in the living area 
> of the
> > house.
> 
> The deep-cycle batteries are good.  Those are a lot better suited to 
> supplying 
> power for such operations than normal "starting" type batteries.  
> The starting
> type batteries are designed for delivering a high current burst of 
> power for a 
> short period.  Repeatedly deep cycling starting batteries usually 
> results in a
> fairly short life.
> 
> I show 6 gauge being good for 65 amps, ***IF*** the voltage drop is 
> low
> enough that it doesn't affect the equipment being operated.  It has 
> a
> resistance of .3951 Ohms per 1000 feet.  So, if you installed your 
> shack
> 50 feet from the batteries (and, remember, this isn't linear 
> distance, but
> wire distance, which will have to take into account all of the bends 
> and
> diversions that the wire follows), this is 100 feet of wire (50 feet 
> for the 
> positive side, 50 feet for the negative side).  If you were pulling 
> the maximum
> current of 65 amps, then the voltage drop would be 2.6 volts, which 
> may or
> may not be a problem.
> 
> The lesson here is that it is not only the current carrying capacity 
> that has to 
> be taken into account, but also the voltage drop at the maximum 
> current.  This
> can come into play with house wiring for especially long runs, but 
> it's more of
> a concern with 12 volt circuits due to the reduced voltage drop 
> margins.
> 
> > Okay now the 'lesson learned'
> > 
> > About 5 to 6 months ago(?) I noticed that I was never seeing the 
> green
> > light (auto-shutoff) when I would check on the batteries. I use 
> to. I can
> > see the charger everytime I pull in the garage. I figured it was 
> just
> > because I was pulling more amps than the charger could provide 
> when I had
> > it on the low 2amp trickle setting. So I pulled the manual out to 
> double
> > check and it seemed to read that I would be safe to put the 
> charger on the
> > 10amp settings since my batteries were large enough to handle the 
> higher
> > current (75AH each). So I flicked the switch to 10amp and thought 
> nothing
> > of it. I noticed that the green light still wouldn't come on but I 
> thought
> > maybe that had to do with the constant flow of current and it 
> would
> > 'never' show full. I took some readings while the batteries where 
> under
> > load with my amp/volt meter and everything looked normal.
> 
> Indicators usually mean something.  Of course, all too often they 
> indicate
> that something has failed, at which point, it's too late to do any 
> recovery,
> although prompt action can prevent further failures.  
>  
> > Anyway....more of the story.
> > 
> > In preparation of hooking up these batteries to a solar panel I 
> wanted to
> > cleanup my wiring. I installed circuit breakers, an on/off box, 
> the works
> > in my basement. I tested all the wiring, unplugged the batteries 
> from up
> > in the garage and installed them in the basement. I hadn't seen 
> any
> > problems in the garage so I figured after a year it was safe. 
> (Lesson
> > Learned)
> 
> No, no, no!  Lead acid batteries are outdoor animals (or, at least, 
> garage
> animals) [2].  I learned that the time that a lead acid battery I 
> had in my 
> shack "boiled over", and dumped a six foot diameter puddle of 
> sulfuric 
> acid on the floor.  That was not fun to clean up.
> 
> [2] You do have some minor concerns about outdoor batteries 
> freezing
> in winter, although it takes some VERY cold temperatures to freeze a 
> 
> charged battery.  It takes more moderate temperatures to freeze a 
> discharged battery, though.  If a Lead Acid battery does freeze, it 
> will
> usually crack the case, and allow the electrolyte (Sulfuric Acid) to 
> run out.
> 
> Plus, if you've ever been even somewhat close to one that has 
> exploded,
> you know that you don't want one in your house.  I had the battery 
> on my
> truck explode one morning (due to a manufacturing defect that 
> allowed 
> one of the internal connecting straps to fuse while I was cranking 
> the truck,
> which detonated a hydrogen explosion inside the battery)[1].  From 
> inside
> the cab, it sounded about like an M-80 going off (and, that was with 
> the
> hood closed and all of that sound proofing between the cab and the
> engine compartment).  
> 
> [1]  And, of course, this happened at the worst possible time, while 
> I was 
> 2500 miles from home. 
> 
> > This morning my wife wakes me up with "can you smell that? I think 
> we have
> > a gas leak". Oh great! Just what I need on a monday morning.  I
> > immediately told her it didnt smell like gas to me. It smelled 
> like rotten
> > eggs, not what I remember natural gas smelling like.
> 
> Natural gas is naturally oderless.  But, because so many houses were 
> blown
> up because of gas leaks, and because so many people were killed, the 
> gas 
> companies add a very smelly chemical to the natural gas to allow 
> leaks to be
> easily detected.  I think this chemical is Ethyl Mercaptan, or maybe 
> one of
> the other Mercaptans.  Mercaptans are notoriously smelly.
> 
> The classic "rotten egg" smell is usually Hydrogen Sulphide, which 
> is poisonous, 
> and can be lethal in all but the smallest quantities (Plus, is has 
> the notorious 
> effect of desensitizing the nose, so that you don't realize that you 
> may be 
> inhaling a fatal quantity!).  
> 
> > We go hunting around the house and the smell is definitely 
> stronger in the
> > basement. She heads off to call Cinergy because she swears it's a 
> gas
> > leak. I think it's probably a sewer backup or something. The smell 
> doesn't
> > seem stronger in any one portion of the basement. Which seems odd 
> to my
> > mind.
> > 
> > As a professional troubleshooter/investigator at work my mind 
> starts
> > recapping what has changed that day.  DING DING DING! I moved the
> > batteries into the basement. But they arnt suppose to vent...I 
> know they
> > CAN but they arnt suppose to.  A quick check of the batteries.  
> WARNING
> > SULPHURIC ACID label on them. Sulfur has a rotten egg smell. 
> *sigh*
> 
> If the battery was spewing out Hydrogen Sulphide, which is the 
> chemical 
> usually associated with the "rotten egg" smell, then it was 
> seriously sick.
> 
> > I use my main on/off switch (hey it works!) and turn off all power 
> in and
> > out of the batteries. I touch the batteries, ooh my goodness are 
> they hot.
> > I had felt the batteries when they were in the garage mind you, 
> they were
> > hot but the garage was 90+ degrees at the time...I didnt think 
> anything of
> > it.
> > 
> > I get out my amp/volt meter and test each battery. One shows 13.03 
> V the
> > other shows 9V. What the heck?!?!  13.03V is correct but 9V?!?
> > 
> > I move the batteries up to the garage again and try and charge 
> each
> > battery individually.  The good battery takes a full charge and 
> the
> > battery charger shuts off and shows green.  The 9V battery charges 
> for
> > 30minutes while waiting for the Cinergy guy to show up.  It never 
> makes it
> > passed 12.6 before I turn off the charger. By the time I test the 
> battery
> > with my volt/amp meter the volts have dropped to 11V and are 
> quickly on
> > the way down. I let the battery sit for another 10 minutes and the 
> voltage
> > has dropped down to around 9V again.
> > 
> > Okay..so I have a dead battery.
> >
> > But I don't know why I have a dead battery.
> 
> Usually what happens is that a cell will short.  This may happen 
> because of
> debris being shedded by the plates bridging a pair of plates and 
> shorting
> the cell, or because of the debris accumulating at the bottom of the 
> cell, 
> filling up the dead space there, and shorting a cell.   It may also 
> happen 
> because the plates warp, possibly because of overheating, and touch, 
> causing
> the cell to short.  
> 
> Once a cell has shorted, that drops the battery voltage from the 
> nominal 13.2 
> volts to 11 volts.  This will cause it to hog the current from the 
> charger, and 
> may, depending upon the design of the charger, cause the charger to 
> pump 
> even more current through the battery.  This excessive current 
> overcharges 
> the remaining cells, and may cause them to over heat or to shed 
> material from 
> their plates, which may cause more cells to short.  Additionally, 
> the over 
> current can also electrolyze the electrolyte, decomposing the water 
> into 
> Hydrogen and Oxygen, which forms a violently explosive mixture.  
> Plus, the 
> water that's electrolyzed out reduces the volume of electrolyte, 
> which 
> increases the current density in the cell even more.  The 
> combination of low
> electrolyte level (which means that only part of the plates are 
> covered), the  
> severe electrolysis and violent bubbling, and the increased heating 
> of the
> decreased plate area can cause bad things to happen to the remaining 
> cells.
> 
> If another cell shorts, then the voltage drops to 8.8 volts (2.2 
> volts per cell +/-
> a bit), which would explain the 9 volt reading.  And, this can cause 
> that 
> battery to hog even more of the current, and for the charger to pump 
> even 
> more current into that battery.  
> 
> You didn't indicate if these were sealed batteries or not.  It might 
> be interesting
> to pop the inspection ports to check the electrolyte levels (but, 
> remember that
> there's sulfuric acid in there, and probably a goodly concentration 
> of Hydrogen
> gas and Oxygen!).
> 
> Also, when a cell shorts on one of the batteries, think what the 
> current that the
> other battery will be supplying into that battery with the shorted 
> cell.  Let's see,
> 13.2 volts minus 11 volts divided by the internal resisance of the 
> batteries, which
> is somewhere around .001 Ohms...
> 
> > I drew a picture of the physical wiring of my system.
> > http://www.allisonhouse.com/battery.jpg
> > 
> > Could the way I had the system configured been the cause of the 
> damage?
> 
> I've seen some designs that use paralleled batteries to have 
> isolating diodes
> between the batteries so that a shorted cell on one of the batteries 
> doesn't cause
> the good batteries to dump their charge through the bad one.  Of 
> course, you
> need a goodly sized handful of very high current diodes to 
> accomplish this, and
> you need a charger that understands the .7 volt diode forward drop 
> (and, a load
> that will tolerate the .7 volt diode forward drop and still operate 
> correctly).
> 
> > Any thoughts on what happened?
> 
> Shorted cell(s).
> 
> > ps: Cinergy guy showed up. I didnt tell him about the batteries 
> until he
> > did his check. He swears no gas leak. He asks if I have any 
> punctured
> > 'things' in the basement. I mention I was charging car batteries. 
> He says
> > "that's what that smells like".  *sigh*
> 
> Hopefully, you won't be billed for a service call (Maybe he had 
> enough of a 
> chuckle that he'll write it off.).
> 
> > -Tyler
> > KI4BUM
> > 
> 
> Dave
> WA4QAL
> 
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